CN109238355B - Device and method for simultaneously sensing and measuring distributed dynamic and static parameters of optical fiber - Google Patents
Device and method for simultaneously sensing and measuring distributed dynamic and static parameters of optical fiber Download PDFInfo
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01D—MEASURING NOT SPECIALLY ADAPTED FOR A SPECIFIC VARIABLE; ARRANGEMENTS FOR MEASURING TWO OR MORE VARIABLES NOT COVERED IN A SINGLE OTHER SUBCLASS; TARIFF METERING APPARATUS; MEASURING OR TESTING NOT OTHERWISE PROVIDED FOR
- G01D21/00—Measuring or testing not otherwise provided for
- G01D21/02—Measuring two or more variables by means not covered by a single other subclass
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B11/00—Measuring arrangements characterised by the use of optical techniques
- G01B11/16—Measuring arrangements characterised by the use of optical techniques for measuring the deformation in a solid, e.g. optical strain gauge
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01H—MEASUREMENT OF MECHANICAL VIBRATIONS OR ULTRASONIC, SONIC OR INFRASONIC WAVES
- G01H9/00—Measuring mechanical vibrations or ultrasonic, sonic or infrasonic waves by using radiation-sensitive means, e.g. optical means
- G01H9/004—Measuring mechanical vibrations or ultrasonic, sonic or infrasonic waves by using radiation-sensitive means, e.g. optical means using fibre optic sensors
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01K—MEASURING TEMPERATURE; MEASURING QUANTITY OF HEAT; THERMALLY-SENSITIVE ELEMENTS NOT OTHERWISE PROVIDED FOR
- G01K11/00—Measuring temperature based upon physical or chemical changes not covered by groups G01K3/00, G01K5/00, G01K7/00 or G01K9/00
- G01K11/32—Measuring temperature based upon physical or chemical changes not covered by groups G01K3/00, G01K5/00, G01K7/00 or G01K9/00 using changes in transmittance, scattering or luminescence in optical fibres
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01K—MEASURING TEMPERATURE; MEASURING QUANTITY OF HEAT; THERMALLY-SENSITIVE ELEMENTS NOT OTHERWISE PROVIDED FOR
- G01K11/00—Measuring temperature based upon physical or chemical changes not covered by groups G01K3/00, G01K5/00, G01K7/00 or G01K9/00
- G01K11/32—Measuring temperature based upon physical or chemical changes not covered by groups G01K3/00, G01K5/00, G01K7/00 or G01K9/00 using changes in transmittance, scattering or luminescence in optical fibres
- G01K11/322—Measuring temperature based upon physical or chemical changes not covered by groups G01K3/00, G01K5/00, G01K7/00 or G01K9/00 using changes in transmittance, scattering or luminescence in optical fibres using Brillouin scattering
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01K—MEASURING TEMPERATURE; MEASURING QUANTITY OF HEAT; THERMALLY-SENSITIVE ELEMENTS NOT OTHERWISE PROVIDED FOR
- G01K11/00—Measuring temperature based upon physical or chemical changes not covered by groups G01K3/00, G01K5/00, G01K7/00 or G01K9/00
- G01K11/32—Measuring temperature based upon physical or chemical changes not covered by groups G01K3/00, G01K5/00, G01K7/00 or G01K9/00 using changes in transmittance, scattering or luminescence in optical fibres
- G01K11/324—Measuring temperature based upon physical or chemical changes not covered by groups G01K3/00, G01K5/00, G01K7/00 or G01K9/00 using changes in transmittance, scattering or luminescence in optical fibres using Raman scattering
Abstract
The invention discloses a device and a method for simultaneously sensing and measuring distributed dynamic and static parameters of an optical fiber, wherein the device comprises: the broadband light source and the narrow-band DFB laser source are connected with the polarization scrambler through the wavelength multiplexer; the optical/acousto-optical modulator is connected with the polarization scrambler; the modulator driving module is connected with the electro-optical/acousto-optical modulator; the erbium optical fiber amplifier EDFA is connected with the electro-optic/acousto-optic modulator; the data acquisition and signal processing module is connected with the four photoelectric detectors and is used for acquiring signals and carrying out phase demodulation, so that quasi-static measurement of the narrow-band weak grating array and dynamic sensing measurement of the wide-band chirped weak grating array are realized. The invention can realize the simultaneous sensing measurement of the distributed dynamic and static parameters of the optical fiber.
Description
Technical Field
The invention relates to the technical field of optical fiber sensing, in particular to a device and a method for simultaneously sensing and measuring distributed dynamic and static parameters of an optical fiber.
Background
Fiber optic sensing technology has many advantages over electrical sensors. In the face of the great demand of the high-speed development of the internet of things industry, the optical fiber sensing technology faces new opportunities and challenges, but the contradiction between the diversity of the optical fiber sensing demand and the unicity of the optical fiber sensing function exists. At oil gas well exploitation and detection, oil gas pipeline, bridge, large-scale piping lane etc. if can monitor dynamic and static signal simultaneously, then the cost of monitored control system that can significantly reduce to improve the validity and the reliability of monitoring.
The method is based on optical backscattering technology sensing, and can be used for measuring quasi-static physical quantities such as temperature and strain, for example, the Brillouin scattering technology can measure the temperature or the strain in a distributed manner; another method is to use interference effect in the optical fiber to measure dynamic signals such as vibration, for example, based on rayleigh scattered light polarization effect, C-OTDR, Sagnac interference and Mach-Zehnder interference, which uses phase or polarization information of light waves in the optical fiber to be very sensitive to fast changing dynamic signals, but cannot measure quasi-static temperature/strain parameters. Part of scholars realize distributed demodulation of dynamic and static sensing signals by using Raman scattering or Brillouin scattering and phi-OTDR fusion, but the system has poor signal-to-noise ratio and high system cost.
The invention patent CN 20151011446.0 discloses an on-line fiber grating system, wherein the on-line preparation of FBG array means that during the fiber drawing process, the technique of directly writing low-reflectivity fiber grating array with single pulse laser energy output by excimer laser, and then performing secondary coating to form large-capacity low-reflectivity weak grating sensor array, and the preparation technique has high production efficiency, thereby greatly reducing cost, flexible process, uniform coating, no welding spot on the grating array, low fiber transmission loss, the same mechanical tensile strength as fiber, convenient engineering construction, generally using time division multiplexing and wavelength division multiplexing techniques to demodulate FBG wavelength, compared with the common high-reflectivity wavelength division multiplexing system, the multiplexing capacity of the method greatly increases the number of sensors to form large-capacity fiber sensor system. The technology for dynamically and continuously preparing the fiber grating array at the university of Wuhan Dynasty is mature and is published in Chinese Optics letters.2013,11(3): 030602. The invention patent CN201710744196.9 discloses a device and a method for automatically and rapidly switching a phase mask to write a weak grating array with multiple wavelengths in an online wire drawing state. The invention patent CN201710122717.7 discloses a device and method for accurately controlling the grating pitch to realize on-line writing of a vibration sensing weak grating array.
Disclosure of Invention
Aiming at the difficulty of simultaneously realizing the monitoring of distributed static signals and dynamic signals at present, the invention realizes a device and a method for monitoring a quasi-static and dynamic measurement sensor array by continuously preparing a large-capacity weak grating array on line, and has high monitoring precision and low system cost.
The technical scheme adopted by the invention is as follows:
the utility model provides a device that optic fibre distributed state dynamic and static parameter was sensory simultaneously measured which characterized in that includes:
the broadband light source and the narrow-band DFB laser source are connected with the polarization scrambler through the wavelength multiplexer;
the electro-optical/acousto-optical modulator is connected with the polarization scrambler;
the modulator driving module is connected with the electro-optical/acousto-optical modulator;
the erbium-doped fiber amplifier EDFA is connected with the electro-optic/acousto-optic modulator;
a first port of the first circulator is connected with an erbium-doped fiber amplifier (EDFA), a second port of the first circulator is connected with a sensing fiber, a narrow-band weak grating array and a broadband chirped weak grating array are arranged on the sensing fiber at intervals, and the reflection spectrums of the two grating arrays are not overlapped;
a first port of the second circulator is connected with a third port of the first circulator, a second port of the second circulator is connected with the high-reflectivity chirped grating, and the high-reflectivity chirped grating is connected with the first photoelectric detector through a dispersion compensation optical fiber; the bandwidth of the chirped grating with high reflectivity is larger than that of a broadband chirped weak grating array on the single-mode fiber, and the central wavelengths are consistent;
a first port of the third circulator is connected with a third port of the second circulator, and a second port of the third circulator is connected with the second photoelectric detector;
a first coupling port of the coupler is connected with a third port of the third circulator, a second coupling port of the coupler is connected with the third photoelectric detector, a third coupling port of the coupler is connected with the fourth photoelectric detector, a fourth coupling port of the coupler is connected with the first Faraday rotator mirror, a fifth coupling port of the coupler is connected with one end of piezoelectric ceramic, and the other end of the piezoelectric ceramic is connected with the second Faraday rotator mirror;
the data acquisition and signal processing module is connected with the four photoelectric detectors and is used for acquiring signals and carrying out phase demodulation, so that quasi-static measurement of the narrow-band weak grating array and dynamic sensing measurement of the wide-band chirped weak grating array are realized.
According to the technical scheme, the single-mode optical fiber writes the narrow-band weak grating array and the wide-band chirp weak grating array by automatically and quickly switching the uniform phase mask plate and the chirp phase mask plate.
According to the technical scheme, the reflection spectrums of the narrow-band weak grating array and the wide-band chirped weak grating array are not overlapped, the grating intervals are more than 5nm, the reflectivity of the grating is 0.01-0.1%, the narrow-band weak grating and the wide-band weak grating are switched in a wheel flow mode, the grating intervals are all L, therefore, the interval between adjacent wide-band chirped gratings is 2L, and the error of the grating intervals is less than 1 cm.
According to the technical scheme, the wavelength of the broadband light source is lambda1The bandwidth is about 5 nm; the wavelength of the narrow-band DFB laser source is lambda2The 3dB bandwidth is about 1 kHz; lambda [ alpha ]1And λ2The difference is more than 5 nm.
According to the technical scheme, the sensing optical fiber is a single-mode optical fiber.
The invention also provides an optical fiber distributed dynamic and static parameter simultaneous sensing measurement method based on the technical scheme, which is characterized by comprising the following steps of:
(1) the laser of the broadband light source and the narrow-band DFB laser is connected to an electro-optic/acousto-optic modulator through a wavelength division multiplexer and a polarization scrambler, and is modulated into a periodic pulse signal with high extinction ratio through a modulator driving module; pulse signals enter the sensing optical fiber after passing through an erbium-doped fiber amplifier (EDFA);
(2) after passing through the sensing optical fiber, the pulse light with different wavelengths is reflected and then respectively demodulated after passing through the first circulator, the light with the first wavelength is connected to the chirped grating with high reflectivity at the second port of the second circulator, the bandwidth of the pulse light with the first wavelength is not overlapped with that of the chirped grating, the pulse light with the first wavelength is transmitted by the chirped grating, and the pulse light with the second wavelength is totally reflected; a first narrow-band grating in the sensing optical fiber is a reference grating;
(3) after being transmitted, the pulse light with the first wavelength passes through the dispersion compensation optical fiber and is received by the first photoelectric detector; pulse light with a second wavelength enters the coupler after passing through the third circulator, the coupler and the two Faraday rotators form an interferometer, and interference signals respectively enter the second, third and fourth photoelectric detectors through three ports of the coupler;
(4) for the wavelength demodulation of the narrow-band grating array, the length of the ith narrow-band grating from the reference grating is 2(i-1) L, and the time difference between the reference grating and the ith narrow-band sensing fiber compensated by measuring dispersion is delta ti＝2(i-1)Lneff/c+DLDCF(λi-λr) When the central wavelength of the sensing grating is lambdaiWhen changed, Δ t thereofiWill change, Δ λi＝Δti/(DLDCF) By measuring the time difference Δ t from the sensing fiber to the reference fiberiIs obtained and transmittedA wavelength change of the optical sensing fiber; wherein L isDCFFor the length of the dispersion compensating fiber, neffThe refractive index of the optical fiber, c the speed of light and D the dispersion coefficient parameter of the dispersion compensation optical fiber;
(5) for wavelength demodulation of a broadband chirped grating array, the distance between adjacent chirped gratings is 2L, piezoelectric ceramics are adjusted, the arm length difference of two Faraday rotators is equal to 2L, a Michelson interferometer is formed, an interference signal is generated, signals are acquired through a data acquisition and signal processing module and are demodulated to obtain the phase of the interference signal between the chirped gratings, and dynamic signals of each position point, including vibration or sound wave signals, are obtained.
The invention has the following beneficial effects: the invention discloses a sensing device and a method for simultaneously monitoring static signals and dynamic signals in a distributed manner on a single optical fiber. The system has the characteristics of low cost, high performance, full automation of the preparation of the sensing probe, convenience in cabling construction and the like, and has application prospects in the aspects of oil and gas exploitation, oil and gas pipelines, mineral exploitation, geophysical prospecting and the like.
Furthermore, the invention 1 adopts the large-capacity fiber grating array fiber, a plurality of weak fiber gratings with the reflectivity of 0.01-0.1% are dynamically and continuously written by utilizing the fiber drawing tower technology in the single-mode fiber drawing process, the mechanical strength of the grating per se is the same as that of the fiber, no welding spot exists, large-strain and high-precision sensing can be provided, and thousands of sensing units can be realized due to the use of the weak gratings with ultralow reflectivity, so that the problems of few sensing units, low mechanical strength and incapability of adapting to large-strain sensing change caused by the traditional strong grating series connection technology are solved; 2. the invention can simultaneously measure static and dynamic signals in a distributed manner, and the reflectivity of the invention is 2-3 orders of magnitude higher than that of random back scattering signals, so the signal-to-noise ratio of the invention is much higher than that of a conventional phi-OTDR technology sensing system. 3. The wavelength demodulation uses a dispersion compensation module, and the wavelength deviation of each sensing grating is obtained by measuring the time delay difference between the wavelength demodulation and the reference grating. 4. Only one sensing optical fiber is needed, and the sensing system is low in cost.
Drawings
The invention will be further described with reference to the accompanying drawings and examples, in which:
FIG. 1 is a schematic structural diagram of a device for simultaneously sensing and measuring optical fiber distributed dynamic and static parameters according to an embodiment of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
FIG. 1 is a structural diagram of an optical fiber distributed dynamic and static parameter simultaneous sensing measurement device, which comprises a broadband light source 1; 2 narrow band DFB laser source; 3 wavelength multiplexer; 4, a polarization disturbing device; 5 electro-optic/acousto-optic modulators; 6 a modulator driving module; 7 erbium-doped fiber amplifier EDFA; 8 chirp grating with high reflectivity and 12-14 three-port circulator; 9 single mode fiber (sensing fiber); 10 narrow-band grating; 11 broadband grating; 15 a dispersion compensating fiber; 16-17 Faraday rotators; 183 x 3 coupler; 19 piezoelectric ceramics PZT; 20-23 photoelectric detectors 1-4; and 24, a data acquisition and signal processing module.
The broadband light source 1 and the narrow-band DFB laser source 2 are connected with the polarization scrambler 4 through the wavelength multiplexer 3;
the electro-optical/acousto-optical modulator 5 is connected with the polarization scrambler 4;
the modulator driving module 6 is connected with the electro-optical/acousto-optical modulator 5;
the erbium-doped fiber amplifier EDFA7 is connected with the electro-optic/acousto-optic modulator 5;
a first port of the first circulator 12 is connected with an erbium-doped fiber amplifier EDFA, a second port is connected with a sensing fiber, a narrow-band weak grating array and a broadband chirped weak grating array are arranged on the sensing fiber at intervals, and the reflection frequency spectrums of the two grating arrays are not overlapped;
a second circulator 13, a first port of which is connected to a third port of the first circulator, a second port of which is connected to a chirped grating with high reflectivity, the chirped grating with high reflectivity being connected to the first photodetector through a dispersion compensation fiber; the bandwidth of the chirped grating with high reflectivity is larger than that of a broadband chirped weak grating array on the single-mode fiber, and the central wavelengths are consistent;
a third circulator 14, a first port of which is connected to a third port of the second circulator, and a second port of which is connected to the second photodetector;
3 a 3 x 3 coupler 18, a first coupling port of which is connected with a third port of the third circulator, a second coupling port of which is connected with a third photoelectric detector, a third coupling port of which is connected with a fourth photoelectric detector, a fourth coupling port of which is connected with a first faraday rotator, a fifth coupling port of which is connected with one end of piezoelectric ceramic, and the other end of the piezoelectric ceramic is connected with a second faraday rotator; the first Faraday rotator mirror 16 and the second Faraday rotator mirror 17 can form an interferometer, and when the interferometer is formed, the length difference of two arms of the first Faraday rotator mirror and the second Faraday rotator mirror is 2L, and 2L is the distance between adjacent broadband chirped gratings.
The data acquisition and signal processing module 24 is connected with the four photodetectors 20-23, and is used for demodulating according to signals acquired by the photodetectors, so as to realize quasi-static measurement of the narrow-band weak grating array and dynamic sensing measurement of the wide-band chirped weak grating array.
The device for simultaneously sensing and measuring the dynamic and static parameters by utilizing the optical fiber distributed mode comprises the following specific steps:
1) an online drawing tower technology is used for online writing of a weak grating array optical fiber 9, wherein the optical fiber comprises two types of gratings, a narrow-band grating array 10 and a chirped grating array 11, the phase mask plate and the chirped phase mask plate are automatically and uniformly switched, and an excimer laser is used for sequentially writing the narrow-band grating and the chirped grating (the invention patent CN201710744196.9 technology can be used), the reflection spectrums of the narrow-band grating and the chirped grating are required to be not overlapped and are separated by more than 5nm, signal crossing is prevented, the reflectivity of the grating is 0.01-0.1%, the narrow-band grating and the wideband chirped grating are switched in turn, the grating interval is L, and therefore, the interval between adjacent wideband chirped gratings is 2L. Because the grating is continuously engraved on line, the sensing probe does not have any welding spot, the strength is the same as that of the conventional optical fiber, the optical fiber loss is 0.2-0.4 dB, and the optical fiber cabling construction is convenient. The device and the method for accurately controlling the grating spacing and realizing the online writing of the vibration sensing weak grating array by utilizing the technology of the invention patent CN201710122717.7 can ensure that the spacing error of the grating is less than 1cm, is irrelevant to the grating spacing and has no accumulated error. The quasi-static measurement is realized by measuring the central wavelength of the uniform narrow-band weak grating array, and the dynamic sensing measurement is realized by measuring the interference signal of the reflection signal between adjacent chirped wide-band weak gratings, so that the distributed dynamic and static sensing measurement is realized.
2) Wavelength of broadband light source is lambda1The bandwidth is about 5nm, and the device is used for demodulating narrow-band weak grating and narrow-band light source lambda2Is a DFB laser with a 3dB bandwidth of<1kHz for demodulating interference signals between chirped gratings, and a broadband light source spectrum lambda1And DFB wavelength λ2The phase difference is more than 5nm, a broadband light source and narrow-band DFB laser are transmitted through a wavelength coupler 3, a polarization scrambler 4, a modulator 5 and a signal are modulated into a pulse signal with high periodicity extinction ratio, the pulse signal is amplified through an erbium-doped fiber amplifier EDFA7, and the amplified signal enters a sensing fiber through a circulator 12. The first narrow band grating 10 acts as a reference grating, keeping the grating unaffected by temperature and strain. The spacing between the narrow band gratings is 2L. The broadband light source is reflected after passing through the narrow-band weak grating 10 and transmits the chirped grating 11; the signal light of the DFB laser is transmitted through the narrow-band grating 10 and reflected by the chirped grating 11. The grating 8 is a broadband grating having a center wavelength equal to that of the chirped grating 11 and a bandwidth greater than that of the chirped grating 11, such that the wavelength λ is1Is transmitted by the broadband grating 8, while the wavelength lambda is transmitted2Is totally reflected.
3) The broadband chirp grating 8 with the reflectivity of more than 99 percent has the same spectrum as the chirp grating 11; pulse signal light of the broadband light source is reflected by the narrow-band grating, passes through the circulators 12 and 13, is transmitted, and is subjected to dispersion compensationThe compensation fiber 15 is received by the detector 20. Wavelength lambda1After the pulse light is transmitted through a section of dispersion compensation optical fiber with high dispersion coefficient, the length of the dispersion compensation optical fiber is LDCFReception by the first photodetector 20; wavelength lambda2After passing through the third circulator 14, the pulse light enters a 3 × 3 coupler 18, which forms an interferometer with two faraday rotators, and the length difference between the two arms of each faraday rotator is 2L, that is, the distance between two adjacent chirped gratings 11.
4) For the wavelength demodulation of the narrow-band grating, the first narrow-band grating 10 is used as a reference grating, and the time delay difference between the signal light of the ith narrow-band grating 10 and the reference grating after reaching the first photodetector 20 is delta ti＝2(i-1)Lneff/c+DLDCF(λi-λr) Wherein L isDCFFor the length of the dispersion compensating fiber, neffIs the refractive index of the fiber, c is the speed of light, and D is the dispersion coefficient parameter of the dispersion compensating fiber. The former part is the transmission time delay between the optical fibers, the latter part is the time delay after passing through the dispersion compensation optical fiber 15, and because the wavelength of the reference grating is not changed, when the wavelength of the ith narrow-band grating 10 changes with the temperature, the time delay is generated by passing through the dispersion compensation optical fiber, and the change of the wavelength delta lambda of the narrow-band grating 10 can be obtained by measuring the change of the time delayi＝Δti/(DLDCF) The total dispersion of the dispersion compensating fiber is constant, and thus, the wavelength variation varies linearly with the delay variation. By measuring the time delay of each narrow-band grating 10 and the reference grating, the wavelength variation of all the narrow-band gratings 10 can be obtained, so as to obtain a quasi-static sensing signal.
5) Narrow band signal lambda2The transmission narrow-band grating 10, the reflection chirp grating 11, after passing through three circulators 12-13, the broadband chirp grating 8 with high reflectivity, after passing through a circulator 14, enters an interferometer composed of two Faraday rotators 16-17 and a 3X 3 coupler, a piezoelectric ceramic PZT 19 is used for modulating the length difference of two arms of the Faraday rotator, so that the arm length difference is equal to the distance 2L between the chirp gratings 11, because the interval error of the chirp gratings in the sensing optical fiber is very small and less than 1cm, when the piezoelectric ceramic PZT is adjusted, one pair of the gratings generates strong forceWhen the interference signal is strong, other interference signals are automatically matched, so that the phase of the interference signal between the chirped gratings can be quickly demodulated, and a dynamic signal (vibration or sound wave signal) of each position point can be obtained. After passing through the second, third and fourth photodetectors 21-23, the interference signals are acquired by the data acquisition and signal processing module and processed, so that the phase change of the interference signals between adjacent chirped gratings can be obtained, and vibration or sound wave signals, i.e. dynamic signals, caused by the external environment can be obtained.
In summary, the invention adopts the large-capacity fiber grating array fiber, and dynamically and continuously writes a plurality of weak fiber gratings with the reflectivity of 0.01-0.1% by using the fiber drawing tower technology in the single-mode fiber drawing process, the mechanical resistance strength of the gratings is the same as that of the fiber, no welding spot exists, and large-strain and high-precision sensing can be provided.
In addition, the invention can simultaneously measure static and dynamic signals in a distributed manner, and because the weak grating array with the reflectivity of 0.01-0.1% is used, the reflectivity is 2-3 orders of magnitude higher than that of random back scattering signals, so the signal-to-noise ratio is far higher than that of a conventional phi-OTDR technology sensing system. The wavelength demodulation uses a dispersion compensation module, and the wavelength deviation of each sensing grating is obtained by measuring the time delay difference between the wavelength demodulation and the reference grating. And only one sensing optical fiber is needed, and the sensing system is low in cost.
It will be understood that modifications and variations can be made by persons skilled in the art in light of the above teachings and all such modifications and variations are intended to be included within the scope of the invention as defined in the appended claims.
Claims (6)
1. The utility model provides an optical fiber distribution type static and dynamic parameter simultaneous sensing measurement's device which characterized in that includes:
the broadband light source and the narrow-band DFB laser source are connected with the polarization scrambler through the wavelength multiplexer;
the electro-optical/acousto-optical modulator is connected with the polarization scrambler;
the modulator driving module is connected with the electro-optical/acousto-optical modulator;
the erbium-doped fiber amplifier EDFA is connected with the electro-optic/acousto-optic modulator;
a first port of the first circulator is connected with an erbium-doped fiber amplifier (EDFA), a second port of the first circulator is connected with a sensing fiber, a narrow-band weak grating array and a broadband chirped weak grating array are arranged on the sensing fiber at intervals, and the reflection spectrums of the two grating arrays are not overlapped;
a first port of the second circulator is connected with a third port of the first circulator, a second port of the second circulator is connected with the high-reflectivity chirped grating, and the high-reflectivity chirped grating is connected with the first photoelectric detector through a dispersion compensation optical fiber; the bandwidth of the chirped grating with high reflectivity is larger than that of the broadband chirped weak grating array on the sensing fiber, and the central wavelengths are consistent;
a first port of the third circulator is connected with a third port of the second circulator, and a second port of the third circulator is connected with the second photoelectric detector;
a first coupling port of the coupler is connected with a third port of the third circulator, a second coupling port of the coupler is connected with the third photoelectric detector, a third coupling port of the coupler is connected with the fourth photoelectric detector, a fourth coupling port of the coupler is connected with the first Faraday rotator mirror, a fifth coupling port of the coupler is connected with one end of piezoelectric ceramic, and the other end of the piezoelectric ceramic is connected with the second Faraday rotator mirror;
the data acquisition and signal processing module is connected with the four photoelectric detectors and is used for acquiring signals and carrying out phase demodulation, so that quasi-static measurement of the narrow-band weak grating array and dynamic sensing measurement of the wide-band chirped weak grating array are realized.
2. The apparatus for simultaneously sensing and measuring distributed dynamic and static parameters of optical fiber according to claim 1, wherein the sensing optical fiber writes a narrowband weak grating array and a broadband chirped weak grating array by automatically and rapidly switching a uniform phase mask plate and a chirped phase mask plate, and the narrowband weak grating and the broadband chirped weak grating are alternately switched at a distance of L.
3. The apparatus for simultaneously sensing and measuring dynamic and static parameters in an optical fiber distribution manner according to claim 1, wherein the reflection spectra of the narrow-band weak grating array and the wide-band chirped weak grating array are not overlapped, the grating spacing is more than 5nm, the reflectivity of the grating is 0.01-0.1%, the interval of the wide-band chirped grating is 2L, and the error of the grating spacing is less than 1 cm.
4. The apparatus for simultaneously sensing and measuring the distributed dynamic and static parameters of the optical fiber as claimed in claim 1, wherein the broadband light source has a wavelength λ1The bandwidth is 5 nm; the wavelength of the narrow-band DFB laser source is lambda2The 3dB bandwidth is less than or equal to 1 kHz; lambda [ alpha ]1And λ2The difference is more than 5 nm.
5. The apparatus for simultaneously sensing and measuring distributed dynamic and static parameters of optical fiber according to claim 1, wherein the sensing optical fiber is a single mode optical fiber.
6. An optical fiber distributed dynamic and static parameter simultaneous sensing measurement method based on the optical fiber distributed dynamic and static parameter simultaneous sensing measurement device of claim 1, characterized by comprising the following steps:
(1) the laser of the broadband light source and the narrow-band DFB laser passes through a wavelength multiplexer, passes through a polarization scrambler, then is accessed into an electro-optic/acousto-optic modulator, and is modulated into a pulse signal with a periodic high extinction ratio through a modulator driving module; pulse signals enter the sensing optical fiber after passing through an erbium-doped fiber amplifier (EDFA);
(2) after passing through the sensing optical fiber, the pulse light with different wavelengths is reflected and then respectively demodulated after passing through the first circulator, the light with the first wavelength is connected to the chirped grating with high reflectivity at the second port of the second circulator, the bandwidth of the pulse light with the first wavelength is not overlapped with that of the chirped grating, the pulse light with the first wavelength is transmitted by the chirped grating, and the pulse light with the second wavelength is totally reflected; a first narrow-band grating in the sensing optical fiber is a reference grating;
(3) after being transmitted, the pulse light with the first wavelength passes through the dispersion compensation optical fiber and is received by the first photoelectric detector; pulse light with a second wavelength enters the coupler after passing through the third circulator, the coupler and the two Faraday rotators form an interferometer, and interference signals respectively enter the second, third and fourth photoelectric detectors through three ports of the coupler;
(4) for the wavelength demodulation of the narrow-band grating array, the length of the ith narrow-band grating from the reference grating is 2(i-1) L, and the time difference between the reference grating and the ith narrow-band sensing fiber through the measurement of dispersion compensation is delta ti＝2(i-1)Lneff/c+DLDCF(λi-λr) When the central wavelength of the sensing grating is lambdaiWhen changed, Δ t thereofiWill change, Δ λi＝Δti/(DLDCF) By measuring the time difference Δ t from the sensing fiber to the reference fiberiObtaining the wavelength change of the sensing optical fiber; wherein L isDCFFor the length of the dispersion compensating fiber, neffThe refractive index of the optical fiber, c the speed of light and D the dispersion coefficient parameter of the dispersion compensation optical fiber;
(5) for wavelength demodulation of the broadband chirped grating array, the distance between adjacent broadband chirped gratings is 2L, piezoelectric ceramics are adjusted to enable the arm length difference of two Faraday rotators to be equal to 2L, a Michelson interferometer is formed, interference signals are generated, signals are collected through a data collection and signal processing module and are demodulated to obtain the phase of the interference signals between the chirped gratings, and dynamic signals of all position points, including vibration or sound wave signals, are obtained.
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