CN108507662B - Optical fiber distributed sensing method and device based on multi-wavelength double-optical pulse - Google Patents
Optical fiber distributed sensing method and device based on multi-wavelength double-optical pulse Download PDFInfo
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- G—PHYSICS
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- 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
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- 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
- G01D5/00—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable
- G01D5/26—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light
- G01D5/32—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light
- G01D5/34—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells
- G01D5/353—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells influencing the transmission properties of an optical fibre
- G01D5/35306—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells influencing the transmission properties of an optical fibre using an interferometer arrangement
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- G01D5/35319—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells influencing the transmission properties of an optical fibre using an interferometer arrangement using multiple waves interferometer using other multiple wave interferometer
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Abstract
The invention discloses an optical fiber distributed sensing method and device based on multi-wavelength double-optical pulse, wherein the method comprises the following steps: s1, generating multi-wavelength double-light pulses, and injecting the multi-wavelength double-light pulses into a sensing optical fiber, wherein each pulse in the multi-wavelength double-light pulses comprises a plurality of wavelength components; s2, obtaining Rayleigh optical signals in the sensing optical fibers and interference light intensity of a sensing channel corresponding to the Rayleigh optical signals; and S3, calculating the interference light intensity to acquire the phase information of the Rayleigh optical signal so as to acquire the information of the signal sensed by the sensing optical fiber. The invention has the advantages of being used for the phi-OTDR technology based on the PGC phase demodulation technology, reducing the influence of Rayleigh optical fiber signal intensity fading on the measurement noise on the premise of not increasing the signal processing workload, eliminating the detection blind area caused by high phase noise and the like.
Description
Technical Field
The invention relates to an optical fiber distributed sensing technology, in particular to an optical fiber distributed sensing method and device based on multi-wavelength double optical pulses, which are particularly suitable for vibration or sound detection.
Background
The phase-sensitive optical time domain reflectometer (phi-OTDR) technology is widely applied to the application fields of distributed vibration, sound detection and the like, and has great application value. The phase-sensitive optical time domain reflectometer injects optical pulses into the sensing optical fiber and collects Rayleigh optical signals generated by the optical pulses at each position of the optical fiber. And obtaining the phase information of the Rayleigh signal by using the intensity change of the Rayleigh signal to realize the information of the external vibration signal.
To obtain the phase information of the rayleigh signal, Yuelan Lu et al propose a Φ -OTDR system based on coherent detection structure, which obtains the phase information of the rayleigh signal using coherent detection Technology [ Yuelan Lu et al, Distributed vision sensor based on coherent detection of phase-OTDR, Journal of Lightwave Technology,2010 ]. Pan et al, Shanghai Optical engine, China academy of sciences, proposed the demodulation of the Phase of Rayleigh scattering signals in real time by heterodyne method and digital coherent detection [ Z.Pan et al, Phase-sensitive OTDR system based on digital coherent detection, in Optical Sensors and Biophotonic, 2011 ]. Masoudi et al, university of south Anmpton, proposed to add an unbalanced Mach-Zender interferometer (M-ZI) and a 3 × 3 coupler to the receiving end of the backscattered signal of the conventional Φ -OTDR and obtain the phase information of the Rayleigh signal using a 3 × 3 phase demodulation algorithm [ A. Masoudi et al, A distributed optical fiber dynamic spectrum sensor based on phase-OTDR, measurementcience and Technology, 2013 ]. Fang et al, the semiconductor institute of the middle academy, applies a Phase Generated Carrier (PGC) Algorithm to the Φ -OTDR technique to achieve rayleigh signal Phase acquisition [ gamesheng Fang et al, Phase-Sensitive Optical Time Domain Reflectometer Based on Phase-Generated Carrier Algorithm, Journal of Lightwave Technology,2015 ].
The rayleigh light signal intensity is determined by the interference result of the multiple rayleigh scattered lights in the optical fiber covered by the pulsed light. Because the scattering points inside the optical fiber are not uniformly distributed along the optical fiber, the intensity of Rayleigh optical signals fluctuates along the optical fiber. The measurement noise of the optical fiber position with rayleigh signal fading is high, and the sensing accuracy of the physical quantity of the position is seriously influenced. To address the effect of coherent fading on vibration sensing noise, k.shimizu et al used coherent detection techniques, combined with frequency shift averaging, to change the frequency of the local and probe lights synchronously at each measurement to suppress the effect of coherent fading noise on the system [ k.shimizu et al, Characteristics and reduction of coherent fading noise in radar interference detection for optical fibers and components, Lightwave Technology Journal of 1992 ]. Izumita et al, using frequency hopping, performed multiple averages of Rayleigh signals, reducing the fluctuation curve of the probe curve to 0.05dB [ H.Izumita et al, stored amplitude fluctuation in coherent OTDR and a new Technology for recording the synthetic frequency response sounding, Journal of Lightwave Technology,2002 ]. The theoretical model of coherent detection type Φ -OTDR was studied by mon et al, institute of Shanghai optical machinery, and proposed a method of suppressing coherent fading by combining incident light phase modulation with coherent detection [ mon et al, phase demodulation technology for comprehensively identifying interference fading false signals in Φ -OTDR system based on multiple frequencies, china laser, 2013 ].
The reported method is to filter and extract the rayleigh lights with different frequencies, process the rayleigh lights with different frequencies respectively, and synthesize the processing result to obtain the coherent fading suppression effect. The process greatly increases the workload of back-end signal processing, and cannot meet the requirement of distributed vibration real-time measurement. Meanwhile, the methods are only suitable for the coherent detection-based phi-OTDR technology. Compared with the phi-OTDR based on the PGC phase demodulation technology, the phi-OTDR based on coherent detection is more seriously influenced by the phase noise of a light source, and is reflected in high noise of vibration detection, and the influence is particularly obvious in long-distance distributed vibration sensing.
Disclosure of Invention
The technical problem to be solved by the invention is as follows: aiming at the technical problems in the prior art, the invention provides an optical fiber distributed sensing method and device based on multi-wavelength double optical pulses, which can be used for a phi-OTDR technology based on a PGC phase demodulation technology, reduce the influence of Rayleigh optical fiber signal intensity fading on measurement noise on the premise of not increasing the signal processing workload, and eliminate a detection blind area caused by high-phase noise.
In order to solve the technical problems, the technical scheme provided by the invention is as follows: an optical fiber distributed sensing method based on multi-wavelength double optical pulses comprises the following steps:
s1, generating multi-wavelength double-light pulses, and injecting the multi-wavelength double-light pulses into a sensing optical fiber, wherein each pulse in the multi-wavelength double-light pulses comprises a plurality of wavelength components;
s2, obtaining Rayleigh optical signals in the sensing optical fibers and interference light intensity of a sensing channel corresponding to the Rayleigh optical signals;
and S3, calculating the interference light intensity to acquire the phase information of the Rayleigh optical signal so as to acquire the information of the signal sensed by the sensing optical fiber.
Further, two pulsed lights in the dual light pulse have a preset phase difference.
Further, the dual optical pulses are generated from pulsed light by an unbalanced interferometer with a preset arm difference.
Further, the power difference of each wavelength component in the dual optical pulses is smaller than a preset threshold value.
Further, the specific step of step S3 includes: according to the signal intensity information of the Rayleigh light, obtaining the phase information of the Rayleigh light through a differential cross multiplication algorithm, thereby obtaining the information of the signals sensed by the sensing optical fiber, wherein the information of the sensed signals comprises amplitude, frequency and phase information; the signal intensity information of the rayleigh light is intensity information in which wavelength components in the rayleigh light are superimposed.
An optical fiber distributed sensing device based on multi-wavelength double-light pulse comprises a multi-wavelength double-light pulse generating component, a circulator, a photoelectric detector, a data acquisition unit, a signal processor and a signal generator;
the multi-wavelength dual-optical pulse generation component is used for generating multi-wavelength dual-optical pulses, and each pulse in the multi-wavelength dual-optical pulses comprises a plurality of wavelength components;
the circulator is used for injecting the multi-wavelength double-light pulse into a sensing optical fiber, receiving a Rayleigh optical signal generated in the sensing optical fiber by the multi-wavelength double-light pulse and outputting the Rayleigh optical signal;
the photoelectric detector is used for detecting the interference light intensity of the Rayleigh light signal output by the circulator;
the data acquisition unit is used for acquiring the interference light intensity detected by the photoelectric detector to obtain a light intensity signal;
the signal processor is used for calculating the light intensity signal to obtain the phase information of the Rayleigh light signal so as to obtain the information of the signal sensed by the sensing optical fiber;
the signal generator is used for providing a driving signal and a clock synchronization signal for the multi-wavelength double-light pulse generating assembly and the data acquisition unit.
Further, the multi-wavelength dual optical pulse generation assembly comprises: the device comprises a laser, a beam combiner, a light intensity modulator and a double-light pulse modulation component;
the laser is used for generating multi-wavelength laser with a plurality of different wavelengths;
the beam combiner is used for spatially combining the multi-wavelength laser;
the light intensity modulator is used for modulating the intensity of the multi-wavelength laser to generate periodically repeated multi-wavelength single light pulses;
the double-light pulse modulation component is used for modulating the multi-wavelength single-light pulse and modulating the multi-wavelength single-light pulse into a multi-wavelength double-light pulse with a preset phase difference.
Further, the laser comprises a plurality of narrow linewidth lasers.
Further, the dual optical pulse modulation assembly comprises a first coupler, an unbalanced interferometer, a phase difference modulator, and a second coupler;
the first coupler is used for injecting the multi-wavelength single optical pulse to two optical paths of the unbalanced interferometer;
the phase difference modulator is used for modulating the phase of the laser in one light path in the unbalanced interferometer;
the second coupler is used for spatially combining the laser in the two optical paths.
Further, the signal processor has means for: according to the signal intensity information of the Rayleigh light, obtaining the phase information of the Rayleigh light through a differential cross multiplication algorithm, thereby obtaining the information of the signals sensed by the sensing optical fiber, wherein the information of the sensed signals comprises amplitude, frequency and phase information; the signal intensity information of the rayleigh light is intensity information in which wavelength components in the rayleigh light are superimposed.
Compared with the prior art, the invention has the advantages that:
1. the invention utilizes the polarization correlation and the wavelength correlation of the incident pulse light of the Rayleigh signal intensity, adopts a multi-wavelength light pulse scheme, and because the wavelength and the polarization state are different, the Rayleigh signal intensity generated by each wavelength component in the pulse light can not fade at the same position of the optical fiber at the same time, and the influence of the Rayleigh optical fiber signal intensity fading on the measurement noise can be reduced on the premise of not increasing the signal processing workload.
2. The invention utilizes the Rayleigh signal of each wavelength component with superposed intensity to obtain higher Rayleigh signal intensity signal-to-noise ratio, inhibits the detection noise deterioration caused by the Rayleigh optical signal intensity fading and eliminates the detection blind area caused by high detection noise.
Drawings
FIG. 1 is a schematic flow chart of an embodiment of the present invention.
Fig. 2 is a schematic structural diagram of an embodiment of the present invention.
Illustration of the drawings: 1. a multi-wavelength dual-light pulse generating component; 11. a laser; 12. a beam combiner; 13. a light intensity modulator; 14. a dual optical pulse modulation assembly; 141. a first coupler; 142. a non-equilibrium interferometer; 1421. a long arm; 1422. a short arm; 143. a phase difference modulator; 144. a second coupler; 2. a circulator; 3. a photodetector; 4. a data acquisition unit; 5. a signal processor; 6. a signal generator; 7. a sensing fiber.
Detailed Description
The invention is further described below with reference to the drawings and specific preferred embodiments of the description, without thereby limiting the scope of protection of the invention.
As shown in fig. 1, the optical fiber distributed sensing method based on multi-wavelength dual optical pulses of this embodiment includes the steps of: s1, generating multi-wavelength double-light pulses, and injecting the multi-wavelength double-light pulses into a sensing optical fiber, wherein each pulse in the multi-wavelength double-light pulses comprises a plurality of wavelength components; s2, obtaining Rayleigh optical signals in the sensing optical fibers and interference light intensity of a sensing channel corresponding to the Rayleigh optical signals; and S3, calculating the interference light intensity to acquire the phase information of the Rayleigh light signal so as to acquire the information of the signal sensed by the sensing optical fiber.
In the present embodiment, two pulsed lights in the dual light pulse have a predetermined phase difference therebetween. Dual optical pulses are generated from pulsed light by an unbalanced interferometer with a preset arm difference. The number of wavelength components contained in each pulse in the multi-wavelength double-light pulse is recorded as m, and m is larger than or equal to 2. The wavelengths of the wavelength components are respectively recorded as: lambda [ alpha ]1，λ2，…,λm-1，λm. The power of each wavelength component is the same or equivalent, which means that the power difference of each wavelength component in the dual optical pulse is smaller than a preset threshold value. After the multi-wavelength double-light pulse is injected into the sensing optical fiber, Rayleigh light is generated at each position of the sensing optical fiber. The Rayleigh light generated by the sensing optical fiber is obtained and has a distance LChannelInterference intensity of Rayleigh light at each position in the sensing fiberChannelThe optical fibers between the positions form a sensing channel, LChannelIs the length of the sensing channel. In this embodiment, the arm difference L is presetInterferometerGenerates multi-wavelength dual optical pulses, if a Mach-Zender interferometer is used, then LChannel＝LInterferometer(ii) a If a Michelson interferometer is used, then LChannel＝2LInterferometer。
In this embodiment, a certain wavelength component λ of one pulse (p ═ 1,2) of the multiwavelength two-photon pulsesi＝1,2,…,mThe intensity of the rayleigh optical signal (b) is the interference intensity of rayleigh scattered light at each position in the optical fiber covered by the optical pulse, and is shown in formula (1):
in the formula (1), Ip＝1,2Is the interference light intensity of the rayleigh scattered light,
a wavelength component of λiThe vector amplitude of the kth rayleigh scattered light of (1), ω, including polarization information and amplitude information of the rayleigh scattered lighti、βi,kAnd phii,kRespectively expressed as a wavelength component of λiI refers to the ith wavelength component on the optical pulse spectrum, k is the kth rayleigh scattered light in the pulse, j is the unit imaginary number, and e is the natural base number.
The rayleigh signal intensity of a wavelength component of the optical pulse in the optical fiber is the interference intensity of rayleigh scattered light at each position in the optical fiber covered by the optical pulse, and therefore the rayleigh signal intensity is accumulated by the transmission accumulated phase phi of each rayleigh scattered light in the optical pulsei,kAmplitude and polarization state.
In this embodiment, the specific step of step S3 includes: according to the signal intensity information of the Rayleigh light, the phase information of the Rayleigh light is obtained through a differential cross multiplication algorithm, so that the information of the signals sensed by the sensing optical fiber is obtained, and the information of the sensed signals comprises amplitude, frequency and phase information; the signal intensity information of the rayleigh light is intensity information in which each wavelength component in the rayleigh light is superimposed.
In this embodiment, after rayleigh light generated in the sensing position in the sensing fiber is output, interference light intensity of rayleigh light is obtained by the photodetector, and interference light intensity of the sensing channel at position z in the sensing fiber satisfies the following equation (2):
in formula (2), I (z) is the interference intensity of the sensing channel at position z, I1,iLambda being light pulse passing through short arm of unbalanced interferometeriComponent in optical fiber z + LChannelIntensity of Rayleigh light generated at2,iLambda being light pulse passing through long arm of unbalanced interferometeriThe intensity of Rayleigh light generated at the optical fiber z is the component, m is the number of wavelength components, z is position information, LChannelFor the length of the sensing channel, phi0Generating an initial phase difference, phi, of the Rayleigh light signal for the dual light pulsessIs in the position [ z, z + LChannel]The optical phase change of the optical fiber in the interval caused by the physical quantity to be measured is the phase of the signal to be measured, phicosThe phase of the light pulse passing through the long arm of the unbalanced interferometer is cosine modulated by the piezoelectric ceramics.
Representing light pulses passing through the short arm of an unbalanced interferometer at z + L of the fiberChannelThe intensity of the rayleigh light generated at the site,
representing the intensity of the rayleigh light produced at the fiber z by the light pulse of the long arm of the unbalanced interferometer.
Because the polarization state and propagation constant of the optical pulse are related to the wavelength of the light, and the accumulated phase of transmission is determined by the propagation constant and the polarization state of the light, the polarization state and the accumulated phase phi of different wavelength components in the Rayleigh signali,kDifference, resulting in intensity I of each wavelength component in Rayleigh signalp＝1,2Different, i.e. the intensity of each wavelength component in the rayleigh optical signal does not fade simultaneously. Thus, the amplitude of the AC signal of the interference intensity I (z) of the sensing channel at the z position of the optical fiber
Always at a stable level without fading. By using interference signal I (z) formed by multi-wavelength Rayleigh signal and combining phase demodulation technology, signal phase phi can be obtainedsAnd the detection noise deterioration phenomenon caused by the rayleigh signal light intensity fading is avoided.
As shown in fig. 2, the optical fiber distributed sensing apparatus based on multi-wavelength dual optical pulses of the present embodiment includes a multi-wavelength dual optical pulse generating component 1, a circulator 2, a photodetector 3, a data collector 4, a signal processor 5, and a signal generator 6; the multi-wavelength double-light pulse generating component 1 is used for generating multi-wavelength double-light pulses, and each pulse in the multi-wavelength double-light pulses comprises a plurality of wavelength components; the circulator 2 is used for injecting the multi-wavelength double-light pulse into the sensing optical fiber 7, receiving a Rayleigh light signal generated by the multi-wavelength double-light pulse in the sensing optical fiber 7 and outputting the Rayleigh light signal; the photoelectric detector 3 is used for detecting the interference light intensity of the Rayleigh light signal output by the circulator 2; the data acquisition unit 4 is used for acquiring the interference light intensity detected by the photoelectric detector 3 to obtain a light intensity signal; the signal processor 5 is used for calculating the light intensity signal to obtain the phase information of the rayleigh optical signal, so as to obtain the information of the signal sensed by the sensing optical fiber 7; the signal generator 6 is used for providing a driving signal and a clock synchronization signal for the multi-wavelength dual-optical pulse generation assembly 1 and the data collector 4.
In the present embodiment, the multi-wavelength dual optical pulse generation module 1 includes: a laser 11, a beam combiner 12, a light intensity modulator 13 and a double-light pulse modulation component 14; the laser 11 is used for generating multi-wavelength laser light with a plurality of different wavelengths; the beam combiner 12 is used for spatially combining the multi-wavelength laser; the light intensity modulator 13 is used for modulating the intensity of the multi-wavelength laser to generate periodically repeated multi-wavelength single light pulses; the dual-optical pulse modulation component 14 is configured to modulate the multi-wavelength single optical pulse to obtain a multi-wavelength dual-optical pulse with a predetermined phase difference. The laser 11 comprises a plurality of narrow linewidth lasers. Each narrow linewidth laser produces laser light of one wavelength. As shown in fig. 2, comprising m narrow linewidth lasers, the narrow linewidth laser λ1Generating a wavelength of λ1Laser of (2), narrow linewidth laser lambdaiGenerating a wavelength of λiLaser of (2), narrow linewidth laser lambdamGenerating a wavelength of λmThe laser of (1). The m narrow linewidth lasers generate lasers with different wavelengths with the same or equivalent power, which means that the power difference of each wavelength component in the dual optical pulse is smaller than a preset threshold value. Multiple lasers with different wavelengths generated by multiple narrow linewidth lasers are spatially combined by a beam combiner 12A wavelength division multiplexer. The light intensity modulator 13 modulates the intensity of the multi-wavelength laser according to the control pulse signal output from the signal generator 6.
It should be noted that, in this embodiment, not only the above-mentioned manner is used to generate multi-wavelength dual optical pulses, but also the manner and apparatus disclosed in the prior art can be used to generate multi-wavelength dual optical pulses, for example, by using an Electro-optical intensity modulator (EOIM) to perform sinusoidal intensity modulation on a single-wavelength laser, sidebands can be generated on two sides of the central wavelength of the laser to form multi-wavelength output, and the frequency interval between adjacent sidebands is equal to the modulation frequency of the sinusoidal intensity modulation; the specific device is a photo line MX-LN-10 electro-optical intensity modulator. Are intended to fall within the scope of the present invention.
In the present embodiment, the dual optical pulse modulation assembly 14 includes a first coupler 141, an unbalanced interferometer 142, a phase difference modulator 143, and a second coupler 144; the first coupler 141 is used to inject multi-wavelength single optical pulses into the two optical paths of the unbalanced interferometer 142; the phase difference modulator 143 is configured to modulate the phase of the laser in one optical path of the unbalanced interferometer 142; the second coupler 144 is used to spatially combine the laser light in the two optical paths. The signal processor 5 has means for: according to the signal intensity information of the Rayleigh light, the phase information of the Rayleigh light is obtained through a differential cross multiplication algorithm, so that the information of the signals sensed by the sensing optical fiber 7 is obtained, and the information of the sensed signals comprises amplitude, frequency and phase information; the signal intensity information of the rayleigh light is intensity information in which each wavelength component in the rayleigh light is superimposed.
In this embodiment, the interferometer 142 has two fiber arms, a long arm 1421 and a short arm 1422, and the long arm 1421 and the short arm 1422 have a predetermined arm difference therebetween. The phase difference modulator 143 is made of piezoelectric ceramics, is wound around the long arm 1421, and phase-modulates the light pulse in the long arm 1421 by driving the phase difference modulator with a control signal output from the signal generator 6. The modulated light pulses in the long arm 1421 and the non-modulated light pulses in the short arm 1422 are combined by the second coupler 144 to form a multi-wavelength dual light pulse. And then injected into the sensing fiber 7 through the circulator 2.
In the present embodiment, the multi-wavelength dual-optical pulse in the sensing fiber 7 generates rayleigh light under the action of the sensing signal, and the rayleigh light is output through the circulator 2. Certain wavelength component lambda of one pulse (p ═ 1,2) in multi-wavelength dual-light pulsei＝1,2,…,mThe intensity of the rayleigh optical signal (b) is the interference intensity of rayleigh scattered light at each position in the optical fiber covered by the optical pulse, and is represented by the above equation (1). After rayleigh light generated at a sensing position in the sensing optical fiber 7 is output, interference light intensity of the rayleigh light is obtained through the photoelectric detector 3, and the interference light intensity of a sensing channel at a position z in the sensing optical fiber 7 meets the requirement of the formula (2). Because the polarization state and propagation constant of the optical pulse are related to the wavelength of the light, and the accumulated phase of transmission is determined by the propagation constant and the polarization state of the light, the polarization state and the accumulated phase phi of different wavelength components in the Rayleigh signali,kDifference, resulting in intensity I of each wavelength component in Rayleigh signalp＝1,2Different, i.e. the intensity of each wavelength component in the rayleigh optical signal does not fade simultaneously. Thus, the amplitude of the AC signal of the interference intensity I (z) of the sensing channel at the z position of the optical fiber
Always at a stable level without fading. By using interference signal I (z) formed by multi-wavelength Rayleigh signal and combining phase demodulation technology, signal phase phi can be obtainedsAnd the detection noise deterioration phenomenon caused by the rayleigh signal light intensity fading is avoided.
The foregoing is considered as illustrative of the preferred embodiments of the invention and is not to be construed as limiting the invention in any way. Although the present invention has been described with reference to the preferred embodiments, it is not intended to be limited thereto. Therefore, any simple modification, equivalent change and modification made to the above embodiments according to the technical spirit of the present invention should fall within the protection scope of the technical scheme of the present invention, unless the technical spirit of the present invention departs from the content of the technical scheme of the present invention.
Claims (8)
1. The utility model provides an optical fiber distributed sensing device based on multi-wavelength double optical pulses which characterized in that: the device comprises a multi-wavelength double-light pulse generating assembly (1), a circulator (2), a photoelectric detector (3), a data collector (4), a signal processor (5) and a signal generator (6);
the multi-wavelength dual-optical pulse generation component (1) is used for generating multi-wavelength dual-optical pulses, and each pulse in the multi-wavelength dual-optical pulses comprises a plurality of wavelength components;
the circulator (2) is used for injecting the multi-wavelength dual-light pulse into a sensing optical fiber (7), receiving a Rayleigh optical signal generated in the sensing optical fiber (7) by the multi-wavelength dual-light pulse and outputting the Rayleigh optical signal;
the photoelectric detector (3) is used for detecting the interference light intensity of the Rayleigh light signal output by the circulator (2);
the data acquisition unit (4) is used for acquiring interference light intensity detected by the photoelectric detector (3) to obtain a light intensity signal;
the signal processor (5) is used for calculating the light intensity signal to obtain the phase information of the Rayleigh light signal so as to obtain the information of the signal sensed by the sensing optical fiber (7);
the signal generator (6) is used for providing a driving signal and a clock synchronization signal for the multi-wavelength double-light pulse generation assembly (1) and the data acquisition unit (4);
the multi-wavelength dual optical pulse generation assembly (1) comprises: the device comprises a laser (11), a beam combiner (12), a light intensity modulator (13) and a double-light pulse modulation component (14);
the laser (11) is used for generating multi-wavelength laser with a plurality of different wavelengths;
the beam combiner (12) is used for spatially combining the multi-wavelength lasers;
the light intensity modulator (13) is used for modulating the intensity of the multi-wavelength laser to generate periodically repeated multi-wavelength single light pulses;
the double-light pulse modulation component (14) is used for modulating the multi-wavelength single light pulse and modulating the multi-wavelength single light pulse into a multi-wavelength double-light pulse with a preset phase difference;
the signal processor (5) has a processor for: according to the signal intensity information of the Rayleigh light, obtaining the phase information of the Rayleigh light through a differential cross multiplication algorithm, thereby obtaining the information of the signals sensed by the sensing optical fiber, wherein the information of the sensed signals comprises amplitude, frequency and phase information; the signal intensity information of the rayleigh light is intensity information in which wavelength components in the rayleigh light are superimposed.
2. The multi-wavelength dual optical pulse-based optical fiber distributed sensing apparatus of claim 1, wherein: the laser (11) comprises a plurality of narrow linewidth lasers (11).
3. The multi-wavelength dual optical pulse-based optical fiber distributed sensing apparatus of claim 1, wherein: the dual optical pulse modulation assembly (14) comprises a first coupler (141), an unbalanced interferometer (142), a phase difference modulator (143), and a second coupler (144);
the first coupler (141) is used for injecting the multi-wavelength single light pulse to two light paths of the unbalanced interferometer (142);
the phase difference modulator (143) is used for modulating the phase of the laser in one optical path in the unbalanced interferometer (142);
the second coupler (144) is used for spatially combining the laser light in the two optical paths.
4. A method for multi-wavelength double-optical-pulse optical fiber distributed sensing based on the optical fiber distributed sensing device of any one of claims 1 to 3, comprising the following steps:
s1, generating multi-wavelength double-light pulses, and injecting the multi-wavelength double-light pulses into the sensing optical fiber, wherein each pulse in the multi-wavelength double-light pulses comprises a plurality of wavelength components;
s2, acquiring Rayleigh optical signals in the sensing optical fibers and interference light intensity of sensing channels corresponding to the Rayleigh optical signals;
and S3, calculating the interference light intensity to obtain the phase information of the Rayleigh light signal, thereby obtaining the information of the signal sensed by the sensing optical fiber.
5. The method of claim 4 wherein: and a preset phase difference exists between two pulse lights in the double-light pulse.
6. The method of claim 5 wherein: the dual optical pulses are generated from pulsed light by an unbalanced interferometer with a preset arm difference.
7. The method of claim 5 wherein: and the power difference of each wavelength component in the double optical pulses is smaller than a preset threshold value.
8. The method of claim 7 wherein: the specific steps of step S3 include: according to the signal intensity information of the Rayleigh light, obtaining the phase information of the Rayleigh light through a differential cross multiplication algorithm, thereby obtaining the information of the signals sensed by the sensing optical fiber, wherein the information of the sensed signals comprises amplitude, frequency and phase information; the signal intensity information of the rayleigh light is intensity information in which wavelength components in the rayleigh light are superimposed.
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