CN107643120A - The distributed fiber Rayleigh of polarization decay is avoided to scatter vibration sensing system and method - Google Patents
The distributed fiber Rayleigh of polarization decay is avoided to scatter vibration sensing system and method Download PDFInfo
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Abstract
Vibration sensing system is scattered the invention discloses a kind of distributed fiber Rayleigh for avoiding polarization decay and method, wherein method comprise the following steps：By the light of super-narrow line width, by acousto-optic modulator, after EDFA Erbium-Doped Fiber Amplifier, the pulsed light for becoming super-narrow line width is entered in sensing optic cable by circulator；The pulsed light of super-narrow line width produces the reflection Rayleigh scattering light for carrying signal message in sensing optic cable；Rayleigh scattering light is reflected to be mixed into integrated receiver with local light after amplification；The signal of mixing passes through data collecting card synchronous acquisition；The data of collection are demodulated by demodulating algorithm unit, to demodulate the vibration information on optical cable.The present invention can avoid polarization decay problem, reduce the rate of false alarm of system.
Description
Technical field
The present invention relates to distributed fiber Rayleigh to scatter vibration sensing system technical field, more particularly to one kind avoids polarizing
The coherent demodulation system and method for the distributed optical fiber vibration sensor of decline.
Background technology
Distributed optical fiber vibration sensor is the one kind developed in recent decades for real-time measurement space vibration information point
The optical fiber sensing system of cloth.By the development of decades, the Technical comparing is ripe.The technology generally use coherent reception carries
High sensitivity.By the way of coherent detection, the influence of polarization decay noise is just inevitably brought.Light passes in a fiber
Broadcast, because effect of the optical fiber by external environment and itself inhomogeneities are influenceed so that the polarization state of light occur continuously with
Machine changes.There is the unmatched situation of polarization state with local oscillator light in the Rayleigh scattering optical signal for so allowing for returning, so as to serious
Weakening two-beam it is relevant after obtained signal intensity, reduce the signal to noise ratio of system, have a strong impact on the detection performance of system.Solve
The unmatched generally way of polarization state is to add high speed scrambler in systems.Cause reference path by the effect of scrambler
Light is traveled through with very high speed, and so when the Rayleigh scattering light with being returned in sensing light path is relevant, total energy ensures one
The polarization state of light splitting is matching.When two-beam polarization state completes parallel, signal is most strong.But always there is certain probability two-beam
Polarization state is near vertically, then signal can be very weak.
According to the method for scrambler, a polarization state of light is only considered, the probability of polarization decay can only be reduced, still
It is not avoided that.
The content of the invention
The defects of scattering vibration polarization decay sensing technology for existing distributed fiber Rayleigh or Improvement requirement, the present invention
Provide a kind of distributed fiber Rayleigh for avoiding polarization decay and scatter vibration sensing system and method, its object is to avoid partially
Shake fading problem, reduce rate of false alarm.
The technical solution adopted for the present invention to solve the technical problems is：
A kind of frequency mixing method for avoiding polarization decay is provided, comprised the following steps：
Two-way input light is each separated into X, the crossed polarized light of Y-direction, and first via input light is divided into the first X polarised lights,
One Y polarised lights；Second tunnel input light is divided into the 2nd X polarised lights, the 2nd Y polarised lights；
First X polarised lights are divided into two-beam；2nd X polarised lights are also divided into two-beam；Four road light match two-by-two, its
In do not process direct conversion for a pair and export the first differential signal；The light beam of another pair produces 90 ° of phases by phase-modulation
Difference, then export the second differential signal through mixing；
First differential signal and the second differential signal export Ix electric signals and Qx electric signals each via opto-electronic conversion；
Similarly, the first Y polarised lights and the second polarised light export Iy telecommunications after the above-mentioned processing with X polarised lights identical
Number and Qy electric signals.
Present invention also offers a kind of QPSK coherent receivers for avoiding polarization decay, including：
The first polarization beam apparatus, the first optical splitter, the first frequency mixer and the first balance receiver being sequentially connected with；It is defeated all the way
Enter light and be divided into the first X polarised lights, the first Y polarised lights through the first polarization beam apparatus, two-beam X, the crossed polarized light of Y-direction,
First X polarised lights are divided into two-beam through the first optical splitter；
The second polarization beam apparatus for being sequentially connected with, the second optical splitter, first phase modulator, the second frequency mixer and second are flat
Weigh receiver；The output end of second optical splitter is connected with an input of the first frequency mixer；One input of the second frequency mixer
End is connected with the output end of the first optical splitter；Another way input light is divided into the 2nd X polarised lights, the 2nd Y through the second polarization beam apparatus
Polarised light, two-beam X, the crossed polarized light of Y-direction, the 2nd X polarised lights are divided into two-beam through the second optical splitter, wherein one
The light beam of the optical splitters of Shu Guangyu first output, which does not process, is directly entered the first frequency mixer, is exported after the mixing of the first frequency mixer
First differential signal；Second optical splitter output another light beam through first phase modulator adjust produce 90 ° of phase differences after again with
The another light beam of first optical splitter output enters the second frequency mixer, and the second differential signal is exported after the mixing of the second frequency mixer；The
One differential signal is connect by exporting Ix electric signals, the second differential signal after the first balance receiver opto-electronic conversion by the second balance
Qx electric signals are exported after receiving device opto-electronic conversion；
The QPSK coherent receivers also include the 3rd optical splitter, three-mixer and the 3rd balance reception being sequentially connected with
Device, wherein the 3rd optical splitter is connected with input with the first polarization beam apparatus；
The QPSK coherent receivers also include the 4th optical splitter, second phase modulator, the 4th frequency mixer being sequentially connected with
With the 4th balance receiver, wherein the 3rd optical splitter is connected with input with the first polarization beam apparatus；4th optical splitter
One output end is connected with an input of three-mixer, the input and the 3rd optical splitter of the 4th frequency mixer
An output end connection；
First Y polarised lights are divided into two-beam through the 3rd optical splitter；2nd Y polarised lights are divided into two beams through the 4th optical splitter
The light beam of light, wherein light beam and the 3rd optical splitter output, which does not process, is directly entered three-mixer, through three-mixer
The 3rd differential signal is exported after mixing；The another light beam of 4th optical splitter output adjusts through second phase modulator produces 90 ° of phases
Another light beam after potential difference again with the output of the 3rd optical splitter enters the 4th frequency mixer, and output the 4th is poor after the mixing of the 4th frequency mixer
Sub-signal；3rd differential signal is passed through by exporting Iy electric signals, the 4th differential signal after the 3rd balance receiver opto-electronic conversion
Qy electric signals are exported after 4th balance receiver opto-electronic conversion.
Oscillating pickup system is scattered based on the above-mentioned distributed fiber Rayleigh for avoiding polarization decay present invention also offers a kind of
System, including：
Laser, coupler, acousto-optic modulator, the first EDFA Erbium-Doped Fiber Amplifier, the first wave filter, circulator, second are mixed
Bait fiber amplifier, the second wave filter, QPSK coherent receivers, data collecting card, demodulating algorithm unit and lock-out pulse plate with
And sensing optic cable；
The input port of laser output and coupler connects, and an output port of coupler is sequentially connected acousto-optic tune
Device processed, the first EDFA Erbium-Doped Fiber Amplifier, the first port of the first wave filter and circulator；The second port connection sensing of circulator
Optical cable, the 3rd port of circulator are sequentially connected the second erbium-doped fiber amplifier, the second wave filter；The two of QPSK coherent receivers
Individual output port connects another output port of coupler and the output port of the second wave filter respectively；QPSK coherent receivers
Output port and the input of data collecting card connect, the input of the output end of data collecting card connection demodulating algorithm unit
End；
Two deferent segments of lock-out pulse plate connect the electrical interface input of acousto-optic modulator and data collecting card respectively.
In system of the present invention, the electrical interface input of acousto-optic modulator and capture card and the output of lock-out pulse plate
The connection at end, the connection of the output end of QPSK coherent receivers and the input of data collecting card, the output end of data collecting card
With the connection of the input of demodulating algorithm unit, connected using radio frequency electric wire；Connected between other devices using single-mode fiber.
Vibrating sensor is scattered based on the above-mentioned distributed fiber Rayleigh for avoiding polarization decay present invention also offers a kind of
Method, mainly include the following steps that：
S1, the light by super-narrow line width, by acousto-optic modulator, after EDFA Erbium-Doped Fiber Amplifier, become the pulse of super-narrow line width
Light, then entered by circulator in sensing optic cable；
S2, the pulsed light of super-narrow line width produce the reflection Rayleigh scattering light for carrying signal message in sensing optic cable；
S3, reflection Rayleigh scattering light are mixed after amplification with local light by QPSK coherent receivers；
Signal after S4, mixing passes through data collecting card synchronous acquisition；
S5, the data of collection are demodulated by demodulating algorithm unit, to demodulate the vibration information on sensing optic cable.
Above-mentioned technical proposal is connect, is specifically demodulated as follows in step S5：
From QPSK coherent receivers output four road electric signals be：
Subscript x in formula (1), y represent two polarization directions of light；As,AoRepresent that signal light amplitude and local light shake respectively
Width；Δ w represents offset caused by acousto-optic modulator；Represent the vibration information of sensing optic cable；Obtained by digital filtering：
Amplitude and phase information are calculated according to formula (2)
The beneficial effect comprise that：Then the present invention is synthesized, after synthesis by two polarization states of demodulated signal
Signal intensity is more than or equal to signal intensity when only considering a polarization, avoids polarization decay problem.
Brief description of the drawings
Below in conjunction with drawings and Examples, the invention will be further described, in accompanying drawing：
Fig. 1 is that the embodiment of the present invention avoids the distributed fiber Rayleigh of polarization decay from scattering vibration sensing system structural representation
Figure；
Fig. 2 is that the embodiment of the present invention avoids the distributed fiber Rayleigh of polarization decay from scattering vibration sensing method flow chart；
Fig. 3 is that optical signal polarizes perspective view, and this programme avoids the principle place of polarization decay；
Fig. 4 is the QPSK coherent receiver structural representations that the embodiment of the present invention avoids polarization decay.
Embodiment
In order to make the purpose , technical scheme and advantage of the present invention be clearer, it is right below in conjunction with drawings and Examples
The present invention is further elaborated.It should be appreciated that specific embodiment described herein is only to explain the present invention, not
For limiting the present invention.
Fig. 1 shows the system structure diagram for avoiding the distributed fiber Rayleigh of polarization decay from scattering vibrating sensor, is
It is easy to illustrate, illustrate only the part related to the embodiment of the present invention, details are as follows：Whole system includes laser 1, coupling
Device 2, acousto-optic modulator 3, the first EDFA Erbium-Doped Fiber Amplifier 4, the first wave filter 5, circulator 6, the second EDFA Erbium-Doped Fiber Amplifier 7,
Second wave filter 8,2 × 8QPSK coherent receivers 9, data collecting card 10, demodulating algorithm unit 11 and lock-out pulse plate 12, pass
Sensing optical cable 13.
The output end of laser 1 is connected with the input port of coupler 2.One output port of coupler 2 is sequentially connected sound
Optical modulator 3, the first EDFA Erbium-Doped Fiber Amplifier 4,1 port of the first wave filter 5 and circulator 6.The 2 ports connection of circulator 6
Sensing optic cable 13,3 ports of circulator 6 are sequentially connected the second erbium-doped fiber amplifier 7, the second wave filter 8.Coupler 2 it is another
The output port of one output port and the second wave filter 8 connects two output ports of 2 × 8QPSK coherent receivers 9 respectively.
The output port of 2 × 8QPSK coherent receivers 9 is connected with the input of data collecting card 10, the output connection of data collecting card 10
The input of demodulating algorithm unit 11.The electrical interface input of acousto-optic modulator 3 and data collecting card 10 and lock-out pulse plate 12
Output connection.The electrical interface input of acousto-optic modulator 3 and capture card 10 and the connection of the output of lock-out pulse plate 12,2 ×
The connection of the output of 8QPSK coherent receivers 9 and the input of data collecting card 10, the output of data collecting card 10 and demodulating algorithm
The connection of the input of unit 11, all connected using radio frequency electric wire.The connection of other devices is connected using single-mode fiber.
During light source works, laser 1 exports ultra-narrow, the continuous light of high stable.Two-beam is separated after coupler 2, the
After light beam is by acousto-optic modulator 3, the pulsed light of a frequency amount of offsetting is modulated into, the frequency and pulsewidth of pulsed light are by same
Pace pulse plate 12 controls.The pulsed light of modulation is very weak, it is necessary to which erbium-doped fiber amplifier 4 carries out light amplification, the pulsed light warp of amplification
Wave filter 5 filters 1 port that spontaneous radiation noise comes circulator 6, and then pulsed light incides from 1 port into 2 ports
In sensing optic cable 13, backward Rayleigh scattering occurs.The rear orientation light for carrying vibration information reaches 3 ends from 2 ports of circulator 6
Mouthful.Because Rayleigh scattering signal light is very weak, it is necessary to which the progress light amplification of the second erbium-doped fiber amplifier 7, subsequently enters the second filtering
Device 8 filters spontaneous radiation noise.The the second beam light and the light of the second wave filter 8 output that coupler 2 separates enter 2 × 8QPSK phases
Two inputs of dry receiver 9 carry out coherent reception, and four obtained road electric signals enter data collecting card 10, data collecting card
10, which are connected to the triggering electric pulse synchronous with the identical of acousto-optic modulator 3 that synchronised clock plate 12 is sent, just starts working, then by solving
Algorithm unit 11 is adjusted to demodulate the vibration information of whole sensing optic cable 13.An output port of coupler 2 enters 2 in this programme
The not small 0dB of power is required before × 8QPSK coherent receivers.The line width of the output light of laser 1 is less than 10kHz, and output light is inclined
Polarization state does not have particular/special requirement.1 to 6 in system really produces a high-quality pulsed light, is the generation for follow-up signal
Business is taken after mixing with liquid in reconciliation.
As shown in figure 4, the QPSK coherent receivers for avoiding polarization decay of the embodiment of the present invention include：
The first polarization beam apparatus 910, the first optical splitter 911, the first frequency mixer 912 and the first balance reception being sequentially connected with
Device 913；Input light is divided into the first X polarised lights, the first Y polarised lights, two-beam X, Y side through the first polarization beam apparatus 910 all the way
To crossed polarized light, the first X polarised lights are divided into two-beam through the first optical splitter 911；
The second polarization beam apparatus 920, the second optical splitter 914, the first phase modulator 915, second being sequentially connected with are mixed
The balance receiver 917 of device 916 and second；The output end of second optical splitter 914 and an input of the first frequency mixer 912 connect
Connect；One input of the second frequency mixer 916 is connected with the output end of the first optical splitter 911；Another way input light is inclined through second
The beam splitter 920 that shakes is divided into the 2nd X polarised lights, the 2nd Y polarised lights, two-beam X, the crossed polarized light of Y-direction, the 2nd X polarizations
Light is divided into two-beam through the second optical splitter 914, and wherein light beam and the light beam of the first optical splitter 911 output does not process directly
Tap into the first frequency mixer 912, the first differential signal is exported after the mixing of the first frequency mixer 912；The output of second optical splitter 914
The another light beam that another light beam exports with the first optical splitter 911 again after first phase modulator 915 adjusts and produces 90 ° of phase differences
Into the second frequency mixer 916, the second differential signal is exported after the mixing of the second frequency mixer 916；First differential signal passes through first
Ix electric signals are exported after the opto-electronic conversion of balance receiver 913, the second differential signal passes through the opto-electronic conversion of the second balance receiver 917
Qx electric signals are exported afterwards, and subscript x, y represent two polarization directions of light；Balance receiver is mainly two ways of optical signals (two-way
Have direct current in signal theory and exchange, their AC phases are opposite) electric signal is converted into, then make the difference output.Making the difference can be
Direct current signal eliminates, and obtains differential signal.Frequency mixer can also interfere two-way light compositing except two-way light is carried out into mixing.
The QPSK coherent receivers also include the 3rd optical splitter 921, the balance of three-mixer 922 and the 3rd being sequentially connected with
Receiver 923, wherein the 3rd optical splitter 921 is connected with input with the first polarization beam apparatus 910；
The QPSK coherent receivers also include the 4th optical splitter 924, the second phase modulator the 925, the 4th being sequentially connected with
The balance receiver 927 of frequency mixer 926 and the 4th, wherein the 3rd optical splitter 921 connects with input and the first polarization beam apparatus 910
Connect；One output end of the 4th optical splitter 924 is connected with an input of three-mixer 922, the 4th mixing
One input of device 926 is connected with an output end of the 3rd optical splitter 921；
First Y polarised lights are divided into two-beam through the 3rd optical splitter 921；2nd Y polarised lights are divided equally through the 4th optical splitter 924
Into two-beam, wherein light beam and the light beam of the 3rd optical splitter 921 output does not process and is directly entered three-mixer 922,
The 3rd differential signal is exported after the mixing of three-mixer 922；The another light beam of 4th optical splitter 927 output is adjusted through second phase
The adjustment of device 926 processed produces the another light beam exported again with the 3rd optical splitter 921 after 90 ° of phase differences and enters the 4th frequency mixer 926, passes through
The 4th differential signal is exported after the mixing of 4th frequency mixer 926；3rd differential signal passes through the opto-electronic conversion of the 3rd balance receiver 923
Iy electric signals are exported afterwards, and the 4th differential signal is by exporting Qy electric signals after the opto-electronic conversion of the 4th balance receiver 927.
The innovative point and characteristic of this patent are two polarization states for considering flashlight, and demodulation and then synthesis, are avoided respectively
Polarization decay problem, principle is as follows in demodulating algorithm unit：
From 2 × 8QPSK coherent receivers output four road electric signals be：
Subscript x in formula (1), y represent two polarization directions of light；As,AoRepresent respectively the second wave filter 8 be input to 2 ×
The signal light amplitude of 9 one inputs of 8QPSK coherent receivers, the second beam light that coupler 2 separates are input to 2 × 8QPSK phases
The local light amplitude of dry 9 one inputs of receiver；Δ w represents offset caused by acousto-optic modulator 3；Represent optical cable 13
Vibration information.It can be obtained by digital filtering：
Amplitude and phase information so can be obtained by formula above
From formula (3) it can be seen that this programme considers two polarization directions of light, using local light as reference, signal light polarization
Direction is any, is projected to local light, value can not possibly be zero.Square of respectively x, y direction projection rear mold.
As shown in figure 3, flashlight projects to x or y, always there is one to be not zero, i.e., the amplitude after two projections being added is not zero, so
Avoid polarization decay.If using scrambler scheme, that is, consider a polarization direction, it is possible to local light polarization direction
It is vertical or near vertical with signal light polarization direction, then the amplitude of demodulation is almost nil, generates polarization decay, produces system
Raw wrong report.
The embodiment of the present invention avoids the method that the distributed fiber Rayleigh of polarization decay scatters vibrating sensor, based on upper
System is stated, as shown in Fig. 2 mainly including the following steps that：
S1, the light by super-narrow line width, by acousto-optic modulator, after EDFA Erbium-Doped Fiber Amplifier, become the pulse of super-narrow line width
Light, then entered by circulator in sensing optic cable；
S2, the pulsed light of super-narrow line width produce the reflection Rayleigh scattering light for carrying signal message in sensing optic cable；
S3, reflection Rayleigh scattering light are mixed after amplification with local light by QPSK coherent receivers；
Signal after S4, mixing passes through data collecting card synchronous acquisition；
S5, the data of collection are demodulated by demodulating algorithm unit, to demodulate the vibration information on sensing optic cable.
A kind of wherein frequency mixing method for avoiding polarization decay of step S3 concrete applications, specifically includes following steps：
The two-way light for being input to QPSK coherent receivers passes through two by two polarization beam apparatus, two-way input light respectively
Polarization beam apparatus, is each separated into X, the crossed polarized light of Y-direction, and first via input light is divided into the first X polarised lights, the first Y polarizations
Light；Second tunnel input light is divided into the 2nd X polarised lights, the 2nd Y polarised lights；
First X polarised lights are divided into two-beam through the first optical splitter；2nd X polarised lights are also divided into two through the second optical splitter
Shu Guang；Four road light match two-by-two, and one pair of which, which does not process, is directly entered the first frequency mixer the first differential signal of output；Another pair
Light beam by phase-modulator produce 90 ° of phase differences, enter back into the second frequency mixer export the second differential signal；
First differential signal and the second differential signal are each via output Ix electric signals after balance receiver opto-electronic conversion
With Qx electric signals；
Similarly, the first Y polarised lights and the second polarised light export Iy telecommunications after the above-mentioned processing with X polarised lights identical
Number and Qy electric signals.
To sum up, main advantages of the present invention have：
(1) the polarization decay problem of sensor-based system is avoided.Two polarization states of flashlight are considered, are demodulated respectively then
Synthesis, avoids polarization decay problem, is an important improvement in distributed sensing.
(2) measurement accuracy of sensor is improved.The precision key influence factor of measurement is signal to noise ratio, it is contemplated that two partially
Shake direction, and signal intensity is more than or equal to signal intensity when only considering a polarization after synthesis.
(3) versatility is good.This method can also be related in the distributed sensor of principle of interference used in other.Such as light
Frequency-domain reflectometer OFDR, based on the Distributed Optical Fiber Sensing Techniques of Brillouin scattering principle, there is also polarization decay problem, uses
This patent method can also avoid.
It should be appreciated that for those of ordinary skills, can according to the above description be improved or converted,
And all these modifications and variations should all belong to the protection domain of appended claims of the present invention.
Claims (6)
1. a kind of frequency mixing method for avoiding polarization decay, it is characterised in that comprise the following steps：
Two-way input light is each separated into X, the crossed polarized light of Y-direction, and it is inclined that first via input light is divided into the first X polarised lights, the first Y
Shake light；Second tunnel input light is divided into the 2nd X polarised lights, the 2nd Y polarised lights；
First X polarised lights are divided into two-beam；2nd X polarised lights are also divided into two-beam；Four road light match two-by-two, wherein one
The first differential signal is exported to not processing direct conversion；The light beam of another pair produces 90 ° of phase differences by phase-modulation, then
The second differential signal is exported through mixing；
First differential signal and the second differential signal export Ix electric signals and Qx electric signals each via opto-electronic conversion；
Similarly, the first Y polarised lights and the second polarised light be after the above-mentioned processing with X polarised lights identical, output Iy electric signals and
Qy electric signals.
A kind of 2. QPSK coherent receivers for avoiding polarization decay, it is characterised in that including：
The first polarization beam apparatus, the first optical splitter, the first frequency mixer and the first balance receiver being sequentially connected with；Input light all the way
It is divided into the first X polarised lights, the first Y polarised lights, two-beam X, the crossed polarized light of Y-direction, the first X through the first polarization beam apparatus
Polarised light is divided into two-beam through the first optical splitter；
The second polarization beam apparatus, the second optical splitter, first phase modulator, the second frequency mixer and the second balance being sequentially connected with connect
Receive device；The output end of second optical splitter is connected with an input of the first frequency mixer；One input of the second frequency mixer with
The output end connection of first optical splitter；Another way input light is divided into the 2nd X polarised lights through the second polarization beam apparatus, the 2nd Y is polarized
Light, two-beam X, the crossed polarized light of Y-direction, the 2nd X polarised lights are divided into two-beam, wherein light beam through the second optical splitter
Do not processed with the light beam of the first optical splitter output and be directly entered the first frequency mixer, first is exported after the mixing of the first frequency mixer
Differential signal；The another light beam of second optical splitter output is after first phase modulator adjusts and produces 90 ° of phase differences again with first
The another light beam of optical splitter output enters the second frequency mixer, and the second differential signal is exported after the mixing of the second frequency mixer；First is poor
Sub-signal passes through the second balance receiver by exporting Ix electric signals, the second differential signal after the first balance receiver opto-electronic conversion
Qx electric signals are exported after opto-electronic conversion；
The QPSK coherent receivers also include the 3rd optical splitter, three-mixer and the 3rd balance receiver being sequentially connected with, its
In the 3rd optical splitter be connected with input with the first polarization beam apparatus；
The QPSK coherent receivers also include the 4th optical splitter, second phase modulator, the 4th frequency mixer and the being sequentially connected with
Four balance receivers, wherein the 3rd optical splitter is connected with input with the first polarization beam apparatus；One of 4th optical splitter
Output end is connected with an input of three-mixer, an input of the 4th frequency mixer and the one of the 3rd optical splitter
Individual output end connection；
First Y polarised lights are divided into two-beam through the 3rd optical splitter；2nd Y polarised lights are divided into two-beam through the 4th optical splitter,
Wherein light beam and the light beam of the 3rd optical splitter output does not process and is directly entered three-mixer, is mixed through three-mixer
The 3rd differential signal is exported afterwards；The another light beam of 4th optical splitter output adjusts through second phase modulator produces 90 ° of phase differences
The another light beam again with the output of the 3rd optical splitter enters the 4th frequency mixer afterwards, and the 4th difference letter is exported after the mixing of the 4th frequency mixer
Number；3rd differential signal passes through the 4th by exporting Iy electric signals, the 4th differential signal after the 3rd balance receiver opto-electronic conversion
Qy electric signals are exported after balance receiver opto-electronic conversion.
3. a kind of distributed fiber Rayleigh for avoiding polarization decay based on claim 2 scatters vibration sensing system, its feature
It is, including：
Laser (1), coupler (2), acousto-optic modulator (3), the first EDFA Erbium-Doped Fiber Amplifier (4), the first wave filter (5), ring
Shape device (6), the second EDFA Erbium-Doped Fiber Amplifier (7), the second wave filter (8), QPSK coherent receivers (9), data collecting card (10),
Demodulating algorithm unit (11) and lock-out pulse plate (12) and sensing optic cable (13)；
Laser (1) output end is connected with the input port of coupler (2), and an output port of coupler (2) is sequentially connected
Acousto-optic modulator (3), the first EDFA Erbium-Doped Fiber Amplifier (4), the first port of the first wave filter (5) and circulator (6)；Circulator
(6) second port connection sensing optic cable (13), the 3rd port of circulator (6) is sequentially connected the second erbium-doped fiber amplifier
(7), the second wave filter (8)；Two output ports of QPSK coherent receivers connect another output end of coupler (2) respectively
The output port of mouth and the second wave filter (8)；The output port of QPSK coherent receivers (9) and the input of data collecting card (10)
End connection, the input of the output end connection demodulating algorithm unit (11) of data collecting card (10)；
Two deferent segments of lock-out pulse plate (12) connect acousto-optic modulator (3) respectively and the electrical interface of data collecting card (10) is defeated
Enter end.
4. system according to claim 3, it is characterised in that the electrical interface of acousto-optic modulator (3) and capture card (10) is defeated
Enter end and the connection of the output end of lock-out pulse plate (12), output end and the data collecting card (10) of QPSK coherent receivers (9)
Input connection, the connection of the output end of data collecting card (10) and the input of demodulating algorithm unit (11), use
Radio frequency electric wire connects；Connected between other devices using single-mode fiber.
5. a kind of distributed fiber Rayleigh for avoiding polarization decay based on claim 3 scatters vibration sensing method, its feature
It is, mainly includes the following steps that：
S1, the light by super-narrow line width, by acousto-optic modulator, after EDFA Erbium-Doped Fiber Amplifier, become the pulsed light of super-narrow line width, then
Entered by circulator in sensing optic cable；
S2, the pulsed light of super-narrow line width produce the reflection Rayleigh scattering light for carrying signal message in sensing optic cable；
S3, reflection Rayleigh scattering light are mixed after amplification with local light by QPSK coherent receivers；
Signal after S4, mixing passes through data collecting card synchronous acquisition；
S5, the data of collection are demodulated by demodulating algorithm unit, to demodulate the vibration information on sensing optic cable.
6. according to the method for claim 5, it is characterised in that specifically demodulated as follows in step S5：
From QPSK coherent receivers output four road electric signals be：
Subscript x in formula (1), y represent two polarization directions of light；As,AoSignal light amplitude and local light amplitude are represented respectively；
Δ w represents offset caused by acousto-optic modulator；Represent the vibration information of sensing optic cable；Obtained by digital filtering：
Amplitude and phase information are calculated according to formula (2)
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| Application Number | Priority Date | Filing Date | Title |
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| CN201711104429.5A CN107643120A (en) | 2017-11-10 | 2017-11-10 | The distributed fiber Rayleigh of polarization decay is avoided to scatter vibration sensing system and method |
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| CN201711104429.5A CN107643120A (en) | 2017-11-10 | 2017-11-10 | The distributed fiber Rayleigh of polarization decay is avoided to scatter vibration sensing system and method |
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