Distributed optical fiber sound wave sensing system and optical fiber sensing equipment

Abstract

The utility model specifically relates to a distributed optical fiber sound wave sensing system and optical fiber sensing equipment. The utility model provides a distributed optical fiber sound wave sensing system which at least comprises a narrow linewidth laser, a main optical path structure, an auxiliary optical path structure, a first coupler and a signal processor. The output end of the narrow linewidth laser is connected with the input end of the first coupler, the first output end of the first coupler is connected with the input end of the main optical path structure, the first output end of the main optical path structure is connected with the first input end of the signal processor, and the second output end of the main optical path structure is used for being externally connected with a measured optical fiber; the auxiliary light path structure comprises a delay module, a photoelectric converter and a first signal acquisition circuit; the output end of the delay module is connected with the input end of the photoelectric converter, the output end of the photoelectric converter is connected with the input end of the first signal acquisition circuit, and the output end of the first signal acquisition circuit is connected with the second input end of the signal processor; and the delay module is used for delaying the time of the entering laser beam.

Description

TECHNICAL FIELD

[0001] The utility model relates to the field of optical fiber sensing technology, more particularly to a distributed optical fiber acoustic sensing system and an optical fiber sensing device. BACKGROUND

[0002] The distributed optical fiber acoustic sensing system (DAS) utilizes optical fibers as sensors to perceive sound vibration, and based on the demodulation technology of back Rayleigh scattering phase change or spectrum shift, the amplitude, frequency and phase information of vibration can be linearly recovered, the linear response characteristic is provided, more abundant and accurate information is provided for subsequent data processing technology (such as array signal processing algorithm), so that the sensing system has better comprehensive performance, and in more and more applications, the distributed optical fiber acoustic sensing system (DAS) replaces the position of the distributed optical fiber vibration sensing system (DVS).

[0003] The optical path of the traditional distributed optical fiber acoustic sensing system (DAS) is a heterodyne coherent architecture composed of sensing light and local oscillation light, and the coherence between the sensing light and the local oscillation light is utilized to improve the sensitivity of signal detection. A narrow linewidth laser is usually used as a laser emission source, and since the linewidth of the narrow linewidth laser is limited, the laser provided by the narrow linewidth laser has phase noise, so the local oscillation light and the sensing light carry the phase noise of the laser itself, and the performance of the sensing system is worse than the theoretical calculation. UTILITY MODEL CONTENT

[0004] The utility model aims at overcoming at least one defect (deficiency) of the prior art, providing a distributed optical fiber acoustic sensing system and an optical fiber sensing device, so as to achieve the effect of compensating for the phase noise of laser.

[0005] The technical scheme adopted by the utility model is that a distributed optical fiber acoustic sensing system is provided, and the distributed optical fiber acoustic sensing system at least comprises a narrow linewidth laser, a main optical path structure, an auxiliary optical path structure, a first coupler and a signal processor.

[0006] The output end of the narrow linewidth laser is connected with the input end of the first coupler, the first output end of the first coupler is connected with the input end of the main optical path structure, the first output end of the main optical path structure is connected with the first input end of the signal processor, and the second output end of the main optical path structure is used for externally connecting a measured optical fiber.

[0007] The auxiliary optical path structure comprises a delay module, a photoelectric converter, and a first signal acquisition circuit.

[0008] The second output end of the first coupler is connected to the input end of the delay module, the output end of the delay module is connected to the input end of the photoelectric converter, the output end of the photoelectric converter is connected to the input end of the first signal acquisition circuit, and the output end of the first signal acquisition circuit is connected to the second input end of the signal processor.

[0009] In the scheme, the auxiliary optical path structure is used to monitor and compensate the main optical path structure, the delay module delays the laser beam in time, the delay of the propagation of the optical signal can obtain the phase information of the laser beam, and the phase information is used to obtain the phase noise; the photoelectric converter converts the delayed optical signal in the auxiliary optical path structure into an electrical signal and transmits it to the first signal acquisition circuit, the first signal acquisition circuit acquires phase difference information according to the electrical signal, the signal processor processes the phase difference information to obtain phase noise information, and compensates the sensing light detection result in the main optical path structure according to the phase noise information.

[0010] Further, the delay module at least comprises a third coupler, a delay optical path structure, a reference optical path structure, and a fourth coupler; the second output end of the first coupler is connected to the input end of the third coupler, the first output end of the third coupler is connected to the input end of the delay optical path structure, the second output end of the third coupler is connected to the input end of the reference optical path structure, the first input end of the fourth coupler is connected to the output end of the delay optical path structure, the second input end of the fourth coupler is connected to the output end of the reference optical path structure, and the output end of the fourth coupler is connected to the input end of the photoelectric converter.

[0011] In the scheme, the delay module comprises a delay optical path structure, a reference optical path structure, a third coupler, and a fourth coupler; the reference optical path structure is used as a reference for the propagation of the laser beam in the main optical path structure, the delay optical path structure delays the laser beam in time, the third coupler and the fourth coupler are used for beam splitting and coupling respectively, the delay module is the core part of the auxiliary optical path structure and plays a key role.

[0012] Further, the delay optical path structure comprises a delay optical fiber.

[0013] In the scheme, the delay optical path structure can only comprise a delay optical fiber, and the delay optical fiber realizes the delay processing of the electrical signal or the optical signal by controlling the propagation time of the optical signal in the optical fiber.

[0014] Further, the main light path structure comprises a second coupler, an acousto-optic modulator, a first optical signal processing unit, a circulator, a second optical signal processing unit, a demodulation module and an acousto-optic modulator driving circuit; a first output end of the first coupler is connected to an input end of the second coupler, a first output end of the second coupler is connected to a first input end of the acousto-optic modulator, an output end of the acousto-optic modulator is connected to an input end of the first optical signal processing unit, an output end of the first optical signal processing unit is connected to a first transmission end of the circulator, a second transmission end of the circulator is used for connecting a measured optical fiber, a third transmission end of the circulator is connected to an input end of the second optical signal processing unit, an output end of the second optical signal processing unit is connected to a first input end of the demodulation module, and a second input end of the demodulation module is connected to a second output end of the second coupler.

[0015] An output end of the demodulation module is connected to a first input end of the signal processor, an output end of the signal processor is connected to an input end of the acousto-optic modulator driving circuit, and an output end of the acousto-optic modulator driving circuit is connected to a second input end of the acousto-optic modulator.

[0016] In the scheme, the main light path structure is used for externally connecting a measured optical fiber, and laser emitted by a narrow linewidth laser is divided into two laser beams through the first coupler. One of the laser beams is divided into local light and sensing light through the second coupler. After the sensing light enters the acousto-optic modulator, the acousto-optic modulator performs corresponding frequency modulation on the sensing light, and the sensing light is modulated into pulsed light and then enters the circulator to reach the measured optical fiber. The sensing light propagates in the measured optical fiber and scatters. The scattered sensing light is reflected by the circulator and then reflected to the demodulation module. The sensing light and the local light interfere in the demodulation module, and the demodulation module extracts fiber vibration information according to the interference result.

[0017] Further, the first optical signal processing unit comprises a first erbium-doped amplifier and a first optical filter; an output end of the acousto-optic modulator is connected to an input end of the first erbium-doped amplifier, an output end of the first erbium-doped amplifier is connected to an input end of the first optical filter, and an output end of the first optical filter is connected to the first transmission end of the circulator.

[0018] In the scheme, the first erbium-doped amplifier in the first optical signal processing unit amplifies the sensing light signal, and the first optical filter filters the amplified sensing light signal, and selectively transmits or blocks the wavelength of the sensing light, etc.

[0019] Further, the first optical signal processing unit further comprises a first isolator; an output end of the acousto-optic modulator is connected to an input end of the first isolator, and an output end of the first isolator is connected to a first transmission end of the ring oscillator through the first erbium-doped amplifier and a first optical filter.

[0020] In the scheme, the first isolator in the first optical signal processing unit is used to prevent the reverse propagation of the sensing optical signal and keep the consistency of the propagation.

[0021] Further, the second optical signal processing unit comprises a second erbium-doped amplifier and a second optical filter; a third transmission end of the ring oscillator is connected to an input end of the second erbium-doped amplifier, an output end of the second erbium-doped amplifier is connected to an input end of the second optical filter, and an output end of the second optical filter is connected to a first input end of the demodulation module.

[0022] In the scheme, the second erbium-doped amplifier in the second optical signal processing unit is used to amplify the optical signal after scattering, and the second optical filter is used to filter the amplified optical signal, and the wavelength of the light is selectively transmitted or blocked, etc.

[0023] Further, the second optical signal processing unit further comprises a second isolator; an output end of the second optical filter is connected to an input end of the second isolator, and an output end of the second isolator is connected to a first input end of the demodulation module.

[0024] In the scheme, the second isolator in the second optical signal processing unit is used to prevent the reverse propagation of the sensing optical signal and keep the consistency of the propagation.

[0025] Further, the demodulation module comprises a fifth coupler, a balanced detector, and a second signal acquisition circuit.

[0026] An output end of the second optical signal processing unit is connected to a first input end of the fifth coupler, a first output end of the fifth coupler is connected to a first input end of the balanced detector, a first output end of the balanced detector is connected to a first input end of the second signal acquisition circuit; a second output end of the second coupler is connected to a second input end of the fifth coupler, a second output end of the fifth coupler is connected to a second input end of the balanced detector, a second output end of the balanced detector is connected to a second input end of the second signal acquisition circuit, and an output end of the second signal acquisition circuit is connected to a first input end of the signal processor.

[0027] In the scheme, the demodulation module comprises a fifth coupler, a balanced detector and a second signal acquisition circuit, the interference process of sensing light and local light is carried out in the demodulation module, and vibration information of the measured optical fiber is extracted, the sensing light after scattering enters a second optical signal processing unit through a third transmission end of the circulator, the output end of the second optical signal processing unit is connected with the first input end of the fifth coupler in the demodulation module, the local light passes through the second input end of the fifth coupler in the demodulation module, the two interfere with each other in the fifth coupler, the fifth coupler feeds back the interference signals of the two to the balanced detector, the balanced detector extracts the vibration information of the measured optical fiber and feeds back to the second signal acquisition circuit, the vibration information contains the detection result of the measured light, and thus the second signal acquisition circuit converts the collected information into an electrical signal and feeds back to the signal processor, that is, the task of the demodulation module is completed.

[0028] Further, an optical fiber sensing device comprises:

[0029] an OTDR system;

[0030] a distributed optical fiber acoustic sensing system as described above;

[0031] an optical switch, a first selection end of the optical switch is connected with the OTDR system, a second selection end of the optical switch is connected with the distributed optical fiber acoustic sensing system, and a transmission end of the optical switch is used for connecting the measured optical fiber;

[0032] the OTDR system and the distributed optical fiber acoustic sensing system are connected with the measured optical fiber through the optical switch.

[0033] In the scheme, the optical fiber sensing device is provided with an OTDR system and a distributed optical fiber acoustic sensing system, the OTDR system is used for measuring the loss and length of the optical fiber link and locating the fault point in the optical fiber, the characteristics of the optical fiber are determined by emitting optical pulses and receiving reflected optical signals and analyzing the signals, the distributed optical fiber acoustic sensing system can provide long-distance, high-resolution and real-time monitoring capability, and focuses on detecting external vibration or acoustic signals through phase change. System switching is realized through the optical switch, multiple measurements of the measured optical fiber are realized, comprehensive monitoring and measurement of the optical fiber network can be realized, and the maintenance efficiency and reliability of the optical fiber network are improved.

[0034] Compared with the prior art, the beneficial effects of the utility model are that: the auxiliary optical path structure is added on the optical path structure of the traditional distributed optical fiber acoustic sensing system, the phase noise compensation is carried out through the auxiliary optical path structure, and the performance of the distributed optical fiber acoustic sensing system can be improved. BRIEF DESCRIPTION OF DRAWINGS

[0035] Figure 1 It is the optical path structure diagram of the utility model.

[0036] Figure 2 The structure diagram of the delay module 11 of the utility model.

[0037] Figure 3 The structure diagram of the demodulation module 204 of the utility model.

[0038] 1, auxiliary light path structure, 2, main light path structure, 3, narrow line width laser, 4, first coupler, 5, signal processor, 6, measured optical fiber, 11, delay module, 12, photoelectric converter, 13, first signal acquisition circuit, 111, third coupler, 112, delay light path structure, 113, reference light path structure, 114, fourth coupler, 201, second coupler, 202, acoustooptic modulator, 203, circulator, 204, demodulation module, 205, acoustooptic modulator drive circuit, 206, first isolator, 207, first erbium-doped amplifier, 208, first optical filter, 209, second isolator, 210, second optical filter, 211, second erbium-doped amplifier, 2041, fifth coupler, 2042, balanced detector, 2043, second signal acquisition circuit. DETAILED DESCRIPTION

[0039] The utility model provides distributed optical fiber acoustic wave sensing system and optical fiber sensing equipment, for the purpose, technical scheme and effect of the utility model are clearer, more definite, the following refers to the drawing and raises example to this utility model further detailed explanation. It should be understood that the specific embodiment described here is only used to explain the utility model, and is not used to limit the utility model.

[0040] Those skilled in the art can understand that, unless specifically stated, the singular form "a", "an", "said" and "the" used herein also includes the plural form. It should be further understood that the phrase "comprising" used in the specification of the present application means that the features, integers, steps, operations, elements and / or components exist, but does not exclude the existence or addition of one or more other features, integers, steps, operations, elements, components and / or their groups. It should be understood that when we say that an element is "connected" or "coupled" to another element, it can be directly connected or coupled to other elements, or there can be intermediate elements. In addition, "connected" or "coupled" used herein can include wireless connection or wireless coupling. The phrase "and / or" used herein includes all or any single unit and all combinations of the associated listed items.

[0041] As will be understood by one of ordinary skill in the art upon reading the present disclosure, all terms used herein (including technical and scientific terms) have the same meaning as commonly understood by one of ordinary skill in the art unless otherwise defined herein. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.

[0042] The utility model content will be further explained through the description of the embodiments in combination with the drawings.

[0043] The drawings of the utility model are only used for illustrative description, and cannot be understood as the limitation of the utility model. In order to better explain the following embodiments, some components of the drawings will be omitted, enlarged or reduced, and the size of actual product is not represented;For those skilled in the art, it is understandable that some well-known structures in the drawings and their description can be omitted.

[0044] Embodiment 1

[0045] As Figure 1 shown, the embodiment proposes a kind of distributed optical fiber acoustic wave sensing system, the distributed optical fiber acoustic wave sensing system at least includes narrow line width laser 3, main optical path structure 2, auxiliary optical path structure 1, first coupler 4, signal processor 5;

[0046] The output end of the narrow line width laser 3 is connected to the input end of the first coupler 4, the first output end of the first coupler 4 is connected to the input end of the main optical path structure 2, the first output end of the main optical path structure 2 is connected to the first input end of the signal processor 5, and the second output end of the main optical path structure 2 is used to be connected to the measured optical fiber;

[0047] The auxiliary optical path structure 1 includes delay module 11, photoelectric converter 12, first signal acquisition circuit 13;

[0048] The second output end of the first coupler 4 is connected to the input end of the delay module 11, the output end of the delay module 11 is connected to the input end of the photoelectric converter 12, the output end of the photoelectric converter 12 is connected to the input end of the first signal acquisition circuit 13, and the output end of the first signal acquisition circuit 13 is connected to the second input end of the signal processor 5;The delay module 11 is used to carry out time delay to the incoming laser beam;

[0049] The output signal of the signal processor 5 is used to feedback to the main optical path structure 2.

[0050] In the embodiment, the narrow line width laser 3 emits a laser beam, the laser beam enters the first coupler 4, two laser beams are formed by the first coupler 4, the first coupler 4 is provided with a first output end and a second output end, the second output end of the first coupler 4 is connected with the auxiliary optical path structure 2, and the first output end of the first coupler 4 is connected with the main optical path structure 2; the laser beam entering the main optical path structure 2 is input into the measured optical fiber 6 after being processed by the main optical path structure 2; when the laser beam is transmitted in the measured optical fiber 6, Rayleigh scattering occurs, and backscattered light is generated, which contains the change information of physical quantities along the line of the measured optical fiber 6, such as vibration, strain and temperature change, that is, the detection task is completed; the detection result is obtained by demodulating the scattered sensing light through the main optical path structure 2, and the detection result is fed back to the signal processor 5; the laser beam entering the auxiliary optical path structure 1 obtains a laser beam with a light signal delayed for a certain time through the delay module 11 in the auxiliary optical path structure 1, the laser beam can realize functions such as signal synchronization, phase adjustment and time compensation, the laser beam after delay enters the photoelectric converter 12, the light signal of the laser beam in the photoelectric converter 12 is converted into an electric signal, the first signal acquisition circuit 13 collects the electric signal and transmits the electric signal to the signal processor 5, the signal processor 5 processes the electric signal to obtain noise information of the auxiliary optical path structure 1; the corresponding software module is integrated in the signal processor 5, an optimization algorithm is provided to complete optimization of the detection result, and the noise information obtained by the auxiliary optical path structure 1 is used to compensate the detection result.

[0051] Optionally, in combination with Figure 1 and Figure 2 The scheme of the utility model is further described as follows, Figure 2 The delay module 11 comprises a third coupler 111, a delay optical path structure 112, a reference optical path structure 113 and a fourth coupler 114, the second output end of the first coupler 4 is connected with the input end of the third coupler 111, the first output end of the third coupler 111 is connected with the input end of the delay optical path structure 112, the second output end of the third coupler 111 is connected with the input end of the reference optical path structure 113, the first input end of the fourth coupler 114 is connected with the output end of the delay optical path structure 112, the second input end of the fourth coupler 114 is connected with the output end of the reference optical path structure 113, and the output end of the fourth coupler 114 is connected with the input end of the photoelectric converter 12.

[0052] In implementation, a laser beam is outputted from the second output end of the first coupler 4 into the delay module 11, and then into the third coupler 111 in the delay module 11, which divides the laser beam into two and makes them enter the delay optical path structure 112 and the reference optical path structure 113 respectively. The delay optical path structure 112 is used to time-delay the laser beam so that its phase is consistent with that of the laser beam in the reference optical path structure 113, which is used to show the phase of the sensing light after detection in the main optical path structure 2. The laser beams in the reference optical path structure 113 and the delay optical path structure 112 enter the fourth coupler 114, and the light signal outputted from the fourth coupler 114 reaches the photoelectric converter 12. The delay module includes but is not limited to the above.

[0053] Optionally, the delay optical path structure 112 includes a delay optical fiber.

[0054] In implementation, the delay optical fiber in the delay optical path structure 112 can precisely control the propagation time of the light signal in the optical fiber by adjusting the length of the optical fiber or using a special structure (such as a fiber Bragg grating) in the optical fiber, so as to realize the delay of the signal. The delay mode is not specifically limited.

[0055] The main optical path structure 2 includes a second coupler 201, an acousto-optic modulator 202, a first light signal processing unit, a circulator 203, a second light signal processing unit, a demodulation module 204 and an acousto-optic modulator driving circuit 205. The first output end of the first coupler 4 is connected to the input end of the second coupler 5, the first output end of the second coupler 5 is connected to the first input end of the acousto-optic modulator 202, the output end of the acousto-optic modulator 202 is connected to the input end of the first light signal processing unit, the output end of the first light signal processing unit is connected to the first transmission end of the circulator 203, the second transmission end of the circulator 203 is used to connect the measured optical fiber 6, the third transmission end of the circulator 203 is connected to the input end of the second light signal processing unit, the output end of the second light signal processing unit is connected to the first input end of the demodulation module 204, and the second input end of the demodulation module 204 is connected to the second output end of the second coupler 15.

[0056] The output end of the demodulation module 204 is connected to the first input end of the signal processor 5, and the output end of the signal processor 5 is connected to the input end of the acousto-optic modulator driving circuit 20. The output end of the acousto-optic modulator driving circuit 20 is connected to the second input end of the acousto-optic modulator 202.

[0057] In specific implementation, the laser beam emitted by the narrow linewidth laser 3 enters the first coupler 4 and is divided into two laser beams, one of which enters the main optical path structure 2. The second coupler 201 in the main optical path structure 2 divides the laser beam into sensing light and local oscillator light. The sensing light first passes through the acousto-optic modulator 202, the first optical signal processing unit, and the circulator 203, and then enters the measured optical fiber 6. In the measured optical fiber 6, scattering occurs and Rayleigh scattering light is generated. The generated Rayleigh scattering light, as sensing light, is reflected by the circulator 203 to the second optical signal processing unit and then enters the demodulation module 204. In the demodulation module 204, the sensing light is demodulated to obtain a detection result. The detection result is processed by the signal processor 5 to obtain noise information. The laser beam entering the auxiliary optical path structure 1 passes through the delay module 11 in the auxiliary optical path structure 1 to obtain a laser beam with a delayed optical signal. The laser beam can realize functions such as signal synchronization, phase adjustment, and time compensation. The laser beam enters the photoelectric converter 12, and the optical signal of the laser beam in the photoelectric converter 12 is converted into an electrical signal. The first signal acquisition circuit 13 collects the electrical signal and transmits it to the signal processor 5. The signal processor 5 processes the electrical signal to obtain noise information of the auxiliary optical path structure 1. The signal processor 5 receives noise information of the main optical path structure 2 from the demodulation module 204 and noise information of the auxiliary optical path structure 1 from the first signal acquisition circuit 13. Subsequently, the noise information of the two can be calculated by difference. According to the obtained difference, the detection result of the main optical path structure 2 is compensated for noise. The specific compensation method is not limited.

[0058] Optionally, the first optical signal processing unit includes a first erbium-doped amplifier 207 and a first optical filter 208. The output end of the acousto-optic modulator 202 is connected to the input end of the first erbium-doped amplifier 207. The output end of the first erbium-doped amplifier 207 is connected to the input end of the first optical filter 208. The output end of the first optical filter 208 is connected to the first transmission end of the circulator 203.

[0059] In specific implementation, the laser beam entering the main optical path structure 2 is divided into local oscillator light and sensing light by the second coupler 201. The sensing light enters the acousto-optic modulator 202 for modulation, which includes noise compensation. The modulated sensing light enters the first erbium-doped amplifier 207, which amplifies the sensing light signal and transmits it to the first optical filter 208. The first optical filter 208 can transmit light of a specific wavelength and reflect or absorb light of other wavelengths, realizing wavelength selection of light waves. The remaining sensing light beam passes through the first optical filter 208 and then enters the circulator 203 to detect the measured optical fiber 6. The filtered sensing light beam can improve the performance of the sensing system to a certain extent.

[0060] Optionally, the first optical signal processing unit further comprises a first isolator 206; an output end of the acousto-optic modulator 202 is connected to an input end of the first isolator 206, and an output end of the first isolator 206 is connected to a first transmission end of the ring oscillator 203 through the first erbium-doped amplifier 207 and the first optical filter 208.

[0061] In implementation, the first isolator 206 receives sensing light from the acousto-optic modulator 202, and allows the optical signal of the sensing light to transmit in one direction and prevents the optical signal of the sensing light from transmitting in the opposite direction, thereby improving the propagation efficiency of the sensing light.

[0062] Optionally, the second optical signal processing unit comprises a second erbium-doped amplifier 211 and a second optical filter 210; a third transmission end of the ring oscillator 203 is connected to an input end of the second erbium-doped amplifier 211, an output end of the second erbium-doped amplifier 211 is connected to an input end of the second optical filter 210, and an output end of the second optical filter 210 is connected to a first input end of the demodulation module 204.

[0063] In implementation, the laser beam entering the main optical path structure 2 is divided into local light and sensing light through the second coupler 201, the sensing light enters the acousto-optic modulator 202 to be modulated into pulsed light, the sensing light after the modulation enters the first isolator 206, then enters the first erbium-doped amplifier 207, and finally enters the ring oscillator 203 through the first optical filter 208; the ring oscillator 203 is provided with a first output end and a second output end, the sensing light enters the measured optical fiber 6 through the first output end of the ring oscillator 203, the sensing light enters the measured optical fiber 6 to be scattered in the measured optical fiber 6, the scattered sensing light is reflected by the ring oscillator 203, the reflected sensing light enters the second erbium-doped amplifier 211 through the second output end of the ring oscillator 203, the second erbium-doped amplifier 211 amplifies the signal of the scattered sensing light to overcome certain fiber loss, and then the sensing light enters the second optical filter 210; the second optical filter 210 can transmit light of a specific wavelength and reflect or absorb light of other wavelengths, thereby realizing wavelength selection of the light wave; finally, the scattered sensing light after the second optical signal processing unit enters the demodulation module 204 to be demodulated to extract the detection result of the measured optical fiber; the optical path structure includes but is not limited to this.

[0064] Optionally, the second optical signal processing unit further comprises a second isolator 209; an output end of the second optical filter 210 is connected to an input end of the second isolator 209, and an output end of the second isolator 209 is connected to a first input end of the demodulation module 204.

[0065] In specific implementation, the output end of the second optical filter 210 is connected to the input end of the demodulation module 204, the output end of the second optical filter 208 is connected to the input end of the demodulation module 204 through the second isolator 209, the second isolator 209 receives the sensing light from the second optical filter 208 and allows the transmission of the sensing light signal in one direction while preventing the propagation of the sensing light signal in the opposite direction, thereby improving the propagation efficiency of the light signal.

[0066] Optionally, in combination with Figure 1 and Figure 3 The scheme of the utility model is further described as follows. Figure 3 As shown in the figure, the demodulation module 204 comprises a fifth coupler 2041, a balanced detector 2042, and a second signal acquisition circuit 2043.

[0067] The output end of the second optical signal processing unit is connected to the first input end of the fifth coupler 2041, the first output end of the fifth coupler 2041 is connected to the first input end of the balanced detector 2042, and the first output end of the balanced detector 2042 is connected to the first input end of the second signal acquisition circuit 2043; the second output end of the second coupler 15 is connected to the second input end of the fifth coupler 2041, the second output end of the fifth coupler 2041 is connected to the second input end of the balanced detector 2042, the second output end of the balanced detector 2042 is connected to the second input end of the second signal acquisition circuit 2043, and the output end of the second signal acquisition circuit 2043 is connected to the first input end of the signal processor 5.

[0068] In specific implementation, after the sensing light is scattered in the circulator 203, it is output through the third transmission end of the circulator 203 and then enters the second optical signal processing unit and the demodulation module 204; when the scattered sensing light and the local oscillation light interfere in the fifth coupler 2041, a beat frequency signal is generated; the beat frequency signal is received by the balanced detector 2042 and subjected to fast Fourier transform (FFT), thereby obtaining the frequency distribution of the reflectivity or scattering signal distributed along the optical fiber; the second signal acquisition circuit 2043 acquires the signal related to the vibration information of the measured optical fiber 6, that is, obtains the detection result of the measured optical fiber 6 and feeds it back to the signal processor 5; the structure of the demodulation module 204 includes but is not limited to the above.

[0069] Optionally, an optical fiber sensing device comprises:

[0070] an OTDR system;

[0071] The distributed optical fiber acoustic sensing system as described above;

[0072] An optical switch, a first selection end of the optical switch is connected to the OTDR system, a second selection end of the optical switch is connected to the distributed optical fiber acoustic sensing system, and a transmission end of the optical switch is used to connect the measured optical fiber 6;

[0073] The OTDR system and the distributed optical fiber acoustic sensing system are connected to the measured optical fiber 6 through the optical switch.

[0074] In particular implementation, the OTDR (Optical Time Domain Reflectometer), also known as optical time domain reflectometer, is a system for detecting, positioning and testing parameters of cable faults in optical fiber communication system; the distributed optical fiber acoustic sensing system as claimed in any one of claims 1-9 is a monitoring system for providing intensity, phase and frequency information of sound vibration events by detecting signals such as sound or vibration in audio frequency range; an optical fiber sensing device can integrate the OTDR system and the distributed optical fiber acoustic sensing system, and is provided with an optical switch, the integrated device has the OTDR system and the distributed optical fiber acoustic sensing system, and system switching is realized through the optical switch, so that multiple measurements of the measured optical fiber are realized, and the optical fiber acoustic sensing device includes but is not limited to the above.

[0075] Further to the utility model scheme content is explained, in the scheme, the laser beam that narrow line width laser 3 sent enters first coupler 4, the laser beam that enters first coupler 4 is divided into two laser beams, respectively enters auxiliary light path structure 1 and main light path structure 2, one of which laser beam enters auxiliary light path structure 1, first enters the delay module 11, passes through third coupler 111 in delay module 11, third coupler 111 further divides into two laser beams and makes it respectively enter delay light path structure 112 and reference light path structure 113, delay light path structure 112 is used to carry out time delay to laser beam, makes its phase with the phase of laser beam in reference light path structure 113 consistent, facilitates to present the phase condition after the sensing light in main light path structure 2 completes detection, the laser beam in reference light path structure 113 is the contrast of laser beam in main light path structure 2, the laser beam that enters reference light path structure 113 and delay light path structure 112 re-enters fourth coupler 114, reaches photoelectric converter 12 by fourth coupler 114, photoelectric converter 12 converts the optical signal of laser beam into electric signal, by this first signal acquisition circuit 13 gathers the electric signal and is fed back to signal processor 5, signal processor 5 carries out analysis to the electric signal gathered and obtains noise information;Another laser beam enters second coupler 5 of main light path structure 2 and is divided into sensing light and local oscillator light, sensing light enters acousto-optic modulator 202, acousto-optic modulator 202 receives the drive signal from acousto-optic modulator drive circuit 205, the drive signal is sent by signal processor 5, signal processor 5 at this time executes modulation drive task.The modulated sensing light enters the first optical signal processing unit, specifically, enters the first isolator 206 first, the first isolator 206 can prevent the reverse propagation of the sensing light, then enters the first erbium-doped amplifier 207, the first erbium-doped amplifier 207 can amplify the sensing light signal, improve the propagation efficiency, and finally enters the first optical filter 208, filters out some unnecessary wavelength light, and the filtered sensing light enters the measured optical fiber 6 through the circulator 203. When propagating in the measured optical fiber 6, the sensing light will scatter to generate corresponding scattered light. The scattered light is reflected into the second optical signal processing unit through the circulator 203, specifically, the reflected scattered light first enters the second erbium-doped amplifier 211, the second erbium-doped amplifier 210 can amplify the reflected scattered light signal, then enters the second optical filter 210, filters out some unnecessary wavelength light, and finally enters the second isolator 209. The second isolator 209 can prevent the reverse propagation of the sensing light. The scattered light contains the physical quantity change information of the measured optical fiber along the line, such as vibration, strain and temperature change. The detection result can be obtained according to the scattering of the sensing light in the measured optical fiber 6. The detection result is fed back to the signal processor 5 through the demodulation module 204. In the demodulation module 204, the sensing light after scattering and the local oscillator light interfere with each other, and the detection result is obtained by obtaining the phase of the interference signal. The detection result is fed back to the signal processor 5, and the signal processor 5 processes the detection result to obtain noise information. The signal processor 5 receives the noise information of the main optical path structure 2 from the demodulation module 204 and the noise information of the auxiliary optical path structure 1 collected by the first signal acquisition circuit 13, processes the noise information of the two, at this time, the signal processor 5 performs the noise information processing and noise compensation task. The algorithm can be combined to perform the task. The signal processor performs difference calculation on the noise information of the two, compensates the detection result of the main optical path structure according to the obtained difference, and the compensation mode is not limited. At the same time, the detection and noise compensation are continuous processes. Noise compensation of the detection result can provide accurate, real-time and reliable detection results.

[0076] Obviously, the above embodiments of the utility model are only examples for clearly illustrating the technical scheme of the utility model, and are not a limitation on the specific embodiments of the utility model. Any modification, equivalent replacement and improvement made within the spirit and principle of the utility model claim should be included in the protection scope of the utility model claim.

Claims

1. A distributed fiber optic acoustic sensing system, comprising: The distributed optical fiber acoustic wave sensing system comprises at least a narrow linewidth laser, a main optical path structure, an auxiliary optical path structure, a first coupler, and a signal processor. An output end of the narrow linewidth laser is connected to an input end of the first coupler, a first output end of the first coupler is connected to an input end of the main optical path structure, a first output end of the main optical path structure is connected to a first input end of the signal processor, and a second output end of the main optical path structure is used for connecting a measured optical fiber. The auxiliary optical path structure comprises a delay module, an optoelectronic converter, and a first signal acquisition circuit. A second output end of the first coupler is connected to an input end of the delay module, an output end of the delay module is connected to an input end of the optoelectronic converter, an output end of the optoelectronic converter is connected to an input end of the first signal acquisition circuit, and an output end of the first signal acquisition circuit is connected to a second input end of the signal processor.

2. A distributed optical fibre acoustic wave sensing system according to claim 1, characterised in that, The delay module comprises a third coupler, a delay optical path structure, a reference optical path structure, and a fourth coupler.

3. A distributed optical fibre acoustic wave sensing system according to claim 2, wherein, The second output end of the first coupler is connected to an input end of the third coupler, a first output end of the third coupler is connected to an input end of the delay optical path structure, a second output end of the third coupler is connected to an input end of the reference optical path structure, a first input end of the fourth coupler is connected to an output end of the delay optical path structure, a second input end of the fourth coupler is connected to an output end of the reference optical path structure, and an output end of the fourth coupler is connected to an input end of the optoelectronic converter.

4. A distributed optical fibre acoustic wave sensing system according to any one of claims 1 to 3, wherein, The delay optical path structure comprises a delay optical fiber. The main optical path structure comprises a second coupler, an acousto-optic modulator, a first optical signal processing unit, a circulator, a second optical signal processing unit, a demodulation module, and an acousto-optic modulator driving circuit. The first output end of the first coupler is connected to an input end of the second coupler, a first output end of the second coupler is connected to a first input end of the acousto-optic modulator, an output end of the acousto-optic modulator is connected to an input end of the first optical signal processing unit, an output end of the first optical signal processing unit is connected to a first transmission end of the circulator, a second transmission end of the circulator is used for connecting a measured optical fiber, a third transmission end of the circulator is connected to an input end of the second optical signal processing unit, an output end of the second optical signal processing unit is connected to a first input end of the demodulation module, and a second input end of the demodulation module is connected to a second output end of the second coupler. An output end of the demodulation module is connected to a first input end of the signal processor, an output end of the signal processor is connected to an input end of the acousto-optic modulator driving circuit, and an output end of the acousto-optic modulator driving circuit is connected to a second input end of the acousto-optic modulator.

5. A distributed optical fibre acoustic wave sensing system according to claim 4, wherein, The first optical signal processing unit comprises a first erbium-doped amplifier and a first optical filter; an output end of the acousto-optic modulator is connected to an input end of the first erbium-doped amplifier, an output end of the first erbium-doped amplifier is connected to an input end of the first optical filter, and an output end of the first optical filter is connected to a first transmission end of the circulator.

6. A distributed optical fibre acoustic wave sensing system according to claim 5, wherein, The first optical signal processing unit further comprises a first isolator; an output end of the acousto-optic modulator is connected to an input end of the first isolator, and an output end of the first isolator is connected to the first transmission end of the circulator through the first erbium-doped amplifier and the first optical filter.

7. A distributed optical fibre acoustic wave sensing system according to claim 4, wherein, The second optical signal processing unit comprises a second erbium-doped amplifier and a second optical filter; a third transmission end of the circulator is connected to an input end of the second erbium-doped amplifier, an output end of the second erbium-doped amplifier is connected to an input end of the second optical filter, and an output end of the second optical filter is connected to a first input end of the demodulation module.

8. A distributed optical fibre acoustic wave sensing system according to claim 7, wherein, The second optical signal processing unit further comprises a second isolator; an output end of the second optical filter is connected to an input end of the second isolator, and an output end of the second isolator is connected to the first input end of the demodulation module.

9. A distributed optical fibre acoustic wave sensing system according to any one of claims 5 to 8, wherein, The demodulation module comprises a fifth coupler, a balanced detector, and a second signal acquisition circuit; an output end of the second optical signal processing unit is connected to a first input end of the fifth coupler, a first output end of the fifth coupler is connected to a first input end of the balanced detector, a first output end of the balanced detector is connected to a first input end of the second signal acquisition circuit; a second output end of the second coupler is connected to a second input end of the fifth coupler, a second output end of the fifth coupler is connected to a second input end of the balanced detector, a second output end of the balanced detector is connected to a second input end of the second signal acquisition circuit, and an output end of the second signal acquisition circuit is connected to a first input end of the signal processor.

10. An optical fiber sensing device, characterized by, comprise: an OTDR system; a distributed optical fiber acoustic sensing system according to any one of claims 1-9; an optical switch, a first selection end of the optical switch is connected to the OTDR system, a second selection end of the optical switch is connected to the distributed optical fiber acoustic sensing system, and a transmission end of the optical switch is used to connect a measured optical fiber; the OTDR system and the distributed optical fiber acoustic sensing system are connected to the measured optical fiber through the optical switch.

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