CN112033523A - Optical fiber distributed disturbance sensing system based on double Michelson interferometers - Google Patents
Optical fiber distributed disturbance sensing system based on double Michelson interferometers Download PDFInfo
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Abstract
The invention discloses an optical fiber distributed disturbance sensing system based on a double-Michelson interferometer, which mainly comprises a dual-wavelength light source, a light intensity modulator, an optical isolator, an optical beam splitter, a first wavelength division multiplexer, a second wavelength division multiplexer, a first Michelson interferometer, a second Michelson interferometer, a first disturbance signal demodulation module, a second disturbance signal demodulation module, a disturbance signal positioning module, a disturbance sensing optical fiber and an optical signal transmission optical fiber. Aiming at the requirements of the optical fiber distributed disturbance sensor on reducing the optical fiber resource occupation and the signal detection noise, the invention can realize the monitoring and the positioning of the disturbance signal by adopting one disturbance sensing optical fiber, can realize the monitoring and the positioning of the disturbance signal of a long-distance pipeline, a land optical cable or a submarine cable and the like by adding one optical signal transmission optical fiber, has less optical fiber resource occupation and is suitable for the application occasion with short optical fiber resources.
Description
Technical Field
The invention relates to the field of optical fiber sensing, in particular to an optical fiber distributed disturbance sensing system based on a double Michelson interferometer.
Background
The optical fiber distributed disturbance sensing system usually adopts an optical interferometry technology, can measure the change of a phase disturbance signal on the whole optical fiber length dimension along with time, has the advantages of high sensitivity, long detection distance, easiness in installation and maintenance and the like, and has wide application in the fields of perimeter security, pipeline monitoring, submarine cable monitoring and the like. The optical fiber distributed disturbance sensing system usually adopts various interferometers and combinations thereof to realize disturbance detection and positioning, such as a double sagnac interferometer (patent CN101487723), a double mach-zehnder interferometer (patent CN101008583), and the like. According to the distributed disturbance sensing system based on the bidirectional mach-zehnder interferometer, which is proposed in patent CN101008583, the position of a disturbance point is obtained by using the time difference of transmission of a disturbance signal on two arms of the bidirectional mach-zehnder interferometer, the sensitivity is high, and the real-time performance is strong, but when the distributed disturbance sensing system is applied to remote distributed disturbance detection, the problem of interference signal attenuation caused by the difference of polarization states of two arms of the mach-zehnder interferometer needs to be considered, and polarization control needs to be added in an optical path system, as described in patent CN 103149639. And the distributed disturbance sensing system needs 4 optical fibers to realize signal detection and transmission, wherein two optical fibers are used as interferometer double-arm sensing optical fibers, and the other two optical fibers are used as signal transmission optical fibers. In practical engineering applications, the optical fiber resources in the optical communication cables and the optical submarine cables are increasingly strained, and the excessive optical fiber occupation may cause difficulty in optical fiber distribution. Patent CN104729548 proposes an improved distributed disturbance sensing system based on a bidirectional mach-zehnder interferometer, which uses a circulator to replace part of an optical fiber coupler, and can use 3 optical fibers to realize signal detection and positioning, thereby reducing the occupation of optical fiber resources. For all the distributed disturbance sensing systems based on the double Mach-Zehnder interferometers, the same light source is adopted for transmission in a direction after being shunted, and the back scattering light of the light transmitted in one direction is superposed to the interference light signal in the other direction, so that the demodulation noise of the interference signal is increased, and the detection capability of the system on the weak disturbance signal is weakened.
Disclosure of Invention
The invention aims to overcome the defects in the prior art and provides an optical fiber distributed disturbance sensing system based on a double Michelson interferometer.
The purpose of the invention is achieved by the following technical scheme: the optical fiber distributed disturbance sensing system based on the double Michelson interferometer mainly comprises a double-wavelength light source, a light intensity modulator, an optical isolator, an optical beam splitter, a first wavelength division multiplexer, a second wavelength division multiplexer, a first Michelson interferometer, a second Michelson interferometer, a first disturbance signal demodulation module, a second disturbance signal demodulation module, a disturbance signal positioning module, a disturbance sensing optical fiber and an optical signal transmission optical fiber, wherein input and output ports of the double-wavelength light source, the light intensity modulator, the optical isolator and the optical beam splitter are sequentially connected, PASS ends of the first wavelength division multiplexer and the second wavelength division multiplexer are respectively connected with two output ports of the optical beam splitter, REFLECT ends of the first wavelength division multiplexer and the second wavelength division multiplexer are respectively connected with the first disturbance signal demodulation module and the second disturbance signal demodulation module, two ports of a first Michelson interferometer are respectively connected with a COMMOM end of a first wavelength division multiplexer and one end of a disturbance sensing optical fiber, two ports of a second Michelson interferometer are respectively connected with the other end of the disturbance sensing optical fiber and one end of an optical signal transmission optical fiber, the other end of the optical signal transmission optical fiber is connected with a COMMOM end of a second wavelength division multiplexer, and outputs of a first disturbance signal demodulation module and a second disturbance signal demodulation module are connected with the input of a disturbance signal positioning module.
The first Michelson interferometer and the second Michelson interferometer are composed of 50/50 optical fiber couplers, a first 90-degree Faraday rotating mirror, an optical fiber delay coil and a second 90-degree Faraday rotating mirror, and the first Michelson interferometer and the second Michelson interferometer have the same interference arm length difference.
The dual-wavelength light source emergent light comprises two wavelengths which are respectively matched with PASS end transmission wavelengths of the first wavelength division multiplexer and the second wavelength division multiplexer.
The types of the light intensity modulator include an electro-optic modulator, an acousto-optic modulator, and an optical switch.
The optical beam splitter is 50/50 optical fiber coupler, and one of the wavelength division multiplexers of the first wavelength division multiplexer and the second wavelength division multiplexer is connected with the PASS end and the REFLECT end respectively.
The disturbance sensing optical fiber is a common single-mode optical fiber and a single-mode optical fiber adopting a vibration sensitization design.
The optical signal transmission fiber is a single mode fiber.
And the signal demodulation of the first disturbing signal demodulation module and the signal demodulation of the second disturbing signal demodulation module are synchronized in time.
And the disturbing signal positioning module calculates the position of an external disturbing signal on the disturbing sensing optical fiber according to the correlation and time delay of the disturbing signal demodulation results output by the first disturbing signal demodulation module and the second disturbing signal demodulation module.
The invention has the beneficial effects that: aiming at the requirements of the optical fiber distributed disturbance sensor on reducing the occupation of optical fiber resources and reducing signal detection noise, the invention can realize the monitoring and positioning of disturbance signals by adopting one disturbance sensing optical fiber, can realize the monitoring and positioning of disturbance signals of long-distance pipelines, land optical cables or submarine cables and the like by adding one optical signal transmission optical fiber, has less occupation of the optical fiber resources and is suitable for the application occasion with short optical fiber resources; the dual-wavelength light source and the corresponding wavelength division multiplexer are combined, the wavelengths of two paths of sensing optical signals transmitted in opposite directions are different, the influence of the back scattering light of the sensing and transmitting optical signals in one direction on the sensing optical signals in the other direction is avoided, the back scattering noise of disturbance demodulation signals is low, the detection capability of weak disturbance signals is enhanced, and the method is particularly suitable for long-distance distributed disturbance sensing; the optical fiber resource occupation is less, the influence of optical backscattering noise is small, and the method is particularly suitable for long-distance distributed disturbance sensing; the distributed acoustic signal demodulation method is applied to a sounding integration project and is used as a signal demodulation scheme of a sounding integration cable, and distributed acoustic signal detection and positioning are achieved.
Drawings
FIG. 1 is a block diagram of the system architecture of the present invention.
Fig. 2 is a block diagram of the michelson interferometer of the present invention.
Fig. 3 is a schematic diagram of optical signal transmission and interference according to the present invention.
Fig. 4 is a schematic diagram of synchronous demodulation results output by the first disturbing signal demodulating module and the second disturbing signal demodulating module after a certain disturbing signal is applied.
Description of reference numerals: the optical fiber disturbance sensor comprises a dual-wavelength light source 1, a light intensity modulator 2, an optical isolator 3, an optical beam splitter 4, a first wavelength division multiplexer 5, a second wavelength division multiplexer 6, a first Michelson interferometer 7, a second Michelson interferometer 8, a first disturbance signal demodulation module 9, a second disturbance signal demodulation module 10, a disturbance signal positioning module 11, a disturbance sensing optical fiber 12, an optical signal transmission optical fiber 13, a single-pulse optical signal 14, a double-pulse optical signal 15, a double-pulse time-delay optical signal 16, a disturbance optical signal 17, an 50/50 optical fiber coupler 701, a first 90-degree Faraday rotator 702, an optical fiber delay coil 703 and a second 90-degree Faraday rotator 704.
Detailed Description
The invention will be described in detail below with reference to the following drawings:
example (b): as shown in fig. 1-2, the optical fiber distributed disturbance sensing system based on the double-michelson interferometer mainly includes a dual-wavelength light source 1, a light intensity modulator 2, an optical isolator 3, an optical splitter 4, a first wavelength division multiplexer 5, a second wavelength division multiplexer 6, a first michelson interferometer 7, a second michelson interferometer 8, a first disturbance signal demodulation module 9, a second disturbance signal demodulation module 10, a disturbance signal positioning module 11, a disturbance sensing optical fiber 12, and an optical signal transmission optical fiber 13, where the dual-wavelength light source 1, the light intensity modulator 2, the optical isolator 3, and the optical splitter 4 are connected in sequence, and the light intensity modulator 2 includes an electro-optical modulator, an acousto-optical modulator, and an optical switch. PASS ends of the first wavelength division multiplexer 5 and the second wavelength division multiplexer 6 are respectively connected with two output ports of the optical splitter 4, reflex ends of the first wavelength division multiplexer 5 and the second wavelength division multiplexer 6 are respectively connected with a first disturbing signal demodulating module 9 and a second disturbing signal demodulating module 10, two ports of the first michelson interferometer 7 are respectively connected with a COMMOM end of the first wavelength division multiplexer 5 and one end of a disturbing sensing optical fiber 12, two ports of the second michelson interferometer 8 are respectively connected with the other end of the disturbing sensing optical fiber 12 and one end of an optical signal transmission optical fiber 13, and the disturbing sensing optical fiber 12 is a common single-mode optical fiber and a single-mode optical fiber adopting a vibration sensitivity enhancing design. The optical signal transmission fiber 13 is a single mode fiber. The other end of the optical signal transmission fiber 13 is connected with the COMMOM end of the second wavelength division multiplexer 6, and the outputs of the first disturbing signal demodulating module 9 and the second disturbing signal demodulating module 10 are connected with the input of the disturbing signal positioning module 11. The first michelson interferometer 7 and the second michelson interferometer 8 are composed of 50/50 fiber coupler 701, a first 90 ° faraday rotator 702, a fiber delay coil 703, and a second 90 ° faraday rotator 704, and the first michelson interferometer 7 and the second michelson interferometer 8 have the same difference in arm length. The light emitted by the dual-wavelength light source 1 comprises two wavelengths which are respectively matched with the PASS end transmission wavelengths of the first wavelength division multiplexer 5 and the second wavelength division multiplexer 6. The optical splitter 4 is 50/50 optical fiber coupler, and one of the wavelength division multiplexers of the PASS end and the reflex end respectively connected with the first wavelength division multiplexer 5 and the second wavelength division multiplexer 6. The signal demodulation of the first and second disturbing signal demodulation modules 9, 10 is synchronized in time. The disturbing signal positioning module 11 calculates the position of the external disturbing signal on the disturbing sensing optical fiber 12 according to the correlation and the time delay of the disturbing signal demodulation results output by the first disturbing signal demodulation module 9 and the second disturbing signal demodulation module 10.
The principle of the invention is as follows: the optical fiber distributed disturbance sensing system adopts sensing optical fibers to respond to disturbance signals such as external vibration, sound and the like. The sensing optical fiber converts the disturbance signal into the interference phase change of the optical interferometer, and disturbance information is obtained through optical phase demodulation. The invention adopts one sensing optical fiber to realize the sensing response of the disturbance signal, and saves the optical fiber resource compared with the traditional Mach-Zehnder interferometer which needs two optical fibers as two arms of the interferometer. The sensing optical fiber transmits a double-pulse signal with a certain time delay, and when external disturbance exists on the sensing optical fiber, the response of front and back pulses in a group of double-pulse signals to the same external disturbance signal has time delay. When the two optical pulses are superposed to generate interference, the interference phase difference is a time delay difference signal of the disturbance signal, and the external disturbance information can be obtained by demodulating the phase signal of the time delay difference. Unidirectional disturbance signal demodulation cannot acquire disturbed position information. The invention solves the disturbance position information according to the time delay between two-way disturbance signals by synchronously demodulating the two-way disturbance signals.
The output light of the dual-wavelength light source 1 is modulated by the light intensity modulator 2 to become a single-pulse light signal 14 with a certain period and duty cycle, as shown in fig. 3. The light intensity modulator 2 may be any of various types of optical devices having a light intensity modulation function, such as electro-optical, acousto-optic, or on-beam. The optical splitter 4 may be an 50/50 fiber coupler or a wavelength division multiplexer having a PASS terminal and a REFLECT terminal connected to the first wavelength division multiplexer 5 and the second wavelength division multiplexer 6, respectively. The optical isolator 3 is used to isolate the optical signal returned through the optical splitter 4. The single pulse optical signal 14 passes through the optical isolator 3 and the optical beam splitter 4 and then is divided into two paths of optical signals to be transmitted in opposite directions. After the single pulse optical signal 14 transmitted clockwise in fig. 3 passes through the first wavelength division multiplexer 5, only the first optical wavelength matching the PASS wavelength of the first wavelength division multiplexer 5 can enter the first michelson interferometer 7, and exits from the other end of the first michelson interferometer 7 to form the dual pulse optical signal 15. When the double-pulse optical signal 15 is transmitted through the disturbance sensing optical fiber 12, there is a time delay in the response of the double-pulse to the external disturbance signal, so that different phase differences are accumulated between the double-pulse signals, and the phase differences include external disturbance information. After the double-pulse optical signal 15 passes through the second michelson interferometer 8, the double-pulse optical signal 15 and the double-pulse time delay optical signal 16 output by the double arms of the second michelson interferometer 8 are overlapped and interfered to obtain an interference optical signal 17. Because the arm length differences of the two michelson interferometers are consistent, 3 optical pulses exist in one period of the interference optical signal 17, wherein the middle optical pulse is an interference pulse, and the interference phase difference contains external disturbance information. The output light from the other output port of the optical splitter 4 is transmitted counterclockwise, and the interference optical signal 17 is similar to the clockwise direction, but the optical signal wavelength is the second optical wavelength matching the PASS wavelength of the second wavelength division multiplexer 6. The interference optical signals 17 in the clockwise direction and the counterclockwise direction respectively enter the second disturbing signal demodulation module 10 and the first disturbing signal demodulation module 9 to perform synchronous interference phase demodulation, so as to obtain external disturbance information sensitive in the clockwise direction and the counterclockwise direction, and a typical phase demodulation result is shown in fig. 4. The two paths of bidirectional synchronous demodulation signals enter the disturbing signal positioning module 11, and are subjected to operations such as correlation time delay calculation, so that the position information of the external disturbing signal on the disturbing sensing optical fiber 12 is obtained.
Due to the existence of time delay in response of the clockwise transmission light and the counterclockwise transmission light to the external disturbance signal, a certain time delay exists between the two demodulation phase signals in fig. 4, and the time delay Δ t of the two signals is 0.0002544 s. The disturbance sensing fiber 12 and the optical signal transmission fiber 13 corresponding to the test result in fig. 4 are respectively ordinary single-mode fibers with a nominal length of about 25km of a manufacturer, and a 1kHz sinusoidal disturbance signal is applied to one end of the disturbance sensing fiber 12 close to the first michelson interferometer 7. Assuming that the total length of the disturbance sensing fiber 12 and the optical signal transmission fiber 13 is L0, and v is the transmission rate of the optical signal in the optical fiber, the length of the disturbance signal from the COMMOM end of the second wavelength division multiplexer 6 is L1 ═ L0+ v Δ t)/2, and the disturbance signal positioning module 11 performs positioning calculation according to this formula. For the test signal shown in fig. 4, Δ t is 0.0002544s, L0 is measured by the factory nominal length of 50km, and the optical signal transmission rate v is measured by 2.04 × 108m/s, then the calculated disturbance position L1 is (L0+ v Δ t)/2 is 51.00km, which is substantially consistent with the factory nominal length of 50km, which illustrates the feasibility of the distributed disturbance sensing system for detecting and positioning the disturbance signal. The calculated result and the nominal result have 2% deviation, mainly resulting from the deviation between the nominal value and the actual length of the optical fiber length, the deviation between the calculated value and the actual value substituted by the optical signal transmission speed, and the like, and the actual system design can be optimized by accurately calibrating the optical fiber length, accurately measuring the refractive index of the optical fiber, and the like.
It should be understood that equivalent substitutions and changes to the technical solution and the inventive concept of the present invention should be made by those skilled in the art to the protection scope of the appended claims.
Claims (9)
1. The utility model provides an optic fibre distributed disturbance sensing system based on two michelson interferometers which characterized in that: the optical fiber disturbance sensor comprises a dual-wavelength light source (1), a light intensity modulator (2), an optical isolator (3), an optical beam splitter (4), a first wavelength division multiplexer (5), a second wavelength division multiplexer (6), a first Michelson interferometer (7), a second Michelson interferometer (8), a first disturbance signal demodulation module (9), a second disturbance signal demodulation module (10), a disturbance signal positioning module (11), a disturbance sensing optical fiber (12) and an optical signal transmission optical fiber (13), the dual-wavelength light source (1), the light intensity modulator (2), the input and output ports of the optical isolator (3) and the optical beam splitter (4) are sequentially connected, PASS ends of the first wavelength division multiplexer (5) and the second wavelength division multiplexer (6) are respectively connected with two output ports of the optical beam splitter (4), REFLECT ends of the first wavelength division multiplexer (5) and the second wavelength division multiplexer (6) are respectively connected with the first disturbance signal demodulation module (9) and the second wavelength division multiplexer (6) Two disturbance signal demodulation modules (10) are connected, two ports of a first Michelson interferometer (7) are respectively connected with a COMMOM end of a first wavelength division multiplexer (5) and one end of a disturbance sensing optical fiber (12), two ports of a second Michelson interferometer (8) are respectively connected with the other end of the disturbance sensing optical fiber (12) and one end of an optical signal transmission optical fiber (13), the other end of the optical signal transmission optical fiber (13) is connected with a COMMOM end of a second wavelength division multiplexer (6), and outputs of the first disturbance signal demodulation module (9) and the second disturbance signal demodulation module (10) are connected with an input of a disturbance signal positioning module (11).
2. The optical fiber distributed disturbance sensing system based on double michelson interferometers according to claim 1, wherein: the first Michelson interferometer (7) and the second Michelson interferometer (8) are composed of 50/50 optical fiber couplers (701), a first 90-degree Faraday rotator mirror (702), an optical fiber delay coil (703) and a second 90-degree Faraday rotator mirror (704), and the first Michelson interferometer (7) and the second Michelson interferometer (8) have the same interference arm length difference.
3. The optical fiber distributed disturbance sensing system based on double michelson interferometers according to claim 1, wherein: emergent light of the dual-wavelength light source (1) comprises two wavelengths, and the two wavelengths are respectively matched with the PASS end transmission wavelengths of the first wavelength division multiplexer (5) and the second wavelength division multiplexer (6).
4. The optical fiber distributed disturbance sensing system based on double michelson interferometers according to claim 1, wherein: the types of the light intensity modulator (2) comprise an electro-optical modulator, an acousto-optical modulator and an optical switch.
5. The optical fiber distributed disturbance sensing system based on double michelson interferometers according to claim 1, wherein: the optical beam splitter (4) is one of 50/50 optical fiber couplers, and wavelength division multiplexers with PASS ends and REFLECT ends respectively connected with a first wavelength division multiplexer (5) and a second wavelength division multiplexer (6).
6. The optical fiber distributed disturbance sensing system based on double michelson interferometers according to claim 1, wherein: the disturbance sensing optical fiber (12) is a common single-mode optical fiber and a single-mode optical fiber adopting a vibration sensitization design.
7. The optical fiber distributed disturbance sensing system based on double michelson interferometers according to claim 1, wherein: the optical signal transmission fiber (13) is a single mode fiber.
8. The optical fiber distributed disturbance sensing system based on double michelson interferometers according to claim 1, wherein: the signal demodulation of the first disturbing signal demodulation module (9) and the signal demodulation of the second disturbing signal demodulation module (10) are synchronized in time.
9. The optical fiber distributed disturbance sensing system based on double michelson interferometers according to claim 1, wherein: and the disturbing signal positioning module (11) calculates the position of an external disturbing signal on the disturbing sensing optical fiber (12) according to the correlation and the time delay of the disturbing signal demodulation results output by the first disturbing signal demodulation module (9) and the second disturbing signal demodulation module (10).
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Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN112556824A (en) * | 2020-12-22 | 2021-03-26 | 北京航天控制仪器研究所 | Ultra-high sound pressure noise test optical fiber microphone system for engine |
| CN112683383A (en) * | 2020-12-31 | 2021-04-20 | 广东瀚天融创科技有限公司 | Noise monitoring method based on distributed sensor, storage medium and system |
| CN114111855A (en) * | 2021-11-15 | 2022-03-01 | 复旦大学 | Distributed optical fiber sensing positioning system based on bidirectional Michelson interferometer |
| CN116105848A (en) * | 2023-04-13 | 2023-05-12 | 北京信维科技股份有限公司 | Method and device for improving quality of optical fiber sensing signal |
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2020
- 2020-08-20 CN CN202010844095.0A patent/CN112033523A/en active Pending
Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN112556824A (en) * | 2020-12-22 | 2021-03-26 | 北京航天控制仪器研究所 | Ultra-high sound pressure noise test optical fiber microphone system for engine |
| CN112683383A (en) * | 2020-12-31 | 2021-04-20 | 广东瀚天融创科技有限公司 | Noise monitoring method based on distributed sensor, storage medium and system |
| CN112683383B (en) * | 2020-12-31 | 2023-06-20 | 广东瀚天融创科技有限公司 | Noise monitoring method, storage medium and system based on distributed sensor |
| CN114111855A (en) * | 2021-11-15 | 2022-03-01 | 复旦大学 | Distributed optical fiber sensing positioning system based on bidirectional Michelson interferometer |
| CN114111855B (en) * | 2021-11-15 | 2024-02-09 | 复旦大学 | Distributed optical fiber sensing positioning system based on two-way Michelson interferometer |
| CN116105848A (en) * | 2023-04-13 | 2023-05-12 | 北京信维科技股份有限公司 | Method and device for improving quality of optical fiber sensing signal |
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