distributed detection method, and distributed optical fiber sensor

专利摘要:
DISTRIBUTED METHOD OF PROTECTION, METHOD FOR PROCESSING DATA FROM A DISTRIBUTED FIBER OPTICAL SENSOR, DISTRIBUTED OPTICAL FIBER SENSOR, PROCESSING DEVICE, COMPUTER PROGRAM, AND, FIBER OPTIC SENSOR. A method of optical detection of distributed fiber is described in which an optical fiber (104) is interrogated with electromagnetic radiation; backscattered radiation is detected; and the returns are processed to provide a measurement signal (310) for each of a plurality of longitudinal detection portions of the optical fiber. The method comprises analyzing the measurement signals from a first subset of longitudinal detection portions to provide a first zone (306a) with a first detection function and analyzing the measurement signals from at least a second subset of longitudinal detection portions to provide at least a second zone (306b) with a different second detection function. The different detection functions can include detecting different events of interest. In some embodiments, the fiber geometry can provide different detection zones (406a, 406b).
公开号:BR112012011223B1
申请号:R112012011223-6
申请日:2010-11-11
公开日:2020-12-29
发明作者:David John Hill；Magnus McEwen-King
申请人:Optasense Holdings Limited；
IPC主号:

专利说明:

[001] The present invention relates to optical fiber distributed detection and, especially, optical fiber distributed acoustic detection. In particular, the invention relates to methods and apparatus for distributed acoustic detection providing a plurality of independent detection functions.
[002] Several sensors using optical fibers are known. Many such sensors are based on fiber optic point sensors or discrete reflection locations such as fiber Bragg networks or the like that are arranged along the length of an optical fiber. The returns of the spot sensors or discrete reflection locations can be analyzed to provide an indication of temperature, deformation and / or vibration in the vicinity of the discrete reflection or sensor locations.
[003] Such sensors using reflection locations or discrete fiber optic point sensors require that the optical fiber including the sensor portions be specially manufactured. Additionally, the distribution of sensors in the optical fiber is fixed.
[004] Fully distributed fiber optic sensors are also known, in which the intrinsic dispersion of a continuous length of optical fiber is used. Such sensors allow the use of standard fiber optic cable without deliberately introducing reflection sites such as fiber Bragg networks or the like. Any optical fiber from which a backscattered signal can be detected can be used as part of the sensor. Time-splitting techniques are typically used to split the signal returns into numerous time boxes, with the returns in each time box corresponding to a different portion of the optical fiber. Such optical fiber sensors are referred to as distributed fiber optical sensors, since the sensor options are completely distributed across the entire optical fiber. In the form used in this specification, the terms distributed optical fiber sensor will be used to mean a sensor in which the optical fiber itself constitutes the sensor and which is not based on the presence of specific point sensors or deliberately introduced reflection or interference locations, which is an intrinsic fiber optical sensor.
[005] Various types of distributed fiber optic sensor or distributed acoustic sensor (DAS) are known and have been proposed for use in various applications.
[006] U.S. patent 5,194,847 describes a distributed acoustic fiber optical sensor for intrusion detection. A continuous optical fiber without any specific spot sensors or reflection locations is used. Coherent light is released into the optical fiber and any light that undergoes Rayleigh backscattering within the optical fiber is detected and analyzed. A change in backscattered light in a time box is indicative of an acoustic or pressure wave incident on the relevant portion of the optical fiber. In this way, acoustic disturbances from any portion of the fiber can be detected.
[007] The GB 2,444,745 patent specification describes a distributed acoustic fiber optical sensor system in which acoustic vibrations are detected by launching a plurality of pulse-modulated electromagnetic wave groups on a standard optical fiber. The frequency of one pulse within a group differs from the frequency of another pulse in the group. Rayleigh's backscattering of light from intrinsic reflection sites within the fiber is sampled and demodulated in the frequency difference between pulses in a group.
[008] US patent 6,380,534 describes a distributed optical fiber deformation and temperature detection system that analyzes the Brillouin backscatter frequency distribution of light shed on the fiber to determine the temperature and deformation along the various portions of the fiber detection, which can be embedded in a structure.
[009] WO02 / 057805 describes the use of temperature sensors, strain and / or optical fiber acoustics distributed in a variety of applications including monitoring of flow line parameters in the oil and gas industry.
[0010] Optical distributed fiber detection, therefore it provides adequate and convenient detection solutions that can monitor long lengths of optical fiber with good spatial resolution. For example, a distributed fiber optic acoustic sensor, such as can be used to monitor a pipe, can be implemented with detection portions of 10 meters in length in up to 40 km or more of optical fiber. This clearly results in 4,000 separate acoustic channels that would be very difficult for a human operator to monitor. Even with automatic detection of signals above a threshold, the amount of data can be overwhelming.
[0011] It is an objective of the present invention to provide methods and apparatus for optical detection of distributed fiber that mitigate the aforementioned problems and / or increase the utility and / or flexibility of optical fiber detection systems.
[0012] Thus, according to the present invention, a distributed detection method is provided comprising the steps of: interrogating an optical fiber with electromagnetic radiation; detect electromagnetic radiation that is backscattered by optical fiber; process said detected back-scattered radiation to provide a measurement signal for each of a plurality of longitudinal detection portions of the optical fiber and analyze the measurement signals from the longitudinal detection portions to detect events of interest in which the method comprises analyzing the measurement signals from a first subset of longitudinal detection portions to provide a first zone with a first detection function and analyze the measurement signals from at least a second subset of longitudinal detection portions to provide at least a second zone with a second different detection function.
[0013] The method of the present invention thus interrogates an optical fiber, detects back-scattered radiation and processes the detected radiation in analysis boxes, to provide measurement signals corresponding to a plurality of longitudinal detection portions of the fiber. The method also processes the measurement signals to detect events of interest, that is, to detect measurement signals that are characteristic of the events of interest. The method of the present invention further identifies at least first and second subsets of the longitudinal detection portions to provide respective first and second zones and analyzes each subset to provide a different detection function. In this way, a single detection fiber can be used to provide a plurality of different detection functions in different parts of the fiber. This can increase the flexibility of the distributed fiber optic sensor, reduce false alarms and provide a more intelligible and expressive output for an operator to monitor the sensor system, as will be explained in more detail below.
[0014] The different detection functions can comprise detection of different events. Thus, measurement signals from the first zone can be analyzed to detect a first event of interest, while signals from the second zone can be analyzed to detect a second event of different interest.
[0015] The detection of an event of interest may comprise identifying a predetermined characteristic of the event in the measurement signals coming from one or more longitudinal detection portions of the optical fiber. For example, a distributed fiber optic acoustic sensor can compare the measurement signals, that is, the detected acoustic signals, coming from each longitudinal detection portion, or groups of adjacent longitudinal detection portions, with an acoustic signature of an event. interest. If the measured signal matches the acoustic signature of the particular event of interest, this can be considered a detection of the particular event of interest.
[0016] The method of the present invention can therefore involve analyzing the measurement signals from the first zone to detect a first feature or signature and analyzing the measurement signals from the second zone to detect a second feature or signature.
[0017] The method, therefore, allows a part of a detection fiber to be used to detect a first event of interest and another part of the same detection fiber to detect a second event of interest. By zoning the detection fiber in this way, the detection accuracy can be improved and the amount of information generated is processed more efficiently to provide a more meaningful and concise output.
[0018] As an example, suppose that a distributed acoustic fiber optical sensor is implanted along the perimeter or edge, part of which is protected by a barrier such as a solid wall, but part of which is completely open without physical obstacles. The sensor comprises a single optical fiber implanted along both edge sections. The sensor can be arranged with the first zone corresponding to the part of the optical fiber close to the barrier and the second zone corresponding to the part of the optical fiber that is arranged along the open edge. In the first zone, the measurement signals can be monitored to detect acoustic events associated with sabotage or destruction of the barrier. The second zone can be monitored to detect movement of a land vehicle crossing or approaching the perimeter. Thus, although both zones of the sensor may be performing acoustic detection, the first zone is monitored for different acoustic events for a second zone. Thus, the method of the present invention provides the ability to perform different detection functions on different parts of the fiber, in a manner appropriate for the particular environment.
[0019] Monitoring and processing of data detected in this way can help an operator and result in more effective and reliable monitoring of the system. When an event of interest is detected, the method can comprise generating an alert, which could be one or more of a graphic alert in a display, an audible alarm, a visible alarm, sending a message to a remote device, for example, sending an alert by email or text message, etc. The system operator can therefore respond only to the alerts generated.
[0020] In the above example, suppose that part of the perimeter that is protected by the barrier is located close to a road. Processing the measurement signals from the entire length of the optical fiber to detect ground vehicles can lead to many detections of this part of the optical fiber. Consequently, a large number of alerts can be generated, most of which will be false alarms. A large number of false alarms can be very time consuming for a system operator and / or potentially mask the presence of a real alarm. The method of the present invention, however, allows each zone to be monitored only for events of interest that are relevant to that zone. Thus, an alert is only generated for the event of relevant interest that decreases the load on an operator and increases the chance that the alert will be noticed and generate an action.
[0021] It should be noted that subsets of longitudinal detection portions of the optical fiber that comprise each of the zones do not necessarily have to comprise a set of contiguous detection portions. Thus, the first zone can comprise two or more groups of longitudinal detection portions, with the detection portions within each group being contiguous, but the groups not being contiguous. For example, back to the above example, if the open section of the perimeter is encased on both sides by the wall sections of the perimeter, the second zone can correspond to that section of optical fiber that is along the open part of the perimeter and the first zone can correspond to the rest of the optical fiber. Thus, the first zone could comprise the longitudinal detection portions of the optical fiber sections on either side of the open section. Alternatively, the optical fiber could be arranged with a first zone corresponding to the first perimeter wall section, a second zone corresponding to the longitudinal detection portions of the fiber along the open part of the perimeter and a third zone corresponding to the other wall section of perimeter. perimeter. The first and third zones can be monitored to provide the same detection function - with the second zone providing a different detection function. The method of the present invention can therefore comprise identifying more than two zones, each zone related to a different subset of longitudinal detection portions. There can be several different zones, each of which has a different detection function, although measurement signals from at least two different zones can be analyzed to provide the same detection function.
[0022] The detection functions can comprise detecting more than one event of interest. Providing different detection functions in the first zone and in the second zone can therefore comprise detecting a first set of events of interest in the first zone and detecting a second set of events of interest in the second zone, with the first set of events being different from second set of events. The first and second sets may comprise mutually exclusive events of interest, but in some embodiments, the first and second sets of events may comprise one or more events of common interest. Thus, one or more events of common interest can be detected in both the first and second zones. The different detection function is provided in the first and second zones by detecting at least one event of interest in one of the zones that is not detected in the other zone.
[0023] For example, back to the example discussed above, the first zone of the fiber corresponds to a section of perimeter wall and the set of events of interest may include destruction of the wall. The second zone of the fiber corresponds to an open part of the perimeter and the set of events to be detected includes land vehicles approaching or crossing the perimeter. In both zones, however, detecting an event of interest may include detecting a characteristic corresponding to the movement of people. Along the entire length of the perimeter, you may want to monitor a standing intruder having both scaled the wall and crossed the open edge section.
[0024] Thus, the same event of interest can be detected in more than one zone, but the total set of events of interest varies between a first and a second zone.
[0025] In some modalities, all events of interest in the second zone may be events of common interest with the first zone, but the first zone also detects at least one event of additional interest. In other words, the detection function of the second zone can comprise detecting any of numerous events of interest. Exactly the same events of interest can also be detected in the first zone, but the first zone also detects at least one event of additional interest. So, back to the same example, you may want to actually detect vehicles approaching the perimeter wall section corresponding to the first zone. Thus, the detection function of the first zone comprises detecting vehicles, people or destruction or damage to the wall. The edge section corresponding to the second zone has no wall and therefore there is no need to detect damage to the wall. Therefore, the second detection function comprises detecting land vehicles and people.
[0026] The set of events of interest in the first zone can thus comprise at least one event of interest that is not relevant for the second zone. However, as previously described, it may be suitable to avoid detecting certain events, which may otherwise be events of interest, in areas where a large number of false or unnecessary alarms can be generated.
[0027] The method can therefore comprise arranging the second zone so as not to detect at least one event of interest that is detected in the first zone.
[0028] For example, consider a distributed fiber optic acoustic sensor implanted along the length of a buried pipe and arranged to monitor interference with the pipe. Typically, the entire length of the pipe can be monitored to detect vehicles or people in the vicinity of the pipe and any characteristics related to excavation or tunneling near the pipe. However, in the event that some genuine field work is being carried out near the pipeline, but does not cause danger to the pipeline, you may want to interrupt the detection characteristics related to the excavation or tunneling in those surroundings to avoid a constant alarm. . Thus, a subset of longitudinal detection portions of the fiber in the vicinity of work on the ground can be designated as a zone, say a second zone, with the remaining fiber detection portions constituting the first zone. The detection of excavation or tunnel opening can be disabled in the second zone for the duration of the work on the ground. This avoids the presence of a constant alarm, which, while correctly identifying the excavation near the pipeline, is known to not be a threat.
[0029] The method can therefore comprise selecting a subset of longitudinal detection portions of the fiber from at least one of the zones. Selection can be carried out by an operator via an interface and can be carried out in a number of ways. Conveniently, however, at least one group of contiguous fiber detection portions is user defined, and any or all groups allocated to a particular zone. Any portions of fiber not so defined or allocated can be automatically allocated to a standard zone. An operator can select groups by selecting a portion of fiber in a graphical user interface including a representation of the fiber.
[0030] The method may also involve allocating a detection function to at least one zone by selecting the events of interest that should be detected in that zone. This may include deselecting certain events from a standard list.
[0031] The detection portion groups selected by the operator may, in some cases, overlap, or a selected group may be a subset of the previous selected group. For example, a first group of detection portions can be selected and allocated to a first set of events of interest. A second group of detection portions can then be selected, which overlaps the first group at least partially, and allocated to a second set of events of interest. If there are at least some areas of each group that do not overlap, this defines three zones, the first zone corresponding to those detection portions that belong to the first group only, the second zone corresponding to those detection portions that belong to the second group only and one third zone corresponding to those detection portions that belong to both groups. The first zone detects only the first set of events of interest, the second zone, the second set of events of interest, and the third zone detects events of interest from both sets.
[0032] The second group selected may be a subset of the first group which makes one of the zones effectively a subzone of the other zone.
[0033] The arrangement of the zones and the detection function performed by each zone can be established by an operator. In some embodiments, the function of detecting and / or activating or deactivating zones can be varied automatically based on a defined time interval. For example, if a distributed fiber acoustic sensor is deployed along a pipe to monitor interference with the pipe, but if scheduled maintenance is taking place along a section of the pipe, the relevant sensor section can be configured as a zone. that ignores digging activity. This zone can be assigned with a fixed life, however, based on the expected duration of the work, after which it will automatically revert to detect all events of interest. This can help to prevent the existence of a zone that is examined with the loss of the desired detection function, once maintenance is completed. Additionally, in some applications, there may be acoustic disturbances expected at regular times. For example, the expected acoustic disturbances during the day may vary from those expected at night, so different zones can be established to activate / deactivate at set times to provide different overnight monitoring.
[0034] It should be noted that, although the method of the present invention can detect, that is, identify and / or alert to the occurrence of an event of interest, the detection process can comprise the classification or categorization of the measurement signals of according to the characteristics or subscriptions of events that are not of interest. For example, there may be a set of possible events that can occur in a particular zone and the set of events of interest may be a subset of the set of possible events. The measurement signals from the relevant zone can be compared with the characteristics of all possible events to determine whether the signals match any particular event. Signs that are a strict marriage with the characteristic of a possible event can be classified as being generated by that event. If the particular event is an event of interest, the method detects that the event of interest has occurred and can generate an appropriate alert. If the event is not an event of interest, then the signals can be ignored, although the classification can be recorded for future analysis.
[0035] For example, as previously described, a zone can be arranged to not detect a particular event, such as excavation or tunnel opening near a pipe, because it is known that the event in question is occurring in the vicinity of that zone . In this situation, however, the measurement signals from the second zone can still be compared with the characteristics of the event in question, that is, excavation and tunnel opening. If the measurement signals are classified as representing excavation or tunneling, they can be safely ignored. By identifying the measurement signals as being generated by an event that is not of interest, the chance of a false alarm being generated by those signals being mistaken for an event of interest, for example, approaching a land vehicle, can be reduced .
[0036] The deselection of an event of interest, that is, the establishment of a zone so that a particular event is not detected for that zone, represents an unprecedented aspect of the invention. Also, the use of event characteristics that are not of interest in the analysis, in order to improve the detection of events that are of interest, represents another aspect of the present invention.
[0037] In some modalities, there may be some events that may occur in one zone that are not appropriate for another zone and therefore the set of possible events for the zones may be different. For example, if a perimeter includes a body of water, a single fiber can be buried in the ground on a piece of land on the edge and also implanted in the water. A first zone can be established corresponding to the parts of the fiber on land and a second zone can be match the part of the fiber in the water. The first zone can be arranged to detect land-based intrusion and the second zone can monitor water-borne intrusions, for example, detection of signals characteristic of external engines or the like. The fiber can be cleared in the water and so it may be necessary to classify various measurement signals that would be expected because of the movement of the fiber in the water as signals of no interest. At least some of these could potentially be similar to the characteristics of an event of interest for the land-based portions of the fiber and thus, in this situation, events that are relevant to the second zone may not be absolutely relevant to the first zone.
[0038] The different detection functions of the first and second zones can also include monitoring the signals coming from the zones for different purposes. For example, while the above examples are generally concerned with detecting intruders or interference, distributed fiber optic sensors can also be used for condition monitoring. For example, a fiber optic distributed acoustic sensor can be implanted along the length of a buried pipe, such as an oil or gas pipe. At least part of the fiber can be used to detect possible interference with the piping, as previously described. Thus, detection of acoustic signals corresponding to the movement of people or vehicles in the vicinity of the pipeline, or especially associated with excavation or opening of a tunnel, can comprise events of interest to be detected. The pipeline itself, however, can generate or propagate acoustic signals that can be used for condition monitoring. As described in the copending patent application PCT / GB2009 / 002058, the acoustic signals generated, for example, by a pressure pulse moving along the pipe, or an object moving through the pipe, can be used to give a piping condition indication. Thus, the detection function of at least one zone can comprise condition monitoring. Condition monitoring can comprise comparing the measurement signal from one or more longitudinal detection portions with a previously acquired measurement signal to detect any significant changes. The measurement signals used in condition monitoring can be acquired in response to a particular stimulus, for example, a pressure pulse inside a pipe, say, and / or can comprise the steady state measurement signals obtained in routine operation of the sensor. The measurement signals used in condition monitoring can be integrated or represented by the average over a period of time or normalized in some way and / or they can be compared with signals properly represented by the average or normalized previously acquired.
[0039] The condition monitoring and detection of events of interest can be performed simultaneously in any given zone of the sensor. The measurement signals from the relevant zone can be analyzed to detect a characteristic of an event of interest and can also be compared with at least one signal previously acquired to detect any significant change. The ability to perform condition monitoring and detection of events of interest simultaneously represents another aspect of the present invention.
[0040] Certainly, detection of an event of interest can be related to condition monitoring in which a sudden failure or rapid change in the condition of a structure being monitored can give rise to an associated characteristic signal that can be detected as a event of interest. For example, taking the example of pipe monitoring, a significant sudden failure of the pipe at a particular point, such as the onset of a sudden leak, can generate a characteristic signal. This can be detected as an event of interest.
[0041] Other detection functions may include object tracking, monitoring of operational parameters, seismic monitoring, etc.
[0042] As previously described, the first and second zones correspond to the first and second subsets of longitudinal detection portions of the optical fiber and, in some embodiments, a zone can be defined by an operator in use selecting any given subset of detection portions longitudinal. In one embodiment, however, the first subset of longitudinal detection portions corresponds to the portions of the optical fiber with a first physical arrangement and the second subset of longitudinal detection portions corresponds to the portions of the optical fiber with a different second physical arrangement. In other words, the first and second zones comprise sections of the optical fiber with a different physical arrangement, that is, the optical fiber is implanted differently in the first zone and the second zone.
[0043] The different arrangement may comprise the geometry of the fiber. The fiber geometry in part determines the detection function that the fiber can perform.
[0044] The geometry of the optical fiber can be arranged to provide a different effective spatial resolution in each zone. It should be understood that, in a distributed fiber optic sensor that is interrogated by pulsed radiation, the spatial resolution of the fiber's longitudinal detection portions can typically depend on the duration of the interrogation pulse. For example, in an optical acoustic fiber sensor distributed as described in GB2.442.745, the spatial length of the longitudinal detection portions is about 12 m. If the optical fiber is implanted in such a way that the fiber is relatively straight, in lengths of a few tenths of meters, it will be clear that the effective spatial resolution of the sensor will be the same as the spatial resolution of the longitudinal detection portions, that is, the portions 12 m long fiber optic longitudinal detection monitors monitor the incident acoustic signals in a 12 m long stretch of the environment. The spatial resolution of the sensor can be varied by changing the interrogation radiation, but this can have an effect on the fiber length that can be monitored.
[0045] However, if the fiber geometry is such that the fiber is arranged in a curved or bent arrangement, for example, with a helical or spiral path or a tortuous path, the effective spatial resolution of the sensor can be reduced, compared to the native spatial resolution of the fiber. For example, if the optical fiber is arranged in such a way that a length of optical fiber of 12 m is contained with a section of ground of 1 m, although the length of the longitudinal portions of the fiber can be 12 m each, such a portion of detection only receives the acoustic signals incident within 1 m of the environment. Thus, the effective spatial resolution of the sensor with respect to the environment would be 1 m.
[0046] Thus, the geometry of the fiber in the first zone and in the second zone can vary in order to provide the sensor with different effective spatial resolutions in each of the zones. For example, in the first zone, the optical fiber can be implanted in an arrangement that is generally straight or gently curved (in scales of lengths of a few tenths of meters) to provide a sensor in which the spatial resolution of the sensor is equal to the spatial resolution of the longitudinal detection portions of the fiber. In a second zone, the fiber can be implanted in a spiral or folded arrangement, in such a way that the effective spatial resolution of the sensor is lower.
[0047] Therefore, the different detection functions in the first and second zones can comprise detection with a different effective spatial resolution in the first and second zones. The optical fiber can therefore be implanted to have a particular geometry that varies along the general path of the optical fiber in order to provide different zones with different effective spatial resolutions. The arrangement of an optical fiber from a fiber optic sensor distributed so as to provide zones with different effective spatial resolutions represents another aspect of the present invention.
[0048] Sections with a lower effective spatial resolution can be interspersed, periodically or not periodically, with sections of higher spatial resolution to provide a sensor that has a base spatial resolution along the length of the sensor, but with sections of lower spatial resolution arranged along the length of the sensor. Alternatively, the optical fiber can be arranged to give a lower spatial resolution at certain points where a better resolution is desired. In this way, a balance between spatial sensitivity and overall length can be achieved. Clearly, spiraling or folding the optical fiber to reduce the effective spatial resolution of the sensor means that the length of the entire sensor will be reduced (for a given length of optical fiber).
[0049] The geometry of the optical fiber can be determined when the optical fiber is installed by arranging the optical fiber in the desired geometry. Fiber optics are typically implanted within a fiber optic cable and so the fiber optic cable can be installed in a spiral or bent arrangement. Alternatively, the optical fiber could be arranged within a fiber optic cable with a geometry that varies along the length of the cable, that is, a section of cable could comprise a coiled fiber optic arrangement, whereas the other section comprises optical fiber running directly along the cable. The cable itself can then be deployed in a relatively straight path - although the cable itself can certainly be additionally coiled or bent in the required manner.
[0050] In some modalities, where the physical arrangement of the fiber provides a different effective spatial resolution, the measurement signals from the first subset of longitudinal detection portions can be analyzed in the same way as the measurement signals from the second subset. This can also provide the first zone with a first detection function in a first effective spatial resolution and the second zone with a second detection function in a second effective spatial resolution. In some embodiments, however, the first and second subsets of longitudinal detection portions may require or allow different analysis. The change in effective spatial resolution means that a feature that is detected in a longitudinal detection portion of the signal in the highest spatial resolution is detectable in more than an adjacent longitudinal detection portion in the lowest spatial resolution. Thus, different characteristics of events of interest can be used in the different zones.
[0051] The geometry of the optical fiber can be additionally, or alternatively, arranged to provide additional detection functions in at least one zone. For example, the optical fiber can be arranged in a zone in order to allow the direction of incidence of an optical fiber disturbance to be determined. As those skilled in the art can perceive, a disturbance, such as a propagating acoustic wave, can be detected by an appropriate distributed fiber optic sensor. However, using a single optical fiber arranged along a relatively straight path, it may not be possible to determine the direction of travel of the disturbance. Thus, in a zone, the fiber geometry can be arranged to allow the direction of incidence of the disturbance to be determined. The direction of incidence can be determined in one dimension, that is, on which side of the sensor the disturbance originated, in a two-dimensional or three-dimensional plane, depending on the fiber arrangement. The geometry of the fiber in a zone can be arranged in such a way that the magnitude or intensity of a disturbance can be resolved in its components in two or three dimensions.
[0052] The fiber geometry can also be such that the fiber rewires itself so that different sections of the fiber that are not adjacent or are separated from each other along the length of the fiber, however, monitor substantially the same section, or adjacent sections, of the environment in which the fiber is implanted. For example, consider a fiber optic distributed acoustic sensor used as a perimeter sensor. A long fiber length, such as 40 km in length, can be implanted in a spiral arrangement around a perimeter of the site. For example, the fiber can be implanted to form a first loop near an external fence, a second loop on dead ground between the external fence and the inner wall and a third loop near the inner wall. A person walking directly from the outer fence to the inner wall can therefore cross three different sections of fiber. The method may therefore involve identifying different sections of the fiber as being linked zones so that a detection of a walking event in the zone corresponding to a detection of a walking event in the linked zone corresponding to the dead ground is interpreted as a single detection. Linking processing in this way can reduce false alarms and improve detection accuracy (for example, an alarm can only be generated if detected in the two linked zones), but it also allows information such as the speed and direction of movement of a source acoustics to be traced.
[0053] The method of the present invention can be used with a variety of distributed fiber optical sensors, but, in a preferred embodiment, the sensor is a distributed optical fiber optical sensor, that is, a sensor in which the measurement signals correspond to the acoustic signals. Acoustic sensor, in the context of this patent application, means a sensor that can detect mechanical vibration from the fiber sensor or pressure waves incident on the fiber at relatively high frequencies. The distributed fiber optic acoustic sensor can detect and process Rayleigh backscattered radiation through the optical fiber as the measurement signals. The method may comprise interrogating the optical fiber with interrogation radiation and processing the backscattered radiation detected as described in GB2.442.745.
[0054] The step of analyzing the measurement signals from the various zones to provide different detection functions therefore preferably comprises using the same type of measurement signals in each zone, that is, measurement signals that measure the same parameter. Thus, for a distributed fiber optic acoustic sensor, the measurement signals comprising the acoustic information, for example, Rayleigh's backscattered radiation, are analyzed in each zone. The method of the present invention can therefore provide different detection functions in an optical fiber sensor that provides only acoustic detection (ie, vibration).
[0055] Certainly, in optical fiber sensors that can provide different detections for more than one parameter, for example, deformation and temperature, the method can comprise providing a first detection function for one or more of the parameters in the first zone and a second detection function for one or more of the parameters in the second zone.
[0056] Although the method has been described in terms of interrogating the fiber and processing the acquired data, the data does not need to be processed at the location of the optical source and detector. The data could be transmitted to a remote location for processing.
[0057] Thus, in another aspect of the invention, a method of processing data from a distributed optical fiber sensor is provided comprising the steps of: obtaining data corresponding to the detected electromagnetic radiation that has been backscattered by an optical fiber; process said data to provide a measurement signal for each of a plurality of longitudinal detection portions of the optical fiber and analyze the measurement signals from the longitudinal detection portions to detect events of interest in which the method comprises analyzing the signals of measuring a first subset of longitudinal detection portions to provide a first zone with a first detection function and analyzing the measurement signals from at least a second subset of longitudinal detection portions to provide at least a second zone with a second detection function different detection.
[0058] This method of processing can use all of the above described modalities with respect to the first aspect of the invention and also benefit from exactly all the advantages.
[0059] The invention also relates to a distributed optical fiber sensor that has different zones that provide different detection functions. Thus, according to another aspect of the invention, a distributed optical fiber sensor apparatus is provided comprising: an optical fiber; a source of electromagnetic radiation configured to emit electromagnetic radiation on said fiber; a detector for detecting electromagnetic radiation backscattered by said fiber; and a processor configured to: analyze back-scattered radiation to determine a measurement signal for a plurality of discrete longitudinal detection portions of the optical fiber; wherein the distributed optical fiber sensor comprises a first zone with a first detection function, the first zone corresponding to a first subset of said longitudinal detection portions and at least a second zone with a different second detection function, the second zone corresponding to a second subset different from said longitudinal detection portions.
[0060] The apparatus of this aspect of the invention provides exactly the same advantages and can be implemented in exactly the same modalities described above with reference to other aspects of the invention.
[0061] In particular, the processor can be configured to analyze the measurement signals from said first subset of longitudinal detection portions to provide said first zone with a first detection function and analyze the measurement signals from at least said second subset of longitudinal detection portions to provide at least said second zone with a different second detection function.
[0062] The different detection functions can include the detection of different events of interest. As described earlier, the different detection functions can comprise detecting a first set of events of interest in the first zone and a second set of events of interest in the second zone. The first and second sets of events of interest may or may not have an event of interest in common. The first set of events of interest can be a subset of the second set of events of interest, or vice versa.
[0063] The processor can be configured to classify the measurement signals based on whether they match one or more predetermined characteristics. The predetermined characteristics can comprise the characteristics of events of interest. The predetermined characteristics may also comprise the characteristics of other events, which are not events of interest. As previously described in relation to the method, by matching the measurement signals with the predetermined characteristics of probable events, including events not currently of interest, the sensor can correctly identify those signals generated by an event that is not of interest, and thus reduce alarms false.
[0064] The sensor apparatus preferably comprises a graphical display. The processor can be arranged to generate a graphical alert on the display when an event of interest is detected. The graphic alert can comprise an alert that is displayed in a representation of the fiber optic path in the relevant part of the path. The graphical display can be colocalized with the processor and / or a graphical display can comprise part of a control station for the sensor device that is remote from the processor. The processor can therefore be configured to transmit data corresponding to the measurement signals of the longitudinal detection portions and / or the results of the analysis of said measurement signals to one or more remote devices. For example, the processor may generate one or more warning signals.
[0065] The method may involve generating different levels of alert and / or alarm. The alert level can vary based on the type of event detected, the duration or event, the intensity of the event, the range determined up to the event and / or movement of the event source. For example, a color-coded alert can be generated so that a green alert is simply an information alert to confirm a detection. An amber alert can alert a potential threat and a red alert can alert a threat that requires action. The highest alert levels may involve audible alarms and / or automatic message generation, for example, to a response team.
[0066] Conveniently, the device is adapted in such a way that a user can establish one or more zones for the sensor device in use. In one embodiment, the device is adapted in such a way that a user can select a subset of longitudinal portions of the fiber, selecting a portion of the optical fiber path representation or a representation of the optical fiber measurement channels that is shown in the graphical display . In other words, the user may be able to configure sensor zones by selecting, for example, by placing a selection window on a representation of the optical fiber path or a representation of the sensor's measurement channels.
[0067] The graphical display can be configurable to display a set of events that can be detected and the device can be adapted in such a way that a user can select the events to be detected in a chosen zone.
[0068] The optical fiber may have a first physical arrangement in the first zone and a second physical arrangement, which is different from the first physical arrangement, in the second zone. The different physical arrangement in the first and second zones can comprise a different fiber geometry in each zone. The geometry in each zone can provide an effective spatial resolution different from the sensor in each zone, as previously described with respect to the method.
[0069] The geometry of the optical fiber can be additionally or alternatively arranged to provide additional detection functions in at least one zone. As previously described, the optical fiber can be arranged in a zone in order to allow the direction of incidence of an optical fiber disturbance to be determined and / or in such a way that the magnitude or intensity of a disturbance can be resolved in its components in two or three dimensions.
[0070] The radiation source and detector will be located at one end of the optical fiber to release radiation into the fiber and detect the radiation backscattered by the optical fiber. The processor can be located with a source and the detector, or it can be located remotely and it can receive data from the detector. In some embodiments, a processor can be located with the source and the detector to perform some initial processing to place the data in a form suitable for transmission. Some processing can also be conducted on the data to reduce the amount of data being transmitted. For example, the data could be processed to provide measurement signals from each of a plurality of longitudinal detection portions prior to transmission.
[0071] In another aspect of the invention, therefore, a processing apparatus is provided to obtain data corresponding to a signal of measurement of retrodispersed radiation detected for each of a plurality of longitudinal detection portions of an optical fiber and to analyze the signals of measurement from longitudinal detection portions to detect events of interest, where the method comprises analyzing the measurement signals of a first subset of longitudinal detection portions to provide a first zone with a first detection function and analyzing the measurement signals of at least a second subset of longitudinal detection portions to provide at least a second zone with a different second detection function.
[0072] The processor can obtain data corresponding to the basic detected radiation that is backscattered by the optical fiber and can therefore be configured to process said detected radiation to provide the measurement signal in each of said longitudinal detection portions.
[0073] This aspect of the present invention provides exactly the same advantages and can be used in exactly the same modalities described above with respect to other aspects of the invention.
[0074] The invention also provides a computer program and a computer program product to perform any of the methods described herein and / or to incorporate any of the apparatus resources described herein, and a computer-readable medium that has stored a program in it perform any of the methods described herein and / or to incorporate any of the apparatus features described herein. A properly programmed computer can control the optical source and receive data from a suitable optical detector. The computer program can be incorporated into a transmission signal.
[0075] As previously described, different zones can, in some modalities, be formed by the physical arrangement of the optical fiber. Thus, in another aspect of the invention, a distributed optical fiber sensor is provided comprising an optical fiber with a first physical arrangement in a first zone to provide a first detection function and a different second physical arrangement in a second zone to provide a second detection function.
[0076] As previously described, the physical arrangement can comprise the geometry of the fiber. The optical fiber can be arranged to provide a first effective spatial resolution in the first zone and a second effective spatial resolution in the second zone. The optical fiber can be arranged in a zone in order to allow the direction of incidence of an optical fiber disturbance to be determined and / or in such a way that the magnitude or intensity of a disturbance can be resolved in its components in two or three dimensions.
[0077] In general, the present invention relates to a distributed optical fiber sensor, especially a distributed acoustic sensor, which performs multiple independent detection functions using the same fiber. The independent detection functions can detect different events for the same general purpose, for example, detect different types of intrusion for the purpose of intrusion detection, or they can comprise detection for different purposes, for example, both intrusion detection and condition monitoring , say, can be performed simultaneously. Providing alerts / alarms only for events of interest relevant to a part of the particular optical fiber can reduce the burden on an operator and reduce the chance that genuine alarms will be lost. You can designate a zone where an alarm was detected and effectively for the detection of that event, in the sense of generating an alarm, it means that only genuine alarms will be presented to an operator.
[0078] The invention extends to methods, apparatus and / or use in the manner substantially described herein with reference to the accompanying drawings.
[0079] Any feature in one aspect of the invention can be applied to other aspects of the invention, in any appropriate combination. In particular, aspects of methods can be applied to aspects of apparatus, and vice versa.
[0080] In addition, resources implemented in hardware can generally be implemented in software, and vice versa. Any reference to software and hardware resources here should be interpreted in this way.
[0081] Preferred features of the present invention will now be described, purely by way of example, with reference to the accompanying drawings, in which: Figure 1 illustrates the basic components of a distributed fiber optic sensor; Figure 2 illustrates part of a detection fiber path buried in the ground along part of an edge and the discrete fiber detection portions; Figure 3 illustrates part of a detection fiber path buried in the ground along a pipe; Figure 4 illustrates a detection fiber with different geometries in different zones to provide a different effective spatial resolution; Figure 5 shows an alternative geometry to provide a different spatial resolution; Figures 6a and 6b show sectional and plan views of a fiber buried in an alternative geometry; and Figure 7 illustrates that different zones of the fiber can be connected by unpacking the fiber.
[0082] Figure 1 shows a schematic of an optical fiber distributed detection arrangement. A length of detection fiber 104 is connected at one end to an interrogator 106. The output of the interrogator 106 is passed to a signal processor 108, which can be colocalized with the interrogator, or can be remote from it, and optionally an interface of user / graphic display 110, which in practice can be performed by a duly specified PC. The user interface can be colocalized with the signal processor, or it can be remote from it.
[0083] Detection fiber 104 can be many kilometers long and, in this example, is approximately 40 km long. The detection fiber is a standard unmodified single-mode optical fiber such as those routinely used in telecommunications applications. In conventional applications of distributed fiber optic sensors, the detection fiber is contained at least partially in a medium to be monitored. For example, fiber 104 can be buried in the ground to provide monitoring of a perimeter or monitoring of a buried item such as a pipe or the like.
[0084] The invention will be described in relation to a distributed acoustic sensor, although versed in the technique realize that the precept can be generally applicable to any type of distributed optical fiber sensor.
[0085] In operation, interrogator 106 releases electromagnetic interrogation radiation, which can, for example, comprise a series of optical pulses with a selected frequency pattern, on the detection fiber. Optical pulses may have a frequency pattern described in the GB2.442.745 patent specification, whose contents are hereby incorporated by reference. As described in GB2.442.745, Rayleigh's backscattering phenomenon causes a certain fraction of the light to enter the fiber to be reflected back into the interrogator, where it is detected to provide an output signal that is representative of acoustic disturbances in the vicinity of the fiber. . The interrogator therefore conveniently comprises at least one laser 112 and at least one optical modulator 114 to produce a plurality of optical pulses separated by a known optical frequency difference. The interrogator also comprises at least one photodetector 116 arranged to detect radiation that is backscattered by the intrinsic dispersion sites within the fiber 104.
[0086] The signal from the photodetector is processed by the signal processor 108. The signal processor conveniently demodulates the returned signal based on the frequency difference between the optical pulses as described in GB2.442.745. The signal processor can also apply a phase unpacking algorithm as described in GB2.442.745.
[0087] The shape of the optical input and the detection method allow a simple continuous fiber to be spatially resolved in discrete longitudinal detection portions. That is, the acoustic signal detected in a detection portion can be provided substantially independent of the signal detected in an adjacent portion. The spatial resolution of the optical fiber detection portions can, for example, be approximately 10 m, which, for a fiber length of 40 km, makes the interrogator's output take the form of 4,000 independent data channels.
[0088] In this way, the only detection fiber can provide detected data that are analogous to a multiplexed array of adjacent independent sensors, arranged in a linear path.
[0089] Figure 2 illustrates part of the detection fiber arranged along the path of a perimeter or edge 204. As shown in figure 2, the detection fiber can be arranged in a generally straight path along the line of the edge 204 Divisions 208 represent the spacing of the longitudinal detection portions of the fiber (on no particular scale).
[0090] In one embodiment, different subsets of the longitudinal detection portions of the fiber are arranged to provide different zones with different detection functions. The zones thus correspond to the sections of the detection fiber and the detection function can be chosen to match the detection function required in that part of the detection fiber.
[0091] For example, as shown in figure 2, the detection fiber is implanted exactly at the perimeter with a path that is located parallel to the perimeter. Part of perimeter 204 is protected by a wall 202, however, another part of the perimeter is opened without a barrier to pass through the perimeter, or at least no barrier that would represent a significant impediment to crossing the perimeter. In the open section of the perimeter you may therefore want to detect movement of land vehicles and / or people in the vicinity of the perimeter.
[0092] In the perimeter section that is protected by wall 202, the detection of a land vehicle near the perimeter may be of interest, as it could indicate suspicious activity. However, it can be considered that no land vehicle can cross the perimeter at this point without demolishing the wall. If part of this section of the perimeter is located near a public road, say, the detection of land vehicles can cause several false positives to be generated.
[0093] Thus, in one embodiment of the present invention, the subset of longitudinal detection portions corresponding to the section of detection fiber implanted along the open perimeter section is designated as a zone. This is illustrated in figure 2 as section 206b.
[0094] The zone 206b signals are therefore analyzed to detect any vehicles approaching or crossing the detection fiber and also to detect anyone walking near or crossing the detection fiber.
[0095] This can be achieved by monitoring the acoustic signals of the relevant detection portions of the detection fiber for the acoustic signals that are characteristic of the movement of vehicles or personnel in the vicinity of the fiber. As experts in the art realize, acoustic signature analysis can be performed to detect acoustic signatures that are representative of land vehicles, or various types of land vehicles and also acoustic signatures that are representative of the movement of people on foot. The analysis of the acoustic signature can comprise analyzing the evolution of the signal of a longitudinal detection portion of the fiber against a known signature. In some embodiments, signals from more than one adjacent fiber detection portion can be analyzed together to detect a particular characteristic.
[0096] The signs of the longitudinal sections of fiber corresponding to the perimeter wall section on either side of the open part, i.e., subsets 206a and 206c comprise another zone. Therefore, it is realized that a zone of the fiber may comprise multiple non-continuous sections of the fiber and that a zone may, in effect, be a subzone of another zone. In practice, however, it may be easier to analyze the signals from section 206a as one zone and the signals from section 206c as another zone, but apply the same detection function to each of those zones.
[0097] The signals from sections 206a and 206c can therefore be analyzed to detect damage to wall 202, for example, acoustic signals characteristic of hammering, drilling or hammering the wall using acoustic signature analysis. In addition, signals could be monitored for particularly strong signals that could be indicative of a collision with the wall or an explosion in the wall.
[0098] The signals from the zone (s) corresponding to sections 206a and 206c of the detection fiber can therefore be analyzed to detect events of interest, that is, acoustic signals that match the predetermined characteristics of events to be detected, and the signals in section 206b can be analyzed to detect different events of interest.
[0099] However, you may also want to detect movement of people in the perimeter wall section to detect people who have climbed the wall. Thus, signals from section 206a and 206c can also be analyzed to detect acoustic signals characteristic of people movement using the same signature analysis for people detection used in section 206b.
[00100] The detection fiber can thus be divided into a plurality of different zones and only those events that are relevant to the particular fiber section can be detected.
[00101] As another example, figure 3 illustrates part of the path of a detection fiber 104 which is buried side by side in a buried pipe, such as an oil and gas pipe. The detection fiber can be used to monitor possible interference with the pipeline. Thus, the detection fiber can be monitored to detect the acoustic characteristics associated with excavation or tunneling near the pipeline. In addition, signals can be monitored to detect characteristics associated with the movement of people and / or vehicles near the pipeline as, in unpopulated areas, the movement of people or vehicles near the pipeline can be indicative of potential interference. However, a 302 road crosses the pipe for part of its length. Thus, vehicle movement is expected in the vicinity of the road and detecting the movement of vehicles in this part of the pipeline can generate numerous false alarms. In one embodiment of the present invention, therefore, a section of the detection fiber at a road location is designated as a separate zone 306a. In this zone 306a, the presence or movement of vehicles is not detected as an event of interest. The signals from the longitudinal fiber detection portions in this zone are not analyzed to detect vehicles. These signals are analyzed to detect any characteristic signs indicative of excavation or tunneling in the vicinity of the pipeline.
[00102] The signals from longitudinal detection portions of section 306a can also be analyzed using analysis of the acoustic signature that includes the acoustic signature of land vehicles in order to correctly classify any signal. In other words, if acoustic signals that are a good match to the acoustic signature of a moving vehicle are detected, the signals can be classified as such and ignored. In this way, all measurement signals can be identified where possible and the identification used to detect events of interest. By identifying the signals that are being generated by an event not of interest to that area, false detections can be avoided.
[00103] In operation therefore the radiation backscattered by the detection fiber can be processed to provide measurement signals from each portion of longitudinal fiber detection. Representative histogram 310 illustrates the type of data that can be collected and shows the average intensity of acoustic disturbance measured by each longitudinal detection portion for a short period of time. The X axis represents the distance along the fiber. The change in intensity over time can be automatically analyzed to detect events of interest as previously described.
[00104] If an event of interest is detected, an alarm or alert can be generated. For example, an audible and / or visible alert can be generated at one or more control stations. The visible alert can produce the nature of the events identified and the location of the event detected along the fiber. In one mode, an alert icon, which may be relevant to the detected event, is displayed at the correct location on a pipe / fiber map.
[00105] For example, consider that the standard detection function of all sections of the fiber is to detect excavation or tunnel opening near the pipe as a critical event and also to detect the presence of vehicles or people near the pipe. Fiber section 306a near the road has been arranged as a separate zone, however, where vehicle detection is disabled to prevent false alarms.
[00106] Suppose some excavation starts at location 308. This will cause acoustic vibrations to pass through the terrain, which will cause the sensing fiber to vibrate in the vicinity of the excavation. These vibrations will increase the intensity of the acoustic disturbances measured in that part of the fiber, as illustrated in histogram 310. The signals from this part of the fiber are analyzed using acoustic signature analysis and the signals are identified as a matched characteristic associated with mechanical excavation. At this point, the processor communicates with the control station and an alarm is generated. An audible alarm is issued to get the operator's attention and details of the nature of the alarm are displayed on the graphical display. This includes an identification of the type of event of interest, that is, the excavation, and the position detected. An automatic alert can also be sent to a patrol unit. The operator can verify that any field work is scheduled at that location and / or further send a patrol to investigate.
[00107] If the excavation becomes benign, that is, if the excavators have the appropriate permissions to excavate a safe distance from the pipeline and / or know the location of the pipeline, the work is allowed to continue. At this point, you may want to remove the alarm from that section of the pipeline to prevent unnecessary alarms potentially masking the presence of a new genuine alarm.
[00108] The operator can therefore select a portion of fiber 306b involving the detected event and designate it as another zone. Once zone 306b has been established, the operator can select the events of interest to be detected and can deselect excavation detection in that zone. The duration of a zone can be limited in time. For example, the zone may only last as long as the work is expected. In addition, the zone can be arranged to apply only during daylight hours, depending on the nature of the work being carried out. Thus, the zone can persist for hours of normal work. Once night comes, zone 306b is no longer a separate zone and the standard detection function is reapplied. At the beginning of the next day, however, zone 306b with the designated detection function will be automatically reapplied.
[00109] The zones can therefore be designated by an operator via a user interface. A user may be presented with a graphical indication of the detection portions of the fiber sensor and may be able to select any group or groups of detection portions to designate as a zone. The operator may then be able to select or deselect events of interest from a master list that applies to the selected group (s) of detection portions.
[00110] In another mode, however, a zone can be created by arranging the detection fiber in that zone.
[00111] Figure 4 illustrates a detection fiber 104 which is arranged in a first zone 406a with a first geometry and a second zone 406b with a second geometry. In the first zone, the fiber is arranged completely extended in a generally straight or slightly curved path, at least compared to the length scale of the longitudinal detection portions. Figure 4 represents the length 402a of fiber which corresponds to a single longitudinal fiber detection portion.
[00112] The length of the longitudinal detection portions is determined by the characteristics of the interrogation radiation and the processing, but in general, the shortest fiber length that can be resolved as an independent detection portion is related to the duration of the interrogation pulse. . Thus, a longer pulse results in a longer detection portion length and a shorter pulse results in a shorter detection portion length. The interrogation pulse duration also has an effect on the overall range of the system, that is, the length of continuous fiber that can be interrogated. As those skilled in the art realize, the range depends on how much light is transmitted in the fiber. For a Rayleigh backscatter distributed acoustic sensor, however, the interrogation pulse must be below the nonlinear threshold for the optical fiber. Thus, a limit is placed on the maximum instantaneous intensity that can be transmitted in the optical fiber. Thus, to reach a certain range, a certain pulse duration is required which effectively establishes the minimum spatial length of fiber that can be resolved separately. As an example, a fiber optic length of 40 km can be monitored with a spatial length of the detection portions of 10 m.
[00113] The modality shown in figure 4 varies the effective spatial resolution of the sensor in the two zones by varying the fiber geometry. As mentioned here, in the first zone, the fiber is arranged completely extended. Thus, the effective spatial resolution of the sensor is the same as the spatial resolution of the longitudinal detection portions. In the second zone, however, the optical fiber has an axis that extends in general, but it has a tortuous path with respect to that axis, in such a way that each 1 m along the axis comprises significantly more than 1 m in the length of optical fiber. Figure 4 illustrates the length 402b along the axis corresponding to the fiber section equal to the length of a longitudinal detection portion. Therefore, it is clear that each individual fiber detection portion in the second zone receives acoustic signals of a much shorter ambient length than those in the first zone. The effective spatial resolution of the sensor is therefore reduced, that is, the sensor as a whole can be seen with detection portions that extend along the sensor axis and that are smaller in length than the discrete detection portions of the fiber.
[00114] Tortuosity could be achieved when the detection fiber is installed. As skilled in the art, the optical sensing fiber, comprising a core and sheath, may comprise an optical fiber cable with a protective jacket. The cable may comprise one or more optical fibers. The cable itself can be arranged in a desired tortuous path around a general axis when implanted. Depending on the maximum degree of curvature that is acceptable for the particular fiber or cable, several different degrees of tortuosity could be used. For example, a tortuosity with a transverse amplitude of about 50 cm and a step of about 10 cm would mean that 10 m of optical fiber would extend about 1 m along the sensor path.
[00115] Other arrangements are possible, however. For example, the optical fiber in at least one zone can have a spiral or helical geometry. Figure 5 shows a first section 502a in which the fiber is fully extended and a second section 502b where the fiber is coiled in a helical structure around the axis of the sensor. The spiraling of the fiber can allow a relatively long fiber length to be arranged in a small spatial length without a large transverse extent. For example, compared to the tortuous path, a propeller with a diameter slightly above 30 cm and a 10 cm pitch could compress 10 m of fiber into 1 m of sensor length. Even more compact turns can allow a loop to be part of the cable itself. For example, a fiber could be coiled with a diameter of 5 cm and a pitch of 1.5 cm in a cable. In this case, 10 m of optical fiber would be arranged with 1 m of cable. The cable could be easily deployed along the desired sensor path like any other type of cable and no special arrangement would be required when installing the cable.
[00116] Clearly, however, the arrangement of the optical fiber for use as a detection fiber in a distributed acoustic sensor should not restrict the fiber's ability to react to acoustic waves and vibrations. Experienced in the technique, they will easily understand how the cable could be implanted and / or they could easily test the fiber response in possible geometries.
[00117] The arrangement of the optical fiber can also be such as to provide additional sensor functionality, such as the ability to determine the direction of incidence of an acoustic wave arriving in one or more dimensions.
[00118] Figures 6a and 6b show an example where the optical fiber is arranged so as to have two parallel detection portions separated along the horizontal direction in order to allow the determination of the direction of incidence of an acoustic wave. Figure 6a shows a plan view of the cable arrangement and Figure 6b shows a sectional view along line A-A. The cable has a Z-shaped arrangement with a first straight section 602a that extends to at least the length of a longitudinal detection portion in a first direction parallel to a second straight section 602c which is also at least the length of a longitudinal detection portion. These two parallel sections are spaced a short distance apart and totally or partially overlap the first direction. Connecting the two sections is an angled 602c section.
[00119] Using the acoustic signals received in section 602a and the acoustic signals received in section 602b, the direction of incidence of the acoustic signals (perpendicular to sections 602a and 602b) can be determined by identifying a response attributed to the same acoustic impulse in both the fiber sections and looking at the relative arrival times of the signal on that part of the fiber. Fiber section 206c can be used as a detection portion, or returns from this fiber section can be ignored.
[00120] Other geometries could be used to allow the direction of incidence to be determined. A geometry with three parallel detection portions spaced in two dimensions would allow the point of origin on a plane perpendicular to the detection portions to be determined.
[00121] Referring back to figure 3, modalities of the present invention also allow detection with different purposes. As previously described, a detection fiber implanted along the length of the pipe can be used to detect potential interference with the pipe. At the same time, however, the fiber can also be used to monitor the condition of the pipe itself. The copending patent application PCT / GB2009 / 002058, whose contents are hereby incorporated by reference, describes how a distributed acoustic fiber can be used to monitor the condition of the conduit, such as a pipe, acoustically exciting the pipe and recording the response of each fiber detection portion. This response can be compared to a previous baseline response to detect any significant changes. Significant changes along the length of the pipe could be indicative of pipe decay or the accumulation of deposits in the flow line. The tubing can be excited by a device that generates acoustic waves and / or an opportunity signal, such as caused by the passage of a scraper through the tubing, could be used. Alternatively, the response of the detection fiber sections along the length of the pipe could be monitored based on ambient acoustic noise and compared with previously acquired reference signals to detect any significant changes.
[00122] In some modalities, condition monitoring may only be appropriate over part of the length of the detection fiber and thus the sensor can be divided into a zone where condition monitoring is performed and another zone where condition monitoring is not relevant.
[00123] When events of interest for the relevant zone are detected, an alarm or alert can be generated. There can be different types of alerts for different types or severity of detected events and alerts can be graded in terms of severity. For example, consider a pipe monitoring application in which the sensor is adapted to provide condition monitoring and also interference detection. Detection of an acoustic signature corresponding to people walking near the pipe may be of interest, but not as significant in itself. Thus, personnel detection can generate a low level alert, for example, an alert icon may appear in a graphical indication of the relevant pipe section. This type of alert can be color-coded and can, for example, be green to indicate detection only. Detection of a signal that is indicative of a vehicle in a section where a vehicle is not expected can be more severe, however, as this may be more indicative of potential interference. Thus, a detection like this can lead to a higher alert state, for example, an amber alert possibly accompanied by an audible alert. The detection of a signature corresponding to the excavation can generate a high alert state, although, in this case, the alert state may depend on the duration and intensity (or, if appropriate, detected range) of the event. If the signal lasts only a very short time or is of low intensity, it may not be a concern and can only be signaled as a detection. However, a prolonged strong signal can generate a full alert that may involve sounding an audible alert and generating an automatic message to a response unit.
[00124] The geometry of the fiber can also be such that different areas of the fiber can be connected. For example, Figure 7 illustrates a single fiber 104 implanted to provide different layers of perimeter monitoring. Fiber 104 is implanted with three loops. For example, an external loop can be arranged outside the perimeter fence, for example, to provide detection of personnel or vehicles. An intermediate loop can be provided adjacent to the perimeter fence or the like to detect damage to the fence and an inner loop can be provided within the perimeter fence to detect movement within the perimeter. Thus, each fiber loop can be designated as a separate zone with slightly different detection functions. In any case, however, one may wish to detect movement of people. In this case, the fact that different sections of the fiber are arranged nearby, the same section of the perimeter can be used to provide greater functionality. For example, the fiber detection portions of the outer loop that form the group 701 can be linked to the fiber detection portions 702 of the intermediate loop that correspond to the same perimeter section and similarly to those 703 portions of the inner loop that correspond to the same section perimeter. If the same type of acoustic event is detected in the zones connected in sequence, these individual detections can be categorized as belonging to a single event. For example, a person approaching along path 704 will be successively detected by zones 701, 702 and then 703. By comparing the detected signals from those zones, individual detections from the three linked zones can be identified as belonging to the same event. This may allow, for example, the speed and direction of movement to be tracked, but it also clarifies that a source of disturbance within the perimeter detected by zone 703 originally started outside the perimeter and has been deviated somewhat from the perimeter fence.
[00125] It should be understood that the present invention has been described here merely as an example, and modification of details can be made within the scope of the invention. For example, a single processor or other unit may fulfill the functions of several units or subunits mentioned in the claims.
[00126] It is also noted that each feature revealed in the description and, where appropriate, in the claims and drawings can be provided independently or in any appropriate combination.

权利要求:
Claims (37)
[0001]
1. Distributed detection method comprising the steps of: interrogating an optical fiber (104) with electromagnetic radiation; detect electromagnetic radiation that is backscattered by optical fiber; processing the detected back-scattered radiation to provide a measurement signal for each of a plurality of longitudinal detection portions (208) of the optical fiber; analyze the measurement signals from the longitudinal detection portions to detect events of interest, and analyze the measurement signals from a first subset of longitudinal detection portions to provide a first zone (206a, 306a) with a first detection function and analyze measuring signals from at least a second subset of longitudinal detection portions to provide at least a second zone (206b, 306b) with a different second detection function; characterized by the fact that it also comprises analyzing the measurement signals from the first zone to detect a first feature or signature and analyzing the measurement signals from the second zone to detect a second feature or signature.
[0002]
2. Method, according to claim 1, characterized by the fact that the different detection functions include detection of different events.
[0003]
3. Method according to claim 1 or 2, characterized by the fact that the measurement signals from the first zone are analyzed to detect a first event of interest and the signals from the second zone are analyzed to detect a second event of interest different.
[0004]
Method according to any one of claims 1 to 3, characterized in that at least one of the first zone or second zone comprises two or more groups of longitudinal detection portions, wherein the detection portions in each group are contiguous, but the groups are not contiguous.
[0005]
Method according to any one of claims 1 to 4, characterized by the fact that it comprises identifying more than two zones, each zone related to a different subset of longitudinal detection portions.
[0006]
6. Method according to any one of claims 1 to 5, characterized by the fact that providing different detection functions in the first zone and in the second zone comprises detecting a first set of events of interest in the first zone and detecting a second set of events. events of interest in the second zone, with the first set of events being different from the second set of events.
[0007]
7. Method, according to claim 6, characterized by the fact that the first and second sets comprise mutually exclusive events of interest.
[0008]
8. Method according to claim 6, characterized by the fact that the first and second sets of events comprise one or more events of common interest.
[0009]
Method according to any one of claims 1 to 6, characterized in that the different detection function is provided in the first and second zones by detecting at least one event of interest in one of the zones that is not detected in the another zone.
[0010]
10. Method according to any one of claims 1 to 5, characterized in that the analysis of measurement signals from the second zone is arranged to not detect at least one event of interest that is detected in the analysis of the measurement signals from the first zone.
[0011]
Method according to any one of claims 1 to 10, characterized in that it comprises the step of selecting a subset of longitudinal detection portions of the fiber to form at least one of the zones.
[0012]
12. Method according to claim 11, characterized in that the step of selecting a subset of longitudinal detection portions comprises selecting a fiber portion in a graphical display showing a representation of the fiber.
[0013]
13. Method according to any one of claims 1 to 12, characterized in that it comprises the step of allocating a detection function to at least one zone by selecting the events of interest that must be detected in that zone.
[0014]
14. Method according to any one of claims 1 to 13, characterized in that the step of analyzing the measurement signals comprises classifying and / or categorizing the measurement signals according to the characteristics of events that are not of interest .
[0015]
15. Method according to any one of claims 1 to 14, characterized by the fact that the different detection functions include analyzing the signals coming from the zones for intruder detection or interference detection.
[0016]
16. Method according to any one of claims 1 to 15, characterized by the fact that the detection function of at least one zone comprises condition monitoring.
[0017]
17. Method, according to claim 16, characterized by the fact that condition monitoring comprises comparing the measurement signals from one or more longitudinal detection portions with a previously acquired measurement signal to detect any significant change indicative of decay of piping or deposit build-up in a runoff line.
[0018]
18. Method according to any one of claims 1 to 17, characterized in that the first subset of longitudinal detection portions corresponds to the optical fiber portions with a first physical arrangement and the second subset of longitudinal detection portions corresponds to portions of the optical fiber with a different second physical arrangement.
[0019]
19. Method according to claim 18, characterized in that the first physical arrangement comprises a first fiber geometry and the second physical arrangement comprises a second fiber geometry.
[0020]
20. Method, according to claim 19, characterized by the fact that the first geometry provides a first effective spatial resolution in the first zone and a second geometry provides a different effective second spatial resolution in the second zone.
[0021]
21. Method according to claim 19 or 20, characterized in that one of the first or second geometry comprises an arrangement, generally straight or slightly curved and another of the first or second geometry comprises a spiral or folded arrangement.
[0022]
22. Method according to any one of claims 1 to 21, characterized in that the different detection functions in the first and second zones comprise detecting with a different effective spatial resolution in the first and second zones.
[0023]
23. Method according to any one of claims 1 to 22, characterized in that it comprises a method of distributed acoustic detection.
[0024]
24. Method according to claim 23, characterized by the fact that the measured signals comprising acoustic information are analyzed in each zone.
[0025]
25. Distributed optical fiber sensor apparatus comprising: an optical fiber (104); an electromagnetic radiation source (112, 114) configured to deliver electromagnetic radiation to the fiber; a detector (116) for detecting electromagnetic radiation backscattered by said fiber; and a processor (108) configured to: analyze backscattered radiation to determine a measurement signal for a plurality of discrete longitudinal detection portions of the optical fiber; wherein the distributed optical fiber sensor comprises a first zone with a first detection function, the first zone corresponding to a first subset of the longitudinal detection portions and at least a second zone with a different second detection function, the second zone corresponding to to a second subset different from the longitudinal detection portions characterized by the fact that the processor is configured to analyze the measurement signals from the first zone to detect a first feature or signature and to analyze the measurement signals from the second zone to detect a second feature or signature.
[0026]
26. Distributed optical fiber sensor apparatus according to claim 25, characterized by the fact that the processor is configured to analyze the measurement signals of the first subset of longitudinal detection portions to provide the first zone with a first detection function and analyzing the measurement signals from at least the second subset of longitudinal detection portions to provide at least the second zone with a different second detection function.
[0027]
27. Fiber optic sensor apparatus distributed according to claim 25 or 26, characterized by the fact that the processor is configured to classify the measurement signals based on whether they match one or more predetermined characteristics.
[0028]
28. Distributed optical fiber sensor apparatus according to claim 27, characterized by the fact that the predetermined characteristics comprise the characteristics of events of interest.
[0029]
29. The distributed optical fiber sensor apparatus according to claim 28, characterized by the fact that the predetermined characteristics additionally comprise the characteristics of other events, which are not events of interest.
[0030]
30. Distributed optical fiber sensor apparatus according to any one of claims 25 to 29, characterized by the fact that it additionally comprises a graphic display, in which the processor is configured to generate a graphic alert in the display when an event of interest is detected .
[0031]
31. Fiber optic sensor apparatus distributed, according to claim 30, characterized by the fact that the graphic alert comprises an alert that is displayed in a representation of the optical fiber path in the relevant part of the path.
[0032]
32. Fiber optic sensor apparatus distributed according to any one of claims 25 to 31, characterized by the fact that the device is adapted in such a way that a user can establish one or more zones for the sensor device in use.
[0033]
33. Distributed optical fiber sensor apparatus according to claim 32, characterized by the fact that the apparatus is adapted in such a way that a user can select a subset of longitudinal portions of the fiber, selecting a portion of the representation of the optical fiber path or a representation of the fiber optic measurement channels that are displayed in a graphical display.
[0034]
34. Fiber optic sensor apparatus distributed according to any one of claims 25 to 33, characterized by the fact that the device is adapted in such a way that a user can select the events to be detected in a chosen zone.
[0035]
35. Distributed optical fiber sensor apparatus according to any one of claims 25 to 34, characterized by the fact that the optical fiber comprises a first physical arrangement in the first zone and a second physical arrangement, which is different from the first physical arrangement, in the second zone.
[0036]
36. Distributed optical fiber sensor apparatus according to claim 35, characterized by the fact that the different physical arrangement in the first and second zones comprises a different fiber geometry in each zone.
[0037]
37. Distributed optical fiber sensor apparatus according to claim 36, characterized by the fact that the optical fiber has a first geometry in the first zone that provides a first effective spatial resolution and a second geometry in the second zone that provides a second spatial resolution different effective.

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公开号 | 公开日

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EA028306B1|2017-11-30|

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ES2675897T3|2018-07-13|

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EP2499465A2|2012-09-19|

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CN102292622A|2011-12-21|

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EP2499465B1|2018-04-04|

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CA2780673C|2017-10-17|

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CN102292622B|2015-05-27|

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CA2780673A1|2011-05-19|

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AU2010317790A1|2012-07-05|

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MY170488A|2019-08-07|

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US20120230629A1|2012-09-13|

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US9739645B2|2017-08-22|

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AU2010317790B2|2015-03-19|

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AU2010317790A2|2012-12-06|

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BR112012011223A2|2018-04-03|

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EA201290304A1|2012-12-28|

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TR201807987T4|2018-06-21|

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GB0919899D0|2009-12-30|

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PL2499465T3|2018-09-28|

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WO2011058312A2|2011-05-19|

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WO2011058312A3|2011-07-28|

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法律状态:
2019-01-08| B06F| Objections, documents and/or translations needed after an examination request according [chapter 6.6 patent gazette]|

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2019-07-16| B06T| Formal requirements before examination [chapter 6.20 patent gazette]|

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2020-03-31| B06A| Patent application procedure suspended [chapter 6.1 patent gazette]|

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2020-10-27| B09A| Decision: intention to grant [chapter 9.1 patent gazette]|

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2020-12-29| B16A| Patent or certificate of addition of invention granted [chapter 16.1 patent gazette]|Free format text: PRAZO DE VALIDADE: 10 (DEZ) ANOS CONTADOS A PARTIR DE 29/12/2020, OBSERVADAS AS CONDICOES LEGAIS. |

优先权:

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申请号 | 申请日 | 专利标题

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