CN106768277B - A kind of demodulation method of distributed optical fiber vibration sensing device - Google Patents
A kind of demodulation method of distributed optical fiber vibration sensing device Download PDFInfo
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Abstract
The invention discloses a kind of distributed optical fiber vibration sensing devices based on coherent phase detection, comprising: light source module generates the continuous narrow-linewidth laser of two-way, wherein inputting optical modulator module all the way, another way inputs coherent reception module；Optical modulator module is by the continuous narrow-linewidth laser shift frequency of the first via and is modulated to short light pulse sequence；Short light pulse sequence enters sensor fibre, reflects output reflection photon sequence by weak reflection Bragg grating array after vibration signal is modulated；It reflects after photon sequence and the continuous narrow-linewidth laser of another way are interfered in relevant optical receiver module and is converted into electric signal and export multiple beat frequency subsequences, multiple beat frequency subsequences are demodulated to position and the vibrational waveform for obtaining all vibration signals on entire sensor fibre by signal processing module；The present invention uses coherent phase optical time domain reflection technology, and positioning accuracy is high, and vibration frequency response range is big, and vibrational waveform signal-to-noise ratio is high, can be realized long-distance distributed detection.
Description
Technical field
The present invention relates to a kind of technologies of sensory field of optic fibre, are a kind of based on coherent phase detection more specifically
Distributed optical fiber vibration sensing device.
Background technique
Optical fiber sensing technology has emerged rapidly since the 1970s, optical fiber was by invention, by decades research and
Development is widely used for multiple fields.In addition to perceiving outside since optical fiber also has other than remote high rate communication field
The ability of various physical parameters, researcher's invention have made a series of fiber optic sensing device.Optical fiber sensing system Yin Qinai
Corrosion, the advantages that electromagnetism interference compared with traditional electromechanical transducer system, more suitable for detection information in adverse circumstances and
Ability with distributed sensing and remote recording, so Distributed Optical Fiber Sensing Techniques have become a hot topic of research in recent years.
Distributed Optical Fiber Sensing Techniques not only have ordinary optic fibre sensing technology high sensitivity, high temperature resistant, anticorrosive and anti-
The advantageous characteristics such as electromagnetic interference, and the advantage of fiber distribution extension can be more embodied, the optical fiber on wiring path can be made
All as sensing element, there is the information parameter for obtaining be measured in entire sensitive zones in real time, transmission and sensing are closed two
It is one, reduces the cost for laying senser element.Distributed optical fiber vibration sensing technology transmits phase using light wave in a fiber
Position, polarization etc. monitor the vibration near optical fiber to the characteristic of vibration sensing in real time, and fault point or disturbance point are determined in realization
Position, is an important branch of Distributed Optical Fiber Sensing Techniques.Especially in the monitoring required over long distances with high spatial resolution
In, the advantage that distributed optical fiber vibration sensor has electronic sensing devices incomparable, in intrusion detection, Community Safety, oil
The fields such as feed channel leakage and building structure monitoring have wide application prospect.
Most popular, most popular research at present is based on optical time domain reflectometer OTDR (Optical Time
Domain Reflectometer) distributed optical fiber vibration sensing technology.It is with compact-sized, demodulating algorithm is simple, spirit
The advantages that sensitivity height, accurate positioning, is divided into phase optical time domain reflectometer, polarized light time domain reflection according to sensing principle is different again
Instrument, Brillouin optical time-domain reflectometer etc..Optical time domain reflectometer is to detect load by the back-scattering light in detection fiber to exist
Outer signals on optical fiber.But since the backscattering optical signal power in ordinary optic fibre is very low so as to cause signal light
Signal-to-noise ratio it is low, be easy to appear the erroneous judgement of vibration signal positioning, and the average detection time takes long time, and significantly limits biography
The detection accuracy of sensor, sensitivity, the performance indicators such as frequency response range.Especially above-mentioned first two mode is difficult to detect
The quasi-static vibration signal of 0Hz or so.
Summary of the invention
For disadvantages described above, the present invention proposes a kind of distributed optical fiber vibration detection device based on coherent phase detection,
Aim to solve the problem that the technical issues of existing vibration sensor signal-to-noise ratio is low, and frequency response range is small, position inaccurate.
To achieve the above object, the present invention provides a kind of distributed optical fiber vibration detection dress based on coherent phase detection
It sets, comprising:
Light source module, for generating continuous narrow-linewidth laser；
Optical modulator module, input terminal are connect with light source module output end, for continuous narrow-linewidth laser to be carried out shift frequency
And modulation treatment, export short light pulse sequence；
Sensor fibre, inscription have weak reflection Bragg grating array, and input terminal is connect with optical modulator module output end, short
Pulsed light sequence modulates by vibration signal and exports multiple reflection photon sequences by the reflection of weak reflection Bragg grating array；
Relevant optical receiver module, one input end are connect with light source module output end, and another input terminal and sensor fibre are defeated
Outlet connection, for allowing continuous narrow-linewidth laser and multiple reflection photon sequences to interfere to form multiple sub- sequences of beat frequency optical signal
Column, and electric signal is converted by optical signal by multiple beat frequency optical signal subsequences, and export multiple beat frequency subsequences；
Signal processing module, input terminal are connect with the output end of relevant optical receiver module, are used for the sub- sequence of multiple beat frequencies
Column carry out phase demodulating and obtain each position vibration signal.
Vibration letter is carried out by grating array of the short light pulse sequence inputting of continuous narrow-linewidth laser into sensor fibre
Number detection, returns to reflection photon sequence, due to the short light pulse sequence using continuous narrow-linewidth laser, between each short light pulse
Every can be sufficiently small, can be realized the measurement of high-frequency vibration signal, due to using the enhancing of Bragg grating array backwards to dissipating
Luminous intensity is penetrated, signal-to-noise ratio is high, and the backscattering light pulse sequence and reference light of return can generate beat frequency, while use cross-correlation
Algorithm obtains the phase information in region between adjacent Bragg grating in bragg grating array, then also using phase unwrapping algorithm
Original goes out vibration signal waveforms, and vibration signal waveforms reduction rate is fast, can be realized when acquiring high-frequency vibration signal in real time
Vibration signal is restored, so that the frequency response range of vibration sensor is big.The position of vibration signal passes through the short arteries and veins received
Subsequences sequencing obtain, by each beat frequency electric signal in beat frequency subsequence position, determine each beat frequency electric signal
Corresponding reflected light can determine that reflected light corresponds to optical fiber cloth in reflected light sequence location in reflected light sequence location, by reflected light
Loudspeaker lattice grating determines vibration signal position according to Fiber Bragg Grating, so that vibration signal accurate positioning.
Further, light source module includes:
Continuous narrow linewidth laser, for exporting continuous narrow-linewidth laser；
Fiber coupler, input terminal are connect with continuous narrow linewidth laser output end, the first output end and light modulation
Module input connection, second output terminal connect with relevant optical receiver module, is used to continuous narrow-linewidth laser beam splitting be the
The continuous narrow-linewidth laser of continuous narrow-linewidth laser and the second road all the way.
Further, optical modulator module includes:
First output end of acousto-optic modulator, input terminal and fiber coupler connects, for by the continuous narrow line of the first via
Wide laser carries out shift frequency processing and modulation treatment exports the first short light pulse sequence；
The output end of erbium-doped fiber amplifier, input terminal and acousto-optic modulator connects, for the first short light pulse sequence
Column amplify processing the second short light pulse sequence of output；
Narrow linewidth bandpass filter, input terminal are connect with erbium-doped fiber amplifier output end, for the second short pulse
Light sequence carries out Denoising disposal, exports short light pulse sequence.
It further, further include circulator, input terminal is connect with optical modulator module output end, the first output end and sensing
Optical fiber, second output terminal are connect with relevant optical receiver module, realize that short light pulse sequence is being sensed with multiple reflection photon sequences
Transmitted in both directions in optical fiber.
Further, relevant optical receiver module includes:
Coherent optical-fiber coupler, first input end are connect with circulator second output terminal, the second input terminal and optical fiber
The connection of coupler second output terminal, for interfering multiple reflection photon sequences with the continuous narrow-linewidth laser in the second road, shape
It is the multiple sub- sequences of beat frequency optical signal of the first via at multiple beat frequency optical signal subsequences, and by multiple beat frequency optical signal subsequence beam splitting
The multiple beat frequency optical signal subsequence outputs of column and the second tunnel；
Balanced detector, first input end are connect with the first output end of coherent optical-fiber coupler, and it is multiple to receive the first via
Beat frequency optical signal subsequence, the second input terminal are connect with coherent optical-fiber coupler second output terminal, receive the multiple bats in the second tunnel
Frequency optical signal subsequence, it is poor that the multiple beat frequency optical signal subsequences of the multiple beat frequency optical signal subsequences of the first via and the second tunnel are carried out
Divide processing, obtains amplified multiple beat frequency optical signal subsequences, and by amplified multiple beat frequency optical signal subsequences by light
Signal is converted into electric signal, exports multiple beat frequency subsequences.
Further, all weak reflection Bragg gratings are spacedly distributed in weak reflection Bragg grating array.
It is convenient for being positioned according to beat frequency subsequence using the weak reflection Bragg grating array being spacedly distributed and obtains vibration letter
Number position, accelerate signal processing module demodulation vibration signal speed.
Further, all weak reflection Bragg grating reflection wavelengths are equal, and continuous narrow-linewidth laser wavelength and weak anti-
It is identical to penetrate Bragg grating reflection wavelength.
Further, the duration of each short light pulse is in short light pulse sequenceTwo adjacent short pulses
The interval of light
Wherein, n is optical fibre refractivity, and l is the spacing of two adjacent Bragg gratings, and c is the light velocity；N is weak reflection cloth loudspeaker lattice
The number of weak reflection Bragg grating in grating array.
It is non-overlapping between each reflected light signal subsequence, then each reflected light signal subsequence and continuous narrow-linewidth laser
The beat frequency optical signal subsequence of generation is not overlapped, and improves signal processing module to the demodulation rate of beat frequency electric signal, increases vibration
The response frequency range of sensing device.
As another aspect of the present invention, the present invention provides a kind of demodulation sides of distributed optical fiber vibration sensing device
Method includes the following steps:
(1) to+1 beat frequency of kth in k-th of beat frequency in i-th of beat frequency subsequence and i-th of beat frequency subsequence using mutual
Correlation method obtains the phase difference of+1 beat frequency of kth in k-th of beat frequency and i-th beat frequency subsequence in i-th of beat frequency subsequence；
(2) by the phase of+1 beat frequency of kth in k-th of beat frequency in i-th of beat frequency subsequence and i-th of beat frequency subsequence
Difference carries out phase unwrapping and obtains in i-th of beat frequency subsequence+1 beat frequency of kth in k-th of beat frequency and i-th of beat frequency subsequence
Solution twines rear phase difference, and by the solution of+1 beat frequency of kth in k-th of beat frequency in i-th of beat frequency subsequence and i-th of beat frequency subsequence
Twine rear phase difference as k-th of vibration signal i-th of beat frequency subsequence initial time intensity；
(3) judge whether beat frequency order k is equal to P-1, if so, entering step (4)；Otherwise, k=k+1 is enabled, is entered step
(1)；
(4) judge whether beat frequency subsequence order i is equal to beat frequency subsequence quantity Q, if so, entering step (5)；Otherwise,
I=i+1 is enabled, (1) is entered step；
(5) intensity according to kth vibration signal in i-th of beat frequency subsequence initial time obtains kth vibration signal waveforms；
K-th of vibration signal is positioned at the corresponding weak reflection Bragg grating of k-th of beat frequency and+1 beat frequency pair of kth
The vibration signal between weak reflection Bragg grating answered, 1≤k≤P-1,1≤i≤Q, Q are the quantity of beat frequency subsequence, and P is
Beat frequency quantity in each beat frequency subsequence.
The demodulation method of distributed optical fiber vibration sensing device provided by the invention, being capable of fast demodulation by cross-correlation method
Vibration signal out, and it is not necessarily to other additional demodulation devices.
Technical solution of the present invention compared with prior art, there is following technical effect:
1, due to enhancing back-scattering light, the light of signal light using weak reflection Bragg grating array in sensor fibre
Power is multiplied compared to other schemes, improves system signal noise ratio.
2, the positioning of vibration signal is to be reflected back reflected light by the weak reflection Bragg grating of each in sensor fibre to connect
The time sequencing of receipts corresponds to corresponding weak reflection Bragg grating, and weak reflection Bragg grating position is that sensor fibre made
Fixed in journey, positioning accuracy is high.
3, since the reflection photon sequence that will be loaded with vibration signal and continuous narrow-linewidth laser are in relevant optical receiver module
Middle that relevant, generation beat frequency occurs, then by cross-correlation method demodulation phase, realization demodulates vibration signal, and demodulation speed is fast,
Real-time frequency response range is up to number kHz；In the quasi-static vibration signal of detection low frequency, by weak reflection Bragg grating array
Reflected optical power it is big, signal-to-noise ratio is high, and can remove the low frequency environments noise signal in reflected light, energy using cross correlation algorithm
Enough realize demodulates the quasi-static vibration signal of low frequency.
4, in low frequency vibration measurement, distance sensing is primarily limited to reflected optical power intensity, using -50dB reflectivity
Grating can realize the cascade of thousands of a gratings, and detection range is up to tens of kms.
Detailed description of the invention
Fig. 1 is the schematic diagram of the distributed optical fiber vibration sensing device provided by the invention based on coherent phase detection；
Fig. 2 is the embodiment signal of the distributed optical fiber vibration sensing device provided by the invention based on coherent phase detection
Figure；
Fig. 3 is the time-frequency spectrum for the beat frequency subsequence that signal processing module receives in embodiment in the present invention；
Fig. 4 is demodulated rear weak anti-positioned at the 299th weak reflection Bragg grating and the 300th in embodiment in the present invention
Penetrate the vibrational waveform figure of vibration signal between Bragg grating；
Specific embodiment
In order to make the objectives, technical solutions, and advantages of the present invention clearer, with reference to the accompanying drawings and embodiments, right
The present invention is further elaborated.It should be appreciated that described herein, specific examples are only used to explain the present invention, not
For limiting the present invention.
Fig. 1 is the schematic diagram of the distributed optical fiber vibration sensing device provided by the invention based on coherent phase detection, vibration
Dynamic sensing device includes light source module 1, and output end is connect with 2 input terminal of optical modulator module, and light source module 1 is for generating two-way
Continuous narrow-linewidth laser, optical modulator module 2 is by the continuous narrow-linewidth laser shift frequency of the first via and is modulated to short light pulse sequence, light tune
2 output end of molding block is connect with sensor fibre 5, and inscribing in sensor fibre 5 has transonic Bragg grating array, continuous narrow line
The wavelength of wide laser is identical as weak reflection Bragg grating wavelength, and all weak reflection Bragg grating wavelengths are identical.Short pulse
After each pulsed light enters sensor fibre 5 in light sequence, vibration signal is modulated each short light pulse, and process is modulated
Each short light pulse is reflected via transonic Bragg grating array, exports a reflection photon sequence, sensor fibre 5 it is defeated
Outlet is connect with relevant 3 second input terminal of optical receiver module, the second output terminal of light source module 1 and relevant optical receiver module 3
First input end connection, relevant 3 output end of optical receiver module are connect with 4 input terminal of signal processing module, multiple reflection photon sequences
It arranges the continuous narrow-linewidth laser in the second road exported with light source module to interfere in relevant optical receiver module 3, forms multiple beat frequencies
Optical signal subsequence, while multiple beat frequency optical signal subsequences are converted into electric signal by optical signal, multiple beat frequency subsequences are exported,
Signal processing module 4 is by carrying out the vibration signal waveforms that phase demodulating restores each position to beat frequency subsequence.
Using the sensor fibre for being carved with weak reflection Bragg grating array in the present invention, short light pulse sequence passes through weak reflection
Bragg grating reflected optical power is big, and the wavelength of continuous narrow-linewidth laser is identical as weak reflection Bragg grating wavelength, and all
Weak reflection Bragg grating wavelength is identical, can further increase the optical power of weak reflection Bragg grating reflection, improve noise
Than.Using the short light pulse sequence of continuous narrow-linewidth laser, each short light pulse interval in short light pulse sequence can be made enough
It is small, it can to improve sample frequency, while the reflection photon sequence for being loaded with vibration signal and continuous narrow-linewidth laser being allowed to occur
Interference, and vibration signal is restored using phase demodulating, demodulation speed is fast, and without other demodulation devices, so that the vibration passes
Induction device response frequency range is big.In the quasi-static vibration signal of detection low frequency, by the reflection of weak reflection Bragg grating array
Optical power is big, and signal-to-noise ratio is high, and can be removed using cross correlation algorithm and obtain noise signal in reflected light, can be realized to low frequency standard
The demodulation of static vibration signal.The position of each vibration signal according in sensor fibre it is weak reflection Bragg grating position really,
The accurate positioning of vibration signal may be implemented.
In the embodiment of distributed optical fiber vibration sensing device provided by the invention, the short pulse of the output of optical modulator module 2
The duration of light sequence, each short light pulse isTwo adjacent applied in short pulse intervalsWherein, n is
Optical fibre refractivity, l are the spacing of two adjacent transonic Bragg gratings, and c is the light velocity, and N is transonic Bragg grating
Number.Since two adjacent short light pulse intervals are greater than short light pulse maximum transmission time back and forth in sensor fibre, often
Beat frequency non-overlapping between a reflected light signal subsequence, then that each reflected light signal subsequence and continuous narrow-linewidth laser generate
Optical signal subsequence is not overlapped, and improves signal processing module to the demodulation rate of beat frequency subsequence, effectively increases vibrating sensing dress
The response frequency range set.
Fig. 2 is the schematic diagram of the embodiment of distributed optical fiber vibration sensing device provided by the invention, and light source module 1 includes
Continuous narrow linewidth laser 11 and fiber coupler 12, the input of continuous narrow linewidth laser 11 output end and fiber coupler 12
End connection, the first output end of fiber coupler 12 are connect with 21 input terminal of acousto-optic modulator in optical modulator module 2, optical fiber coupling
The second output terminal of clutch 12 is connect with 31 first input end of coherent optical-fiber coupler in relevant optical receiver module 3, continuous narrow line
Wide laser 11 is used to continuous narrow-linewidth laser beam splitting be the first via for exporting continuous narrow-linewidth laser, fiber coupler 12
Continuous narrow-linewidth laser and the continuous narrow-linewidth laser in the second road.Optical modulator module 2 further includes erbium-doped fiber amplifier 22 and narrow line
Broadband-pass filter 23,21 output end of acousto-optic modulator are connect with 22 input terminal of erbium-based amplifier, the output of erbium-based amplifier 22
End is connect with narrow linewidth bandpass filter 23, and the continuous narrow-linewidth laser of the first via is carried out shift frequency and is modulated by acousto-optic modulator 23
First short light pulse sequence, erbium-doped fiber amplifier 22 are used to amplifying short light pulse sequence into the second short light pulse sequence of output
Column, narrow linewidth bandpass filter 23 are used to noise remove in the second short light pulse sequence exporting short light pulse sequence.Narrow linewidth
23 output end of bandpass filter is connect with 6 input terminal a of circulator, and 6 first output end b of circulator and 5 input terminal of sensor fibre connect
It connects, 6 second output terminal c of circulator is connect with 31 second input terminal of coherent optical-fiber coupler.Short light pulse sequence enters sense light
It after fibre, modulates by vibration signal, and is reflected by weak reflection Bragg grating array, export multiple reflected light signal subsequences,
The continuous narrow-linewidth laser of multiple reflection photon sequences and the second road is interfered in coherent optical-fiber coupler 31, generates multiple bats
Frequency optical signal subsequence, while multiple beat frequency optical signal subsequences are the multiple bats of the first via via 31 beam splitting of coherent optical-fiber coupler
The multiple beat frequency optical signal subsequences of frequency optical signal subsequence and the second tunnel, 32 first input end of balanced detector and coherent optical-fiber coupling
The connection of 31 first output end of clutch, 32 second input terminal of balanced detector are connect with 31 second output terminal of coherent optical-fiber coupler,
The multiple beat frequency optical signal subsequences of the first via and the multiple beat frequency optical signal subsequence phase by pi in the second tunnel, by the first via
After the multiple beat frequency optical signal subsequences of multiple beat frequency optical signal subsequences and the second tunnel carry out difference, amplified multiple bats are exported
Frequency optical signal subsequence, and electric signal is converted by optical signal by amplified multiple beat frequency optical signal subsequences, it exports multiple
The output end of beat frequency subsequence, balanced detector 32 is connect with signal processing module input terminal, and signal processing module 4 passes through phase
Multiple beat frequency subsequences are reverted to the vibration signal of each position by demodulation.
In embodiment provided by the invention, the optical maser wavelength that continuous narrow linewidth laser 11 issues is 1550.7nm, optical fiber
The splitting ratio of coupler 12 is 99:1, that is, enters the light intensity of acousto-optic modulator 21 and enter light intensity in coherent optical-fiber coupler 31
Than for 99:1.3 shift frequency of acousto-optic modulator is 200MHz, and the shortest pulse duration modulated is 20 nanoseconds, pulse spacing 20
Microsecond.Sensor fibre 5 is general single mode telecommunication optical fiber, overall length 1.3km, using wire-drawer-tower at grid technique, in drawing optical fibers system
Good weak reflection Bragg grating array is inscribed during making, wherein the weak reflection Bragg grating array overall length 1.2km in optical fiber,
The weak reflection Bragg grating of 4m distribution is spaced comprising 300, the reflectivity of weak reflection Bragg grating is about -50dB, cloth loudspeaker
Long lattice wave is about 1550.7nm.31 splitting ratio of coherent optical-fiber coupler is 50:50, and the bandwidth of balanced detector 9 is 1GHz.It is preferred that
Ground, the splitting ratio of the fiber coupler are 50:50.The sample rate of digital signal processing module 4 is 2G/s, and resolution ratio is
8bit。
In embodiment provided by the invention, acousto-optic modulator 31 carries out shift frequency to continuous narrow-linewidth laser and modulates short pulse
When light sequence, trigger signal is sent to digital signal processing module 4, realizes the synchronous acquisition of beat frequency subsequence, while short to M
Pulse marks in chronological order, it may be assumed that { xm}；M=1,2,3 ..., M, each short light pulse enter in sensor fibre 5, are located at 300
Vibration signal between a weak reflection Bragg grating is modulated short pulse, changes the phase of each short light pulse, is adjusted
Each short light pulse after system reflects to form reflected light signal subsequence by the weak reflection Bragg grating that 300 are successively arranged,
The vibration letter being located at before the weak reflection Bragg grating by some weak reflection Bragg grating reflection back reflection optical signal load
Number, therefore phase difference can react adjacent weak positioned at corresponding two between two neighboring reflection optical signals in reflected light signal subsequence
The intensity for reflecting vibration signal between Bragg grating, sequentially in time marks reflected light signal subsequence are as follows: { xm(k)；
K=1,2 ..., 300 }, m-th of reflected light signal subsequence xm(k) the Time Domain Reflectometry spectrum of 300 Bragg gratings is respectively corresponded,
Since M applied in short pulse intervals time is greater than each short light pulse maximum transmission time back and forth, each reflection in sensor fibre
It is non-overlapping between optical signal subsequence.Each reflected light signal subsequence { xm(k)；K=1,2 ..., 300 } it is connect in coherent light
It receives in module and is coherent to form beat frequency optical signal subsequence with continuous narrow-linewidth laser, beat frequency optical signal subsequence is turned by optical signal
Electric signal is turned to, beat frequency subsequence is exported, beat frequency quantity is identical as grating quantity in beat frequency subsequence, the quantity of beat frequency subsequence
It is identical as short light pulse quantity in short light pulse sequence, and k-th of beat frequency is corresponded to by k-th of weak reflection cloth in beat frequency subsequence
The optical signal of loudspeaker lattice optical grating reflection.Fig. 3 is the beat frequency subsequence time-domain diagram detected, and beat frequency subsequence is by allowing single short arteries and veins
Pulsed light signal { xm}；The relevant bat generated of reflected light signal subsequence and continuous narrow-linewidth laser that n=1,2,3 ..., M are formed
Frequency optical signal subsequence is simultaneously converted into electric signal acquisition.
Multiple beat frequency subsequences are reverted to the vibration signal of each position by phase demodulating by signal processing module, including
Following steps:
(1) to+1 beat frequency of kth in k-th of beat frequency in i-th of beat frequency subsequence and i-th of beat frequency subsequence using mutual
Correlation method obtains the phase difference of+1 beat frequency of kth in k-th of beat frequency and i-th beat frequency subsequence in i-th of beat frequency subsequence.
(2) by the phase of+1 beat frequency of kth in k-th of beat frequency in i-th of beat frequency subsequence and i-th of beat frequency subsequence
Difference carries out phase unwrapping and obtains in i-th of beat frequency subsequence+1 beat frequency of kth in k-th of beat frequency and i-th of beat frequency subsequence
Solution twines rear phase difference；
In the i-th beat frequency subsequence, if compared to two adjacent beat frequencies of phase difference between+1 beat frequency of k-th of beat frequency and kth
Between phase difference there is phase difference maximum value and become phase difference minimum value or phase difference minimum value becoming phase difference maximum value
Jump, and above-mentioned two adjacent beat frequency is before k-th of beat frequency, then to phase difference phase between+1 beat frequency of k-th of beat frequency and kth
Plus or minus 2 π, realization twine phase difference solution between+1 beat frequency of k-th of beat frequency and kth；
And after the solution of+1 beat frequency of kth in k-th of beat frequency in i-th of beat frequency subsequence and i-th of beat frequency subsequence is twined
Phase difference as kth vibration signal i-th of beat frequency subsequence initial time intensity；
Wherein, kth vibration signal is positioned at the corresponding weak reflection Bragg grating of k-th of beat frequency and+1 beat frequency pair of kth
The vibration signal between weak reflection Bragg grating answered.
(3) judge whether beat frequency order k is equal to P-1, if so, entering step (4)；K=k+1 is enabled, (1) is entered step；
(4) judge whether beat frequency subsequence order i is equal to beat frequency subsequence quantity Q, if so, (5) are entered step, otherwise,
I=i+1 is enabled, (1) is entered step；
(5) wave of kth vibration signal is obtained in the intensity of i-th of beat frequency subsequence initial time according to kth vibration signal
Shape；
1≤k≤P-1,1≤i≤Q, Q are the quantity of beat frequency subsequence, and P is beat frequency quantity in each beat frequency subsequence.
Apply 2Hz, 5Hz respectively between the 299th weak reflection Bragg grating and the 300th weak reflection Bragg grating,
2kHz, 5kHz vibration signal, the vibration signal waveforms obtained by demodulation method provided by the invention are as shown in Figure 4.
The present embodiment realizes the distributed vibrating sensing of 4m resolution ratio in 1.2km length, and system signal noise ratio is relative to general
Light passing time-domain reflectomer sensor-based system improves about 9dB.
The demodulation method of distributed optical fiber vibration sensing device provided by the invention, being capable of fast demodulation by cross-correlation method
Vibration signal out, and other additional demodulation devices are not necessarily to, it can adapt to distributed optical fiber vibration sensing device provided by the invention
Bigger vibration frequency range is responded, while also can be realized the demodulation of alignment static vibration signal.
It should be noted last that the above specific embodiment is only used to illustrate the technical scheme of the present invention and not to limit it,
Although being described the invention in detail referring to preferred embodiment, those skilled in the art should understand that, it can be right
Technical solution of the present invention is modified or replaced equivalently, without departing from the spirit and scope of the technical solution of the present invention,
It is intended to be within the scope of the claims of the invention.
Claims (7)
1. a kind of demodulation method of distributed optical fiber vibration sensing device, which comprises the steps of:
(1) cross-correlation method is used to+1 beat frequency of kth in k-th of beat frequency in i-th of beat frequency subsequence and i-th of beat frequency subsequence
Obtain the phase difference of+1 beat frequency of kth in k-th of beat frequency and i-th of beat frequency subsequence in i-th of beat frequency subsequence；
(2) phase difference of+1 beat frequency of kth in k-th of beat frequency in i-th of beat frequency subsequence and i-th of beat frequency subsequence is carried out
After the solution that phase unwrapping obtains+1 beat frequency of kth in k-th of beat frequency and i-th of beat frequency subsequence in i-th of beat frequency subsequence twines
Phase difference, and the solution of+1 beat frequency of kth in k-th of beat frequency in i-th of beat frequency subsequence and i-th of beat frequency subsequence is twined into rear phase
Potential difference as k-th of vibration signal i-th of beat frequency subsequence initial time intensity；
(3) judge whether beat frequency order k is equal to P-1, if so, entering step (4)；Otherwise, k=k+1 is enabled, (1) is entered step；
(4) judge whether beat frequency subsequence order i is equal to beat frequency subsequence quantity, if so, entering step (5)；Otherwise, i=i is enabled
+ 1, enter step (1)；
(5) intensity according to k-th of vibration signal in i-th of beat frequency subsequence initial time obtains k-th of vibration signal waveforms；
1≤k≤P-1,1≤i≤Q, Q are the quantity of beat frequency subsequence, and P is beat frequency quantity in each beat frequency subsequence；
The distributed optical fiber vibration sensing device includes:
Light source module (1), for generating continuous narrow-linewidth laser；
Optical modulator module (2), input terminal are connect with the light source module (1) output end, for by continuous narrow-linewidth laser into
Row shift frequency and modulation treatment export short light pulse sequence, in the short light pulse sequence duration of each short light pulse beThe interval of two adjacent short light pulsesWherein, n is optical fibre refractivity, and l is two adjacent weak reflection cloth loudspeakers
The spacing of lattice grating, c are the light velocity；N is the number of weak reflection Bragg grating in weak reflection Bragg grating array；
Sensor fibre (5), inscription have weak reflection Bragg grating array, input terminal and the optical modulator module (2) output end
Connection, short light pulse sequence modulate by vibration signal and export multiple reflection photons by the reflection of weak reflection Bragg grating array
Sequence；
Relevant optical receiver module (3), one input end are connect with the light source module (1) output end, another input terminal with it is described
Sensor fibre (5) output end connection, for allow continuous narrow-linewidth laser and multiple reflection photon sequences interfere to be formed it is multiple
Beat frequency optical signal subsequence, and electric signal is converted by optical signal by multiple beat frequency optical signal subsequences, and export multiple beat frequencies
Subsequence；
Signal processing module (4), input terminal is connect with the output end of relevant optical receiver module (3), for passing through cross-correlation method
Multiple beat frequency subsequences are subjected to phase demodulating and obtain each position vibration signal；
The signal processing module carries out phase demodulating to beat frequency subsequence and obtains vibration signal.
2. demodulation method according to claim 1, which is characterized in that the light source module (1) includes:
Continuous narrow linewidth laser, for exporting continuous narrow-linewidth laser,
Fiber coupler, input terminal are connect with the continuous narrow linewidth laser output end, the first output end and the light
The connection of modulation module (2) input terminal, second output terminal are connect with the relevant optical receiver module (3), and being used for will continuous narrow line
Wide laser beam splitter is the continuous narrow-linewidth laser of the continuous narrow-linewidth laser of the first via and the second road.
3. demodulation method according to claim 2, which is characterized in that the optical modulator module (2) includes:
Acousto-optic modulator, input terminal are connect with the first output end of the fiber coupler, for by the continuous narrow line of the first via
Wide laser carries out shift frequency processing and modulation treatment, exports the first short light pulse sequence；
Erbium-doped fiber amplifier, input terminal are connect with the output end of the acousto-optic modulator, for first short pulse
Light sequence amplifies processing, exports the second short light pulse sequence；
Narrow linewidth bandpass filter, input terminal are connect with the erbium-doped fiber amplifier output end, for the second short pulse
Light sequence carries out Denoising disposal, exports short light pulse sequence.
4. demodulation method according to claim 2, which is characterized in that further include circulator, input terminal and the light tune
The connection of molding block (2) output end, the first output end are connect with the sensor fibre (5), and second output terminal connects with the coherent light
Module (3) connection is received, for realizing short light pulse sequence and multiple reflection photon sequences transmitted in both directions in sensor fibre (5).
5. demodulation method according to claim 4, which is characterized in that the relevant optical receiver module (3) includes:
Coherent optical-fiber coupler, first input end are connect with the circulator second output terminal, the second input terminal with it is described
The connection of fiber coupler second output terminal, it is dry for the continuous narrow-linewidth laser of multiple reflection photon sequences and the second road to occur
It relates to, forms multiple beat frequency optical signal subsequences, and be that the multiple beat frequency light of the first via are believed by multiple beat frequency optical signal subsequence beam splitting
The multiple beat frequency optical signal subsequence outputs of work song sequence and the second tunnel；
Balanced detector, first input end are connect with the first output end of coherent optical-fiber coupler, receive the multiple beat frequencies of the first via
Optical signal subsequence, the second input terminal are connect with coherent optical-fiber coupler second output terminal, receive the multiple beat frequency light in the second tunnel
Signal subsequence carries out the multiple beat frequency optical signal subsequences of the first via and the second tunnel multiple beat frequency optical signal subsequences at difference
Reason obtains amplified multiple beat frequency optical signal subsequences, and by amplified multiple beat frequency optical signal subsequences by optical signal
It is converted into electric signal, exports multiple beat frequency subsequences.
6. demodulation method according to any one of claims 1 to 5, which is characterized in that the weak reflection Bragg grating battle array
All weak reflection Bragg gratings are spacedly distributed in column.
7. demodulation method according to any one of claims 1 to 5, which is characterized in that the weak reflection Bragg grating battle array
All weak reflection Bragg grating reflection wavelengths are equal in column, the continuous narrow-linewidth laser wavelength and the weak reflection cloth loudspeaker lattice
Optical grating reflection wavelength is equal.
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