CN112033521A - A hybrid fiber-optic vibration sensing system with local noise self-filtering - Google Patents

Abstract

The invention relates to a local noise self-filtering hybrid optical fiber vibration sensing system, which adopts a wavelength division multiplexing technology to realize the fusion of forward interference light based on a Michelson interference structure and a Mach-Zehnder interference structure and backward scattering light based on a coherent light time domain reflection structure, and simultaneously realizes the separation of laser with different central wavelengths by means of an optical fiber coupler and a passive filter. The method comprises the steps of utilizing a Mach-Zehnder interference structure to automatically filter local noise, utilizing a Michelson interference structure to carry out waveform reduction on a vibration signal, utilizing a coherent light time domain reflection system to carry out space positioning on the vibration signal, and finally realizing waveform reduction and space positioning of the vibration signal under the local noise. In addition, the forward interference light adopts a random double-feedback phase modulation chaotic light source, so that scattering noise in a light path can be suppressed, and the signal-to-noise ratio of the system is improved.

Description

A hybrid fiber-optic vibration sensing system with local noise self-filtering

technical field

The present invention relates to the technical field of optical fiber sensing, and more particularly, to a hybrid optical fiber vibration sensing system with local noise self-filtering.

Background technique

In recent years, optical fiber vibration sensing technology has the advantages of strong anti-interference and high sensitivity, and is gradually applied in the fields of perimeter security, transportation, and fault diagnosis. The forward interference optical fiber vibration sensing system based on the Michelson interference structure or the Mach-Zehnd interference structure is composed of two single-mode fibers of equal length, which can sense and restore the vibration signal, but the disadvantage is that it is difficult to detect and restore the vibration signal. Vibration signal for positioning. The backscattered optical fiber vibration sensing system based on the coherent light time-domain reflection structure uses the back-scattered light and the intrinsic light to generate the beat frequency signal, which can accurately locate the vibration signal. It is difficult to restore the vibration signal, and at the same time, it is easily interfered by the local environmental noise of the demodulation system, which affects the vibration detection performance of the system.

In order to solve this problem, the present invention adopts wavelength division multiplexing technology, utilizes coupler and passive filter structure, fuses forward interference light and backscattered light, and realizes the pairing of light through Michelson interference structure and coherent light time domain reflection structure. The vibration signal is restored and localized, and the local noise is self-filtered through the Mach Zeid interference structure. In order to suppress noise interference, a wide-spectrum, noise-like chaotic laser is used as the light source of the forward interference structure, which can suppress the scattering noise in the optical fiber and improve the signal-to-noise ratio of the system.

SUMMARY OF THE INVENTION

The invention provides a hybrid optical fiber vibration sensing system with self-filtering of local noise, the purpose of which is to use wavelength division multiplexing technology to fuse forward interference light and backward scattered light, and use Mach Zede interference structure to detect The local noise is self-filtered, and then the vibration signal is restored by the Michelson interference structure. Finally, the vibration signal is spatially located by the coherent optical time-domain reflectometry system, and finally the waveform restoration and spatial positioning of the vibration signal under the local noise are realized. .

The technical solution adopted by the present invention to solve the technical problem is to construct a hybrid optical fiber vibration sensing system for self-filtering of local noise, including:

Laser, first circulator, first fiber coupler, first tunable optical attenuator, first phase modulator, arbitrary waveform generator, first variable fiber delay line, second tunable optical attenuator, second Phase modulator, second variable fiber delay line, second fiber coupler, third fiber coupler, optical isolator, fourth fiber coupler, first filter, fifth fiber coupler, first sensing fiber , the second sensing fiber, the sixth fiber coupler, the first photodetector, the second filter, the third sensing fiber, the first fiber grating device, the fourth sensing fiber, the third filter, the second fiber Grating device, second photodetector, narrow linewidth laser, seventh fiber coupler, acousto-optic modulator, signal generator, erbium-doped fiber amplifier, fourth filter, second circulator, fifth filter, first Eight fiber couplers, balanced photodetectors and data acquisition modules;

The laser is connected to the a port of the first circulator, the b port of the first circulator is connected to the input end of the first fiber coupler, and the output end a port of the first fiber coupler is connected to the first adjustable optical attenuator. The input port is connected to the input port, the output port of the first adjustable optical attenuator is connected to the input port of the first phase modulator, the first phase modulator is connected to the arbitrary waveform generator at the same time, and is modulated and driven by the arbitrary waveform generator. The output port of the switch is connected to the input port of the first variable optical fiber delay line, the output port of the variable optical fiber delay line is connected to the a port of the second optical fiber coupler, and the b port of the first optical fiber coupler is connected to the second adjustable optical fiber. The input port of the attenuator is connected to the input port of the second adjustable optical attenuator, and the output port of the second adjustable optical attenuator is connected to the input port of the second phase modulator; The output port of the modulator is connected to the input port of the second variable fiber delay line, the output port of the second variable fiber delay line is connected to the b port of the second fiber coupler, and the second fiber coupler is connected to the third fiber coupler The b port of the first circulator is connected to the output end of the third fiber coupler, the a port of the third fiber coupler is connected to the input port of the optical isolator, and the above devices form a chaotic light source;

The output port of the optical isolator is connected with the c port of the fourth fiber coupler, the f port of the fourth fiber coupler is connected with the input port of the first filter, and the output port of the first filter is connected with the input port of the fifth fiber coupler The output port a of the fifth fiber coupler is connected to the input port a of the sixth fiber coupler through the first sensing fiber, and the output port b of the fifth fiber coupler is connected to the sixth fiber coupler through the second sensing fiber. The input port b of the six-fiber coupler is connected to the port b, the output port of the sixth fiber coupler is connected to the input port of the first photodetector, the output port of the first photodetector is connected to the data acquisition module, and the output port of the fourth fiber coupler is connected to the data acquisition module. The d port is connected with the input port of the second filter, the output port of the second filter is connected with the first fiber grating device through the third sensing fiber, and the e port of the fourth fiber coupler is connected with the third fiber grating device through the fourth sensing fiber. The input port of the filter is connected, and the output port of the third filter is connected to the second fiber grating device; the b port of the fourth fiber coupler is connected to the input port of the second photodetector, and the output port of the second photodetector is connected to the second fiber grating device. The data acquisition module is connected, the narrow linewidth laser is connected to the input end of the seventh fiber coupler, the output port a of the seventh fiber coupler is connected to the input port a of the eighth fiber coupler, and the output of the seventh fiber coupler The terminal b port is connected with the input port of the acousto-optic modulator. The acousto-optic modulator is connected to the signal generator and is modulated and driven by the signal generator. The output port of the acousto-optic modulator is connected with the input port of the erbium-doped fiber amplifier. The output port of the fourth filter is connected to the input port of the fourth filter, the output port of the fourth filter is connected to the a port of the second circulator, the b port of the second circulator is connected to the a port of the fourth fiber coupler, and the second The c port of the circulator is connected with the input port of the fifth filter, the output port of the fifth filter is connected with the input port b of the eighth fiber coupler, and the output port of the eighth fiber coupler is connected with the input of the balanced photodetector The ports are connected, and the output port of the balanced photodetector is connected with the data acquisition module.

Different from the prior art, a hybrid optical fiber vibration sensing system with local noise self-filtering of the present invention adopts wavelength division multiplexing technology, and realizes Michelson interference by using two laser light sources with large difference in center wavelength. The fusion of the forward interference light based on the structure and the Mach-Zehnder interference structure and the backscattered light based on the coherent light time domain reflection structure, and the use of fiber couplers and passive filter components to achieve the separation of lasers with different center wavelengths; The invention adopts the Michelson interference structure based on the forward interference light, uses the change of the forward interference light intensity formed by the sensing arm and the reference arm of equal length to restore the vibration waveform, and uses the coherent light time domain reflection structure to restore the vibration waveform. Compared with the conventional method, it has the advantages of simple structure, no need for complex demodulation algorithm and demodulation structure, and large system frequency response range; the present invention adopts the Mach-Zehnder interference structure based on forward interference light, and uses the sensing arm and the reference arm of equal length. The change of the forward interference light intensity formed realizes the self-filtering of the local environmental noise of the demodulation system, and improves the anti-interference ability of the system; the present invention adopts the chaotic light source of random double feedback phase modulation as the laser light source of the forward interference light , has the advantages of wide spectrum and noise-like, can suppress the scattered noise in the optical path, and improve the signal-to-noise ratio of the system.

Description of drawings

The present invention will be further described below in conjunction with the accompanying drawings and embodiments, in which:

FIG. 1 is a schematic structural diagram of a hybrid optical fiber vibration sensing system for self-filtering of local noise provided by the present invention.

Detailed ways

In order to have a clearer understanding of the technical features, objects and effects of the present invention, the specific embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

Referring to FIG. 1 , the present invention provides a hybrid fiber-optic vibration sensing system for self-filtering of local noise, including: a laser 1 , a first circulator 2 , a first fiber coupler 3 , and a first tunable optical attenuator 4 , the first phase modulator 5, the arbitrary waveform generator 6, the first variable fiber delay line 7, the second adjustable optical attenuator 8, the second phase modulator 9, the second variable fiber delay line 10, the second Fiber coupler 11 , third fiber coupler 12 , optical isolator 13 , fourth fiber coupler 15 , first filter 16 , fifth fiber coupler 17 , first sensing fiber 18 , second sensing fiber 19 , the sixth fiber coupler 20, the first photodetector 21, the second filter 22, the third sensing fiber 23, the first fiber grating device 24, the fourth sensing fiber 25, the third filter 26, the second fiber grating device 27, second photodetector 28, narrow linewidth laser 29, seventh fiber coupler 30, acousto-optic modulator 31, signal generator 32, erbium-doped fiber amplifier 33, fourth filter 34, second circulator 35, fifth filter 36, eighth fiber coupler 37, balanced photodetector 38 and data acquisition module 39;

The laser 1 is connected to the a port of the first circulator 2, the b port of the first circulator 2 is connected to the input end of the first fiber coupler 3, and the output end a port of the first fiber coupler 3 is connected to the first optical fiber coupler 3. The input port of the dimming attenuator 4 is connected, the output port of the first dimming attenuator 4 is connected with the input port of the first phase modulator 5, and the first phase modulator 5 is connected to the arbitrary waveform generator 6 at the same time. The waveform generator 6 is modulated and driven, the output port of the first phase modulator 5 is connected with the input port of the first variable fiber delay line 7, and the output port of the variable fiber delay line 7 is connected with the a port of the second fiber coupler 11 , the b port of the first fiber coupler 3 is connected to the input port of the second adjustable optical attenuator 8, and the output port of the second adjustable optical attenuator 8 is connected to the input port of the second phase modulator 9; the second phase The modulator 9 is connected to the arbitrary waveform generator 6, and is modulated and driven by the arbitrary waveform generator 6. The output port of the second phase modulator 9 is connected to the input port of the second variable fiber delay line 10, and the second variable fiber delay line 10 The output port is connected to the b port of the second fiber coupler 11, the second fiber coupler 11 is connected to the b port of the third fiber coupler 12, the c port of the first circulator 2 is connected to the output of the third fiber coupler 12 The a port of the third fiber coupler 12 is connected to the input port of the optical isolator 13, and the above components form a chaotic light source 14;

The output port of the optical isolator 13 is connected to the c port of the fourth fiber coupler 15, the f port of the fourth fiber coupler 15 is connected to the input port of the first filter 16, and the output port of the first filter 16 is connected to the fifth The input end of the fiber optic coupler 17 is connected, the output end a port of the fifth fiber optic coupler 17 is connected to the input end a port of the sixth fiber optic coupler 20 through the first sensing fiber 18, and the output end of the fifth fiber optic coupler 17 is connected. The b port is connected to the input port b of the sixth fiber coupler 20 through the second sensing fiber 19, and the output end of the sixth fiber coupler 20 is connected to the input port of the first photodetector 21. The first photodetector 21 The output port of the second filter 22 is connected to the data acquisition module 39, the d port of the fourth fiber coupler 15 is connected to the input port of the second filter 22, and the output port of the second filter 22 is connected to the first fiber grating via the third sensing fiber 23. The device 24 is connected, the e port of the fourth fiber coupler 15 is connected to the input port of the third filter 26 through the fourth sensing fiber 25, and the output port of the third filter 26 is connected to the second fiber grating device 27; The b port of the fiber coupler 15 is connected to the input port of the second photodetector 28 , the output port of the second photodetector 28 is connected to the data acquisition module 39 , and the narrow linewidth laser 29 is connected to the input end of the seventh fiber coupler 30 Connected, the output port a of the seventh fiber coupler 30 is connected with the input port a of the eighth fiber coupler 37, the output port b of the seventh fiber coupler 30 is connected with the input port of the acousto-optic modulator 31, and the sound The optical modulator 31 is connected to the signal generator 32, and is modulated and driven by the signal generator 32. The output port of the acousto-optic modulator 31 is connected to the input port of the erbium-doped fiber amplifier 33, and the output port of the erbium-doped fiber amplifier 33 is connected to the fourth filter. 34 is connected to the input port, the output port of the fourth filter 34 is connected to the a port of the second circulator 35, the b port of the second circulator 35 is connected to the a port of the fourth fiber coupler 15, and the second circulator 35 is connected to the a port of the fourth fiber coupler 15. The c port is connected with the input port of the fifth filter 36, the output port of the fifth filter 36 is connected with the input port b of the eighth fiber coupler 37, and the output port of the eighth fiber coupler 37 is connected with the balanced photodetector 38 is connected to the input port, and the output port of the balanced photodetector 38 is connected to the data acquisition module 39 .

The laser 1 generates a laser with a center wavelength of 1310 nm and reaches the first fiber coupler 3 through the a port of the first circulator 2. The output optical power of the a port of the first fiber coupler 3 accounts for 50%. The laser is adjusted by the first The optical attenuator 4 reaches the first phase modulator 5, the first phase modulator 5 is modulated by the random signal output by the arbitrary waveform generator 6, and the laser output from the first phase modulator 5 reaches the first phase modulator 5 through the first variable fiber delay line 7. Two optical fiber couplers 11, the output optical power of the b port of the first optical fiber coupler 3 accounts for 50% of the laser light to reach the second phase modulator 9 through the second adjustable optical attenuator 8, and the second phase modulator 9 receives any The random signal generated by the waveform generator 6 is modulated, the laser output from the second phase modulator 9 reaches the second fiber coupler 11 through the second variable fiber delay line 10, and the laser output from the second fiber coupler 11 reaches the third fiber coupler At the same time, the laser output from the c port of the first circulator 2 reaches the third fiber coupler 12, and the laser output from the a port of the third fiber coupler 12 reaches the isolator 13. The above components form a chaotic light source 14. The isolator 13 The output chaotic laser is input by the c port of the fourth fiber coupler 15, and the f port of the fourth fiber coupler 15 outputs the chaotic laser with the center wavelength of 1310nm, after being filtered by the first filter 16, reaches the fifth fiber coupler 17 , the output optical power of the port a of the fifth fiber coupler 17 accounts for 50% of the laser light to reach the sixth fiber coupler 20 through the first sensing fiber 18, and the output optical power proportion of the port b of the fifth fiber coupler 17 is 50% of the laser light reaches the sixth fiber coupler 20 through the second sensing fiber 19, and the laser output from the sixth fiber coupler 20 is detected by the first photodetector 21, collected by the data acquisition module 39, and local noise is obtained through data processing The chaotic light with a center wavelength of 1310 nm output by the d port of the fourth fiber coupler 15 is filtered by the second filter 22, and then reaches the first fiber grating device 24 through the third sensing fiber 23, and the first fiber grating The chaotic light with a center wavelength of 1310 nm reflected by the device 24 passes through the third sensing fiber 23 and the second filter 22, and enters the d port of the fourth fiber coupler 15, and the chaotic light output from the e port of the fourth fiber coupler 15 passes through the first fiber. The four sensing fibers 25 reach the second fiber grating device 27 through the third filter 26 . The second fiber grating device 27 reflects back the chaotic light with a center wavelength of 1310 nm, passes through the third filter 26 and the fourth sensing fiber 25 , and enters The e port of the fourth fiber coupler 15, the two beams of chaotic light entering the fourth fiber coupler 15 d port and the fourth fiber coupler 15 e port will interfere when they meet, and the interference light will be generated by the b of the fourth fiber coupler 15. port output, and is converted into an electrical signal in the second photodetector 28, and finally collected by the data acquisition module 39, the interference signal can detect the waveform of the signal to be measured, and the waveform to be measured can be restored through data processing; narrow linewidth laser 29 Generate a narrow linewidth laser with a center wavelength of 1550nm via the seventh fiber coupler The a port of 30 outputs 1% of the intrinsic light to the a port of the eighth fiber coupler 37, and the b port of the seventh fiber coupler 30 outputs 99% of the laser light modulated into pulsed light by the acousto-optic modulator 31, and the acousto-optic modulation The modulated signal of the circulator 31 is sent out by the signal generator 32. After the pulsed light is amplified by the erbium-doped fiber amplifier 33, the noise floor is filtered out by the fourth filter 34, and then enters from the port a of the second circulator 35, from the first The b port output of the second circulator 35 then enters the a port of the fourth fiber coupler 15, and enters the fourth sensing fiber 25 from the e port of the fourth fiber coupler 15, and the pulsed light is in the fourth sensing fiber 25. Backward Rayleigh scattered light carrying vibration information is generated during medium transmission, and the backward Rayleigh scattered light is output through the a port of the fourth fiber coupler 15, enters the b port of the second circulator 35, and passes through the second circulator 35. The c port reaches the fifth filter 36, and filters out the back Rayleigh scattered light with a center wavelength of 1550 nm, and then enters the b port of the eighth fiber coupler 37, and the current input from the a port of the eighth fiber coupler 37 The characteristic light generates a beat frequency, and the beat frequency signal is detected by the balanced photodetector 38 and converted into an electrical signal, which is finally collected by the data acquisition module 39. After data processing, the position information of the vibration to be measured can be obtained. A hybrid optical fiber vibration sensing system with local noise self-filtering composed of the device can realize the waveform restoration and spatial positioning of the vibration signal to be measured under the interference of local noise.

The embodiments of the present invention have been described above in conjunction with the accompanying drawings, but the present invention is not limited to the above-mentioned specific embodiments, which are merely illustrative rather than restrictive. Under the inspiration of the present invention, without departing from the scope of protection of the present invention and the claims, many forms can be made, which all belong to the protection of the present invention.

Claims (1)

1. A local noise self-filtering hybrid fiber optic vibration sensing system, comprising:

the optical fiber phase-change optical fiber laser comprises a laser (1), a first circulator (2), a first optical fiber coupler (3), a first variable optical attenuator (4), a first phase modulator (5), an arbitrary waveform generator (6), a first variable optical fiber delay line (7), a second variable optical attenuator (8), a second phase modulator (9), a second variable optical fiber delay line (10), a second optical fiber coupler (11), a third optical fiber coupler (12), an optical isolator (13), a fourth optical fiber coupler (15), a first filter (16), a fifth optical fiber coupler (17), a first sensing optical fiber (18), a second sensing optical fiber (19), a sixth optical fiber coupler (20), a first photoelectric detector (21), a second filter (22), a third sensing optical fiber (23), a first optical fiber grating device (24), a fourth sensing optical fiber (25), a third filter (26), The device comprises a second fiber grating device (27), a second photoelectric detector (28), a narrow linewidth laser (29), a seventh fiber coupler (30), an acousto-optic modulator (31), a signal generator (32), an erbium-doped fiber amplifier (33), a fourth filter (34), a second circulator (35), a fifth filter (36), an eighth fiber coupler (37), a balanced photoelectric detector (38) and a data acquisition module (39);

wherein, the laser (1) is connected with the port a of the first circulator (2), the port b of the first circulator (2) is connected with the input end of the first optical fiber coupler (3), the port a of the output end of the first optical fiber coupler (3) is connected with the input port of the first variable optical attenuator (4), the output port of the first variable optical attenuator (4) is connected with the input port of the first phase modulator (5), the first phase modulator (5) is simultaneously connected with the arbitrary waveform generator (6) and is driven by the arbitrary waveform generator (6), the output port of the first phase modulator (5) is connected with the input port of the first variable optical fiber delay line (7), the output port of the variable optical fiber delay line (7) is connected with the port a of the second optical fiber coupler (11), the port b of the first optical fiber coupler (3) is connected with the input port of the second variable optical attenuator (8), the output port of the second variable optical attenuator (8) is connected with the input port of a second phase modulator (9); the second phase modulator (9) is connected with the arbitrary waveform generator (6) and is modulated and driven by the arbitrary waveform generator (6), the output port of the second phase modulator (9) is connected with the input port of the second variable optical fiber delay line (10), the output port of the second variable optical fiber delay line (10) is connected with the b port of the second optical fiber coupler (11), the second optical fiber coupler (11) is connected with the b port of the third optical fiber coupler (12), the c port of the first circulator (2) is connected with the output port of the third optical fiber coupler (12), the a port of the third optical fiber coupler (12) is connected with the input port of the optical isolator (13), and the chaotic light source (14) is formed by the devices;

an output port of the optical isolator (13) is connected with a port c of a fourth optical fiber coupler (15), a port f of the fourth optical fiber coupler (15) is connected with an input port of a first filter (16), an output port of the first filter (16) is connected with an input end of a fifth optical fiber coupler (17), an output end port a of the fifth optical fiber coupler (17) is connected with an input end port a of a sixth optical fiber coupler (20) through a first sensing optical fiber (18), an output end port b of the fifth optical fiber coupler (17) is connected with an input end port b of the sixth optical fiber coupler (20) through a second sensing optical fiber (19), an output end of the sixth optical fiber coupler (20) is connected with an input port of a first photoelectric detector (21), an output port of the first photoelectric detector (21) is connected with a data acquisition module (39), a port d of the fourth optical fiber coupler (15) is connected with an input port of a second filter (22), the output port of the second filter (22) is connected with the first fiber grating device (24) through a third sensing fiber (23), the e port of the fourth fiber coupler (15) is connected with the input port of a third filter (26) through a fourth sensing fiber (25), and the output port of the third filter (26) is connected with the second fiber grating device (27); a b port of the fourth optical fiber coupler (15) is connected with an input port of a second photoelectric detector (28), an output port of the second photoelectric detector (28) is connected with a data acquisition module (39), a narrow linewidth laser (29) is connected with an input end of a seventh optical fiber coupler (30), an output end a port of the seventh optical fiber coupler (30) is connected with an input end a port of an eighth optical fiber coupler (37), an output end b port of the seventh optical fiber coupler (30) is connected with an input port of an acousto-optic modulator (31), the acousto-optic modulator (31) is connected with a signal generator (32) and is driven by the signal generator (32) in a modulation way, an output port of the acousto-optic modulator (31) is connected with an input port of a erbium-doped optical fiber amplifier (33), an output port of the erbium-doped optical fiber amplifier (33) is connected with an input port of a fourth filter (34), an output port of the fourth filter (34) is connected with a port a of a second circulator (35), a port b of the second circulator (35) is connected with a port a of a fourth optical fiber coupler (15), a port c of the second circulator (35) is connected with an input port of a fifth filter (36), an output port of the fifth filter (36) is connected with a port b of an input end of an eighth optical fiber coupler (37), an output end of the eighth optical fiber coupler (37) is connected with an input port of a balanced photoelectric detector (38), and an output port of the balanced photoelectric detector (38) is connected with a data acquisition module (39).

Images