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WO2008027959A2 - Détection et localisation d'une intrusion dans un périmètre à l'aide de variables composites issues de mesures de phase - Google Patents

Détection et localisation d'une intrusion dans un périmètre à l'aide de variables composites issues de mesures de phase Download PDF

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Publication number
WO2008027959A2
WO2008027959A2 PCT/US2007/077101 US2007077101W WO2008027959A2 WO 2008027959 A2 WO2008027959 A2 WO 2008027959A2 US 2007077101 W US2007077101 W US 2007077101W WO 2008027959 A2 WO2008027959 A2 WO 2008027959A2
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Prior art keywords
interferometers
interferometer
disturbance
signal
signals
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WO2008027959A3 (fr
Inventor
Jayantilal S. Patel
Zhizhong Zhuang
Yuri Zadorozhny
Francesco A. Annetta
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Optellios Inc
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Optellios Inc
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Publication of WO2008027959A3 publication Critical patent/WO2008027959A3/fr
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    • G—PHYSICS
    • G08—SIGNALLING
    • G08B—SIGNALLING OR CALLING SYSTEMS; ORDER TELEGRAPHS; ALARM SYSTEMS
    • G08B13/00—Burglar, theft or intruder alarms
    • G08B13/02—Mechanical actuation
    • G08B13/12—Mechanical actuation by the breaking or disturbance of stretched cords or wires
    • G08B13/122—Mechanical actuation by the breaking or disturbance of stretched cords or wires for a perimeter fence
    • G08B13/124—Mechanical actuation by the breaking or disturbance of stretched cords or wires for a perimeter fence with the breaking or disturbance being optically detected, e.g. optical fibers in the perimeter fence
    • G—PHYSICS
    • G08—SIGNALLING
    • G08B—SIGNALLING OR CALLING SYSTEMS; ORDER TELEGRAPHS; ALARM SYSTEMS
    • G08B13/00—Burglar, theft or intruder alarms
    • G08B13/18—Actuation by interference with heat, light, or radiation of shorter wavelength; Actuation by intruding sources of heat, light, or radiation of shorter wavelength
    • G08B13/181—Actuation by interference with heat, light, or radiation of shorter wavelength; Actuation by intruding sources of heat, light, or radiation of shorter wavelength using active radiation detection systems
    • G08B13/183—Actuation by interference with heat, light, or radiation of shorter wavelength; Actuation by intruding sources of heat, light, or radiation of shorter wavelength using active radiation detection systems by interruption of a radiation beam or barrier
    • G08B13/186—Actuation by interference with heat, light, or radiation of shorter wavelength; Actuation by intruding sources of heat, light, or radiation of shorter wavelength using active radiation detection systems by interruption of a radiation beam or barrier using light guides, e.g. optical fibres
    • G—PHYSICS
    • G08—SIGNALLING
    • G08B—SIGNALLING OR CALLING SYSTEMS; ORDER TELEGRAPHS; ALARM SYSTEMS
    • G08B13/00—Burglar, theft or intruder alarms
    • G08B13/22—Electrical actuation
    • G08B13/24—Electrical actuation by interference with electromagnetic field distribution
    • G08B13/2491—Intrusion detection systems, i.e. where the body of an intruder causes the interference with the electromagnetic field
    • G08B13/2497—Intrusion detection systems, i.e. where the body of an intruder causes the interference with the electromagnetic field using transmission lines, e.g. cable

Definitions

  • the invention relates to sensing the effects of a physical disturbance along a signal path, especially human activity at a fence, buried sensing line or other extended sensing path.
  • a disturbance produces vibration, impact, acoustic noises, stress and/or pressure variations and the like, locally changing one or more signal paths in a manner that produces a time change in the phase relationships between carrier signals propagating along the signal paths, e.g., one or more optical fibers.
  • These phase effects originate at the point of the disturbance and are carried onward as the carrier signals propagate.
  • Advantageous detection of these phase effects in the present invention allows the location of the disturbance to be discerned.
  • at least two interferometers are configured and comprise, in part, the one or more signal paths affected by the disturbance.
  • the interferometers produce at least two phase variables in which the phase effects of the disturbance are manifested.
  • the at least two interferometers can comprise the same and/or different interferometer configurations, including, but not limited to Mach- Zehnder, Sagnac, and/or Michelson interferometer configurations.
  • the produced phase variables are not directly useful, but they are combined by relationships disclosed herein to produce new composite variables.
  • the relationship between the composite variables enables the location of the disturbance to be discerned.
  • this relationship is the time lag between the variations over time of two composite variables that have identical waveshapes over time.
  • the time lag identifies the location of the disturbance in view of the specific layout of the interferometers used.
  • the ratio of the composite variables identifies the location.
  • Intrusion detection advantageously involves detection of the location of a disturbance that impinges on a boundary such as the perimeter of a protected area, e.g., a person climbing a fence into or out of a secured premises. Aside from sensing a breach of security, it may be desirable to detect activity near a given sensing boundary, or crossing a boundary, or proceeding along a path or other sensing line. Such activities are generally exemplified herein with reference to intrusion detection. Detecting the location of the disturbance refers to determining a point along an elongated line or boundary near or at which activity occurs. The line or boundary is elongated but it might or might not be a straight line.
  • one or more signals are inserted via couplers or junctions that split and/or combine the signals to produce signal components that are carried in fiber optic waveguides placed to define a detection zone.
  • the fiber optic waveguides might be kilometers long and might be placed along any path, e.g., a straight line or a closed path around an area, or defining a complex array like a raster, or perhaps a three dimensional route through a volume or traversing successive tiers or layers.
  • solid and dashed lines distinguish the signals that are inserted at either end of a bidirectional path and propagate in opposite directions.
  • An object is to discern the location of a disturbance from the effects of the disturbance on the signal components.
  • the physical disturbance occurs in the detection zone at some distance Li from the input end of the first interferometer and a distance L 2 from that of the second interferometer.
  • the total distance Li + L 2 is a constant, namely the total length.
  • the physical disturbance e.g., a vibration, a noise, an impact or other physical stress on the fiber optic cable
  • the disturbance modulates the phase of the signal(s) carried in the waveguides.
  • the modulation that is important is a substantially localized time-varying phase shift, typically at a frequency in the range of audible acoustic signals or perhaps including low frequency or higher frequency inaudible signals.
  • the amplitude of the phase modulation typically exceeds the period of the carrier optical signal.
  • the measured phase differences ⁇ i(t) and ⁇ 2 (t) are substantially identical waveforms (because they were induced by the same local disturbance on counter- propagating signals in the same signal paths) except for the substantially constant offset cpoi-cpo2 and a time lag t 2 -ti due to the difference in propagation distances from the disturbance, between the two signal directions.
  • each opposite direction forms an interferometer.
  • the two oppositely oriented signal interferometers in Fig. 1 are each structured as Mach- Zehnder interferometers. In this dual Mach-Zehnder configuration, in each counter propagating direction, a source signal is split by a coupler at one end into components that propagate along two signal legs and interfere with one another at a coupler at the opposite end.
  • the interference signals from the two opposite interferometers do not generally produce intensity waveforms that have the same shape over time.
  • the Mach-Zehnder interferometer structure shown in Fig. 1, and also other interferometer structures are known in the art and have been proposed as sensing means, including in fiber-optic-based embodiments, and including in the context of intrusion detection and location. Detectors have been proposed wherein the interferometers are of the same type and also wherein different interferometer types are used. Furthermore, applications of certain coextensive paired or oppositely- oriented overlaid interferometer structures have been proposed for intrusion detection and location, for example, as in Udd, US Patent 5,694,114.
  • a technique for inferring the location of a disturbance based on the intensity of interference signals is disclosed in Udd, US Patent 5,694,114, including employing oppositely oriented and overlaid Sagnac interferometers.
  • intensity-based techniques such as that of Udd are limited in effectiveness and practicality.
  • the technique can only respond to small disturbances. If a disturbance produces phase modulation that is large in amplitude compared to the period of the carrier signal, the proposed intensity-based techniques fail. In practical situations, there is no routine way to limit the magnitude of the disturbance.
  • the position of a localized disturbance is determined based on signal phase measurements made from a combination of plural sensors, each capable of producing a phase response when disturbed. It is also an object of the present invention to further obtain composite signal from the phase responses of various structures, such that the location of the disturbance can be derived from a relationship between the composite signals.
  • the phase responses that are produced are measured and processed to obtain plural composite signals of a substantially identical shape over time, differing by a time shift that is uniquely determined by the position of the disturbance with respect to ends of a structure in which the carrier signals are propagated.
  • phase responses are processed to produce composite signals, including at least one composite signal, the magnitude of which depends on a position of the disturbance. This signal is transformed to remove other dependences, and a signal parameter is derived from which the location of the disturbance can be determined.
  • Fig. 1 is a diagram showing a dual Mach-Zehnder interferometer structure as a non-limiting example of a plural interferometer location sensing structure.
  • FIG. 2 is a block diagram of an exemplary hybrid interferometer structure with its two interferometers sharing portions of waveguides traversing a detection zone, and including blocks showing the signal source, interferometer ends, and phase receivers for each interferometer, coupled to a processor.
  • Fig. 3 is a diagram showing an exemplary hybrid interferometer structure comprising plural distinct interferometers, in this example, a Mach-Zehnder interferometer and a Sagnac interferometer.
  • Fig. 4 is a diagram showing the structure of Fig. 3 with outputs of an interferometer combiner returning to the origination point for detection.
  • Fig. 5 is a diagram showing an exemplary hybrid interferometer structure comprising a Mach-Zehnder interferometer and a Michelson interferometer.
  • FIG. 6 is a diagram showing an exemplary hybrid structure comprising a
  • Fig. 7 is a diagram showing another example, with two Sagnac interferometers.
  • Fig. 8 is a diagram of another example, comprising two Michelson interferometers.
  • FIG. 9 is an illustration of an exemplary implementation of the structure of
  • FIG. 10 is an illustration of an exemplary implementation of the structure of
  • Fig. 11 is a time plot of the detected phase responses of the two interferometers of the structure in Fig. 6 during a disturbance, it being noted that the signals have do not have corresponding waveshapes over time.
  • Fig. 12 is a time plot showing two processed composite signals derived from the detected signals shown in Fig. 11, it being noted that these composite signals have corresponding waveshapes over time.
  • Fig. 13 is a time plot of a portion of the plot in Fig. 12 with an expanded time scale, this plot showing a time lag between the two substantially identical composite phase signals, said time lag representing the location of a disturbance that produced the variations shown.
  • Fig. 14 is a time plot of the detected phase responses of the two interferometers of the structure in Fig. 3 during a disturbance, which phase responses appear to be uncorrelated.
  • Fig. 15 is a time plot of processed versions of the signals shown in Fig. 14.
  • the ratio of the signal magnitudes yields the location of the disturbance.
  • Fig. 16 is an X-Y plot showing the mutual dependence of the average signal powers for a sequence of disturbances of different strength at the same location, plotted as points.
  • a disturbance such as vibration is detected and located along a fiber optic waveguide.
  • Multiple optical fibers or optical fibers carrying multiple signals are configured as two or more interferometers.
  • the interferometers can be of the same or different interferometer types, according to respective embodiments.
  • Signals split from a source are recombined after the signals propagate through the point of the disturbance, where phase variations are induced.
  • Phase responsive receivers at the combiners each produce mutually independent detector signals representing phase relationships between the combined signals. Variations over time in the phase relationships are processed to produce composite signals.
  • the equations embodied by processing differ based on the specific interferometer configuration used.
  • At least one signal source provides carrier signals.
  • Two interferometers, each interferometer comprising two waveguides and defining two signal paths are coupled at respective input ends, e.g., through a signal splitter, to the signal source.
  • An output end of each interferometer comprises at least one signal combiner configured to combine signals traveling along the signal paths for a respective said interferometer.
  • the signals traveling along the parts of the signal paths that overlap define a detection zone and traverse the detection zone at least once.
  • the disturbance instills a time change in a phase relationship between the signals traveling along the signal paths, at a point where the disturbance occurs, for both of the interferometers. This effect propagates along at the propagation speed of the carrier signals.
  • At least one phase responsive receiver is coupled to the output ends of each respective said interferometer.
  • the phase responsive receiver has at least one detection device coupled to the signal combiner.
  • the detection devices generate two mutually independent detector signals. Each pair of independent detector signals represents a phase relationship of the signals that travel along the signal paths of the respective interferometer.
  • a processor is coupled to derive composite signals from the phase relationships.
  • a relationship between the composite signals for each of said two interferometers varies with a location of the point of disturbance, such that a value of the relationship corresponds to said point in the detection zone at which the disturbance occurred.
  • the specific relationship varies and the operations embodied by the equations producing the composite signal likewise are different.
  • the invention produces a measure of the location of the disturbance according to one or more techniques based on measurements of phase relationships wherein the amplitude of phase displacement is not bounded by the period of the carrier.
  • FIG. 1 The structure in Fig. 1, comprising two Mach-Zehnder-type interferometers, is described, for example, in previous patent application SN 11/570,481, filed December 12, 2006, the entire disclosure of which has been incorporated herein together with that of US Patent 7,139,476.
  • Each interferometer comprises two waveguides defining two signal paths.
  • a disturbance along signal path generates substantially identical but time-shifted phase changes for each of the two interferometers, with which the disturbance can be detected and located.
  • the sensitive signal paths thus define a detection zone, in which the disturbance can be detected and located.
  • Various sensing structures comprising two interferometers may not produce such substantially identical phase responses.
  • the need for time-shifted identical phase responses can be supplanted by introducing a concept of composite signals.
  • the composite signals are signals derived from the measured phase responses, from which the location of a disturbance can be obtained.
  • the conversion from measured phase responses to the composite signals is structure-specific.
  • several non-limiting embodiments are discussed to teach this concept and to demonstrate the location resolving techniques.
  • the Sagnac interferometer and the Michelson interferometer. More complex structures are generally reducible to one, or a combination, of these basic types.
  • the following non- exhaustive list of structures involving different combinations of these basic interferometers is provided to illustrate the operation of the present invention by way of non- limiting examples.
  • one of the interferometers may be configured to function as a Mach-Zehnder interferometer with its two signal paths represented by two waveguides forming interferometer arms.
  • Another interferometer (832) may be configured as a Sagnac interferometer, wherein two waveguides in this case are coupled together at the far end of the structure, or otherwise are formed into a Sagnac loop, in which the two signal paths are the clockwise and the counterclockwise signal propagation directions.
  • the two interferometers may share parts of the signal paths, including parts traversing the detection zone.
  • Each interferometer further comprises a phase- responsive receiver that can be used to obtain the phase response for the respective interferometer.
  • the phase responsive receiver for each of the interferometers may be in a form comprising a 3x3 coupler.
  • the signal splitter for one of the interferometers may also function as the signal splitter as well as combiner for the other interferometer. This configuration is illustrated schematically in Fig. 3.
  • Other non- limiting examples of signal combiners used to implement phase-responsive receivers in the context of intrusion detection and location have been disclosed in US Pat. 7,139,476 and PCT/US05/11045. [0045]
  • the phase responses of the two interferometers for this structure are
  • ⁇ 2 (t) cp(t-ti) - cp(t-t 2 -t 0 )
  • ⁇ (t) is the disturbance-induced relative phase accumulated by the two signals in the two arms of the Mach-Zehnder interferometer, passing through the point of disturbance at time t.
  • the disturbance may affect one of the two shared waveguides forming the two interferometers, or it may affect both of them, generally to a different extent.
  • both waveguides traverse the detection zone, they are arranged co- extensively, so that each point of the detection zone is at substantially the same distance from the ends of the structure whether measured along one or the other waveguide.
  • the signal propagation time from the input ends of the two interferometers to the point of disturbance is t ⁇ .
  • the signal propagation time from the point of disturbance to the output end of the interferometer (831) as well as the midpoint of the Sagnac loop of interferometer (832) is t 2 .
  • the substantially constant background phase offsets are not essential for the present discussion and are therefore omitted for the sake of brevity from here on.
  • interferometer phase response ⁇ (t) is defined up to a constant. The same definitions are used throughout the remainder of the disclosure, adjusted for the structures involved in context.
  • the measured phase responses ⁇ i(t) and ⁇ 2 (t) generally are different and do not have the same shape, nor can one define a time lag between them.
  • the interferometer phase responses can be purposefully combined to produce composite response signals ⁇ 'i(t) and ⁇ ' 2 (t).
  • the composite signals are, indeed, identical, except for the time lag of t 2 -t ls the measurement of which time lag allows the location of the disturbance to be determined.
  • the retarded signal may therefore be simply obtained from the history of the detected phase response ⁇ i(t).
  • the same retardation effect can be achieved by returning the signals derived by the beam combiner of interferometer (841) back to the originating point of interferometer (841), thus adding a trip time of t 0 , before the signals are detected. This is shown schematically in Fig. 4.
  • the same retarded signal ⁇ i(t-t 0 ) can be used for ⁇ 'i(t).
  • phase responses of the two interferometers are either substantially identical in shape, or not substantially identical in the context of the previous discussion, but nonetheless are similar in shape. This property makes it possible to reconstruct the phase response of one of the interferometers based on a single optical intensity signal together with the measured phase response of the second interferometer.
  • phase response does not exceed ⁇ radians.
  • phase response may easily exceed this limit.
  • the phase response exceeds ⁇ radians by orders of magnitude.
  • phase detection becomes essential.
  • the composite signal technique disclosed herein applies to phase variables and generally is not applicable to intensity signals.
  • interferometer (851) is configured as a Mach-Zehnder and (852) as a Michelson interferometer (Fig. 5).
  • FIG. 6 shows another non- limiting embodiment of the present invention.
  • This structure combines a Sagnac-type (loop) interferometer (861) with a Michelson- type (fork) interferometer (862). Because in this structure the returning signals co- propagate along the same physical paths, a means must be provided to separate the signal paths of the different interferometers, before the signal paths can be combined pair- wise for relative phase measurement (as in the illustrated structure) or, alternatively, after they are combined but before the resulting signals are sampled for phase measurement.
  • One embodiment is based on wavelength-division multiplexing (WDM), wherein the signals in the two interferometers are of different wavelength (typically originating from two distinct sources). WDM couplers can then be used to first combine and then separate, then combine and separate again, the signals of different wavelength whose signal paths partially overlap.
  • WDM wavelength-division multiplexing
  • phase variables are inversely proportional to the signal wavelength and may also be affected by dispersion.
  • the latter effect can be made negligible by using low-dispersion signal propagation media and/or closely spaced wavelengths, or can be accounted for based on the prior knowledge of the dispersion relation. Typically, the dispersion is small enough to be safely ignored.
  • the inverse wavelength proportionality effect can be corrected by converting phase variables of signals at different wavelengths to effective phase variables corresponding to a common reference wavelength, e.g., ⁇ o, by means of multiplication factors ⁇ / ⁇ o, where ⁇ is actual signal wavelength. In the subsequent disclosure it is assumed that such conversion has been performed everywhere different signal wavelengths are used in the same embodiment.
  • Other means of separating the signal paths may involve time-domain multiplexing and/or strategic placing of isolators and/or circulators within the structure.
  • more than two interferometers can share the same at least one waveguide using counter-propagation and another means of signal multiplexing such as WDM.
  • ⁇ i(t) cp(t-ti) - cp(t-t 2 -t 0 )
  • the composite signals each yield exactly the relative phase induced by the disturbance (up to a constant) sampled with a time offset.
  • This fact is particularly remarkable for the present configuration since neither Sagnac nor Michelson (unlike Mack-Zehnder) interferometers can be used individually to measure this phase.
  • the final two example structures pair up Sagnac-type interferometers (Fig. 7) and Michelson-type interferometers (Fig. 8), respectively. Both cases require means or techniques for separating the signal paths that belong to the different interferometers.
  • WDM including dual signal sources and wavelength-selective couplers, and wavelength-corrected phase signals, or other ways to maintain separately considered signal paths, can again be used for this purpose.
  • interferometers of the same type must be oppositely oriented with respect to the detection zone, e.g., have input ends on the opposite ends of the overlapping portions of waveguides. Such oppositely superimposed interferometers are illustrated in Figs. 1, 7, and 8 for the basic interferometer types. Interferometers of different types, on the other hand, can generally be combined with either relative orientation, as illustrated for example by Figs. 10a and 1Oe.
  • Figs. 10a and 1Oe For the dual Sagnac structure (Fig. 7):
  • ⁇ i(t) cp(t-ti) - cp(t-t 2 -t 0 )
  • ⁇ 2 (t) ⁇ (t-t 2 ) - ⁇ (t-ti-to)
  • ⁇ i(t) cp(t-ti) + cp(t-t 2 -t 0 )
  • ⁇ 2 (t) ⁇ (t-t 2 ) + ⁇ (t-ti-to)
  • ⁇ 'i(t) ⁇ ⁇ i(t) - ⁇ 2 (t-t 0 ) ⁇ (t-ti) - ⁇ (t-ti-2t 0 )
  • Fig. 9 shows two possible embodiments of the dual Sagnac structure introduced schematically in Fig. 7. One is based on four 3-port WDM couplers, such as the ones utilizing designer-coated selective reflectors, commonly used in telecom equipment.
  • phase-responsive receivers comprising 3x3 couplers and paired signal detectors are shown for illustrative purposes. Other types of phase- responsive receivers can be used in their places.
  • the structures discussed here that utilize a Mach-Zehnder-type interferometer as at least one of the interferometers do not require WDM or other such means for separating the signal paths belonging to different interferometers (the signals are separated by means of counter-propagation). These structures may therefore be implemented with a single signal source, with the emitted signal split between the two interferometers.
  • a special advantage of the Sagnac-type structures and other zero-path- difference interferometer structures stems from the fact that the lengths of their signal paths are precisely equal as they share the same physical path, e.g., the Sagnac loop.
  • the signal paths in other interferometer types are physically separated and their lengths need to be matched to within the coherence length of the source.
  • a broadband source can be used with a Sagnac interferometer, while other structures generally require a narrow-band source such as a distributed- feedback (DFB) laser, given the practical limitations of the length-matching precision.
  • DFB distributed- feedback
  • Michelson-type structures have a unique advantage when implemented using Faraday mirrors to terminate the far ends of each waveguide.
  • the visibility of the interference fringes is always maximum, affected neither by the polarization state of the input signal nor by the polarization transforming properties of the interferometer medium.
  • other structures may require at least limited means of either avoiding or treating the situation in which the polarization states of the signals at the signal combiner become substantially orthogonal.
  • Such means may include polarization control means to advantageously adjust the polarization state of the input signal or polarization detection means to measure the relative phase of the combined signals in said special case when their polarization states are substantially orthogonal.
  • a Sagnac structure can also be used in conjunction with a source of un-polarized or depolarized broad-band signal to mitigate the polarization issue.
  • a depolarizer also needs to be inserted inside a Sagnac loop to mitigate its birefringent properties.
  • the main practical drawback of the Sagnac-type structures is the overall magnitude of its phase response, which is typically smaller or much smaller than that of the other structure types, and correspondingly reduced signal-to-noise ratio, particularly for disturbances occurring close to the center of the Sagnac loop.
  • Fig. 6 The structure in Fig. 6, comprising a Sagnac interferometer as Interferometer (861) and a Michelson interferometer as the other Interferometer (862), utilizes the fewest number of physical paths in the dead-end configuration and is therefore an attractive option from that standpoint.
  • Fig. 10 shows several possible embodiments of this structure based on WDM.
  • Fig. 11 shows the directly measured phase responses ⁇ i(t) and ⁇ 2 (t) of the two interferometers. It is clear that the measured signals differ significantly in shape and magnitude.
  • Fig. 12 shows the composite signals ⁇ 'i(t) and ⁇ ' 2 (t) computed as half of the sum and half of the difference of the measured phase responses, with the constant phase offset removed. These signals are substantially identical in shape, as expected, except for the time lag.
  • Fig. 13 gives a closer view of the same data along the time scale, in which the time lag is readily visible.
  • An alternative means of determining the location of a disturbance is based on comparison of instantaneous or time-averaged magnitudes of composite signals derived from the phase responses of the sensing structure. This approach applies to all example embodiments introduced above as well as to other structures apparent to those skilled in the art. This approach is described here using the structure in Fig. 3 as an illustrative example.
  • the structure combines a Mach-Zehnder interferometer (831) with a Sagnac interferometer (832).
  • ⁇ 2 (t) cp(t-ti) - cp(t-t 2 -t 0 )
  • phase-responsive receiver on interferometer allows to directly measure the relative phase change induced by the disturbance, ⁇ (t-t 2 ).
  • the magnitude of the latter phase response, produced by interferometer (832) depends critically on the disturbance position as measured by t 2 . In particular if the disturbance occurs at the midpoint of the Sagnac loop, t 2 is zero and interferometer (832) produces no response.
  • Composite signals can be constructed as
  • ⁇ t is a fixed time increment that is small compared to the signal propagation time to.
  • ⁇ t can be, for example, a signal sampling interval of a signal digitizer.
  • interferometer (832) which in this case is also the second composite signal ⁇ ' 2 (t)
  • ⁇ '(t) denotes a time derivative of the disturbance-induced phase.
  • This composite signal depends on the location of the disturbance through t 2 , but also depends on the time-varying magnitude and frequency of the disturbance.
  • the differential of the interferometer (831) response which is the first composite signal ⁇ 'i(t)
  • ⁇ '(t-t 2 )- ⁇ t The approximations made above assume that ⁇ '(t) varies slowly on the scale of the signal propagation time to, which condition is generally satisfied.
  • Interferometer (831) and interferometer (832) composite signals also yield approximations of phase derivatives evaluated at slightly different times which may produce a measurable time lag between them.
  • the time lag between the composite signals determined, for example, from the correlation of the two data sets, may therefore provide another estimate of the position of the disturbance.
  • the ratio of the average power of the interferometer (831) signal and the average power of the frequency- weighted interferometer (832) signal can be used for the same purpose.
  • Fig. 16 The latter approach is illustrated in Fig. 16 for a set of 150 segments of phase response signals detected during a disturbance, the duration of each segment about 65ms.
  • the slope of the straight line formed by the individual data points yields the above ratio that can be used to derive the location of the disturbance.
  • the ratio maintains a universal value even as the instantaneous magnitude of the disturbance varies by over 3 orders of magnitude.

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  • General Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
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Abstract

Une perturbation, telle qu'une vibration due à une activité humaine, est localisée le long d'une structure guide d'ondes à fibre optique (301-304) au moyen de deux interféromètres (801, 802) du même type ou de types différents, tels que des interféromètres de Mach-Zehnder, Sagnac et Michelson. Des signaux de porteuse issus d'une source (101) sont décomposés au niveau des entrées (201, 202) des interféromètres et recombinés au niveau des sorties (701, 702) après s'être propagés dans une zone de détection (401) dans laquelle des variations de phase sont produites sous l'effet de la perturbation (501). Des récepteurs (901, 902) sensibles à la phase détectent des relations de phase (1001, 1002) entre les signaux de porteuse au fil du temps. Un processeur (1101) combine les relations de phase en signaux composites en fonction d'équations qui diffèrent selon les configurations d'interféromètres, un retard ou un rapport entre les signaux composites représentant l'emplacement de la perturbation. Les signaux détectés et composites sont dissociés, de sorte que le déplacement de phase puisse excéder la période de la porteuse et permettre la localisation de perturbations d'amplitudes variables.
PCT/US2007/077101 2004-06-15 2007-08-29 Détection et localisation d'une intrusion dans un périmètre à l'aide de variables composites issues de mesures de phase Ceased WO2008027959A2 (fr)

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US12/438,877 US8395782B2 (en) 2004-06-15 2007-08-29 Detection and location of boundary intrusion, using composite variables derived from phase measurements

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CN104677596A (zh) * 2014-12-15 2015-06-03 哈尔滨工程大学 一种Sagnac环形光路内嵌入非平衡Mach-Zehnder型光程扫描器的光学自相关仪
WO2022066059A1 (fr) * 2020-09-28 2022-03-31 Акционерное Общество "Институт "Оргэнергострой" Ligne de retard de partie linéaire d'avertisseur et procédé d'avertissement
RU2778043C2 (ru) * 2020-09-28 2022-08-12 Акционерное Общество "Институт "Оргэнергострой" Комбинированные интерферометры для извещателя охранного волоконно-оптического

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WO2011109895A1 (fr) * 2010-03-12 2011-09-15 Senstar Corporation Capteur interférométrique michelson de télémétrie avec terminaison combinée
CN104677596A (zh) * 2014-12-15 2015-06-03 哈尔滨工程大学 一种Sagnac环形光路内嵌入非平衡Mach-Zehnder型光程扫描器的光学自相关仪
WO2022066059A1 (fr) * 2020-09-28 2022-03-31 Акционерное Общество "Институт "Оргэнергострой" Ligne de retard de partie linéaire d'avertisseur et procédé d'avertissement
RU2778043C2 (ru) * 2020-09-28 2022-08-12 Акционерное Общество "Институт "Оргэнергострой" Комбинированные интерферометры для извещателя охранного волоконно-оптического
RU2781228C2 (ru) * 2020-09-28 2022-10-07 Акционерное Общество "Институт "Оргэнергострой" Совместные интерферометры для извещателя охранного волоконно-оптического
RU2837066C1 (ru) * 2024-11-11 2025-03-25 Общество с ограниченной ответственностью "Т8 Сенсор" (ООО "Т8 Сенсор") Устройство для мониторинга виброакустических характеристик протяженных объектов
RU2844651C1 (ru) * 2025-03-26 2025-08-04 Общество с ограниченной ответственностью "Т8 Сенсор" (ООО "Т8 Сенсор") Устройство для мониторинга виброакустической характеристики протяженного объекта

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