RU2650853C1 - Fiber-optical distribution vibroacoustic sensor based on phase-sensitive reflectometer and method of improving its characteristics of sensitivity - Google Patents

Abstract

FIELD: measurement.

SUBSTANCE: invention relates to distributed vibro-acoustic fiber-optic sensor systems. A fiber-optic distributed vibro-acoustic sensor based on phase-sensitive reflectometer contains narrow-band radiation source, fiber-optic amplifier that amplifies source radiation, acoustic-optical modulator operating in pulsed mode and introducing frequency shift into optical radiation, fiber optic splitter on M channels in case of M>1, each channel consisting of optical fiber, circulator and fiber optic erbium amplifier in receiving part of channel, amplifier of narrowband optical filter and further photodetector module with output to channel of multichannel ADC with input quantity of not less than number of channels involved. Thus, outputs of all channels are connected to their inputs of multichannel ADC. At output of ADC, digital processor for generation of control pulses, controls, processing and transmission of data, board of frequency-pulse shaper and AOM driver; all fibers of M-channels are laid along each other side by side.

EFFECT: technical result consists in increasing sensitivity to weak vibroacoustic influences on sensor element and in increasing length of sensor sensitive element.

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Description

Technical field

The invention relates to distributed vibro-acoustic fiber optic sensor systems. The invention can be used in monitoring systems of long objects, in perimeter security systems, in oil well logging systems, in railway transportation monitoring and diagnostics systems, in vibration systems for monitoring industrial objects.

State of the art

The operating principles of distributed vibro-acoustic fiber optic systems are based on the method of phase-sensitive optical reflectometry. The method allows you to record changes in phase ratios of backscattered radiation. In contrast to the widespread methods of incoherent reflectometry used to diagnose damage to optical fibers, registration of a change in the phase relations of the backscattered signal becomes possible due to the use of a narrow-band radiation source from which scanning pulses are formed, as a result of which backscattered waves are added coherently, taking into account phase relations. A change in the phase relations of backscattered waves is affected by a change in the optical path. The optical path is the product of the geometric path and the refractive index of the optical fiber. When vibrating or acoustic impact on an optical fiber, both the geometric length and the refractive index change.

The signal is backscattering radiation from the inhomogeneities of the optical fiber, and the entire optical fiber is used as a sensor. To isolate certain sections of the fiber, pulse reflectometry methods are used, in which the spatial resolution is determined by the half-width of the probe optical pulse, and the time delay of the backscattering signal corresponds to the remoteness of the section of the optical fiber from the point of introduction of the probe pulse. The term "distributed fiber optic sensor" means the use of all of the optical fiber as a sensor, and it does not require the use of any special point sensors.

The time dependence of the backscattering signal on a single scanning pulse is called a trace. In the absence of vibro-acoustic effects on the optical fiber, the trace from pulse to pulse change by the amount of instability of the components of the optical and electronic circuits of the device. The main contribution, as a rule, is made by the instability of the wavelength of a narrow-band radiation source, and the wavelength is inversely proportional to the radiation frequency (λ = c / (n⋅ν), where λ is the wavelength of light, ν is the radiation frequency). In this case, changes from one trace to another account for a fraction of a percent. In the presence of vibro-acoustic effects on the optical fiber in places where the impact occurs, the change from one trace to another can be up to 100%.

The registration of vibro-acoustic effects by the above method involves the placement of a fiber-optic cable in the zone of vibrational effects. Optical fiber is used as a distributed sensing element. Short light pulses are sent to the optical fiber with a period greater than or equal to the time the light travels twice the optical length of the optical fiber. The time dependence of the power of backscattered radiation is recorded using a photodetector, from which the signal is fed to an analog-to-digital converter (ADC). The digitized signal is subjected to digital processing, as a result of which the places of vibroacoustic impact are allocated, depending on the processing algorithms, the types of effects, their temporal and spectral characteristics can be determined.

One of the basic patents for the invention in the field of devices and a method of coherent reflectometry for recording vibroacoustic effects is known - US patent US 5194847 Apparatus and method for fiber optic intrusion sensing (IPC G01H 9/00; G01L 1/24; G01L 11/02; G08B 13 / 12; G08B 13/186; (IPC1-7): G08B 13/10; G08B 13/18, publ. 1993-03-16), which describes a distributed optical fiber sensor for detecting vibration effects on the optical fiber. The basic method corresponds to the basic circuitry of devices for implementing the method, as well as many derived circuits of coherent reflectometry devices. Further development of variations of the coherent reflectometry method close to the proposed solutions in this patent is reflected, for example, in US patent US 8248589 (B2) Phase Based Sensing (IPC G01N 21/00, publ. 2012-08-21); U.S. Patent No. 8,923,663 (B2) Distributed Fiber Optic Sensing (IPC G01D 5/353; G02B 6/00, publ. 2014-12-30).

, где l_И - длительность импульса в метрах, с - скорость света в вакууме, n - показатель преломления кварца оптического волокна, τ_И - длительность импульса в секундах), период неравномерности может составлять от 5 до 20 метров. Следует отметить, что требуется использование стабильного по частоте (или по центральной длине волны) источника излучения, что при отсутствии виброакустического воздействия на оптическое волокно обуславливает стабильную во времени зависимость мощности обратнорассеянного излучения от длины оптического волокна. Период времени, в течение которого распределение локальных минимумов и максимумов не изменяется, составляет десятки и сотни секунд. Неравномерность чувствительности вдоль оптического волокна приводит к неравномерному отклику на виброакустическое воздействие. В случае применения такой системы для мониторинга вибраций от объектов, формирующих виброакустическое поле больше периода неравномерности чувствительности, отклик системы на единичное воздействие легко спутать с откликом на множественное воздействие. В случае мониторинга вибраций от объектов, формирующих виброакустическое поле меньше периода неравномерности чувствительности, существует вероятность, что отклика системы на такое воздействие не будет вообще.The disadvantages of the operation of optoelectronic circuits in these patents include the uneven sensitivity of the distributed fiber-optic sensor. The unevenness of sensitivity is due to the random, statistical nature of the addition of backscattered waves in phase. As a result, the backscattering pattern represents an uneven dependence of the radiation power on the distance along the optical fiber. Uneven power backscattered radiation leads to uneven sensitivity of the system to vibro-acoustic effects on the optical cable. The non-uniformity reaches 100% with a minimum backscattered radiation power of zero. The period of unevenness is commensurate with half the duration of the scanning pulse. For example, for pulses lasting 40 meters (which corresponds to a time duration of 200 ns, based on the ratio

, where l _И is the pulse duration in meters, s is the speed of light in vacuum, n is the refractive index of quartz of the optical fiber, τ _И is the pulse duration in seconds), the irregularity period can be from 5 to 20 meters. It should be noted that the use of a frequency-stable (or central wavelength) radiation source is required, which, in the absence of a vibro-acoustic effect on the optical fiber, causes a time-stable dependence of the backscattered radiation power on the length of the optical fiber. The period of time during which the distribution of local minima and maxima does not change is tens and hundreds of seconds. The uneven sensitivity along the optical fiber leads to an uneven response to vibroacoustic impact. In the case of using such a system to monitor vibrations from objects forming a vibroacoustic field for more than a period of non-uniformity of sensitivity, the response of the system to a single effect is easily confused with the response to multiple effects. In the case of monitoring vibrations from objects forming a vibro-acoustic field less than the period of non-uniformity of sensitivity, there is a possibility that the system will not respond to such an impact at all.

As the closest analogue (prototype), the proposed technical solution selected the device and the method implemented in it described in the patent of the Russian Federation for invention No. 2562689 Distributed sensor of acoustic and vibration effects (IPC G01D 5/353, G01H 9/00, published on 09/10/2015, .). The distributed acoustic and vibration sensor contains a sensing element in the form of an optical fiber located in a fiber optic cable, and a phase-sensitive optical reflectometer optically connected to the fiber through an interface. The sensor also contains a source of a periodic sequence of optical test signals connected to the interface, made in the form of a serially optically connected cw laser, an acousto-optical modulator (AOM) on a traveling acoustic wave, and a scattered radiation receiver. The specified source is configured to generate test signals in the form of a pair of pulses of equal duration with a delay of the second pulse relative to the first and periodically variable phase difference of the optical carrier wave of the second pulse relative to the phase of the optical carrier wave of the first pulse.

The disadvantages of the known device of the prototype are reduced and uneven sensitivity to vibroacoustic effects and a relatively short range. In this device, an optical pulse is generated from the radiation of a narrow-band low-power source, and then amplified by an optical erbium amplifier. The consequence of this solution is the instability of the pulse shape at the output of an optical erbium-based amplifier operating in a pulsed mode. In addition, an optical erbium amplifier located directly in front of the entrance to the optical line emits spontaneous emission radiation into it, which also leads to additional instability of the backscattering signal, which, in turn, leads to a decrease in the sensitivity of the system.

In the method implemented in the specified prototype device, packets of two pulses are sent to the optical fiber line, the second pulse in the packet being different in phase delay of the radio frequency shift introduced by the AOM into the optical signal. Such a circuit is critical to phase uncertainty (jitter) of the master oscillators, which form the signals supplied to the AOM and to the ADC. Also, this circuit is critical to the jitter of the electronic circuit, forming a sequence of two pulses, to the jitter of the generator signal supplied to the digital demodulation circuit. As a result, the sensitivity to vibration effects of the device described in the patent for the invention of the Russian Federation No. 2562689, is several times worse than that of the proposed device.

Disclosure of invention

The objective of the invention is to improve the sensitivity characteristics of a fiber-optic distributed vibroacoustic sensor based on a phase-sensitive reflectometer, namely: reducing the unevenness of the sensitivity of the distributed vibroacoustic system along the optical fiber throughout its length and eliminating the so-called "signal fading" or "blind zones" (dead zones) .

The technical result is a significant improvement in the sensitivity characteristics, namely, increasing the uniformity of sensitivity to vibroacoustic effects on the sensing element, increasing the sensitivity to weak vibroacoustic effects on the sensing element, significantly reducing the likelihood of signal fading and, as a result, improving the sensitivity, the possibility of increasing the length of the sensor .

The technical result is achieved due to the fact that a long-distance distributed fiber-optic vibro-acoustic sensor for recording vibration effects of the acoustic frequency range includes a narrow-band radiation source (usually a laser with a bandwidth of less than 35 kHz), a fiber-optic amplifier that amplifies the source radiation ( usually up to a power of 1 W), AOM operating in a pulsed mode and introducing a frequency Doppler shift into optical radiation, a fiber optic splitter on M-channels (if there is only one channel, then a splitter is not needed), each channel consists of a sensitive element - an optical fiber, a circulator, an Erbium fiber optic amplifier in the receiving part of the channel, after a narrow-band optical filter amplifier and then a photodetector module with output to the channel M-channel ADC. The outputs of all channels are connected to the M-channel ADC module, at the output of which a digital processor for generating control pulses, control, processing and data transmission, a pulse-frequency driver board, and an AOM driver are installed to control the operation of the AOM. All fibers of the M channels are laid next to each other.

, то есть диапазон Δƒ_ИМ=20-2 МГц. При этом ширина спектра рефлектограммы практически равна ширине спектра сканирующих импульсов

, так как ширина спектра непрерывного излучения узкополосного источника излучения много меньше ширины спектра сканирующих импульсов Δƒ_ИCТ<<Δƒ_ИМ (обычно это лазер с шириной полосы менее 35 кГц). Центральная частота излучения зондирующих импульсов для оптической схемы датчика складывается из центральной частоты источника излучения и допплеровского увеличения частоты, вносимой АОМ. Изменение частоты излучения зондирующих импульсов на величину, большую 1/Т_ИМ (Δƒ_CЧ≤1/Т_ИМ), приводит к формированию новой статистической картины сигналов обратного рассеяния. В результате чего на участках волокна, на которых чувствительность была минимальна, характеристика чувствительности будет больше минимальной. От каждого импульса с определенной центральной частотой формируется рефлектограмма, статистически отличная от рефлектограммы, формируемой импульсом на другой центральной частоте, тем самым вероятность перекрытия «слепых зон» (зон нечувствительности) увеличивается в

раз (где K - количество частот) после формирования комбинированной (составной) рефлектограммы, составленной из участков с максимальными чувствительностями отдельных рефлектограмм. Также возможно применение не одного, а нескольких чувствительных оптических волокон (проложенных рядом друг с другом) в М-каналах. Рефлектограммы оптических волокон каналов с принципиально отличными друг от друга характеристиками также имеют различные статистические характеристики, что в итоге после формирования из отдельных рефлектограмм комбинированной (составной) рефлектограммы увеличивает вероятность перекрытия «слепых зон» в

раз, где N=K*M.The way to equalize the sensitivity characteristics of this distributed fiber-optic vibroacoustic sensor is to change the frequency of single pulses sent to the sensing element - optical fiber. The duration of the scanning pulses is T _MI = 50-500 ns. The width of the spectrum of pulses in a first approximation is determined from the relation

, that is, the range Δƒ _MI = 20-2 MHz. The width of the spectrum of the trace is almost equal to the width of the spectrum of the scanning pulses

, since the width of the continuous emission spectrum of a narrow-band radiation source is much smaller than the spectrum width of the scanning pulses Δƒ _ИТТ << Δƒ _ИМ (usually a laser with a bandwidth of less than 35 kHz). The central radiation frequency of the probe pulses for the optical circuit of the sensor is the sum of the central frequency of the radiation source and the Doppler frequency increase introduced by the AOM. A change in the radiation frequency of the probe pulses by an amount greater than 1 / T _IM (Δƒ _SCh ≤1 / T _IM ) leads to the formation of a new statistical picture of backscattering signals. As a result, in the areas of the fiber where the sensitivity was minimal, the sensitivity characteristic will be greater than the minimum. A trace is formed from each pulse with a certain central frequency, which is statistically different from a trace generated by a pulse at a different central frequency, thereby increasing the probability of overlapping “blind zones” (dead zones)

times (where K is the number of frequencies) after the formation of the combined (composite) trace composed of sections with the maximum sensitivities of individual reflectograms. It is also possible to use not one, but several sensitive optical fibers (laid next to each other) in the M-channels. OTDR traces of channel optical fibers with fundamentally different characteristics also have different statistical characteristics, which, after forming combined (composite) OTDR traces from individual OTDR traces, increases the probability of overlapping “blind zones” in

times where N = K * M.

Thus, we can note the following significant differences of the proposed technical solution from the prototype:

1. AOM, generating probing pulses, in the proposed scheme is located after the optical erbium amplifier, excluding the emission of spontaneous emission of the optical amplifier into the optical line. This solution allows you to increase the signal-to-noise ratio and thereby increase the sensitivity of the system.

раз после формирования комбинированной (составной) рефлектограммы, составленной из участков с максимальными чувствительностями отдельных рефлектограмм. Кроме того, возможно применение не одного, а проложенных рядом друг с другом нескольких чувствительных оптических волокон в М-каналах. Рефлектограммы оптических волокон каналов с принципиально отличными друг от друга характеристиками также имеют различные статистические характеристики, что в итоге после формирования из отдельных рефлектограмм комбинированной (составной) рефлектограммы, составленной из участков с максимальными чувствительностями отдельных рефлектограмм, увеличивает вероятность перекрытия «слепых зон» уже в

раз, где N=K*М.2. Single pulses are sent to the optical fiber (and the prototype uses packs of pairs of pulses with a variable phase), thereby eliminating, in principle, the influence of phase instability (jitter) between pulses, which leads to a deterioration of the signal-to-noise ratio in the prototype circuit. Moreover, several (K) single probe pulses are sent to the optical fiber in turn with frequencies different from each other by Δƒ _SCh ≤1 / T _IM , where Δƒ _SCh is the frequency offset, T _IM is the duration of the probe pulse. A reflectogram is generated from each probe pulse, which is statistically different from a trace generated by a pulse at a different frequency, thereby increasing the probability of overlapping “blind zones” (dead zones)

times after the formation of a combined (composite) trace, composed of sections with maximum sensitivities of individual reflectograms. In addition, it is possible to use not one, but several sensitive optical fibers laid in the M channels adjacent to each other. OTDR traces of optical fibers of channels with fundamentally different characteristics from each other also have different statistical characteristics, which, as a result, after the formation of individual OTDR traces of a combined (composite) OTDR trace composed of areas with the maximum sensitivity of individual OTDRs, increases the probability of overlapping “blind zones” already in

times where N = K * M.

List of figures

In FIG. 1 shows a diagram of the proposed fiber-optic distributed vibroacoustic sensor based on a phase-sensitive reflectometer (optoelectronic circuit of a coherent reflectometer) with an improved sensitivity characteristic.

In FIG. 2 shows a functional diagram of a pulse-frequency driver.

In FIG. Figure 3 shows an example of the formation of a graph of a combined composite reflectogram from the graphs of four separate reflectograms at N = 4 (possible combinations of K and M in this case: K = 4, M = 1 or K = 2, M = 2).

The implementation of the invention

In FIG. 1 shows a diagram of the proposed device. The device consists of a narrow-band radiation source 1 (a laser with a frequency bandwidth of less than 35 kHz), a fiber-optic erbium amplifier 2, amplifying the source radiation to a power of 1 W, AOM 3, operating in a pulsed mode and introducing a frequency shift into the optical radiation, fiber-optic splitter (on M-channels) 4, each of the M-channels consists of a sensing element - optical fiber 5, circulator 6, fiber-optic erbium amplifier 7 in the receiving part of the channel, after which a narrow-band optical ph liter 8, then a photodetector module 9, the output of which is connected to its channel input of a multi-channel module (at least M-channels) of the ADC 10, the output of which is connected to the input of a digital processor for generating control pulses, control, processing and data transmission 11, then a pulse-frequency shaper 12 and a specialized driver 13 of the acousto-optical modulator 13. Each of the M channels contains components: 5, 6, 7, 8, 9. In these channels, a standard single-mode optical fiber (for example, grades G652, G657) can be used and commercially manufactured fiber optic cable for communication lines. All fibers of the M channels are laid along each other side by side.

The device operates as follows. At the sensing element - optical fiber 5 (Fig. 1) - probing pulses of different frequencies are sent, which form the AOM 3 from the continuous radiation of a narrow-band laser 1. A feature of the proposed optical circuit is that the AOM forming the probe pulses is located after the optical erbium amplifier, excluding the emission of spontaneous emission of an optical amplifier into an optical line. This solution allows you to increase the signal-to-noise ratio and thereby increase the sensitivity of the system. To achieve a sufficient power level, the radiation of a narrow-band laser 1 is amplified using an optical erbium amplifier 2 to values of 200-1000 mW, after which it is fed to AOM 3. After AOM 3, pulsed radiation is supplied to splitter 4, and pulsed radiation is transmitted to each splitter channel to its circulator 6 and then into the optical fiber 5. In the optical fiber 5, the pulsed radiation is scattered by the inhomogeneities of the refractive index of the fiber, and part of it returns back and goes to the circulator 6. P After the circulator 6, the backscattered radiation enters the optical erbium amplifier 7, then the radiation is filtered out by a narrow-band optical filter 8 and enters the photodetector 9. After the photodetector, the radiation converted into an electric signal is fed to its input of the multi-channel ADC 10. From the ADC, a digitized electrical signal arrives at the processor 11, providing synchronous formation of the probe pulses and synchronous reception of the digitized backscattered signal. The formation of probe pulses at different frequencies occurs in the processor 11 and is implemented through the use of a frequency-pulse shaper 12 and driver 13 AOM 3.

AOM 3 forms an optical pulse by creating a Bragg diffraction grating in tellurium dioxide by means of a traveling acoustic wave. The diffraction grating deflects the light beam to the first Bragg diffraction maximum, where the collimator is located. A traveling acoustic wave can be formed at a frequency from 40 to 200 MHz, and at this frequency, due to the Doppler effect, the central frequency of the optical radiation passing through tellurium dioxide increases. The addition of the radio frequency supplied to the AOM with an optical frequency is used to change the total radiation frequency. It should be borne in mind that a change in the radio frequency supplied to AOM 3 leads to a change in the period of the induced Bragg diffraction grating, which, in turn, leads to a change in the Bragg diffraction angle. A change in the Bragg diffraction angle leads to the fact that not the entire light beam arrives at the radiation-output collimator, established from the calculation of a specific frequency. Thus, changing the frequency of the radio frequency signal supplied to the AOM, not only change the frequency of the radiation emerging from the AOM, but also change the insertion loss. AOM allows you to change your own center frequency within Δƒ _AOM ± 10% with an increase in insertion loss of no more than 3 dB.

To solve the problem of a significant reduction of dead zones, a processor 11 is used, which provides:

- the formation of probe pulses with different frequencies by switching the corresponding frequency outputs of the frequency-pulse shaper 12;

- reception and formation of reflectograms for probing pulses with different frequencies;

- the formation in real time of a combined composite reflectogram based on individual N-reflectograms obtained from probe pulses at different frequencies and, possibly, from optical fibers of several channels.

In FIG. 2 is a functional diagram of a frequency-pulse shaper 12. From the processing processor 11, a control signal 12.1 arrives at the frequency-pulse shaper, which is fed to a logic circuit 12.2, which generates a pulse formation signal 12.3 and a frequency channel selection signal 12.4. The signal for selecting the frequency channel 12.4 is supplied to the multiplexer 12.6, which switches the frequency signals arriving at it from the frequency synthesizer 12.5. From the multiplexer 12.6 to the driver 13 AOM 3 receives the signal of the frequency channel 12.7. The pulse formation signal 12.3 and the signal of the frequency channel 12.7 are supplied to the driver 13 AOM 3 synchronously.

After AOM 3, K single probing pulses are sent sequentially to optical fiber 6 (or to fibers 6 after splitter 4, if there are several channels and fibers) (for example, for N = K * M = 4, two combinations are possible: K = 4, M = 1 or K = 2, M = 2, where K - number of frequencies M - the number of fibers) at frequencies that differ from pulse to pulse by an amount greater Δƒ _MF ≤1 / T _IM, wherein Δƒ _Cq - frequency offset, T _IM - duration of the probe pulse. The backscattering signals that came from the optical fibers from each pulse are stored in the random access memory of the digital processor 11 in the form of N reflectograms that come one after the other with their spatial dependence along the length of their fibers.

раз снижена вероятность нахождения участков, на которых отсутствует отклик на виброакустическое воздействие на оптическое волокно.In FIG. Figure 3 shows an example of the implementation of the method for generating a graph of a combined composite trace from the graphs of individual reflectograms at N = 4 (the top 4 graphs are individual reflectograms, the lower graph is the final composite trace, the sections of maximum sensitivity are highlighted with ovals on the graphs of individual reflectograms, from which it is possible to compose a combined trace ) To process individual N reflectograms, the fiber from which the reflectograms are obtained is mathematically divided into equal intervals along the length of the fiber. The length of the interval is selected depending on the period (length) of the repetition of the local maximums of the trace, which depends on the duration of the probe pulse (approximately four times less than the half-width of the probe pulse, i.e., approximately 5 to 10 m). For each fiber interval, the intervals of N reflectograms are compared and the interval of that trace is selected that has the highest signal level, and therefore, the greatest response with possible vibro-acoustic exposure at a given interval of the optical fiber. A comparative analysis of all intervals is carried out sequentially and a composite combined reflectogram is formed. Moreover, in the formed composite trace in

times reduced the likelihood of finding areas in which there is no response to vibro-acoustic effects on the optical fiber.

After the formation of a composite reflectogram, the next cycle of repeating its formation is required to be performed until the speckle pattern of the reflectogram changes, and this period of time can be from tens to hundreds of seconds depending on operating conditions. It should be noted that with the period of formation of a composite reflectogram of 10 seconds, there can be no difficulties with further processing of signals from a composite reflectogram, since the frequency band of the working vibroacoustic signal of a phase-sensitive reflectometer is in the range from units of hertz and higher to almost several hundred kilohertz.

The proposed fiber-optic distributed vibroacoustic sensor based on a phase-sensitive reflectometer and a method for improving its sensitivity characteristics were obtained during the implementation of applied scientific research experimental development (PNIER) under the Agreement on the provision of subsidy No. 14.577.21.0224 between the Ministry of Education and Science of the Russian Federation and MSTU im. N.E. Bauman.

Claims (4)

1. A fiber-optic distributed vibro-acoustic sensor based on a phase-sensitive reflectometer, consisting of: a narrow-band radiation source, a fiber-optic amplifier, amplifying the radiation of the source, an acousto-optical modulator operating in a pulsed mode and introducing a frequency shift in the optical radiation, a fiber optic splitter on M -channels in the case of M> 1, each channel consists of a sensitive element — an optical fiber, a circulator, an optical fiber erbium amplifier in the receiver the first part of the channel, after this an amplifier of a narrow-band optical filter and then a photodetector module with an output to a channel of a multi-channel ADC with the number of inputs not less than the number of channels involved, thus, the outputs of all channels are connected to their inputs of a multi-channel ADC, at the output of which are sequentially installed one after another a digital processor for generating control pulses, control, processing and data transmission, a frequency-pulse shaper board and AOM driver; all fibers of the M channels are laid along each other side by side. 2. The sensor according to claim 1, characterized in that the narrow-band radiation source is a laser with a frequency bandwidth of less than 35 kHz, the erbium amplifier following it has the ability to amplify the radiation power of the source up to 1 W. 3. The method of aligning the sensitivity characteristics of a fiber-optic distributed vibroacoustic sensor according to claim 1, characterized by a change in the frequency of single pulses sent to a sensing element - an optical fiber, the radiation frequency of the scanning pulses for the optical sensor circuit is added up from the frequency of a narrow-band radiation source and Doppler frequency increase, introduced by the AOM, the frequency change Δƒ _MF scanning radiation pulses by an amount greater than or equal Δƒ _MF ≤1 / _MI T, where T _and - the duration of the scanning pulse, leads to the formation of new statistical pattern backscatter signals and, accordingly, formation of the waveform, statistically different from the waveform formed by a pulse at a different frequency, thus the probability of overlap "blind spots" (dead zones) is increased in

times after the formation of a combined composite reflectogram composed of sections with the maximum sensitivities of individual reflectograms, and taking into account the use of several sensitive optical fibers laid along each other next to each other in the M channels, as a result, after forming a combined composite reflectogram from separate reflectograms, the probability of overlapping “blind zones” increases at

times, and N = K * M, where N is the number of traces, K is the number of frequencies, M is the number of fibers. 4. The method according to p. 3, characterized in that the duration of the scanning pulses is T _MI = 50-500 ns, respectively, the frequency range Δƒ _MI = 20-2 MHz.

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