CN105806380B - A kind of multiplexing demodulation equipment based on long-period fiber grating reflection sensor - Google Patents
A kind of multiplexing demodulation equipment based on long-period fiber grating reflection sensor Download PDFInfo
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- CN105806380B CN105806380B CN201610210919.2A CN201610210919A CN105806380B CN 105806380 B CN105806380 B CN 105806380B CN 201610210919 A CN201610210919 A CN 201610210919A CN 105806380 B CN105806380 B CN 105806380B
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- 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
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Abstract
The present invention relates to a kind of multiplexing demodulation equipment based on long-period fiber grating reflection sensor, wherein multiple long-period fiber grating reflection sensors have different optical path differences；The wideband light source is connected with the first port of three port circulators, and the second port of three port circulator is connected with the optical fiber for being in series with the multiple long-period fiber grating reflection sensor, and third port is connected with the input terminal of the first fiber coupler；One output end of first fiber coupler is connected with the input terminal of Polarization Controller, another output end is connected with the input terminal of electronic variable delay line；The output end of the output end of the Polarization Controller and electronic variable delay line is separately connected two input terminals of the second fiber coupler；The output end of second fiber coupler is connected with the input terminal of photodetector, and the output end of the photodetector is connected with data collecting card.The invention enables System spatial resolution height, reusable number are big, of low cost.
Description
Technical field
The present invention relates to technical field of optical fiber sensing, are sensed based on long-period fiber grating reflection-type more particularly to one kind
The multiplexing demodulation equipment of device.
Background technology
In sensory field of optic fibre, long-period fiber grating is since it is to variations such as temperature, stress and strain, ambient refractive index
High susceptibility, and become a kind of highly important senser element.Compared with Bragg grating, long-period grating pair temperature
Degree, stress etc. have higher sensitivity, and its cladding mode is sensitive to extraneous ambient refractive index, can be adapted for liquid
The high-acruracy survey of refractive index.Although having outstanding one point sensing performance, practicality of the long-period fiber grating in application field
Change process lags far behind Bragg grating.For Bragg grating since its frequency domain reflection bandwidth is very narrow, generally less than 1nm can be with
It is very easily built into distributed sensor-based system and is demodulated with wavelength-division multiplex or time-division multiplex technology.Long-period fiber grating
Spectrum signature be that multiple transmission loss peaks coexist, and the spectral bandwidth of each loss peak is very big, to ambient refractive index sensitivity
At least tens nanometers of the bandwidth of higher high-order mode, therefore its frequency domain can not use wavelength-division multiplex system to demodulate.Long period
Fiber grating is sandwich layer mould and the covering mode coupling of symport, and almost without reflecting spectrum, therefore it can not use current skill
The time division multiplex system of art maturation demodulates.Due to lacking multiplexing and demodulation method for long-period fiber grating distributed sensing
Research, the practicalization of long-period fiber grating with excellent sensing characteristics is greatly affected.
Low coherence interference technology is to use wide spectrum optical as light source, is concerned with principle according to white light, utilizes zero order interference fringe
As with reference to position, to obtain a kind of accurate interference system for measuring absolute location information in the larger context.Low coherence
The sensor structure that interference system is used to obtain detectable signal is interferometer, and demodulation part is the interferometer of sweep type, different
Sensor is designed using different optical path differences, and multichannel sensing multiplexing may be implemented.Due to using interferometer side in Low coherence system
Formula demodulates each sensor information amount, can have higher anti-to avoid the ambient noise that factors introduce such as flashing is fixed
Interference；All data of interference pattern are made full use of to evaluate measured signal, with the theoretical average effect favored of accurate measurement
The effect answered obtains higher measurement accuracy；Optical fiber low coherence interference system is built, high coherent interference system is not needed and is used
Tunable laser source, signal analysis and processing do not need the valuable precisions such as spectrometer, Network Analyzer, vector analysis instrument yet and sets
Standby, system cost is well below systems such as now widely used wavelength-division multiplex, time division multiplexings.Multiplexing based on Low coherence principle
Demodulating system is a function admirable and low-cost multiplex system, but this systematic difference research at present is also much fallen
Afterwards in time division multiplex system, wavelength-division multiplex system etc..
Invention content
Technical problem to be solved by the invention is to provide a kind of answering based on long-period fiber grating reflection sensor
With demodulated equipment so that System spatial resolution is high, reusable number is big, of low cost.
The technical solution adopted by the present invention to solve the technical problems is：It provides a kind of based on long-period fiber grating reflection
The multiplexing demodulation equipment of type sensor, including wideband light source and multiple long-period fiber grating reflection sensors, it is the multiple
Long-period fiber grating reflection sensor has different optical path differences；The first end of the wideband light source and three port circulators
Mouthful it is connected, the second port of three port circulator and is in series with the multiple long-period fiber grating reflection sensor
Optical fiber is connected, and third port is connected with the input terminal of the first fiber coupler；One output end of first fiber coupler
It is connected with the input terminal of Polarization Controller, another output end is connected with the input terminal of electronic variable delay line；The polarization control
The output end of the output end of device processed and electronic variable delay line is separately connected two input terminals of the second fiber coupler；Described
The output end of two fiber couplers is connected with the input terminal of photodetector, and output end and the data of the photodetector acquire
Card is connected.
The long-period fiber grating reflection sensor is by stiffness of coupling is prepared for the long-period fiber grating of 3dB
At one end optical fiber of the long-period fiber grating retains so as to access system, and the optical fiber cutter of the other end cut off and adopt
Metallic reflective coating is plated with sputtering method.
The multiple long-period fiber grating reflection sensor is linked into same root by the series connection of third fiber coupler
In optical fiber.
The light source range of the wideband light source covers the bandwidth at the resonance loss peak of the long-period fiber grating sensor.
The single mode optical fiber sandwich layer and cladding-effective-index difference of the long-period fiber grating reflection sensor are 10-2。
The range difference of raster center to end face is greater than or equal in adjacent long-period fiber grating reflection sensor
2.7mm。
The spectral region of the wideband light source is 60nm.
The centre wavelength of the long-period fiber grating reflection sensor is 1550nm, and loss peak bandwidth is 20nm.Have
Beneficial effect
Due to the adoption of the above technical solution, compared with prior art, the present invention having the following advantages that and actively imitating
Fruit：The present invention carries out Fourier transformation extraction frequency to interference signal using Data collection and precessing system and can be obtained interference light
Centre wavelength, to obtain sensor temperature information demodulation.Using electronic variable delay line shuttle-scanning, length is realized
The multiplexing of period optical fiber grating reflection sensor.The present invention have System spatial resolution is high, reusable number is big, at
This cheap advantage.
Description of the drawings
Fig. 1 is the structural schematic diagram of the present invention.
Specific implementation mode
Present invention will be further explained below with reference to specific examples.It should be understood that these embodiments are merely to illustrate the present invention
Rather than it limits the scope of the invention.In addition, it should also be understood that, after reading the content taught by the present invention, people in the art
Member can make various changes or modifications the present invention, and such equivalent forms equally fall within the application the appended claims and limited
Range.
As shown in Figure 1, wideband light source 1 is connect with first port optical signal of three port circulators 2, long period optical fiber light
Grid reflection sensor 4 is connected in series to by a fiber coupler 3 on same root optical fiber, a different light paths of the n that connected (n >=2)
The optical fiber of gap sensor and the second of circulator port optical signal connect, third port and the fiber coupler 5 of circulator
Input terminal light connects.The input terminal light connects of the output end and Polarization Controller 6 of fiber coupler 5, fiber coupler 5
Another output end and electronic variable delay line 7 input terminal light connects, the output end and fiber coupler of Polarization Controller 6
8 input terminal light connects, the output end of electronic variable delay line 7 and another input terminal light connects of fiber coupler 8.Optical fiber
The output end of coupler 8 is connect with 9 input terminal optical signal of photodiode.Photodiode 9 stores and processs equipment with data
10 electric signals connect.It is used as temperature sensor to be preset at above-mentioned multiple long-period fiber grating reflection sensors 4 monitored
Environment in, all in monitoring center, broadband light is entered more by circulator 2 for wideband light source 1, circulator 2 and signal demodulation part
A sensor 4, then pass signal light back monitoring center by single mode optical fiber and carry out signal demodulation and processing.
The long-period fiber grating reflection sensor is by stiffness of coupling is prepared for the long-period fiber grating of 3dB
At one end optical fiber of long-period fiber grating retains so as to access system, and the optical fiber cutter of the other end, which cut off and use, to be splashed
Shooting method plates metallic reflective coating, forms long-period fiber grating reflection sensor.Different long-period fiber grating reflections
Raster center is to the distance between reflection end difference in type sensor.
It is the wideband light source of 60nm that spectral region is selected in present embodiment, and light source range will cover long-period fiber grating
The bandwidth at resonance loss peak, light energy is introduced by the light of light source output by the circulator of three ports is connected on a light
In sensor on fibre.Long-period fiber grating is coupled to 50% light energy in fibre cladding high-order mode in sensor, remains
Remaining light energy is transmitted in fiber core layer, and after one section of optical fiber, transmission is in the light of sandwich layer and covering by the anti-of fiber end face
Film reflection is penetrated, when the light being reflected back again passes by long-period fiber grating, the part light transmitted in covering can be coupled back into again
Sandwich layer converges with the light energy transmitted in sandwich layer.The effective refractive index of fiber core layer and effective refraction of fibre cladding high-order mode
Rate is different, and light can be introduced in the light of sandwich layer transmission and after being coupled to covering and between being coupled back into the light of sandwich layer always in sensor
Path difference is
δ=2 (nco-ncl)·d (1)
Wherein ncoAnd nclIndicate that the effective refractive index of fiber core layer and covering high-order mode, d indicate long week in sensor respectively
Distance of the phase raster center to reflection end face.Raster center is different to reflection end distance in default different sensors, then each to pass
The optical path difference that optical signal introduces in sensor is just different.
The transducing signal that sensor is reflected back using optical fiber collection be transmitted back to come after, by circulator third port into
Enter in an interferometer demodulating system.Optical signal is divided into two beams of isocandela by fiber coupler, and light beam therein passes through one
A electronic variable delay line makes to introduce variable optical path difference between two-way light, with the scanning of variable delay line, the light path of introducing
Difference can compensate the optical path difference of different sensors introducing.Another beam optical fiber light path is constant, accesses the effect of a Polarization Controller
It is that system is allowed to obtain best interference signal.Two-way light after compensation generates interference after another fiber coupler converges.It is dry
It relates to signal and electric signal is converted by photodiode detection, then acquired and stored by data collecting card, data processing equipment is to adopting
The interference signal collected carries out data analysis and information demodulation.
Since the optical path difference that different sensors introduce is different, so when variable delay line scanning to a certain position, some biography
The optical path difference that sensor introduces is compensated for as zero, then the corresponding low-coherent light interference signal of the sensor occurs, and interference fringe is：
Wherein, A (z) is the amplitude external envelope of interference fringe, and P is the period of interference fringe,It is the first phase of interference fringe
Position, z are the positions of variable delay line scanning.The centre wavelength of interference light and the relationship of interference fringe are
λ=2P (3)
After carrying out the frequency that Fourier transformation acquires interference fringe to interference fringe, according to formula (3), it can be joined
With the centre wavelength of the light of interference.Interference center wavelength of light is the centre wavelength at long-period fiber grating transmission loss peak.It is long
The coupling loss peak center wavelength of period optical fiber grating can drift about with temperature change, and wavelength drift and temperature are changing into
Proportional relation, proportionality coefficient can be obtained by testing calibration.This system calculates the resonance loss of sensor by meter
Peak wavelength location, and then demodulate environment temperature information to be measured.The sensitivity of sensor and long period optical fiber light in system
The sensitivity of grid is consistent.The spatial resolution of demodulation scheme depends on the coherence length of long-period fiber grating loss peak.Pass through
A series of sensor of different optical path differences of arranged in series, and scan demodulated interferential instrument wherein by controlling electronic variable delay line
One arm, it can be achieved that multiple sensor multiplexing.
Long-period fiber grating centre wavelength takes optic communication typical case's wave band 1550nm, general long period in present embodiment
It is 20nm that peak bandwidth, which is lost, in fiber grating, then the interference length of long-period fiber grating loss peak is 53 μm.If using it is electronic can
It is 10cm to adjust the scanning range of delay line, and this system can at most demodulate 1886 sensors.In order not to same sensor interferometer
Aliasing does not occur for signal, is about 10 according to single mode optical fiber sandwich layer and cladding-effective-index difference-2, grating in adjacent sensors
The range difference of center to end at least 2.7mm.
Since temperature change can cause the drift that long-period fiber grating resonance loss spike is grown in sensor, to interfere
The centre wavelength of light can change, and carrying out Fourier transformation to interference signal using Data collection and precessing system extracts frequency
The centre wavelength that can be obtained interference light, to obtain sensor temperature information demodulation.Electronic variable delay line is back and forth swept
It retouches, realizes the multiplexing of long-period fiber grating reflection sensor.The present invention has System spatial resolution height, can answer
With big, the of low cost advantage of number.
Claims (8)
1. a kind of multiplexing demodulation equipment based on long-period fiber grating reflection sensor, including wideband light source and multiple long weeks
Phase fiber grating reflection sensor, which is characterized in that the multiple long-period fiber grating reflection sensor has difference
Optical path difference；The wideband light source is connected with the first port of three port circulators, the second port of three port circulator
It is connected with the optical fiber for being in series with the multiple long-period fiber grating reflection sensor, third port and the first fiber coupler
Input terminal be connected；One output end of first fiber coupler is connected with the input terminal of Polarization Controller, another is defeated
Outlet is connected with the input terminal of electronic variable delay line；The output of the output end of the Polarization Controller and electronic variable delay line
End is separately connected two input terminals of the second fiber coupler；The output end of second fiber coupler and photodetector
Input terminal is connected, and the output end of the photodetector is connected with data collecting card；Optical signal is divided by the fiber coupler
Two beams of isocandela, light beam therein make to introduce variable optical path difference between two-way light by the electronic variable delay line,
Another beam optical fiber light path is constant, accesses the Polarization Controller；Two-way light after compensation converges in second fiber coupler
Generate interference afterwards, interference signal is converted into electric signal by photodiode detection, then by data collecting card acquisition and
Storage, data processing equipment carries out data analysis to the interference signal collected and information demodulates.
2. the multiplexing demodulation equipment according to claim 1 based on long-period fiber grating reflection sensor, feature
It is, the long-period fiber grating reflection sensor is prepared by the long-period fiber grating that stiffness of coupling is 3dB,
One end optical fiber of the long-period fiber grating retains so as to access system, and the optical fiber cutter of the other end, which cut off and use, to be splashed
Shooting method plates metallic reflective coating.
3. the multiplexing demodulation equipment according to claim 1 based on long-period fiber grating reflection sensor, feature
It is, the multiple long-period fiber grating reflection sensor is linked into same root optical fiber by the series connection of third fiber coupler
In.
4. the multiplexing demodulation equipment according to claim 1 based on long-period fiber grating reflection sensor, feature
It is, the light source range of the wideband light source covers the bandwidth at the resonance loss peak of the long-period fiber grating sensor.
5. the multiplexing demodulation equipment according to claim 1 based on long-period fiber grating reflection sensor, feature
It is, the single mode optical fiber sandwich layer and cladding-effective-index difference of the long-period fiber grating reflection sensor are 10-2。
6. the multiplexing demodulation equipment according to claim 1 based on long-period fiber grating reflection sensor, feature
It is, the range difference of raster center to end face is greater than or equal to 2.7mm in adjacent long-period fiber grating reflection sensor.
7. the multiplexing demodulation equipment according to claim 1 based on long-period fiber grating reflection sensor, feature
It is, the spectral region of the wideband light source is 60nm.
8. the multiplexing demodulation equipment according to claim 1 based on long-period fiber grating reflection sensor, feature
It is, the centre wavelength of the long-period fiber grating reflection sensor is 1550nm, and loss peak bandwidth is 20nm.
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| CN106442340B (en) * | 2016-09-27 | 2023-06-13 | 山东省科学院生物研究所 | Device and method for detecting seawater salinity by long-period fiber gratings |
| CN106643841B (en) * | 2016-12-30 | 2019-06-25 | 中国科学院深圳先进技术研究院 | A kind of weak inverted-F BG-FIZEAU sensing device |
| CN107631814B (en) * | 2017-09-14 | 2020-09-01 | 电子科技大学 | Optical self-coherent sensing optical path structure, frequency shift change detection method and sensing device |
| GB2568305B (en) | 2017-11-13 | 2022-06-15 | Univ Cranfield | A fibre optic sensing device |
| CN110207849B (en) * | 2019-07-02 | 2020-11-06 | 浙江科技学院 | Temperature sensor based on reflective long-period fiber grating and measuring method |
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| US6448551B1 (en) * | 1999-11-29 | 2002-09-10 | Weatherford/Lamb, Inc. | Fiber Bragg grating sensor system having enhanced strain-to-wavelength responsivity by using a spectral beating based vernier effect |
| CN201242451Y (en) * | 2008-07-15 | 2009-05-20 | 浙江大学 | Equipment for demodulating optical fiber grating sensing array |
| CN101532850B (en) * | 2009-04-20 | 2011-03-30 | 浙江大学 | Method and device for sensing and demodulating Bragg fiber grating |
| CN102183866B (en) * | 2011-05-09 | 2012-08-22 | 哈尔滨工程大学 | Imbalanced-Mach-Zehnder-based demodulation device for multiplexing optical fiber interferometer |
| CN104931081B (en) * | 2015-06-10 | 2017-08-11 | 天津大学 | The fiber grating sensing demodulation apparatus and method referred to based on composite wavelength |
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