CN109282839A - Distributed optical fiber sensing system and method based on multiple-pulse multi-wavelength - Google Patents
Distributed optical fiber sensing system and method based on multiple-pulse multi-wavelength Download PDFInfo
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- CN109282839A CN109282839A CN201811405196.7A CN201811405196A CN109282839A CN 109282839 A CN109282839 A CN 109282839A CN 201811405196 A CN201811405196 A CN 201811405196A CN 109282839 A CN109282839 A CN 109282839A
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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
- 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
- G01D5/35325—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 interferometer with two arms in reflection, e.g. Mickelson interferometer
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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
- 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
- G01D5/344—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 using polarisation
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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
- 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
- G01D5/35338—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 other arrangements than interferometer arrangements
- G01D5/35354—Sensor working in reflection
- G01D5/35358—Sensor working in reflection using backscattering to detect the measured quantity
- G01D5/35361—Sensor working in reflection using backscattering to detect the measured quantity using elastic backscattering to detect the measured quantity, e.g. using Rayleigh backscattering
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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
- 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
- G01D5/3537—Optical fibre sensor using a particular arrangement of the optical fibre itself
- G01D5/35374—Particular layout of the fiber
Abstract
The invention discloses a kind of distributed optical fiber sensing system and method based on multiple-pulse multi-wavelength, belong to distributed fiberoptic sensor technical field, including light source module, modulation module, Postponement module, coupling module, pulse amplifying module, pre-amplifying module, beam splitting system, intervention module, signal detection module, data processing terminal.The present invention is combined using multiple light sources, the light of n wavelength is injected in a cycle T, pass through optical fiber delay line traffic control delay time, light pulse is set to be implanted sequentially sensor fibre according to particular order, the backward Rayleigh scattering light that this n light pulse generates is separated by the grating of different center reflection wavelengths, photoelectric conversion is carried out after into photodetector, the OTDR curve that n item is mutually independent is obtained after acquiring by AD, by demodulating n OTDR curve, the phase information that n repetition rate is f is obtained, curve after the demodulation of n item is interweaved with forming final result by array.
Description
Technical field
The invention belongs to distributed fiberoptic sensor technical field more particularly to a kind of distributions based on multiple-pulse multi-wavelength
Formula optical fiber sensing system and method.
Background technique
Distributing optical fiber sensing is an important application of sensory field of optic fibre, and compared to point sensor, distribution is passed
The advantage that the advantages that sensor is with the obvious advantage, at low cost, easy to process is much applied, on circumference security protection, pipe detection, ground
Matter exploration, distributed temperature measuring etc. have occupied the apparent market advantage in fields, it can detect the vibration along optical cable in real time
The physical quantitys such as dynamic, temperature, strain, good market prospect.
Currently, the system of distributed measurement is based primarily upon back scattering principle, the principle of this system is after utilizing to scattered
The change of properties of light is penetrated to realize detection, phase, polarization state, frequency including rear orientation light change etc..Common principle packet
Include phase-sensitive optical time domain reflectometer (φ-OTDR), polarization sensitive optical time domain reflectometer (P-OTDR), Brillouin light time domain
Reflectometer (B-OTDR), Raman optical time domain reflectometer (R-OTDR).Wherein phase-sensitive optical time domain reflectometer (φ-OTDR) is outstanding
It is suitble to over long distances, high spatial resolution, the use occasion of high s/n ratio.It can be used for vibration detecting, sound sensor, circumference security protection
Equal fields.
The basic principle of Φ-OTDR is the phase of the backward Rayleigh scattering light generated by the pulsed light injected in demodulation optical fiber
Position variation is to realize phase demodulating.When the vibration the effects of on optical fiber, this power will change the refractive index in optical fiber axial direction,
The light phase for further causing the position changes, and vibration signal can be obtained by analysis light phase variation.It is common at present
Distributed sensing system in, common detection demodulation scheme include 3 × 3 coupler demodulations, phase generated carrier demodulation scheme,
Digital coherent demodulation scheme, injected in these schemes every time light pulse in sensor fibre at most only one.Because if injection
More than multiple light pulses, the Rayleigh scattering light that the backward Rayleigh scattering light that previous light pulse generates can be generated with the latter occurs
Aliasing, a part for showing as the backward Rayleigh scattering light intensity of two pulses repeat, and can not demodulate the phase of repeating part
Position.
Therefore with the increase of fiber lengths, the maximum repetition rate of pulse can be reduced, maximum repetition rate and fiber lengths
Relationship is f=2nl/c, and wherein n is optical fiber effective refractive index.Light pulse one by one in Φ-ODTR system in injection fibre, this
Matter is the discrete sampling to last position of optical fiber, therefore according to Shaimon Sampling Theorem, which visits the maximum of vibration signal
Measured frequency is nl/c.It is simple signal since vibration signal is almost impossible, therefore actual detection maximum frequency is logical in actual conditions
It is often nl/2c.In a 100Km system, calculating gained maximum repetition rate is 1KHz, without down-sampled actual detection
Maximum frequency is only 250Hz, this cannot achieve the detection of high-frequency vibration and sound wave.If guaranteeing to detect maximum frequency
10 sets of 10Km systems are then needed in the case where rate, system cost will be greatly improved in this.It is combined using single light source cooperation frequency shifter flat
After monochromatic light source power is divided n times by the schemes such as detector demodulation that weigh, power be will settle toSignal-to-noise ratio will increase quickly with N
Deterioration.N number of different frequency shifters are controlled using N number of asynchronous signal simultaneously and also improve system complexity and cost, and are added without
The circuit devcies such as mixer filter.And full light scheme combination multiple light courcess is used, optical power distribution devices are not used, do not will cause
The decline of single pulse power.Keep the light of different wave length spatially separated using the combination of grating and circulator, while demodulation makes
Circuit devcie is effectively reduced compared to the scheme of balanced detector with fibre optic interferometer, is more advantageous to the anti-electromagnetism spoke of raising system
Penetrate ability.
Summary of the invention
In view of the problems of the existing technology, the invention proposes a kind of, and the distribution type fiber-optic based on multiple-pulse multi-wavelength passes
Sensing system and method；The present invention is combined using multiple light sources, and central wavelength slightly has difference, compared to traditional φ-ODTR system,
The program injects the light of n wavelength in a cycle T.The light of each wavelength is prolonged by optical fiber delay line traffic control by control
The slow time, make light pulse according to sequence be implanted sequentially sensor fibre, this n light pulse generate back rayleigh scattering light pass through
The gratings of different center reflection wavelengths separates, into photodetector after carry out photoelectric conversion, n item is obtained after acquiring by AD
OTDR curve, these curves are mutually independent, and there is interval on the time, by demodulating n OTDR curve, obtain n repetition
Frequency is the phase information of f, and curve after the demodulation of n item is interweaved with forming final result by array, can according to Shannon's sampling theorem
Know, its detectable signal maximum frequency of actual demodulation scheme is improved to n times.
One of the objects of the present invention is to provide a kind of distributed optical fiber sensing systems based on multiple-pulse multi-wavelength, including
Light source module, including the mutually different n narrow-linewidth laser light source of central wavelength；N is the natural number greater than 1；
Modulation module, including n optical fiber optical modulator and a pulse signal generator, the input of each optical fiber optical modulator
End is coupled with the light source output terminal of a narrow-linewidth laser light source, the signal output terminal of above-mentioned pulse signal generator and
The modulation terminal electrical connection of n optical fiber optical modulator；Above-mentioned optical fiber optical modulator is by the light source tune of narrow-linewidth laser light source output
It is made as pulsed light；
Postponement module, including n-1 root fibre delay line；The delay time of every fibre delay line is different, and every
The delay time of fibre delay line isM is the integer from 0 to n-1；F is that the pulse of pulse signal generator repeats frequency
Rate；
One output end of coupling module, including the fiber coupler of a n × 1, above-mentioned n optical fiber optical modulator passes through optical fiber
It is coupled with an input terminal of the fiber coupler of n × 1, other n-1 output end of above-mentioned n optical fiber optical modulator lead to respectively
An input terminal for crossing 1 fibre delay line and the fiber coupler of n × 1 is coupled；
Pulse amplifying module, including a pulse image intensifer, the signal input terminal and the light of n × 1 of the pulse image intensifer
The signal output terminal of fine coupler is connected by optical fiber；
The signal output terminal of pre-amplifying module, including a preamplifier, above-mentioned pulse image intensifer passes sequentially through
It is connect respectively with the signal input terminal of sensor fibre, preamplifier after the polarizer, circulator A；
Beam splitting system, including n group spectral module, every group of spectral module include a circulator B and a fiber grating, often
The circulator B of group spectral module is connected with fiber grating by optical fiber, and n group spectral module is sequentially connected in series by optical fiber, n optical fiber
The central wavelength of optical grating reflection is respectively equal to the central wavelength of n narrow-linewidth laser light source；The signal output end of preamplifier
Son is connect by optical fiber with the signal input terminal of the circulator B of the first spectral module；
Intervention module, including with the one-to-one n fiber optic interferometric component of n circulator B, every group of fiber optic interferometric component by
One 2 × 2 fiber coupler, 3 × 3 fiber couplers and two farad revolving mirrors constitute Michelson's interferometer；
Signal detection module, including n photodetector, the corresponding fiber optic interferometric component of each photodetector；
Data processing terminal is analyzed and processed for receiving the output signal of signal detection module, and to signal.
Further, the bandwidth of above-mentioned narrow-linewidth laser light source is less than 1KHZ.
Further, being directed to each fibre optic interferometer component: above-mentioned 2 × 2 fiber coupler include input terminal A (20),
Input terminal B (27), output terminal A (25) and docking terminal A；Above-mentioned 3 × 3 fiber coupler includes two input terminal C, defeated
Enter terminal D (28), output terminal C (24), output terminal D (26), docking terminal B；Above-mentioned docking terminal A and docking terminal B are logical
Optical fiber connection is crossed, above-mentioned input terminal B (27), input terminal D (28) are vacant by junction loss device；Above-mentioned two input terminal
Sub- C is separately connected a faraday rotation mirror (23).
Further, the range of above-mentioned pulse frequency f is 1 μ Hz to 10Mhz, the pulse duration is less than
Further, above-mentioned data processing terminal includes analog-to-digital conversion module and demodulation analysis machine.
The second object of the present invention is to provide a kind of side of distributed optical fiber sensing system based on multiple-pulse multi-wavelength
Method includes at least following steps:
Step 1: n narrow-linewidth laser light source issues n central wavelength and is followed successively by λ1,λ2…λnLaser, each light source
Connect an optical fiber optical modulator, n optical fiber optical modulator connects the same pulse signal generator, pulse signal generator and
Continuous light modulation is pulsed light by optical fiber optical modulator；
Step 2: under the action of Postponement module, λ will be removed1Other outer n-1 pulsed light pass through different optical fiber delays
Line generates different time delays, λ1,λ2…λnPostpone respectively
Step 3: n pulsed light enters pulse amplifier after delay after the coupler of n × 1, carries out pulse power
Amplification；
Step 4: amplified n pulsed light becomes linearly polarized light after the polarizer, then passes through circulator A injection
Sensor fibre；
Step 5: the backward Rayleigh scattering light returned from circulator A third port enters preamplifier, preamplifier
Processing is amplified to Rayleigh scattering light to rear；
Step 6: amplified backward Rayleigh scattering light enters beam splitting system, and each spectral module in beam splitting system is anti-
The light wave for penetrating a specific central wavelength transmits other light waves, and then the light of different central wavelengths is separated；
Step 7: each central wavelength after separating enters fiber optic interferometric component to Rayleigh scattering light, and each optical fiber is dry
Relate to the three road interference signals that component exports 120 ° of phase differences；
Step 8: the interference ripple signal that signal detection module forms three road interference signals of each fiber optic interferometric component
Be converted to electric signal；
Step 9: data processing terminal is obtained to receiving signal progress digital-to-analogue conversion, carrying out real-time or offline demodulation simultaneously
These results are carried out data interlacing by the φ-OTDR demodulation result of n different wave length.
In conclusion advantages of the present invention and good effect are as follows:
The multi-wavelength multiple-pulse multiplexing and demultiplex that the present invention is constituted using optical delay system, while using pure optics
Beam splitting system and interferometer demodulation scheme, respectively to being interleaved after different wave length OTDR curve processing, so that system surveying tape
Width is improved to n times, the detective bandwidth of the system that effectively improves to vibration signal.Certain system bandwidth can also sacrificed simultaneously
Under the premise of combine and average the methods of down-sampled improve system signal noise ratio.And can flexible configuration light source and light splitting be as needed
System, and full light scheme is used, the introducing of the devices such as electric frequency mixer, analog circuit filter is avoided, the resistance to of system is improved
Electromagnetic radiation.
Detailed description of the invention
Fig. 1 is the structural block diagram of the preferred embodiment of the present invention；
Fig. 2 is the structure chart of fiber optic interferometric component in the preferred embodiment of the present invention；
Fig. 3 is the n OTDR curve that n wavelength generates under pulse signal in the preferred embodiment of the present invention
Fig. 4 is the φ-OTDR demodulation result of each pulse in the case of each simple venation before data interlacing is washed off
Fig. 5 is the demodulation result that sampling is promoted after the multiple pulse optical modulator data interlacings of multiple wavelength.
Specific embodiment
In order to make the objectives, technical solutions, and advantages of the present invention clearer, with reference to embodiments, to the present invention
It is further elaborated.It should be appreciated that the specific embodiments described herein are merely illustrative of the present invention, it is not used to
Limit the present invention.
As depicted in figs. 1 and 2, a kind of distributed optical fiber sensing system based on multiple-pulse multi-wavelength is equipped with cardiac wave in n
It is long that there are the narrow-linewidth laser light source modules of difference, the fiber coupler of n × 1, optical fiber optical modulator, an optical fiber polarizer, light
Grid, fibre delay line, light amplification module, 2 × 2 fiber couplers, 3 × 3 fiber couplers, farad revolving mirror, optical fiber circulator,
Photodetector, pulse signal generator, digital-to-analogue conversion collector, demodulation analysis machine.The bandwidth of above-mentioned narrow-linewidth laser light source
Less than 1KHZ.
Wherein n light source issues the laser of n central wavelength, and each light source connects a modulator, this n modulator connects
Connect the same pulse signal generator.Continuous light modulation is other n-1 after pulsed light, other than first light source by modulator
A light source connects different fibre delay lines after modulator, and different delays time, λ is arranged in each delay line1,λ2…λnLight
Source corresponding delay line delay time is respectivelyWherein f is that the pulse of pulse signal generator repeats frequency
Rate.Then, by the fiber coupler of n × 1, this road n light pool it is a branch of, in a cycleInterior, there are n on chronological order
Light pulse, wavelength respectively correspond λ1,λ2…λn.The fiber coupler of n × 1 input connection pulse image intensifer, is amplified into annular
Device, circulator another port are separately connected long-distance sensing optical fiber and preamplifier.Preamplifier is by after to Rayleigh scattering
Light amplifies, subsequently into the beam splitting system being made of n circulator and fiber grating, the reflection peak difference of each grating
Corresponding λ1,λ2…λn, and to other wavelength light transmissions, by different wave length backwards to Reyleith scanttering light it is spatially separated after respectively enter n
A fibre optic interferometer being made of 3 × 3 fiber couplers and 2 × 2 fiber couplers, interferometer connects photodetector, then connects
Analog-to-digital conversion collector is connect, is analyzed by demodulation analysis instrument using digital signal processing method.
The central wavelength of above-mentioned n narrow-linewidth laser light source is respectively λ1,λ2…λn。
Modulator used is intensity modulation type in the present invention, and function is that continuous light output is converted to pulsed light.
Fibre delay line used in the present invention can make the delay in light pulse generation time.
The fiber coupler of n × 1 is used in the present invention, is acted on as by λ1,λ2…λnLight constant power be coupled into optical fiber.
Pulse signal generator used in the present invention, function are to generate cyclic pulse signal, and pulse frequency f can be from
1 μ Hz to 10Mhz setting, the pulse duration, which should be arranged, to be much smaller thanArbitrary waveform generator realization can be used.
Light amplification module is used in the present invention, is to amplify modulated pulse luminous intensity.
Circulator employed in the present invention is to enter pulsed light emission in sensor fibre, another port receive after to
Rayleigh scattering light.
Preamplifier employed in the present invention is that the backward Rayleigh scattering light for receiving circulator is put again
Greatly.
Heretofore described beam splitting system, including optical circulator and grating, wherein n raster center corresponds to λ1,λ2…λn,
Its function is that selective reflecting returns λ1,λ2…λnCorresponding Reyleith scanttering light, and transmit other band of light.
Fibre optic interferometer employed in the present invention, by 2 × 2 fiber couplers, 3 × 3 fiber couplers, farad revolving mirror
Constitute Michelson's interferometer.It is exported as the interference signal of 120 ° of phase differences two-by-two.；
As shown in Figure 2: be directed to each fibre optic interferometer component: above-mentioned 2 × 2 fiber coupler 21 includes input terminal
A20, input terminal B27, output terminal A25 and docking terminal A；Above-mentioned 3 × 3 fiber coupler includes two input terminal C, defeated
Enter terminal D28, output terminal C24, output terminal D26, docking terminal B；Above-mentioned docking terminal A and docking terminal B pass through optical fiber
Connection, above-mentioned input terminal B27, input terminal D28 are vacant by junction loss device；Above-mentioned two input terminal C connects respectively
Connect a faraday rotation mirror 23.
That is, 2 × 2 fiber coupler, 21 right end is connect with 3 × 3 fiber coupler, 22 left end, by junction loss device by 2
The input terminal B27 of × 2 fiber couplers is vacant.3 × 3 fiber coupler both ends are then connected into faraday rotation mirror 23, it is defeated
It is vacant by junction loss device to enter terminal D28.Then, by 2 × 2 fiber coupler output terminal A25 and 3 × 3 fiber couplings
As output, output result should be 3 tunnels, 120 ° of phase difference of interference letter two-by-two by output terminal C24, the output terminal D26 of device
Number.
Photodetector employed in the present invention is highly sensitive type, each has three identical photodetections of characteristic
Diode, and have noiselike signal enlarging function.
Its function of analog-to-digital conversion collector used in the present invention is that analog voltage/current signal is converted to digital letter
Number.
Demodulation analysis machine of the present invention is will to acquire signal to be analyzed and processed, and obtains n OTDR curve demodulation result,
This n ODTR curve demodulation result is interleaved into again, can be realized by computer or FPGA, DSP, ARM embedded platform etc..
A method of using the big bandwidth distribution formula optical fiber sensing system of multiple-pulse multi-wavelength light, specific implementation step is such as
Under:
Step 1: n light source issues the laser λ of n central wavelength1,λ2…λn, one modulator of each light source connection, n
A modulator connects the same pulse signal generator.Continuous light modulation is pulsed light under external signal input by modulator.
Step 2: λ is removed1N-1 outer pulsed light generates different time delays, λ by different fibre delay lines1,
λ2…λnPostpone respectively
Step 3: n pulsed light enters pulse amplifier after delay after the coupler of n × 1, carries out pulse power
Amplification.
Step 4: amplified multiple pulsed lights sense after becoming linearly polarized light after the polarizer by circulator injection
Optical fiber.
Step 5: the backward Rayleigh scattering light returned from 3 port of circulator enters preamplifier, and amplifier amplification is backward
Rayleigh scattering light.
Step 6: amplified backward Rayleigh scattering light enters beam splitting system, cardiac wave in each optical grating reflection of beam splitting system
Long corresponding light source central wavelength, grating selective reflecting corresponding wavelength, transmits other wavelength, then by the light of different central wavelengths
It separates.
Step 7: the Rayleigh scattering light of each wavelength after separating enters fibre optic interferometer, exports the three of 120 ° of phase differences
Road interference signal.
Step 8: n three road interference signals input photodetector, subsequently enter analog-digital converter, these analog-to-digital conversions
Device works in the case where postpone triggering mode, and the corresponding analog-digital converter of each beam splitting system sets different delays, to realize finally
OTDR curve is synchronous, sends data to host computer after analog-to-digital conversion acquisition.
Step 9: host computer carries out real-time or offline demodulation to collected data, obtains the φ-of n different wave length
These results are carried out data interlacing by OTDR demodulation result, and result is exactly that sample rate improves the result to after n times.
In Fig. 3, λ1, λ2, λ3…λnHomologous thread is respectively that OTDR is strong before the demodulation of acquisition gained after beam splitting system separates
It writes music line, it can be seen that every plot against time interval is identical, in time at periodic arrangement.
In Fig. 4 using 4 wavelength as example, 4 light source center wavelength be respectively 1550.1nm, 1550.3nm,
The each Light source line width of 1550.5nm, 1550.7nm is 1K Hz.Four curves are the vibration position used individually after demodulation
φ-ODTR phase diagram, it can be seen that in sample rate deficiency situation, indeed vibrations signal can not be reappeared.
Fig. 5 is the oscillating curve for describing the curve in Fig. 4 after data interlacing, after the system improves sampling,
High fdrequency component has obtained significant increase, can reappear vibration signal.
The foregoing is merely illustrative of the preferred embodiments of the present invention, is not intended to limit the invention, all in essence of the invention
Made any modifications, equivalent replacements, and improvements etc., should all be included in the protection scope of the present invention within mind and principle.
Claims (6)
1. a kind of distributed optical fiber sensing system based on multiple-pulse multi-wavelength, it is characterised in that: include at least:
Light source module, including the mutually different n narrow-linewidth laser light source of central wavelength；N is the natural number greater than 1；
Modulation module, including n optical fiber optical modulator and a pulse signal generator, the input terminal of each optical fiber optical modulator with
The light source output terminal of one narrow-linewidth laser light source is coupled, the signal output terminal and n of above-mentioned pulse signal generator
The modulation terminal of optical fiber optical modulator is electrically connected；The modulation of source of narrow-linewidth laser light source output is by above-mentioned optical fiber optical modulator
Pulsed light；
Postponement module, including n-1 root fibre delay line；The delay time of every fibre delay line is different, and every optical fiber
The delay time of delay line isM is the integer from 0 to n-1；F is the pulse recurrence frequency of pulse signal generator；
One output end of coupling module, including the fiber coupler of a n × 1, above-mentioned n optical fiber optical modulator passes through optical fiber and n
One input terminal of × 1 fiber coupler is coupled, other n-1 output end of above-mentioned n optical fiber optical modulator pass through 1 respectively
Root fibre delay line and an input terminal of the fiber coupler of n × 1 are coupled；
Pulse amplifying module, including a pulse image intensifer, the signal input terminal and the optical fiber coupling of n × 1 of the pulse image intensifer
The signal output terminal of clutch is connected by optical fiber；
Pre-amplifying module, including a preamplifier, the signal output terminal of above-mentioned pulse image intensifer, which passes sequentially through, to be polarized
It is connect respectively with the signal input terminal of sensor fibre, preamplifier after device, circulator A；
Beam splitting system, including n group spectral module, every group of spectral module include a circulator B and a fiber grating, every component
The circulator B of optical module is connected with fiber grating by optical fiber, and n group spectral module is sequentially connected in series by optical fiber, n fiber grating
The central wavelength of reflection is respectively equal to the central wavelength of n narrow-linewidth laser light source；The signal output terminal of preamplifier is logical
Optical fiber is crossed to connect with the signal input terminal of the circulator B of the first spectral module；
Intervention module, including with the one-to-one n fiber optic interferometric component of n circulator B, every group of fiber optic interferometric component is by one
2 × 2 fiber couplers, 3 × 3 fiber couplers and two farad revolving mirrors constitute Michelson's interferometer；
Signal detection module, including n photodetector, the corresponding fiber optic interferometric component of each photodetector；
Data processing terminal is analyzed and processed for receiving the output signal of signal detection module, and to signal.
2. the distributed optical fiber sensing system according to claim 1 based on multiple-pulse multi-wavelength, it is characterised in that: above-mentioned narrow
The bandwidth of line width laser light source is less than 1KHZ.
3. the distributed optical fiber sensing system according to claim 1 based on multiple-pulse multi-wavelength, it is characterised in that: be directed to
Each fibre optic interferometer component: above-mentioned 2 × 2 fiber coupler includes input terminal A (20), input terminal B (27), output terminal
A (25) and docking terminal A；Above-mentioned 3 × 3 fiber coupler includes two input terminal C, input terminal D (28), output terminal C
(24), output terminal D (26), docking terminal B；Above-mentioned docking terminal A is connected with docking terminal B by optical fiber, above-mentioned input terminal
Sub- B (27), input terminal D (28) are vacant by junction loss device；Above-mentioned two input terminal C is separately connected a faraday
Revolving mirror (23).
4. the distributed optical fiber sensing system according to claim 1 based on multiple-pulse multi-wavelength, it is characterised in that: above-mentioned arteries and veins
The range for rushing frequency f is 1 μ Hz to 10Mhz, and the pulse duration is less than
5. a kind of distributed optical fiber sensing system based on multiple-pulse multi-wavelength, which is characterized in that above-mentioned data processing terminal packet
Include analog-to-digital conversion module and demodulation analysis machine.
6. a kind of method of the distributed optical fiber sensing system based on multiple-pulse multi-wavelength, which is characterized in that include at least as follows
Step:
Step 1: n narrow-linewidth laser light source issues n central wavelength and is followed successively by λ1,λ2…λnLaser, the connection of each light source
One optical fiber optical modulator, n optical fiber optical modulator connect the same pulse signal generator, pulse signal generator and optical fiber
Continuous light modulation is pulsed light by optical modulator；
Step 2: under the action of Postponement module, λ will be removed1Other outer n-1 pulsed light are produced by different fibre delay lines
Raw different time delay, λ1,λ2…λnPostpone respectively
Step 3: n pulsed light enters pulse amplifier after delay after the coupler of n × 1, carries out pulse power and puts
Greatly；
Step 4: amplified n pulsed light becomes linearly polarized light after the polarizer, then passes through circulator A injection sensing
Optical fiber；
Step 5: the backward Rayleigh scattering light returned from circulator A third port enters preamplifier, and preamplifier is to rear
Processing is amplified to Rayleigh scattering light；
Step 6: amplified backward Rayleigh scattering light enters beam splitting system, each spectral module reflection one in beam splitting system
The light wave of a specific central wavelength transmits other light waves, and then the light of different central wavelengths is separated；
Step 7: each central wavelength after separating to Rayleigh scattering light enters fiber optic interferometric component, each fiber optic interferometric group
Part exports three road interference signals of 120 ° of phase differences；
Step 8: the interference ripple signal that signal detection module forms three road interference signals of each fiber optic interferometric component is converted
For electric signal；
Step 9: data processing terminal obtains n to receiving signal progress digital-to-analogue conversion, carrying out real-time or offline demodulation simultaneously
These results are carried out data interlacing by the φ-OTDR demodulation result of different wave length.
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