WO2018028051A1 - 环境变温下波动抑制的光纤光栅传感解调装置与解调方法 - Google Patents

环境变温下波动抑制的光纤光栅传感解调装置与解调方法 Download PDF

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WO2018028051A1
WO2018028051A1 PCT/CN2016/103525 CN2016103525W WO2018028051A1 WO 2018028051 A1 WO2018028051 A1 WO 2018028051A1 CN 2016103525 W CN2016103525 W CN 2016103525W WO 2018028051 A1 WO2018028051 A1 WO 2018028051A1
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fiber
optical frequency
light
optical
peak
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French (fr)
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江俊峰
刘铁根
闫金玲
刘琨
王双
张学智
臧传军
谢仁伟
楚奇梁
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天津大学
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Priority to US16/324,275 priority Critical patent/US11181400B2/en
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    • G—PHYSICS
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    • G01D—MEASURING NOT SPECIALLY ADAPTED FOR A SPECIFIC VARIABLE; ARRANGEMENTS FOR MEASURING TWO OR MORE VARIABLES NOT COVERED IN A SINGLE OTHER SUBCLASS; TARIFF METERING APPARATUS; MEASURING OR TESTING NOT OTHERWISE PROVIDED FOR
    • G01D5/00—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable
    • G01D5/26—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light
    • G01D5/32—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light
    • G01D5/34—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells
    • G01D5/353—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells influencing the transmission properties of an optical fibre
    • G01D5/35306—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells influencing the transmission properties of an optical fibre using an interferometer arrangement
    • G01D5/35309—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells influencing the transmission properties of an optical fibre using an interferometer arrangement using multiple waves interferometer
    • G01D5/35316—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells influencing the transmission properties of an optical fibre using an interferometer arrangement using multiple waves interferometer using a Bragg gratings
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01D—MEASURING NOT SPECIALLY ADAPTED FOR A SPECIFIC VARIABLE; ARRANGEMENTS FOR MEASURING TWO OR MORE VARIABLES NOT COVERED IN A SINGLE OTHER SUBCLASS; TARIFF METERING APPARATUS; MEASURING OR TESTING NOT OTHERWISE PROVIDED FOR
    • G01D5/00—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable
    • G01D5/26—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light
    • G01D5/32—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light
    • G01D5/34—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells
    • G01D5/353—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells influencing the transmission properties of an optical fibre
    • G01D5/35306—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells influencing the transmission properties of an optical fibre using an interferometer arrangement
    • G01D5/35309—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells influencing the transmission properties of an optical fibre using an interferometer arrangement using multiple waves interferometer
    • G01D5/35312—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells influencing the transmission properties of an optical fibre using an interferometer arrangement using multiple waves interferometer using a Fabry Perot
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01D—MEASURING NOT SPECIALLY ADAPTED FOR A SPECIFIC VARIABLE; ARRANGEMENTS FOR MEASURING TWO OR MORE VARIABLES NOT COVERED IN A SINGLE OTHER SUBCLASS; TARIFF METERING APPARATUS; MEASURING OR TESTING NOT OTHERWISE PROVIDED FOR
    • G01D18/00—Testing or calibrating apparatus or arrangements provided for in groups G01D1/00 - G01D15/00
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01D—MEASURING NOT SPECIALLY ADAPTED FOR A SPECIFIC VARIABLE; ARRANGEMENTS FOR MEASURING TWO OR MORE VARIABLES NOT COVERED IN A SINGLE OTHER SUBCLASS; TARIFF METERING APPARATUS; MEASURING OR TESTING NOT OTHERWISE PROVIDED FOR
    • G01D3/00—Indicating or recording apparatus with provision for the special purposes referred to in the subgroups
    • G01D3/028—Indicating or recording apparatus with provision for the special purposes referred to in the subgroups mitigating undesired influences, e.g. temperature, pressure
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01D—MEASURING NOT SPECIALLY ADAPTED FOR A SPECIFIC VARIABLE; ARRANGEMENTS FOR MEASURING TWO OR MORE VARIABLES NOT COVERED IN A SINGLE OTHER SUBCLASS; TARIFF METERING APPARATUS; MEASURING OR TESTING NOT OTHERWISE PROVIDED FOR
    • G01D5/00—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable
    • G01D5/26—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light
    • G01D5/32—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light
    • G01D5/34—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells
    • G01D5/353—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells influencing the transmission properties of an optical fibre
    • G01D5/35306—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells influencing the transmission properties of an optical fibre using an interferometer arrangement
    • G01D5/35325—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells influencing the transmission properties of an optical fibre using an interferometer arrangement using interferometer with two arms in reflection, e.g. Mickelson interferometer
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01D—MEASURING NOT SPECIALLY ADAPTED FOR A SPECIFIC VARIABLE; ARRANGEMENTS FOR MEASURING TWO OR MORE VARIABLES NOT COVERED IN A SINGLE OTHER SUBCLASS; TARIFF METERING APPARATUS; MEASURING OR TESTING NOT OTHERWISE PROVIDED FOR
    • G01D5/00—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable
    • G01D5/26—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light
    • G01D5/32—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light
    • G01D5/34—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells
    • G01D5/353—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells influencing the transmission properties of an optical fibre
    • G01D5/35306—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells influencing the transmission properties of an optical fibre using an interferometer arrangement
    • G01D5/35335—Aspects of emitters or receivers used by an interferometer in an optical fibre sensor arrangement

Definitions

  • the invention belongs to the technical field of optical fiber sensing, and particularly relates to a high-stability fiber grating sensing demodulation device and a demodulation method based on a fiber-assisted interferometer in a variable temperature environment.
  • the fiber Bragg grating sensing system is based on light and the optical fiber is the transmission medium. It has the advantages of small size, light weight, corrosion resistance, electromagnetic interference resistance, good wavelength selectivity, easy reuse, etc. It can sense external stress, vibration, temperature. Changes in physical parameters such as pressure and pressure are reflected by the drift of the Bragg wavelength. Compared with the traditional electric sensing system, this technology has the characteristics of wide measuring range, high precision and high resolution. It has advantages in harsh environments such as strong electromagnetic interference, flammable and explosive or hot vacuum.
  • the tunable FP filtering method is a commonly used fiber grating sensing demodulation method, which is easy to realize high-speed and high-precision demodulation in a wide spectral range, but the tunable FP filter is realized by the inverse piezoelectric effect of PZT in a wide range. Wavelength scanning, while PZT hysteresis, creep and nonlinearity make the transmission wavelength and driving voltage not maintain good linearity and repeatability, which will affect the demodulation accuracy.
  • the FP etalon can introduce multiple optical frequency reference points with uniform spacing in the range matching the source band, and can better calibrate the wavelength sweep nonlinear relationship curve of the tunable filter at steady-state ambient temperature, but at different stability
  • the FP etalon has a wavelength shift at the state temperature. Correction of the reference wavelength of the F-P etalon using a temperature-stable gas reference wavelength enables absolute wavelength demodulation at different steady-state or quasi-steady-state ambient temperatures. However, when the ambient temperature changes rapidly, PZT also increases the random fluctuation of the filter wavelength scanning nonlinear curve. Especially in the case of medium-high speed scanning, it is difficult to avoid the wavelength demodulation result by using FP etalon and fiber-optic gas chamber.
  • a wave suppression device and a demodulation method for the wavelength scanning nonlinear curve By introducing a fiber-assisted interferometer, optical frequency subdivision is performed between adjacent interference lines of the FP etalon to obtain multiple parts.
  • the additional optical frequency reference effectively suppresses the fluctuation of the demodulation result caused by the fluctuation of the nonlinear curve of the tunable filter wavelength scanning.
  • the present invention provides a high-stability fiber grating sensing demodulation device and solution for wave suppression
  • the adjustment method the device realizes the subdivision of the optical wavelength interval of the FP standard by the auxiliary interferometer, and compiles the local optical frequency subdivision demodulation algorithm, which suppresses the large fluctuation of the relative demodulation value of the fiber grating during the temperature change process. Improved wavelength demodulation stability.
  • the invention provides a fiber grating sensing demodulation device for fluctuation suppression under ambient temperature, the device comprising a broadband light source 1, an optical attenuator 2, a tunable FP filter 3, a first fiber isolator 41, an erbium doped fiber amplifier 5.
  • Optical fiber primary beam splitter 6 first optical fiber secondary beam splitter 71, optical fiber circulator 8, optical fiber grating sensing array 9, first photodetector array 161, optical fiber plenum 10, second optical fiber secondary a beam splitter 72, an optical fiber FP etalon 11, a notch filter 12, a fiber-assisted interferometer 13 composed of a second fiber isolator 42, a fiber coupler 14, a Faraday rotator 15 and a second photodetector array 162, Data acquisition card 17 and processor 18;
  • the light emitted by the broadband light source 1 satisfies the entrance optical power requirement of the tunable FP filter 3 via the optical attenuator 2, and then enters the tunable FP filter 3 driven by the triangular wave or the sawtooth wave voltage to output the swept laser, the frequency sweep laser
  • the first fiber optic isolator 41 enters the erbium-doped fiber amplifier 5 for optical power amplification, and then splits into two parts of light through the fiber first-stage beam splitter 6: a part of the light enters the first fiber secondary beam splitter 71 and is divided into N beams.
  • each of the N-1 beams enters the corresponding fiber grating sensor array 9 through a fiber circulator 8 disposed in each path, and the sensor senses the signal of the change of the external parameter to be encoded to the center wavelength of the reflected light of the fiber grating, and reflects The light is then sent to the photodetector array 16 via the fiber circulator 8; the remaining beam enters the fiber plenum 10, and the transmitted light is received by the photodetector array 16; another portion of the light is split by the second fiber multiplexer 72.
  • Two beams of light one beam entering the fiber FP etalon 11 forming comb-like transmitted light of equal optical frequency spacing, using a notch filter 12 to trap the transmission peak of the specified central optical frequency, and As the optical frequency tag, is received by the photodetector array 16; the other auxiliary beam of light into the fiber optic interferometer 13 via a second optical isolator 42, two interfering arms of the reflected light is a Faraday rotator mirror 15 reflection, forming interference fringes at the fiber coupler 14, inserting a plurality of local additional optical frequency references between adjacent transmission peaks of the fiber FP etalon 11, and using the interference fringes to calibrate the nonlinear relationship of the tunable FP filter 3, The interfering light is received by photodetector array 16, which converts all of the optical signals into electrical signals that are sent via data acquisition card 17 to processor 18 for demodulation.
  • the invention also proposes a fiber grating sensing demodulation method for fluctuation suppression under ambient temperature, comprising the following processes:
  • Step (1) after the broadband light source input signal is optically attenuated and optical power tuned and filtered, the narrow-band swept laser is output, and the swept laser is subjected to optical power amplification processing after being isolated and returned to light, and then split into two parts by optical splitting processing.
  • Step (2) dividing the light reaching the sensing link and the fiber chamber into N beams, one of which is converted into a voltage analog signal by the transmitted light signal; each of the remaining N-1 beams is sent to the sensor chain
  • the sensor senses the outside world to be measured and encodes it to the center wavelength of the reflected light of the fiber grating; converts the reflected light signal of the sensing link into a voltage analog signal;
  • Step (3) dividing the light reaching the local additional optical frequency reference link into two parts of light, a part of the light forming a comb-shaped transmitted light, trapping the specified optical frequency of the transmitted optical signal, and marking the designated optical frequency; After a part of the light is split and reflected, it again meets and interferes to obtain the auxiliary interference signal; the two parts of the optical signal are respectively converted into voltage analog signals, and the voltage analog signal is sent to the processing unit for demodulation through the data acquisition card;
  • Step (4) performing peak finding on the collected comb-shaped transmission spectral line, and sequentially searching the obtained peak point X i and the known optical frequency value F i one by one on the basis of the specified optical frequency mark as a reference.
  • obtaining a first-order optical frequency reference point (X i , F i ) within a wide spectral range of the light source to form a first-order optical frequency reference point sequence, i 1, 2, 3...n-1; based on the primary optical frequency reference
  • Step (5) go to the baseline of the acquired interference signal line, and then intercept the auxiliary interference signal in the range E i of the sub-area X i ⁇ X i+1 , and obtain the auxiliary by the extremum method, the centroid method or the fitting method.
  • the peak and valley positions of the interference signal form a sequence of sampling points ( ⁇ 1 , ... ⁇ m+1 ) of the secondary optical frequency reference, and the number of complete half cycles is obtained by counting the number of peaks and valleys, close to the partition
  • the incomplete half-cycle of the start and end points is determined by calculating the percentage of the half-cycle in which it is located, and finally the number of half-cycles of the interference signal within the partition is obtained:
  • the sampling point-optical frequency relationship curve in the partition E i is established by interpolation;
  • Step (7) extracting the strongest absorption peak of the transmission line of the fiber-optic chamber, and finding the peak position after the baseline is obtained, and positioning the peak to a specific partition divided by the adjacent transmission line, based on the sampling point-optical frequency relationship curve
  • the standard value is subjected to temperature drift correction to obtain a final wavelength demodulation value.
  • FIG. 1 is a schematic diagram of a fiber grating sensing demodulation device for fluctuation suppression under ambient temperature
  • FIG. 2 is a schematic diagram of a fiber-assisted interferometer introducing an additional optical frequency reference between optical fiber F-P etalons and extracting optical frequencies;
  • Figure 3 is a line diagram of the interference spectrum of the fiber-assisted interferometer before and after the baseline;
  • FIG. 5 is a schematic diagram showing the rapid temperature change process of the device at -20 ° C to 20 ° C compared with the wavelength demodulation result of the local additional optical frequency reference demodulation method.
  • Embodiment 1 A fiber grating sensing demodulation device for fluctuation suppression under ambient temperature change.
  • the optical attenuator 2 from the broadband light source 1 satisfies the entrance optical work of the tunable F-P filter 3. Rate requirement, and then enter the tunable FP filter 3 driven by the triangular wave or sawtooth voltage to output the swept laser.
  • the swept laser is then passed through the first fiber isolator 41 into the erbium doped fiber amplifier 5 for optical power amplification, and then through the optical fiber.
  • the beam splitter 6 is divided into two beams according to 20%:80%, wherein 80% of the light enters the first fiber secondary beam splitter 71 and is divided into 8 beams, 7 of which are each passed through a fiber circulator provided in each path.
  • the change of the external parameter to be measured is sensed by the sensor, and causes the wavelength of the center of the reflected light of the fiber grating to drift, and the reflected light is sent to the photodetector array 16 via the fiber circulator 8; the remaining bundle Entering the fiber plenum 10, the transmitted light is received by the photodetector array 16; another 20% of the light is split into two beams by the second fiber first-stage beam splitter 72, and one beam enters the fiber FP etalon 11 to form an equal optical frequency.
  • the spaced comb-like transmitted light is trapped by a notch filter 12 with a transmission peak of a specified central optical frequency, and the optical frequency is taken as a mark, which is received by the photodetector array 16; the other light enters the optical fiber.
  • the interferometer 13 passes through the second optical isolator 42 and the reflected light of the two interfering arms is reflected by the Faraday rotator 15 to form interference fringes at the fiber coupler 14 to be inserted between the adjacent transmission peaks of the optical fiber FP etalon 11
  • the interference scanning fringes are used to calibrate the wavelength scanning nonlinearity curve of the tunable FP filter 3
  • the interference light is received by the photodetector array 16, and the photodetector array 16 converts all optical signals into electrical signals. It is sent to the processor 18 via the data acquisition card 17 for demodulation.
  • Broadband light source 1 used to provide wide-spectrum light for the system, including C-band ASE light source, C+L-band ASE light source and SLD light source, with power ranging from 0.1mW to 40mW;
  • the optical attenuator 2 is configured to adjust the output optical power of the light source to meet the limit requirement of the tunable F-P filter for the optical power of the inlet;
  • the tunable FP filter 3 is configured to filter the wavelength-scanned narrow-band spectral signal from the broadband source by controlling its driving voltage, and the tunable FP filter has a spectral width of 10 pm to 400 pm and a free spectral range of 90 nm. ⁇ 200nm;
  • the first and second optical fiber isolators 41 and 42 are configured to isolate the return light and ensure one-way transmission of the light;
  • the erbium-doped fiber amplifier 5 is used for amplifying the scanning light, and the output optical power ranges from 10 dBm to 18 dBm;
  • the fiber-optic first-order beam splitter 6 is configured to split the input light according to a certain ratio, including a planar waveguide type fiber splitter and a fused taper type fiber splitter;
  • the fiber secondary beam splitter 7 is configured to divide the output tunable laser into N beam power and the same type of scanning laser, and the value of N is selected from one of 2, 4, 8, 16, 32, 64, 128 ;
  • the fiber circulator 8 is configured to send the light from the fiber secondary beam splitter to the sensor link and collect the reflected signal light.
  • the fiber coupler may be used instead to reduce the system cost;
  • the fiber grating sensing array 9 is configured to sense the change of the physical quantity to be measured in the external environment, so that the wavelength of the fiber grating reflection spectrum shifts;
  • a fiber optic chamber 10 for providing an absolute optical frequency reference standard including an acetylene gas chamber, a methane gas chamber, a hydrogen cyanide gas chamber, and a carbon dioxide gas chamber;
  • An optical fiber F-P etalon 11 for providing a comb-like wavelength reference of equal optical frequency spacing
  • a notch filter 12 for removing one of the optical fiber F-P etalon
  • the fiber-assisted interferometer 13 is configured to provide an additional optical frequency reference between the adjacent transmission maxima of the optical fiber FP etalon 11 to calibrate the wavelength scanning nonlinear curve of the tunable FP filter during the environmental temperature change process, and the structure includes the fiber Michael The interference ritual and the fiber Mach Zeide interference ritual; the fiber Michelson interference ritual is composed of a fiber coupler 14 and a fiber Faraday rotator 15 , and the fiber coupler 14 divides the input light into two paths to obtain two vibrations having the same direction and the same frequency.
  • the beam light is respectively sent to the fiber Faraday rotator 15 , and the fiber Faraday rotator 15 reflects the interference of the two arms to form an interference arm having a certain optical path difference;
  • the fiber Mach Zeide interference ritual is composed of two fiber couplers
  • the serial connection composition due to the spectral width of the scanning source, the optical path difference of the two arms has an allowable maximum value.
  • a photodetector array 16 for converting an optical signal of the sensing channel and the reference channel into a voltage analog signal
  • the data acquisition card 17 collects the voltage analog signal obtained by the photodetector array
  • the processing unit 18 employs a computer or embedded computing system for demodulating the wavelength of the measured fiber grating.
  • Embodiment 2 Local additional optical frequency reference extraction and demodulation algorithm based on fiber-assisted interferometer and fiber F-P etalon
  • the light emitted by the first broadband source passes through the optical attenuator to make the output optical power meet the requirements of the FP filter for the entrance optical power.
  • the tunable FP filter outputs a narrowband swept laser driven by a triangular wave or a sawtooth voltage, and then passes through the optical fiber.
  • the isolator enters the erbium-doped fiber amplifier for optical power amplification, and then splits into two parts of light through the fiber first-stage beam splitter, one part of the light reaches the sensing link and the fiber plenum, and the other part of the light reaches the local additional optical frequency reference link;
  • the circulator sends the frequency-swept laser to the fiber grating sensor array, and the sensor senses the change to be measured by the outside, so that the center wavelength of the fiber grating inverse spectrum shifts, and the reflected light signal is sent to the photodetector through the fiber circulator;
  • the light that reaches the local additional optical frequency reference link enters the fiber secondary beam splitter and is divided into two parts of light, and a part of the light enters the fiber FP etalon to form comb-like transmitted light of equal optical frequency interval, and adopts a notch filter trap.
  • the optical signal of the specified optical frequency is removed, and the optical frequency is marked; the other part of the light enters the optical fiber auxiliary interferometer, and the reflected light of the two arms forms interference light at the fiber coupler; the two wavelength reference optical signals are respectively sent to the photodetection
  • the photodetector array converts all optical signals into electrical signals and sends them to the processing unit for demodulation via the data acquisition card;
  • the fourth optical fiber FP etalon provides a wavelength reference line with equal optical frequency spacing, and the peak of the collected etalon signal is peak-finished, and the optical frequency mark is in one-to-one correspondence with the known optical frequency value, thereby obtaining the spectral range of the light source.
  • the peak-to-valley position which is the sequence of sampling points ( ⁇ 1 ,... ⁇ m +1 ) of the secondary optical frequency reference, and counts the number of peaks and valleys to the number m of complete half-cycles, close to the starting and ending points of the partition.
  • the non-complete half-cycle is determined by calculating the percentage of the half-cycle in which it is located, and finally the half-cycle number of the interference signal in the partition is obtained.
  • ⁇ n s is a partition of a peak (valley) values of the sampling point spacing starting point and the partition of X i, N s / 2 in which X i is a half-cycle of the interference signal sampling points.
  • ⁇ n e is the sampling point spacing of the last peak (valley) value point in the partition and the partition end point X i+1
  • N e /2 is the number of interference half-cycle sampling points where Xi +1 is located.
  • the primary optical frequency reference provided by the optical fiber FP etalon and the secondary optical frequency reference provided by the optical fiber auxiliary interferometer establish a relationship between the sampling point and the optical frequency in the partition E i by interpolation, thereby reflecting the wavelength scanning.
  • the tunable filter in the stroke scans the more realistic details of the nonlinear curve and suppresses fluctuations in the demodulation results.
  • the phase relationship between each point of the signal is obtained according to the interference characteristics of the double beam of the auxiliary interferometer signal, and more secondary optical frequency references are obtained;
  • Section 6 By finding the peak of the fiber grating sensor reflection line, the peak position is located in a specific partition divided by the adjacent transmission line of the fiber FP etalon, in which the FP etalon and the auxiliary interferometer are based.
  • the sampling point-optical frequency relationship curve is interpolated to obtain the peak center optical frequency f fbg of the fiber Bragg grating sensor.
  • the peak center wavelength ⁇ fbg of the fiber Bragg grating sensor is obtained by the relationship between the optical frequency and the wavelength;
  • the fiber grating transmission signal 20 is peaked and positioned to a specific etalon.
  • the start and end points of the partition are two adjacent peaks of the fiber FP etalon. Points (X i , F i ), (X i+1 , F i+1 ).
  • the signal line 21 (shown in FIG. 2) of the fiber-assisted interferometer in the partition is determined by the centroid method to determine the position of the peak-to-valley value.
  • the sequence of sample points of the secondary optical frequency reference ( ⁇ 1 ,... ⁇ m+1 ), and the number of complete half cycles is obtained by counting the number of peaks and valleys, and the non-complete half cycle near the start and end points of the partition is calculated.
  • the percentage of the half cycle in which it is located is determined, and the number of half cycles of the interference signal in the partition is finally obtained, and then the reference value of each secondary optical frequency is obtained according to the optical frequency value of the optical frequency reference at both ends.
  • the primary optical frequency reference provided by the optical fiber FP etalon and the secondary optical frequency reference provided by the optical fiber-assisted interferometer are interpolated to establish a function relationship between the sampling point and the optical frequency in the partition, and the relationship is obtained according to the relationship.
  • the peak center optical frequency f fbg of the FBG sensor is obtained by the relationship between the optical frequency and the wavelength to obtain the peak center wavelength ⁇ fbg of the FBG sensor.
  • the device is placed in a temperature changing process of -20 ° C to 20 ° C, and the local additional optical frequency reference method of the present invention is used in the thermostatic bath.
  • the insulated FBG sensor is demodulated and compared to other methods. It can be seen that in the case of using other methods, the wave The long demodulation result fluctuates at ⁇ 24 pm; and the wavelength demodulation fluctuation obtained by the local additional optical frequency reference method of the present invention is ⁇ 3.5 pm, and the wavelength demodulation stability is improved by 5.9 times.

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Abstract

一种环境变温下波动抑制的光纤光栅传感解调装置及其解调方法。该解调装置具有宽带光源(1)、光衰减器(2)、可调谐F‑P滤波器(3)、第一光纤隔离器(41)、掺铒光纤放大器(5)、光纤一级分束器(6)、第一光纤二级分束器(71)、光纤环形器(8)、光纤光栅传感阵列(9)、第一光电探测器阵列(161)、光纤气室(10)、第二光纤二级分束器(72)、光纤F‑P标准具(11)、陷波滤波器(12)、由第二光纤隔离器(42)、光纤耦合器(14)、法拉第旋光镜(15)和第二光电探测器阵列(162)构成的光纤辅助干涉仪(13)、数据采集卡(17)和处理器(18)。

Description

环境变温下波动抑制的光纤光栅传感解调装置与解调方法 技术领域
本发明属于光纤传感技术领域，特别是涉及在变温环境下，一种基于光纤辅助干涉仪的高稳定光纤光栅传感解调装置与解调方法。
背景技术
光纤光栅传感系统是以光为载体，光纤为传输媒介，具有体积小、重量轻、耐腐蚀、抗电磁干扰、波长选择性好、易复用等优点，可感知外界应力应变、振动、温度和压力等物理参量的变化，通过布拉格光波长的漂移反映出来。相比传统电学传感系统，该技术具有测量范围宽、高精度和高分辨率的特点，在强电磁干扰、易燃易爆或热真空等严酷环境下更具优势。
可调谐F-P滤波法是常用的光纤光栅传感解调方法，易实现在宽光谱范围内的高速、高精度解调，但因可调谐F-P滤波器是通过PZT的逆压电效应实现宽范围内的波长扫描，而PZT迟滞、蠕变和非线性等特性使透射波长与驱动电压不能保持很好的线性和重复性，会影响解调精度。F-P标准具可在与光源波段匹配的范围内引入间隔均匀的多个光频率参考点，在稳态环境温度下能较好地标定可调谐滤波器的波长扫描非线性关系曲线，但在不同稳态温度下F-P标准具存在波长漂移。使用温度稳定的气体参考波长对F-P标准具的参考波长作校正，实现了不同稳态或准稳态环境温度下的绝对波长解调。但是，当环境温度较快变化时，PZT还会使滤波器波长扫描非线性曲线的随机波动增大，尤其在中高速扫描的场合，采用F-P标准具和光纤气室也难以避免波长解调结果出现大幅度波动，导致测量精度大幅降低。为克服这一问题，我们提出波长扫描非线性曲线的波动抑制装置和解调方法，通过引入光纤辅助干涉仪，在F-P标准具相邻干涉谱线之间进行光频细分，得到多个局部附加光频率参考，有效抑制可调谐滤波器波长扫描非线性曲线波动增大引起的解调结果波动。
发明内容
为了克服环境变温引起的可调谐F-P滤波器波长扫描非线性曲线波动增大对光纤光栅传感器波长解调稳定性的影响，本发明提供一种波动抑制的高稳定光纤光栅传感解调装置与解调方法，该装置通过辅助干涉仪实现了对F-P标准具光波长间隔的细分，并编制了局部光频细分解调算法，抑制了变温过程中光纤光栅相对波长解调值的大幅波动，提高了波长解调稳定性。
本发明提出了一种环境变温下波动抑制的光纤光栅传感解调装置，该装置包括宽带光源1、光衰减器2、可调谐F-P滤波器3、第一光纤隔离器41、掺铒光纤放大器5、光纤一级分束器6、第一光纤二级分束器71、光纤环形器8、光纤光栅传感阵列9、第一光电探测器阵列161、光纤气室10、第二光纤二级分束器72、光纤F-P标准具11、陷波滤波器12、由第二光纤隔离器42、光纤耦合器14、法拉第旋光镜15和第二光电探测器阵列162构成的光纤辅助干涉仪13、数据采集卡17和处理器18；
其中，宽带光源1发出的光经光衰减器2满足可调谐F-P滤波器3的入口光功率要求，然后进入由三角波或锯齿波电压驱动的可调谐F-P滤波器3输出扫频激光，扫频激光再经第一光纤隔离器41进入掺铒光纤放大器5进行光功率放大，再经光纤一级分束器6分成两部分光：其中一部分光进入第一光纤二级分束器71被分成N束，其中N-1束均各自通过每路设置的一个光纤环形器8进入相应的光纤光栅传感器阵列9，传感器感知外界待测参量变化的信号将其编码到光纤光栅反射光的中心波长上，反射光再经光纤环形器8送至光电探测器阵列16；剩余一束进入光纤气室10，透射光由光电探测器阵列16接收；另外一部分的光再经过第二光纤一级分束器72分成两束光，一束进入光纤F-P标准具11形成等光频率间隔的梳状透射光，采用一个陷波滤波器12陷掉指定中心光频率的透射峰，并将该光频率作为标记，由光电探测器阵列16接收；另一束光进入光纤辅助干涉仪13，经第二一光纤隔离器42，两个干涉臂的反射光经法拉第旋光镜 15反射，在光纤耦合器14处形成干涉条纹，在光纤F-P标准具11相邻透射峰之间插入多个局部附加光频率参考，用干涉条纹来标定可调谐F-P滤波器3的非线性关系曲线，干涉光由光电探测器阵列16接收，光电探测器阵列16将所有的光信号转变成电信号经数据采集卡17送至处理器18进行解调。
本发明还提出了一种环境变温下波动抑制的光纤光栅传感解调方法，包括以下流程：
步骤(1)、宽带光源输入信号经过光衰减、光功率调谐滤波后，输出窄带扫频激光，扫频激光经隔离回光处理后，进行光功率放大处理，再经过光分束处理分成两部分光，其中一部分光到达传感链路和光纤气室，另一部分光到达局部附加光频率参考链路；
步骤(2)、将到达传感链路和光纤气室的光分成N束，其中一束由透射光信号转化为电压模拟信号；其余N-1束中的每束光均被发送至传感器链路，传感器感知外界待测量并将其编码到光纤光栅反射光的中心波长上；将传感链路的反射光信号转化为电压模拟信号；
步骤(3)、将到达局部附加光频率参考链路的光分成两部分光，一部分光形成梳状透射光，对该透射光信号陷掉指定光频率，并对该指定光频率作标记；另一部分光经分束和反射后再次相遇并发生干涉得到辅助干涉信号；将两部分光信号分别转化为电压模拟信号，电压模拟信号再经数据采集卡送至处理单元进行解调；
步骤(4)、对采集到的梳状透射光谱线进行寻峰，以指定的光频率标记为基准向两侧依次将寻得的各峰值点Xi与已知的光频率值Fi一一对应，获得光源谱宽范围内的一级光频率参考点(Xi,Fi)，构成一级光频率参考点序列，i＝1,2,3…n-1；基于一级光频率参考点序列，将整个宽带的光源谱划分为n个区域(Ei＝1,2,3…n-1)，每个区域的起点和终点为两个相邻的一级光频率参考点(Xi,Fi)和(Xi+1,Fi+1)；
步骤(5)、对采集到的干涉信号谱线去基线，然后截取分区Ei横坐标范围Xi～Xi+1 内的辅助干涉信号，通过极值法、质心法或拟合法求取辅助干涉信号的峰值、谷值位置，构成次级光频率参考的采样点(χ1，…χm+1)序列，并通过对峰谷点个数计数得到完整半周期的个数m，靠近分区起点和终点的非完整半周期通过计算其在所处半周期中所占百分比确定，最终得到分区内干涉信号的半周期数：
Figure PCTCN2016103525-appb-000001
其中，Δns为分区内第一个峰值或谷值点与分区起点Xi的采样点间距，Ns/2为Xi所处的干涉半周期采样点个数；Δne为分区内最后一个峰值或谷值点与分区终点Xi+1的采样点间距，Ne/2为Xi+1所处的干涉半周期采样点个数。从而得到次级光频率参考点的光频率值fk(k＝1,2,3…m+1)：
Figure PCTCN2016103525-appb-000002
利用一级光频率参考点(Xi,Fi)和次级光频率参考点(χk,fk)共同构成的序列，通过插值建立分区Ei内的采样点-光频率关系曲线；f1、fm+1分别代表k＝1和k＝m+1时的次级光频率参考点的光频率值；
步骤(6)、通过对传感链路的反射光信号谱线寻峰，将峰值位置定位到相邻透射光信号谱线划分的特定分区内，基于采样点-光频率的关系曲线，通过插值得到光纤光栅传感器透射峰的中心光频率ffbg，通过光频率f和波长λ的关系λ＝c/f(c为真空中的光速)得到光纤光栅传感器的峰值中心波长λfbg＝c/ffbg；
步骤(7)、提取光纤气室透射谱线最强吸收峰，去基线后寻峰得到峰值位置，将 峰值定位到由相邻透射谱线划分的特定分区内，基于采样点-光频率关系曲线，通过插值得到最强吸收峰的中心光频率fg，通过光频率和波长的关系得到峰值中心波长λg，λg＝c/fg，再根据气室透射谱线最强吸收峰中心波长的标准值进行温漂校正，得到最终波长解调值。
附图说明
图1为环境变温下波动抑制的光纤光栅传感解调装置示意图；
图2为光纤辅助干涉仪在光纤F-P标准具之间引入附加光频率参考并提取光频率的示意图；
图3为光纤辅助干涉仪干涉谱去基线前后的谱线图；
图4为结合附加光频率参考标定可调谐F-P滤波器的局部非线性曲线；
图5为本发明与以往未引入局部附加光频率参考解调方法的波长解调结果对比，装置处于-20℃～20℃的快速变温过程示意图。
附图标记：1、宽带光源，2、光衰减器，3、可调谐F-P滤波器，41、第一光纤隔离器，5、掺铒光纤放大器，6、光纤一级分束器，71、第一光纤二级分束器，72、第二光纤二级分束器、8、光纤环形器，9、光纤光栅传感阵列，10、光纤气室，11、光纤F-P标准具，12、陷波滤波器，13、光纤辅助干涉仪，42、第二光纤隔离器，14、光纤耦合器，15、法拉第旋光镜，16、光电探测器阵列，17、数据采集卡，18、处理器，19、标准具透射峰，20、光纤光栅透射信号。
具体实施方式
以下结合附图说明及实施例，具体描述本发明的技术方案
实施例1：环境变温下波动抑制的光纤光栅传感解调装置。
如图1所示，宽带光源1发出的经光衰减器2满足可调谐F-P滤波器3的入口光功 率要求，然后进入由三角波或锯齿波电压驱动的可调谐F-P滤波器3输出扫频激光，扫频激光再经第一光纤隔离器41进入掺铒光纤放大器5进行光功率放大，再经光纤一级分束器6按照20％:80％分成两束光，其中80％的光进入第一光纤二级分束器71被分成8束，其中7束均各自通过每路设置的一个光纤环形器8进入相应的光纤光栅传感器阵列9，外界待测参量的变化被传感器感知，并引起光纤光栅反射光中心波长的漂移，反射光再经光纤环形器8送至光电探测器阵列16；剩余一束进入光纤气室10，透射光由光电探测器阵列16接收；另外20％的光经再经过第二光纤一级分束器72分成两束光，一束进入光纤F-P标准具11形成等光频率间隔的梳状透射光，采用一个陷波滤波器12陷掉指定中心光频率的透射峰，并将该光频率作为标记，由光电探测器阵列16接收；另一束光进入光纤辅助干涉仪13，经第二一光纤隔离器42，两个干涉臂的反射光经法拉第旋光镜15反射，在光纤耦合器14处形成干涉条纹，在光纤F-P标准具11相邻透射峰之间插入多个局部附加光频率参考，用干涉条纹来标定可调谐F-P滤波器3的波长扫描非线性曲线，干涉光由光电探测器阵列16接收，光电探测器阵列16将所有的光信号转变成电信号经数据采集卡17送至处理器18进行解调。
宽带光源1，用于为系统提供宽谱光，包括C波段ASE光源、C+L波段ASE光源和SLD光源，功率在0.1mW～40mW；
光衰减器2，用于调节光源输出光功率，以达到可调谐F-P滤波器对入口光功率的限制要求；
可调谐F-P滤波器3，用于通过控制其驱动电压从宽带光源中滤出波长变化的窄带光谱信号，从而实现波长扫描，可调谐F-P滤波器的谱宽在10pm～400pm，自由光谱范围为90nm～200nm；
第一、第二光纤隔离器41、42，用于隔离回光，保证光的单向传输；
掺铒光纤放大器5，用于对扫描光进行放大，输出光功率范围为10dBm～18dBm；
光纤一级分束器6，用于将输入光按照一定的比例分光，包括平面波导型光纤分束器、熔融拉锥式光纤分束器；
光纤二级分束器7，用于将输出的可调谐激光分成N束光功率和谱型相同的扫描激光，N取值选自2，4，8，16，32，64，128中的一个；
光纤环形器8，用于将光纤二级分束器出来的光发送至传感器链路并收集反射信号光，当光源功率大于1mW时，可采用光纤耦合器替代以降低系统成本；
光纤光栅传感阵列9，用于感知外界待测量物理量变化，使光纤光栅反射谱中波长发生漂移；
光纤气室10，用于提供绝对光频参考标准，包括乙炔气室、甲烷气室、氰化氢气室、二氧化碳气室；
光纤F-P标准具11，用于提供等光频间隔的梳状波长参考；
陷波滤波器12，用于去掉光纤F-P标准具中的一条谱线；
光纤辅助干涉仪13，用于在光纤F-P标准具11相邻透射极大之间提供附加光频参考，对环境变温过程中可调谐F-P滤波器的波长扫描非线性曲线进行标定，结构包括光纤迈克尔逊干涉仪式和光纤马赫泽德干涉仪式；光纤迈克尔逊干涉仪式由光纤耦合器14和光纤法拉第旋光镜15组成，光纤耦合器14将输入光均分两路，得到振动方向相同，频率相同的两束光，分别送至由光纤法拉第旋光镜15，光纤法拉第旋光镜15将干涉两臂的光反射，构成有一定光程差的干涉两臂；光纤马赫泽德干涉仪式则由两个光纤耦合器串接组成；由于扫描光源谱宽造成两臂光程差存在允许极大值，在确定两臂几何长度差时，需综合考虑光程差对干涉条纹个数和条纹可见度的相互制约关系；
光电探测器阵列16，用于将传感通道和参考通道的光信号转化为电压模拟信号；
数据采集卡17，采集由光电探测器阵列得到的电压模拟信号；
处理单元18，采用计算机或嵌入式计算系统，用于对被测传感光纤光栅的波长进行解调。
实施例2：基于光纤辅助干涉仪和光纤F-P标准具的局部附加光频率参考提取和解调算法
第1、宽带光源发出的光经过光衰减器使输出光功率满足调谐F-P滤波器对入口光功率的要求，可调谐F-P滤波器在三角波或锯齿波电压驱动下输出窄带扫频激光，再经光纤隔离器进入掺铒光纤放大器进行光功率放大，再经过光纤一级分束器分成两部分光，其中一部分光到达传感链路和光纤气室，另一部分光到局部附加光频率参考链路；
第2、到达传感链路和光纤气室的光进入光纤二级分束器分成N束，其中一束进入光纤气室，透射光信号送至光电探测器；其余每束光均通过一个光纤环形器将扫频激光送至光纤光栅传感器阵列，传感器感知外界待测量的变化，使光纤光栅反谱的中心波长发生漂移，反射光信号再通过光纤环形器送至光电探测器；
第3、到达局部附加光频率参考链路的光进入光纤二级分束器分成两部分光，一部分光进入光纤F-P标准具形成等光频率间隔的梳状透射光，采用一个陷波滤波器陷掉指定光频率的光信号，并将该光频率作标记；另一部分光进入光纤辅助干涉仪，其两臂反射光在光纤耦合器处形成干涉光；两路波长参考光信号分别送至光电探测器；光电探测器阵列将所有的光信号转变成电信号经数据采集卡送至处理单元进行解调；
第4、光纤F-P标准具提供等光频率间隔的波长参考谱线，对采集到的标准具信号进行寻峰，通过光频率标记与已知光频率值一一对应，获得光源谱宽范围内的一级光频率参考点；基于一级光频率参考点序列，将整个光源谱范围划分为多个区域(Ei＝1,2,3…n-1)，每个区域的起点和终点分别由光纤F-P标准具透射谱的两个相邻峰值点(Xi,Fi)和(Xi+1,Fi+1)确定；
第5、对采集到的光纤辅助干涉仪信号谱线去基线，然后在由光纤F-P标准具确定的分区Ei内处理辅助干涉信号，使用质心法、三角函数拟合法，和求导法确定其峰谷值位置，作为次级光频率参考的采样点(χ1，…χm+1)序列，并通过对峰谷点个数计数到得完整半周期的个数m，靠近分区起点和终点的非完整半周期通过计算其在所处半周期中所占百分比确定，最终得到分区内干涉信号的半周期数
Figure PCTCN2016103525-appb-000003
其中Δns为分 区内第一个峰(谷)值点与分区起点Xi的采样点间距，Ns/2为Xi所处的干涉半周期采样点个数。Δne为分区内最后一个峰(谷)值点与分区终点Xi+1的采样点间距，Ne/2为Xi+1所处的干涉半周期采样点个数。从而得到次级光频率参考的光频率值fk(k＝1,2,3…m+1)：
Figure PCTCN2016103525-appb-000004
此时由光纤F-P标准具提供的一级光频率参考和由光纤辅助干涉仪提供的次级光频率参考，通过插值建立分区Ei内的采样点-光频率的关系曲线，从而反映出波长扫描行程中可调谐滤波器扫描非线性曲线更为真实的细节，抑制解调结果的波动。当需进一步进行光频率细化的时候，根据辅助干涉仪信号的双光束干涉特征，得到信号每一点之间的相位关系，求得更多次级光频率参考；
第6、通过对光纤光栅传感器反射谱线寻峰，将其峰值位置定位到由光纤F-P标准具相邻透射谱线划分的特定的分区内，在该分区内，基于F-P标准具和辅助干涉仪的采样点-光频率关系曲线插值得到光纤光栅传感器的峰值中心光频率ffbg，通过光频率和波长的关系得到光纤光栅传感器的峰值中心波长λfbg；
第7、提取光纤气室透射谱线最强吸收峰，去基线后寻峰得到峰值位置，将峰值定位到由光纤F-P标准具相邻透射谱线划分的特定的分区内，基于F-P标准具和辅助干涉仪的采样点-光频率关系曲线，通过插值得到光纤气室的最强吸收峰的中心光频率fg，通过光频率和波长的关系得到光纤气室的峰值中心波长λg，再根据气室透射谱线最强吸收峰中心波长的标准值进行温漂校正，得到最终波长解调值。
如图2所示，在为光纤辅助干涉仪13在光纤F-P标准具相邻干涉极大之间引入局部附加光频率参考的示意图中，对光纤光栅透射信号20寻峰并定位到特定的标准具透射峰19确定的分区Ei(i＝1,2,3…n-1)内，n表示可得到的分区总数，划分时，分区的起点和终点为光纤F-P标准具的两个相邻峰值点(Xi,Fi)、(Xi+1,Fi+1)。
如图3所示，在光纤辅助干涉仪信号去基线前后的谱线图中，对分区内光纤辅助干涉仪信号谱线21(如图2所示)，使用质心法确定峰谷值位置，作为次级光频率参考的采样点序列(χ1，…χm+1)，同时通过对峰谷点个数计数得到完整半周期的个数，靠近分区起点和终点的非完整半周期通过计算其在所处半周期中所占百分比确定，最终得到分区内干涉信号的半周期数，再根据两端一级光频率参考的光频率值求得各次级光频率参考值。
如图4所示，由光纤F-P标准具提供的一级光频率参考和由光纤辅助干涉仪提供的次级光频率参考通过插值建立分区内采样点-光频率的函数关系，根据此关系求出光纤光栅传感器的峰值中心光频率ffbg，通过光频率和波长的关系得到光纤光栅传感器的峰值中心波长λfbg。同理得到光纤气室的最强吸收峰的峰值中心波长λg，而气室最强吸收峰中心波长的标准值为λr，则进行温漂校正后的光纤光栅中心波长为λFBG＝λf-η(λg-λr)，其中
Figure PCTCN2016103525-appb-000005
m1是与光纤气室最强吸收峰中心波长标准值λr最接近的光纤F-P标准具的透射峰的干涉级次，FSR为光纤F-P标准具的自由光谱范围。
如图5所示，为了验证本发明对波长传感测量稳定性的提高效果，将装置置于-20℃～20℃的变温过程，并使用本发明局部附加光频率参考方法对在恒温槽中保温的光纤光栅传感器进行解调，同时与其他方法作对比。可以看出，在使用其他方法的情况下，波 长解调结果波动在±24pm；而利用本发明的局部附加光频率参考方法所得波长解调波动在±3.5pm，波长解调稳定性提高5.9倍。

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  1. 一种环境变温下波动抑制的光纤光栅传感解调装置，其特征在于，该装置具有宽带光源(1)、光衰减器(2)、可调谐F-P滤波器(3)、第一光纤隔离器(41)、掺铒光纤放大器(5)、光纤一级分束器(6)、第一光纤二级分束器(71)、光纤环形器(8)、光纤光栅传感阵列(9)、第一光电探测器阵列(161)、光纤气室(10)、第二光纤二级分束器(72)、光纤F-P标准具(11)、陷波滤波器(12)、由第二光纤隔离器(42)、光纤耦合器(14)、法拉第旋光镜(15)和第二光电探测器阵列(162)构成的光纤辅助干涉仪(13)、数据采集卡(17)和处理器(18)；
    其中，宽带光源(1)发出的光经光衰减器(2)满足可调谐F-P滤波器(3)的入口光功率要求，然后进入由三角波或锯齿波电压驱动的可调谐F-P滤波器(3)输出扫频激光，扫频激光再经第一光纤隔离器(41)进入掺铒光纤放大器(5)进行光功率放大，再经光纤一级分束器(6)分成两部分光：其中一部分光进入第一光纤二级分束器(71)被分成N束，其中N-1束均各自通过每路设置的一个光纤环形器(8)进入相应的光纤光栅传感器阵列(9)，外界待测参量的变化被传感器感知，并引起光纤光栅反射光中心波长的漂移，反射光再经光纤环形器(8)送至光电探测器阵列(16)；剩余一束进入光纤气室(10)，透射光由光电探测器阵列(16)接收；另外一部分的光再经过第二光纤一级分束器(72)分成两束光，一束进入光纤F-P标准具(11)形成等光频率间隔的梳状透射光，采用一个陷波滤波器(12)陷掉指定中心光频率的透射峰，并将该光频率作为标记，由光电探测器阵列(16)接收；另一束光进入光纤辅助干涉仪(13)，经第二一光纤隔离器(42)，两个干涉臂的反射光经法拉第旋光镜(15)反射，在光纤耦合器(14)处形成干涉条纹，在光纤F-P标准具(11)相邻透射峰之间插入多个局部附加光频率参考，用干涉条纹来标定可调谐F-P滤波器(3)的波长扫描非线性曲线，干涉光由光电探测器阵列(16)接收，光电探测器阵列(16)将所有的光信号转变成电信号经数据采集卡(17)送至处理器(18)进行解调。
  2. 一种环境变温下波长扫描波动抑制的光纤光栅传感解调方法，其特征在于，该方法包括以下流程：
    步骤(1)、宽带光源输入信号经过光衰减、光功率调谐滤波后，输出窄带扫频激光，扫频激光经隔离回光处理后，进行光功率放大处理，再经过光分束处理分成两部分光，其中一部分光到达传感链路和光纤气室，另一部分光到达局部附加光频率参考链路；
    步骤(2)、将到达传感链路和光纤气室的光分成N束，其中一束由透射光信号转化为电压模拟信号；其余N-1束中的每束光均被发送至传感器链路，当外界待测参量变化时，光纤光栅反射光的中心波长发生漂移；将传感链路的反射光信号转化为电压模拟信号；
    步骤(3)、将到达局部附加光频率参考链路的光分成两部分光，一部分光形成梳状透射光，对该透射光信号陷掉指定光频率，并对该指定光频率作标记；另一部分光经分束和反射后再次相遇并发生干涉得到辅助干涉信号；将两部分光信号分别转化为电压模拟信号，电压模拟信号再经数据采集卡送至处理单元进行解调；
    步骤(4)、对采集到的梳状透射光谱线进行寻峰，以指定的光频率标记为基准向两侧依次将寻得的各峰值点Xi，并与已知的光频率值Fi一一对应，获得光源谱宽范围内的一级光频率参考点(Xi,Fi)，构成一级光频率参考点序列，i＝1,2,3…n-1；基于一级光频率参考点序列，将整个宽带的光源谱划分为n个区域(Ei＝1,2,3…n-1)，每个区域的起点和终点为两个相邻的一级光频率参考点(Xi,Fi)和(Xi+1,Fi+1)；
    步骤(5)、对采集到的干涉信号谱线去基线，然后截取分区Ei横坐标范围Xi～Xi+1内的辅助干涉信号，通过极值法、质心法或拟合法求取辅助干涉信号的峰值、谷值位置，构成次级光频率参考的采样点(χ1，…χm+1)序列，并通过对峰谷点个数计数得到完整半周期的个数m，靠近分区起点和终点的非完整半周期通过计算其在所处半周期中所占百分比确定，最终得到分区内干涉信号的半周期数：
    Figure PCTCN2016103525-appb-100001
    其中，Δns为分区内第一个峰值或谷值点与分区起点Xi的采样点间距，Ns/2为Xi所处的干涉半周期采样点个数；Δne为分区内最后一个峰值或谷值点与分区终点Xi+1的采样点间距，Ne/2为Xi+1所处的干涉半周期采样点个数，从而得到次级光频率参考点的光频率值fk(k＝1,2,3…m+1)：
    Figure PCTCN2016103525-appb-100002
    利用一级光频率参考点(Xi,Fi)和次级光频率参考点(χk,fk)共同构成的序列，通过插值建立分区Ei内的采样点-光频率关系曲线；f1、fm+1分别代表k＝1和k＝m+1时的次级光频率参考点的光频率值；
    步骤(6)、通过对传感链路的反射光信号谱线寻峰，将峰值位置定位到相邻透射光信号谱线划分的特定分区内，基于采样点-光频率的关系曲线，通过插值得到光纤光栅传感器透射峰的中心光频率ffbg，通过光频率f和波长λ的关系λ＝c/f，c为真空中的光速，得到光纤光栅传感器的峰值中心波长λfbg＝c/ffbg；
    步骤(7)、提取光纤气室透射谱线最强吸收峰，去基线后寻峰得到峰值位置，将峰值定位到由相邻透射谱线划分的特定分区内，基于采样点-光频率关系曲线，通过插值得到最强吸收峰的中心光频率fg，通过光频率和波长的关系得到峰值中心波长λg，λg＝c/fg，再根据气室透射谱线最强吸收峰中心波长的标准值进行温漂校正，得到最终波长解调值。
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