WO2024077503A1 - 利用气体吸收光谱参考的干涉仪绝对位移解调***及方法 - Google Patents

利用气体吸收光谱参考的干涉仪绝对位移解调***及方法 Download PDF

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WO2024077503A1
WO2024077503A1 PCT/CN2022/124758 CN2022124758W WO2024077503A1 WO 2024077503 A1 WO2024077503 A1 WO 2024077503A1 CN 2022124758 W CN2022124758 W CN 2022124758W WO 2024077503 A1 WO2024077503 A1 WO 2024077503A1
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interferometer
interference
wavelength
absorption spectrum
detector
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PCT/CN2022/124758
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English (en)
French (fr)
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宁雅农
刘统玉
杨青山
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广东感芯激光科技有限公司
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Priority claimed from CN202211229340.2A external-priority patent/CN115523948B/zh
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Publication of WO2024077503A1 publication Critical patent/WO2024077503A1/zh

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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01D—MEASURING NOT SPECIALLY ADAPTED FOR A SPECIFIC VARIABLE; ARRANGEMENTS FOR MEASURING TWO OR MORE VARIABLES NOT COVERED IN A SINGLE OTHER SUBCLASS; TARIFF METERING APPARATUS; MEASURING OR TESTING NOT OTHERWISE PROVIDED FOR
    • G01D5/00—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable
    • G01D5/26—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light
    • G01D5/32—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light
    • G01D5/34—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells
    • G01D5/353—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells influencing the transmission properties of an optical fibre
    • G01D5/35306—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells influencing the transmission properties of an optical fibre using an interferometer arrangement
    • G01D5/35309—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
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
    • G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
    • G01N21/25—Colour; Spectral properties, i.e. comparison of effect of material on the light at two or more different wavelengths or wavelength bands
    • G01N21/31—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry
    • G01N21/39—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry using tunable lasers
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
    • G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
    • G01N21/41—Refractivity; Phase-affecting properties, e.g. optical path length
    • G01N21/45—Refractivity; Phase-affecting properties, e.g. optical path length using interferometric methods; using Schlieren methods

Definitions

  • the present invention relates to the technical field of photoelectric measuring instruments and interferometric sensors, and in particular to an interferometer absolute displacement demodulation system, method and application using a gas spectrum reference.
  • interference sensors based on the F-P interference principle generally sense by acting on the F-P cavity to cause the cavity length to change.
  • the two mirrors of the interferometer are the inner surface of the film at one end and the tip of the optical fiber at the other end, which constitute the core sensitive element of the F-P interferometer.
  • the incident light is reflected at the two end faces of the F-P cavity, the reflected light beam generates an interference signal at the signal detector.
  • This interference signal or interference fringes changes with the change of the F-P cavity length. By demodulating the change of the interference fringes, the sensing and measurement of the measured parameter can be realized.
  • the demodulation of interferometer fringes refers to extracting the change value of the interferometer optical cavity length from the interference fringe information of the interferometer.
  • demodulation methods for extracting the cavity length of conventional interferometers which are mainly divided into three categories: light intensity demodulation method, spectral demodulation method and low coherence interference demodulation method.
  • the system structure corresponding to the light intensity demodulation method is simple and the response speed is fast, but the requirements for the control of cavity length accuracy and light source stability are too high.
  • the spectral demodulation method uses a more complex spectrum acquisition system. Due to the generally high cost of spectrometers, the wide application of this method is limited.
  • the cavity length change of the sensor interferometer can be demodulated by using the cross-correlation relationship between different types of interferometers (reference interferometers) and Fabry-Perot cavities (sensing interferometers).
  • This low coherence interference technology can be divided into two types: time scanning type and space scanning type.
  • the reference interferometer generates a series of optical path differences on the time axis or space axis respectively.
  • the interference fringes can be demodulated by using the peak position of any fringe relative to the peak position of the zero-order fringe of the central wavelength interference fringe.
  • This demodulation method has a relatively complex structure and the cost of precision mechanical scanning is also high.
  • the wavelength scanning laser light source By using a wavelength scanning light source as the light source of the interferometer, utilizing the wavelength readability of the wavelength scanning laser light source, plus the wavelength value at the maximum or minimum value of the interference fringe intensity, it is also possible to demodulate the interference fringes and invert the change in the interference cavity length.
  • the wavelength scanning laser light source has high power consumption and high cost, especially for small sensors. Power consumption, cost, and volume limit this method.
  • the wavelength scanning laser light source needs to correct its wavelength reading as a precise measurement value in a large temperature change range. How to achieve small size, low power consumption, low cost, and high-precision interference demodulation is a technical problem in designing fiber optic interferometer sensors.
  • the sensor demodulation principle using F-P interferometer as an example is as follows:
  • the reflected output light intensity of the fiber Fabry-Perot sensor with a specific cavity length of L is in a cosine function relationship with the light frequency, and the distribution formula of the reflected light intensity I is:
  • the output light intensity of the interferometer contains the information of the FP cavity length.
  • the demodulation method of the interferometer is to use the change information of I to invert the change of L.
  • the change of phase is caused by the change of the interference cavity length L and the wavelength ⁇ , so the phase can be changed accordingly by changing the interference cavity length or changing the laser wavelength, that is:
  • the demodulation method using the interference fringe tracking method or the phase change tracking method has the advantages of simple signal processing and fast measurement speed, this method has the problem of limited dynamic range.
  • one of the purposes of the present invention is to provide an interferometer absolute displacement demodulation system using a gas spectrum reference, by using a scanning laser as the light source of the interferometer sensor, using the absorption spectrum of a reference gas with an absorption peak within the wavelength scanning range of the scanning laser as the absolute spectrum reference position, and combining the fixed wavelength and half width of the absorption spectrum line, or a calibration method for time-to-phase conversion of two absorption spectrum lines, thereby completing the absolute value measurement of the interferometer cavity length;
  • the present invention can be applied to the interferometric demodulation of various interferometric sensors, and has the advantages of high resolution and high accuracy in measuring the absolute cavity length of the interferometer cavity;
  • the demodulation method of the interferometer absolute displacement demodulation system using gas absorption spectrum reference of the present invention can be used in various sensor devices based on the interference principle, and has broad application prospects; when this demodulation method is used in an interferometer sensor device, it can not only reduce the power consumption and volume of the sensor, but also can be used in a low-power, miniaturized, and lightweight interferometer sensor, thereby reducing the demodulator cost of the existing interferometer sensor and simplifying the structure of the entire detection device.
  • the second object of the present invention is to provide a demodulation method for an interferometer absolute displacement demodulation system using a gas spectrum reference, using the absorption spectrum of a reference gas having an absorption peak within the wavelength scanning range of the scanning laser as the absolute spectrum reference position, and combining the fixed wavelength and half-width of the absorption spectrum line, or a calibration method for converting two absorption spectrum lines from time to phase, thereby completing the absolute value measurement of the interferometer cavity length.
  • the measured cavity length of the present invention is called the absolute length because the measurement process is based on the fixed wavelength and half-width of the absorption spectrum line, which are physical quantities that will not change under normal temperature and pressure conditions; therefore, the absolute interferometric cavity length measurement characteristics of the present invention overcome the above-mentioned problems of the traditional interference fringe tracking method, and are crucial for all applications requiring long-term static measurement.
  • the third object of the present invention is to provide an interferometer absolute displacement demodulation device using a gas absorption spectrum reference, which uses an adjustable laser as a light source and a gas absorption spectrum as a reference, and calculates the absolute measurement value of the interference cavity length L of the interferometer and the measurement value of its change ⁇ L through a pre-calibrated time-phase relationship, thereby achieving high-efficiency, high-precision, low-power, and low-cost interference demodulation.
  • An interferometer absolute displacement demodulation system using gas absorption spectrum reference is used to measure the absolute cavity length of the interferometer interference cavity;
  • the demodulation system includes a scanning laser connected in the optical path, a fiber isolator, a fiber coupler, an interferometer, a detector, a signal amplifier, and a microprocessor;
  • the detector includes a signal detector and a reference detector;
  • the fiber coupler includes a 2 ⁇ 2 fiber coupler; and also includes a gas reference chamber, the reference chamber is connected to the reference detector, and the gas reference chamber is filled with a reference gas with an absorption peak within the wavelength scanning range of the scanning laser;
  • the scanning laser is driven by a sawtooth wave driver and generates a wavelength scanning beam;
  • the laser beam emitted by the scanning laser passes through the optical fiber isolator and is coupled to the first connection end of the 2 ⁇ 2 optical fiber coupler, and is output from the second connection end of the 2 ⁇ 2 optical fiber coupler to enter the interferometer.
  • the interference reflected light generated by the interferometer returns through the 2 ⁇ 2 optical fiber coupler and is absorbed by the signal detector at the third connection end to generate interference fringes; the interference reflected light is output from the fourth connection end of the 2 ⁇ 2 optical fiber coupler to the gas reference chamber, and the light beam transmitted by the reference gas is connected to the reference detector and generates absorption spectrum lines in the reference detector;
  • the interference fringe signal collected by the signal detector and the absorption spectrum line signal collected by the reference detector are amplified by the signal amplifier respectively, and are sent to the microprocessor for signal intensity normalization processing after analog-to-digital conversion; the microprocessor calculates the absolute measurement value of the interference cavity length L of the interferometer and the measurement value of its change ⁇ L through a pre-calibrated time-
  • the interferometer absolute displacement demodulation system also includes a scanning laser, a fiber isolator, a 1 ⁇ N fiber splitter, N-1 2 ⁇ 1 fiber couplers, N-1 signal detectors, N-1 interferometers, a reference gas chamber and a reference detector, wherein N ⁇ 2;
  • the laser beam emitted by the scanning laser passes through the optical fiber isolator and is coupled to the 1 ⁇ N optical fiber splitter.
  • the laser beam is divided into N paths, one path is output from the 1-path connection end of the 1 ⁇ N optical fiber splitter to the reference gas chamber, and the beam transmitted by the reference gas is connected to the corresponding reference detector, and an absorption spectrum line is generated in the reference detector;
  • the remaining beams are connected from the other N-1 output ends of the 1 ⁇ N optical fiber splitter to the first connection ends of the corresponding N-1 2 ⁇ 1 optical fiber couplers, and are output from the corresponding second connection ends of the 2 ⁇ 1 optical fiber couplers to enter the corresponding N-1 interferometers, and the interference reflection light generated by the interferometer returns through the third connection end of the 2 ⁇ 1 optical fiber coupler to enter the corresponding signal detector, and generates interference fringes;
  • the interference fringe signal is collected by the corresponding signal detector, and the absorption spectrum line signal is collected by the corresponding reference detector and amplified by the signal amplifier respectively
  • the demodulation system includes a scanning laser connected in the optical path, a fiber isolator, a 2 ⁇ 1 fiber coupler, an interferometer, a detector with a reference gas chamber inside, a signal amplifier, and a microprocessor;
  • the laser beam emitted by the scanning laser passes through the optical fiber isolator and is coupled to the first connection end of the 2 ⁇ 1 optical fiber coupler, and is output from the second connection end of the 2 ⁇ 1 optical fiber coupler to enter the interferometer.
  • the interference reflected light generated by the interferometer returns through the third connection end of the 2 ⁇ 1 optical fiber coupler and enters the detector with the reference gas chamber inside to generate interference fringes and absorption spectrum lines.
  • the interference fringe signals and absorption spectrum line signals are collected by the detector and amplified by the signal amplifier, and sent to the microprocessor after analog-to-digital conversion for signal intensity normalization processing.
  • the microprocessor calculates the absolute measurement value of the interference cavity length L of the interferometer and the measurement value of its change ⁇ L through a pre-calibrated time-phase relationship.
  • the interferometer absolute displacement demodulation system further includes a scanning laser, a fiber isolator, a 1 ⁇ N fiber splitter, N 2 ⁇ 1 fiber couplers, N signal detectors, N interferometers, and N detectors with the reference gas chamber inside, wherein N ⁇ 2;
  • the laser beam emitted by the scanning laser passes through the optical fiber isolator and is coupled to the 1 ⁇ N optical fiber splitter. After being divided into N beams by the 1 ⁇ N optical fiber splitter, the laser beam is output from the N-way connection ends of the 1 ⁇ N optical fiber splitter and connected to the first connection ends of N 2 ⁇ 1 optical fiber couplers respectively, and is output from the corresponding second connection ends of the 2 ⁇ 1 optical fiber couplers to enter the corresponding N interferometers.
  • the interference reflected light generated by the interferometer returns through the third connection end of the 2 ⁇ 1 optical fiber coupler and enters the corresponding N detectors with reference gas chambers inside to generate interference fringes and absorption spectra.
  • the detector collects the interference fringe signal and the absorption spectrum line signal and amplifies them respectively through the signal amplifier, and sends them to the microprocessor after analog-to-digital conversion for signal intensity normalization processing.
  • the microprocessor calculates the absolute measurement value of the interference cavity length L of the interferometer and the measurement value of its change ⁇ L through the pre-calibrated time-phase relationship.
  • the output end of the microprocessor is connected to a D/A analog-to-digital converter, and the D/A analog-to-digital converter is used to control the scanning laser current driving circuit to achieve tuning of the scanning laser.
  • Solution 1 Separating the signal detector and the reference gas chamber
  • a demodulation method of the interferometer absolute displacement demodulation system using gas absorption spectrum reference as described above comprises the following steps:
  • S1 The scanning laser light source, under the control of the sawtooth wave driving circuit, outputs a laser beam with a wavelength that changes with time within a scanning cycle;
  • the laser beam in S1 is coupled to the fiber coupler after passing through the fiber isolator and outputted to the interferometer and the gas reference chamber respectively.
  • the interference reflected light generated by the interferometer returns through the fiber coupler and enters the corresponding signal detector.
  • the interference reflected light generates interference fringes in the signal detector.
  • the light beam transmitted from the gas reference chamber is absorbed by the corresponding reference detector and generates absorption spectrum lines in the reference detector synchronously.
  • the signal detector and the reference detector collect the interference fringe signal and the absorption line signal generated in S2 and amplify them through the signal amplifier respectively, and send them to the microprocessor for signal strength normalization after analog-to-digital conversion;
  • S4 The microprocessor receives the interference fringe signal and the absorption spectrum line signal in S3, and calculates the interference cavity length of the interferometer and its change value through the pre-calibrated time-phase relationship.
  • Solution 2 A reference gas chamber is provided inside the detector
  • a demodulation method of the interferometer absolute displacement demodulation system using gas absorption spectrum reference as described above comprises the following steps:
  • S1 The scanning laser light source, under the control of the sawtooth wave driving circuit, outputs a laser beam with a wavelength that changes with time within a scanning cycle;
  • the laser beam in S1 is coupled to the fiber coupler after passing through the fiber isolator and is output and incident on the interferometer respectively.
  • the interference reflected light generated by the interferometer returns through the fiber coupler and enters the detector with the gas reference chamber inside.
  • the interference reflected light generates interference fringes in the detector and synchronously generates absorption spectrum lines.
  • S3 the interference fringe signal and the absorption line signal generated in S2 are collected by the detector, amplified by the signal amplifier, and sent to the microprocessor for signal strength normalization after analog-to-digital conversion;
  • S4 The microprocessor receives the interference fringe signal and the absorption spectrum line signal in S3, and calculates the interference cavity length of the interferometer and its change value through the pre-calibrated time-phase relationship.
  • the method of calibrating the pre-calibrated time-phase relationship and calculating the demodulation interference cavity length value and its change value based on the time-phase calibration is as follows:
  • the scanning laser light source under the control of the sawtooth wave driving circuit, outputs a laser beam whose wavelength changes with time within the actual scanning wavelength range;
  • the detector of the interferometer When there is only one absorption peak in a scanning cycle of the scanning laser, the detector of the interferometer generates interference fringes and absorption spectrum synchronously, and obtains the intensity curve of the corresponding interference fringes and absorption spectrum changing with time; the half width of the absorption spectrum is used to calibrate the time axis, so as to obtain the proportional relationship of converting the time axis value into the wavelength value;
  • the time axis can be calibrated to obtain a proportional relationship of converting the time axis value into the wavelength value; since the measurement error when calibrating with two absorption peaks is relatively small, the calibration accuracy is higher;
  • the minimum wavelength scanning range of the scanning laser can cover one or two absorption lines simultaneously in one scanning cycle; in 2), after obtaining the intensity curves of the corresponding interference fringes and absorption lines changing with time, the half-width of the absorption line relative to the time axis is measured; or, the difference in the relative positions of the central wavelengths of the two absorption lines on the time axis is measured, and the half-width of the absorption line or the difference in the central wavelengths of the two absorption lines is used to obtain the time axis.
  • the numerical value is converted into a proportional relationship of wavelength value to complete the system calibration; in the measurement of 3), the time difference between the Q point with the largest slope of the light intensity change of an interference fringe and the wavelength center of the absorption spectrum is measured and converted into the wavelength difference between the Q point and the wavelength center of the absorption spectrum.
  • the central wavelength of the known absorption spectrum is added or subtracted from this wavelength difference to obtain the absolute wavelength value ⁇ corresponding to the Q point of the interference fringe; in 4), it is described how to obtain the absolute value of the interference cavity length L by measuring the time difference between the two Q points with the largest slope of the light intensity change of an interference fringe; in 5), if the interference fringe is shifted due to the change of the interference cavity length, the change value of the interference cavity length can be obtained as long as the phase difference of the Q point relative to the center point of the absorption spectrum.
  • an interferometer absolute displacement demodulation device using gas absorption spectrum reference including the above-mentioned interferometer absolute displacement demodulation system and method using gas absorption spectrum reference, which uses an adjustable laser as a light source and a gas absorption spectrum as a reference, and calculates the absolute measurement value of the interference cavity length L of the interferometer and the measurement value of its change ⁇ L through a pre-calibrated time-phase relationship, thereby achieving high-efficiency, high-precision, low-power and low-cost interference demodulation.
  • the present invention has at least the following beneficial effects:
  • the present invention uses a scanning laser as the light source of the interferometer sensor. Under the condition that the wavelength scanning range of the scanning laser contains the absorption peak of the reference gas, the absorption spectrum of the reference gas is used as the absolute spectrum reference position, and the scanning time value is converted into a phase or wavelength value calibration method by combining the fixed wavelength and half-width of the absorption spectrum line, or the scanning time difference between two absorption spectrum lines, and the absolute value measurement of the interferometer cavity length is completed in conjunction with the wavelength difference of the half-period of the interference fringe.
  • the change in the interference cavity length is obtained by measuring the change in the Q point of the interference fringe relative to the absorption peak wavelength, so as to achieve the demodulation purpose of the interferometer.
  • the present invention is applied to the interference sensor and has the advantages of high resolution and high accuracy in measuring the absolute cavity length of the interference cavity.
  • the measured cavity length of the present invention is called absolute length because the measurement process is based on the fixed wavelength and half-width of the absorption spectrum, which are physical quantities that will not change under normal temperature and pressure conditions; therefore, the absolute interference cavity length measurement characteristics of the present invention overcome the above-mentioned problems of the traditional interference fringe tracking method, which is crucial for all applications requiring long-term static measurement;
  • the demodulation method of the interferometer absolute displacement demodulation system using gas absorption spectrum reference of the present invention can be used in various sensor devices based on the interference principle, and has a very broad application prospect; when this demodulation method is used in an interferometer sensor device, it can not only reduce the power consumption and volume of the sensor, but also can be used in a low-power, miniaturized, and lightweight interferometer sensor, thereby reducing the demodulator cost of the existing interferometer sensor and simplifying the structure of the entire detection device;
  • the interferometer absolute displacement demodulation system using gas absorption spectrum reference of the present invention can be a single detection channel, or multiple detection channels can reuse a laser light source; the present invention can further simplify the interferometer demodulation device by using a detector with a reference gas chamber, which is convenient for increasing the number of detection channels and has strong practicality;
  • the demodulation method of the present invention can measure the length of the F-P interferometer cavity very quickly, which can reach the microsecond level, therefore, by continuously measuring the length of the F-P interferometer cavity, this demodulation method can also be used to measure the amplitude change and vibration frequency of a mirror of the interferometer caused by mechanical vibration;
  • the demodulation system of the present invention has strong versatility and can be applied to various sensing devices based on the interference principle to achieve high-efficiency, high-precision, low-power and low-cost interference demodulation.
  • FIG1 is a connection diagram of an interferometer absolute displacement demodulation system using a gas absorption spectrum reference according to Example 1 of the present invention
  • FIG2 is a schematic diagram of an interferometer absolute displacement demodulation system using a gas absorption spectrum reference according to embodiments 1-3 of the present invention, in which the system can simultaneously generate interference fringes and reference gas absorption peaks within one wavelength scanning cycle;
  • Example 3 is a schematic diagram of calculating the phase difference ⁇ between the two Q points of an interference fringe where the slope of the light intensity change is the largest in the interferometer absolute displacement demodulation system calibration principle using the gas absorption spectrum reference in Example 1-3 of the present invention;
  • FIG4 is a schematic diagram of the calibration relationship of using two absorption peaks to convert time into phase in the calibration principle of the interferometer absolute displacement demodulation system using gas absorption spectrum reference in Embodiment 1-3 of the present invention
  • FIG5 is a schematic diagram of the connection of an interferometer absolute displacement demodulation system using a gas absorption spectrum reference according to Embodiment 2 of the present invention.
  • FIG6 is a schematic diagram of the connection of 15 detection channels of an interferometer absolute displacement demodulation system using gas absorption spectrum reference according to Embodiment 3 of the present invention.
  • FIG. 7 is a schematic diagram of the connection of 16 detection channels of an interferometer absolute displacement demodulation system using gas absorption spectrum reference in Example 3 of the present invention.
  • an interferometer absolute displacement demodulation system using gas absorption spectrum reference the demodulation system is used to measure the absolute cavity length of the interferometer interference cavity;
  • the demodulation system includes a scanning laser 1 connected to form a path, a fiber isolator 2, a fiber coupler 3, an interferometer 4, a detector 5, a signal amplifier (not shown in the figure), and a microprocessor (not shown in the figure);
  • the detector 5 is a conventional C-band photoelectric detector; specifically, the detector 5 includes a signal detector 51 and a reference detector 52; the fiber coupler 3 includes a 2 ⁇ 2 fiber coupler 31; the demodulation system also includes a gas reference chamber 6, which is connected to the reference detector 52; the gas reference chamber 6 is filled with a reference gas having an absorption peak within the wavelength scanning range of the scanning laser 1; the output end of the microprocessor is connected to a D/A analog-to-digital converter, which is used to control the scanning laser current drive circuit to achieve wavelength tuning of the scanning laser 1; the scanning laser 1 is driven by a sawtooth wave driver (not shown in the drawings) and generates a wavelength scanning beam;
  • the laser beam emitted by the scanning laser 1 passes through the optical fiber isolator 2 and is coupled to the first connection end 311 of the 2 ⁇ 2 optical fiber coupler.
  • One path of the laser beam is output from the second connection end 312 of the 2 ⁇ 2 optical fiber coupler 31 and incident on the interferometer 4.
  • the interference reflected light generated by the interferometer 4 returns through the 2 ⁇ 2 optical fiber coupler 31 and enters the corresponding signal detector 51 through the third connection end 313.
  • Another path of the interference reflected light is output from the fourth connection end 314 of the 2 ⁇ 2 optical fiber coupler 31 to the gas reference chamber 6 and enters the corresponding reference detector 52.
  • the interference reflected light generates interference fringes in the signal detector 51, and the light beam transmitted through the reference gas is absorbed by the corresponding reference detector 52 and generates absorption spectrum lines synchronously.
  • the signal detector 51 and the reference detector 52 collect interference fringe signals and absorption line signals and amplify them respectively through the signal amplifier, and send them to the microprocessor for signal strength normalization processing after analog-to-digital conversion.
  • the microprocessor calculates the absolute measurement value of the interference cavity length L of the interferometer and the measurement value of its change ⁇ L through a pre-calibrated time-phase relationship.
  • the microprocessor drives the scanning laser 1 to send a wavelength scanning signal; the output end of the microprocessor is connected to a D/A analog-to-digital converter (not shown in the drawings), and the D/A analog-to-digital converter (not shown in the drawings) is used to control the scanning laser current drive circuit to achieve tuning of the scanning laser; and the interference fringe signals and absorption spectrum line signals collected by the signal detector and the reference detector are amplified by a linear transimpedance amplifier, digitized by an A/D analog-to-digital converter, and then output to the microprocessor for signal intensity normalization processing.
  • the interferometer 4 is an F-P interferometer
  • the scanning laser 1 is a VCSEL laser.
  • the output wavelength of the VCSEL laser can be changed accordingly to form a scanning wavelength range; at the same time, a gas with a characteristic absorption peak is selected within the scanning wavelength range of the VCSEL laser, such as methane gas, and injected into the reference gas chamber.
  • the laser light wave is synchronously received by the signal detector 51 and the reference detector 52; the F-P interferometer generates interference fringes in the signal detector 51, and the reference gas chamber synchronously generates absorption spectra in the reference detector 52, as shown in FIG2 .
  • the scanning laser 1 may also be other types of scanning lasers, as long as the corresponding gas can be selected as an absorption spectrum reference within its scanning band and the beneficial effects of the present invention can be achieved, which will not be elaborated here.
  • the interferometer demodulation system of this embodiment can also be applied to other interferometers with the same working principle as the F-P interferometer, such as Sagnac interferometer, Michelson interferometer, etc.
  • the optical fiber isolator, optical fiber coupler, interferometer, detector, linear transimpedance amplifier (not shown in the drawings), A/D analog-to-digital converter, D/A analog-to-digital converter, microprocessor (not shown in the drawings), and sawtooth wave driver are all suitable for the interferometric cavity length demodulation system of the present invention, and their installation method, control method, working principle, and setting parameters can all refer to the prior art, and can be implemented as long as the beneficial effects of the present invention can be achieved.
  • This embodiment 1 also provides a demodulation method of an interferometer absolute displacement demodulation system using a gas absorption spectrum reference, comprising the following steps:
  • S1 The scanning laser light source, under the control of the sawtooth wave driving circuit, outputs a laser beam with a wavelength that changes with time within a scanning cycle;
  • the laser beam in S1 is coupled to the fiber coupler after passing through the fiber isolator and output to the interferometer and the gas reference chamber respectively.
  • the interference reflected light generated by the interferometer returns through the fiber coupler and enters the signal detector; the interference reflected light generates interference fringes in the signal detector; the light beam transmitted through the gas reference chamber is connected to the reference detector and generates absorption spectrum lines synchronously in the reference detector;
  • S3 The detector collects the interference fringe signal and the absorption line signal generated in S2 and amplifies them respectively through the signal amplifier, and sends them to the microprocessor for signal strength normalization after analog-to-digital conversion;
  • S4 The microprocessor receives the interference fringe signal and the absorption spectrum line signal in S3, and calculates the interference cavity length of the interferometer and its change value through the pre-calibrated time-phase relationship.
  • the demodulation method of this embodiment adopts a scanning laser as the light source of the interferometer sensor, uses the absorption spectrum of a reference gas with an absorption peak within the wavelength scanning range of the scanning laser as the absolute spectrum reference position, and combines the fixed wavelength and half-width of the absorption spectrum line, or a calibration method for converting the time value to the phase value of two absorption spectrum lines, and uses the interference fringes themselves to complete the absolute value measurement of the interference cavity length; the present invention is applied to the interference sensor, and has the advantages of high resolution and high accuracy in measuring the absolute cavity length of the interference cavity.
  • the method for calibrating the pre-calibrated time-phase relationship and the method for demodulating the interferometric cavity length value and its change value are as follows:
  • the scanning laser light source under the control of the sawtooth wave driving circuit, outputs a laser beam whose wavelength changes with time within the actual scanning wavelength range;
  • the detector of the interferometer synchronously generates interference fringes and absorption spectra, and obtains the intensity curves of the corresponding interference fringes and absorption spectra changing with time; the half width of the absorption spectrum is used to calibrate the time axis, so as to obtain the proportional relationship of converting the time axis value into the wavelength value;
  • the proportional relationship of converting the time axis value into the wavelength value can also be obtained;
  • the minimum wavelength scanning range of the scanning laser can cover one or two absorption lines simultaneously in one scanning cycle; in 2), after obtaining the corresponding interference fringes and the intensity curves of the absorption lines changing with time, the half-width of the absorption lines is measured relative to the time axis, or the difference in the relative positions of the central wavelengths of the two absorption lines on the time axis is measured, and the proportional relationship between the time axis value and the wavelength value is obtained by using the known half-width of the absorption lines or the known difference in the central wavelengths of the two absorption lines, thereby completing the system calibration; in the measurement of 3), an interference fringe is measured.
  • the time difference between the Q point where the slope of the light intensity change is the largest and the wavelength center of the absorption spectrum is converted into the wavelength difference between the Q point and the wavelength center of the absorption spectrum.
  • the absolute wavelength value ⁇ corresponding to the Q point of the interference fringe is obtained by adding or subtracting this wavelength difference from the known central wavelength of the absorption spectrum; in the above 4), it is described how to obtain the absolute value of the interference cavity length L by measuring the time difference between the two Q points where the slope of the light intensity change of an interference fringe is the largest; in the above 5), if the interference fringe is shifted due to the change of the interference cavity length, the change value of the interference cavity length can be obtained as long as the phase difference between the Q point and the center point of the absorption spectrum is obtained.
  • the wavelength value corresponding to each point of the interference fringes and the central wavelength value of the absorption spectrum are relatively fixed at the corresponding position on the time axis and will not change.
  • the half-width of the absorption spectrum is also fixed on the time axis. In this way, the absolute wavelength value can be obtained using the absorption spectrum, and the time axis can be calibrated using the half-width of the absorption spectrum, so that the time axis value can be converted into a wavelength value.
  • the measured value of the wavelength difference ⁇ corresponding to the phase value difference between the two Q points of the interference fringe, or the wavelength difference corresponding to the half-width of the interference fringe can be obtained, and then used Thereby, the absolute measurement value of the interferometer cavity length L is further obtained.
  • the phase change value of the interference fringes Q point can be calculated by measuring the time difference between the Q point where the light intensity change slope of the interference fringes is the largest (as shown in Figure 3) and the center point of the absorption spectrum, and then using the calibration relationship between time and phase.
  • the measured value of the change in the interference cavity length ⁇ L can be obtained, thereby achieving the effect of demodulating the change in the interference cavity length from the interference fringe information.
  • the minimum wavelength scanning range of the scanning laser can simultaneously cover two absorption lines within one scanning cycle; in 3), after obtaining the intensity curves of the corresponding interference fringes and absorption lines changing with time, the data from the signal detector and the reference detector are normalized, and the time difference between the two Q points with the largest light intensity change slope of an interference fringe relative to the central wavelength of the absorption line is measured to obtain the measured value of the wavelength difference ⁇ corresponding to the phase value difference between the two Q points of the interference fringe, or the wavelength difference corresponding to the half-width of the interference fringe.
  • the wavelength scanning range of the VCSEL laser is expanded to about 2.73 nm to ensure that two absorption spectra are covered simultaneously within one scanning cycle; as shown in FIG4 , by measuring the relative positions of the two absorption spectra on the time axis and utilizing the fixed central wavelength characteristics of the two spectra, the time axis is calibrated and the time axis value can be converted into a wavelength value. Since the measurement error when calibrating with two absorption peaks is relatively small, this calibration method has higher accuracy.
  • the present invention can measure the absolute cavity length of the interference cavity by using one of the two calibration methods mentioned above.
  • the cavity length is called absolute length because the measurement process is based on the fixed wavelength of the absorption spectrum and the half-width of the spectrum, which are physical quantities that will not change under normal temperature and pressure conditions.
  • the two calibration methods can also be used at the same time to improve the measurement accuracy by cross-validation.
  • the sensing technology based on monochromatic light interferometry (as opposed to white light interferometry) in the prior art can only measure the relative length change ⁇ L (relative to an arbitrary initial value) and cannot determine the actual cavity length of the interference cavity.
  • the absolute interference cavity length measurement feature of the present invention is crucial for all applications requiring long-term static measurements.
  • the difference between the present embodiment 2 and the embodiment 1 is that the reference gas chamber 6 is provided inside the detector 5; the fiber coupler includes a 2 ⁇ 1 fiber coupler 32; the laser beam emitted by the scanning laser 1 is coupled to the first connection end 321 of the 2X1 fiber coupler 32 after passing through the fiber isolator 2, and is output from the second connection end 322 of the 2 ⁇ 1 fiber coupler 32 to enter the interferometer 4, and the interference reflected light generated by the interferometer 4 returns through the third connection end 323 of the 2 ⁇ 1 fiber coupler 32 to enter the detector 5 with the reference gas chamber 6 inside, and the detector 5 collects the interference fringe signal and the absorption spectrum line signal and amplifies them respectively through the signal amplifier, and sends them to the microprocessor for signal strength normalization processing after analog-to-digital conversion.
  • the detector 5 since a detector 5 having an internal reference gas chamber 6 is adopted, the detector 5 simultaneously collects interference fringe signals and absorption spectrum line signals and sends them after signal amplification and conversion.
  • the detector technology with its own reference gas chamber is independently developed (Chinese invention patent CN201810036930.0 A photoelectric detector with its own reference gas chamber and its preparation method) to design the interferometer absolute displacement demodulation system using the gas absorption spectrum reference, and the reference gas chamber is integrated into the detector, which can further simplify the interferometer demodulation device and make it more practical; and in a low-power, miniaturized, and lightweight interferometer sensor, the demodulator cost of the existing interferometer sensor is reduced and the structure of the entire detection device is simplified.
  • the method for pre-calibrating the time-phase relationship and demodulating the interference cavity length value and its change value may refer to Example 1.
  • this embodiment 3 provides an interferometer absolute displacement demodulation system multi-probe sensor multiplexing system and multi-channel detection using gas absorption spectrum reference on the basis of the above embodiments 1-2 to meet different needs.
  • the interferometer absolute displacement demodulation system further includes a 1 ⁇ 8 optical fiber splitter 7;
  • the optical fiber coupler 3 further includes a 1 ⁇ 2 optical fiber coupler 33;
  • the 1 ⁇ N fiber splitter is a 1 ⁇ 8 fiber splitter 7, as shown in FIG5 , and is composed of one 1 ⁇ 2 fiber coupler 33 and two 1 ⁇ 8 fiber splitters 7, as shown in FIG6 ;
  • the laser beam emitted by the scanning laser 1 is coupled to a first connection end 331 of a 1 ⁇ 2 fiber coupler 33 through the fiber isolator 2, and the second connection end 332 and the third connection end 333 of the 1 ⁇ 2 fiber coupler 33 are respectively connected to one of the 1 ⁇ 8 fiber splitters 7;
  • the 15 connection ends of the two 1 ⁇ 8 fiber splitters 7 are respectively connected to the first connection ends 321 of 15 2 ⁇ 1 fiber couplers 32;
  • the second connection end 322 of the 2 ⁇ 1 fiber coupler 32 is respectively connected to 15 F-P interferometers 4, and the third connection ends 323 of the 15 2 ⁇ 1 fiber couplers 32 are respectively connected to 15 signal detectors;
  • the 16th path of the 1 ⁇ 8 fiber splitter 7 is connected to a reference gas chamber 6 filled
  • the signals measured by all detectors are respectively amplified by a linear transimpedance amplifier, digitized by an analog-to-digital converter (A/D), and then output to the microprocessor for signal intensity normalization processing, and the absolute measurement value of the interference cavity length L of the interferometer and the measurement value of its change ⁇ L are calculated through the pre-calibrated time-phase relationship.
  • the output end of the microprocessor is connected to a digital-to-analog converter (D/A) for controlling the laser current driving circuit to achieve tuning of the VCSEL.
  • D/A digital-to-analog converter
  • the reference gas chamber can be provided inside the detector; using a detector with its own reference gas chamber, that is, the mediation system saves the need to separately divide one optical path to connect to a reference gas chamber filled with methane, but all 16 paths are connected to the corresponding detector, which adds one detection path compared to the implementation scheme of separately setting up a reference gas chamber to connect to the reference detector, so that the number of multiplexed multi-probe sensors of the entire system reaches 16.
  • the interferometer absolute displacement demodulation system using gas absorption spectrum reference is designed, and the reference gas chamber is integrated into the detector, which can further simplify the interferometer demodulation device and make it more practical; and in low-power, miniaturized, and lightweight interferometer sensors, the demodulator cost of existing interferometer sensors is reduced, and the entire detection device is simplified.
  • the number of multi-probe sensors multiplexed in this system can be further increased to meet the needs of different applications.
  • the method for pre-calibrating the time-phase relationship and demodulating the interference cavity length value and its change value may refer to Example 1.
  • the 1 ⁇ 8 optical fiber splitter may also be other optical fiber splitters that split no less than 2 paths, as long as they meet the technical solution of the present invention.
  • the present invention also provides a demodulation device of an interferometer absolute displacement demodulation system and method using a gas absorption spectrum reference, which uses an adjustable laser as a light source and a gas absorption spectrum as a reference, and calculates the absolute measurement value of the interference cavity length L of the interferometer and the measurement value of its change ⁇ L through a pre-calibrated time-phase relationship, thereby achieving high-efficiency, high-precision, low-power, and low-cost interference demodulation.
  • a gas absorption spectrum reference which uses an adjustable laser as a light source and a gas absorption spectrum as a reference, and calculates the absolute measurement value of the interference cavity length L of the interferometer and the measurement value of its change ⁇ L through a pre-calibrated time-phase relationship, thereby achieving high-efficiency, high-precision, low-power, and low-cost interference demodulation.

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Abstract

一种利用气体吸收光谱参考的干涉仪绝对位移解调***及方法，解调***包括连接在光路中的扫描激光器（1）、光纤隔离器（2）、光纤耦合器（3）、干涉仪（4）、信号探测器（51）、参考探测器（52）、信号放大器、微处理器、气体参考气室（6），气体参考气室（6）充满在扫描激光器（1）的波长扫描范围内具有吸收峰的参考气体；解调***及方法利用在扫描激光器（1）的波长扫描范围内具有吸收峰的参考气体的吸收光谱作为绝对光谱参考位置，以及结合吸收谱线的固定波长和谱线半宽度，或两个吸收谱线波长间距进行从时间轴向波长轴或位相轴转换的标定方法，配合利用干涉条纹自身特征点完成干涉腔腔长的绝对值测量，适用于各种基于干涉原理的传感装置中，实现高效率、高精度、低功耗、低成本的干涉解调。

Description

利用气体吸收光谱参考的干涉仪绝对位移解调***及方法 技术领域
本发明涉及光电测量仪器仪表及干涉传感器技术领域，尤其涉及一种利用气体光谱参考的干涉仪绝对位移解调***及方法与应用。
背景技术
基于为了满足医疗、航空航天、桥梁建筑、高温油井、工业监测和国防等领域的压力监测应用的需求，各种微型光纤F-P及光纤MEMS传感技术已经被研发出并应用于不同的应用场景。这些基于F-P干涉原理的干涉传感器一般是通过被测量作用于F-P腔，引起腔长变化来进行传感的。干涉仪的两面镜子分别是位于一端的薄膜内表面和位于另一端的光纤尖端，构成F-P干涉仪的核心敏感元件，当入射光在F-P腔的两个端面形成反射，反射光束在信号探测器处产生干涉信号。这种干涉信号或干涉条纹随着F-P腔长的改变而发生变化，通过对干涉条纹的变化进行解调，就可以实现被测参量传感和测量。
干涉仪条纹的解调就是指从干涉仪的干涉条纹信息提取出干涉仪光学腔长的变化值。常规干涉仪腔长的提取有多种解调方法，主要分光强度解调方法、光谱解调方法以及低相干干涉解调方法三大类。光强度解调方法对应的***结构简单,响应速度快，但是对腔长精度的控制和光源稳定性的要求过高。光谱解调方法采用较为复杂的光谱获取***，由于光谱仪造价普遍较高，该方法的广泛应用受到限制。基于白光干涉解调技术，利用不同类型的干涉仪(参考干涉仪)与法布里-珀罗腔体(传感干涉仪)的互相关关系可以对传感干涉仪的腔长变化进行了解调。这种低相干干涉技术可分为时间扫描型和空间扫描型两类，参考干涉仪分别在时间轴或空间轴上产生一系列的光程差，利用任意条纹峰值位置相对于中心波长干涉条纹的零级条纹峰值位置就可以对干涉条纹进行 解调，这种解调方法结构比较复杂，精密机械扫描的成本也很高。采用波长扫描光源作为干涉仪的光源，利用波长扫描激光光源的波长可读性，加上干涉条纹光强最大值或最小值处的波长值，也可以实现干涉条纹的解调，反演出干涉腔长的变化。但是波长扫描激光光源的功耗大，成本也比较高，特别是对于小型传感器而言，功耗、成本、体积使这种方法受到限制。特别是波长扫描激光光源在大的温度变化范围中，其作为精密测量值的波长读数需要修正。如何实现小尺寸，低功耗，低成本，高精度的干涉解调就是在设计光纤干涉仪传感技术难题。
以F-P干涉仪为例的传感器解调原理如下：
根据F-P原理，当一个腔长为L且两个端面的反射率R相等且较小的F-P传感器受到光波波长为λ的光照射时，对某个特定腔长为L的传感器光纤法－珀传感器的反射输出光强与光频率呈余弦函数关系，其反射光强度I分布公式为：
Figure PCTCN2022124758-appb-000001
其中
Figure PCTCN2022124758-appb-000002
是初始位相，是一个常数；而位相
Figure PCTCN2022124758-appb-000003
I 0为入射光光强，在各波长强度相等的理想光源条件下，I 0是常数；所以干涉仪的输出光强中蕴含着F-P腔腔长信息，干涉仪的解调方法均就是利用I的变化信息来反演出L的变化量。
众所周知，位相的变化是由干涉腔长L及波长λ的变化引起的，所以通过改变干涉腔长度或改变激光波长就可以使得位相做相应的改变，也就是：
Figure PCTCN2022124758-appb-000004
其中，
Figure PCTCN2022124758-appb-000005
分别代表由干涉腔长变化和由激光波长 变化引起的位相变化。当ΔL＝0，
Figure PCTCN2022124758-appb-000006
保持不变，而
Figure PCTCN2022124758-appb-000007
由Δλ改变引起2π的位相变化时，对应的干涉仪的反射光强将变化一个周期，形成一对明暗相间的干涉条纹。这时，如果
Figure PCTCN2022124758-appb-000008
由ΔL改变引起了位相变化，干涉条纹就会相对于ΔL＝0时的条纹发生平移，通过测量干涉条纹平移的量，或位相变化，就可以利用
Figure PCTCN2022124758-appb-000009
反演出ΔL的变化量，从而达到从干涉条纹信息解调出干涉腔长的变化量的效果。
采用测量干涉条纹追踪法，或位相变化追踪法的解调方法虽然有信号处理简单、测量速度快等优点，但是该方法存在动态范围受限的问题，此外，腔长的解调精度很大程度上依赖于记录下ΔL的原点值，即ΔL＝0时的干涉条纹位置，才能够通过比较不同干涉条纹的位置来确定ΔL的值。由于这种方法依靠干涉条纹的准确读取，而输出干涉条纹近似正弦波，不容易准确地确定干涉条纹最大值的位置，因此干涉条纹追踪法有解调精度不高的问题。特别是，当干涉仪断电重启时，***无法确定任何干涉条纹位置变化是否是由于干涉腔长L变化引起的，还是由于激光波长λ变化引起的。
发明内容
为解决上述现有技术中存在的技术问题，本发明的目的之一在于提供一种利用气体光谱参考的干涉仪绝对位移解调***，通过采用扫描激光器作为干涉仪传感器的光源，利用在所述扫描激光器的波长扫描范围内具有吸收峰的参考气体的吸收光谱作为绝对光谱参考位置，以及结合吸收谱线的固定波长和谱线半宽度，或两个吸收谱线进行时间向位相转换的标定方法，从而完成干涉腔腔长的绝对值测量；本发明可以应用于各种干涉传感器的干涉解调，具备可以测量干涉腔绝对腔长的高分辨和高准确度等优势；
此外，本发明的利用气体吸收光谱参考的干涉仪绝对位移解调***的解调 方法可以用于到各种基于干涉原理的传感装置，应用前景十分广阔；当这种解调方法用在干涉仪传感装置时，不但可以减少传感器的功耗和体积，而且可以在低功耗、微型化、轻便式干涉仪传感器中，降低了现有干涉仪传感器的解调仪成本，简化了整个检测装置的结构。
本发明的目的之二在于提供一种利用气体光谱参考的干涉仪绝对位移解调***的解调方法，利用在所述扫描激光器的波长扫描范围内具有吸收峰的参考气体的吸收光谱作为绝对光谱参考位置，以及结合吸收谱线的固定波长和谱线半宽度，或两个吸收谱线进行时间向位相转换的标定方法，从而完成干涉腔腔长的绝对值测量，相对于现有技术中如基于单色光干涉术(与白光干涉术相反)的传感技术，仅能测量长度相对变化ΔL(相对于任意的初始值)，无法确定干涉腔的实际腔长的缺陷，本发明的测量到的空腔长度之所以被称为绝对长度，是因为测量过程是基于吸收谱线的固定波长和谱线半宽度，在常温常压条件下是不会改变的物理量；因此本发明的绝对干涉腔长测量的特性，克服了传统的干涉条纹追踪法存在的上述问题，对于要求长期静态测量的所有应用都是至关重要的。
本发明的目的之三在于提供一种利用气体吸收光谱参考的干涉仪绝对位移解调装置，其以可调激光器为光源、用气体吸收光谱做参考，通过预先标定的时间-位相关系计算出所述干涉仪的干涉腔长L的绝对测量值及其变化量ΔL的测量值，实现高效率、高精度、低功耗、低成本的干涉解调。
本发明的目的之一通过以下技术方案实现：
一种利用气体吸收光谱参考的干涉仪绝对位移解调***，所述解调***用于测量干涉仪干涉腔的绝对空腔长度；解调***包括连接在光路中的扫描激光器、光纤隔离器、光纤耦合器、干涉仪、探测器、信号放大器、微处理器；所 述探测器包括信号探测器、参考探测器；所述光纤耦合器包括2×2光纤耦合器；还包括气体参考气室，所述参考气室连接所述参考探测器，所述气体参考气室充满在所述扫描激光器的波长扫描范围内具有吸收峰的参考气体；所述扫描激光器通过锯齿波驱动器驱动并产生波长扫描光束；
所述扫描激光器发出的激光光束经过所述光纤隔离器后耦合到2×2光纤耦合器的第一连接端，从所述2×2光纤耦合器的第二连接端输出入射所述干涉仪，所述干涉仪产生的干涉反射光返回经过所述2×2光纤耦合器后由第三连接端由所述信号探测器吸收并产生干涉条纹；干涉反射光从所述2×2光纤耦合器的第四连接端输出至所述气体参考气室，经参考气体透射的光束连接到参考探测器并在参考探测器中产生吸收谱线；由所述信号探测器采集干涉条纹信号和参考探测器采集吸收谱线信号分别经过所述信号放大器放大，通过模数转换后发送至所述微处理器进行信号强度归一化处理；所述微处理器通过预先标定的时间-位相关系计算出所述干涉仪的干涉腔长L的绝对测量值及其变化量ΔL的测量值。
进一步地，所述干涉仪绝对位移解调***还包括1个扫描激光器、一个光纤隔离器、1个1×N光纤分路器、N-1个2×1光纤耦合器、N-1个信号探测器、N-1个干涉仪、一个参考气室和一个参考探测器，其中N≥2；
所述扫描激光器发出的激光光束经过所述光纤隔离器后耦合到所述1×N光纤分路器，激光光束在分成N路后，其中1路从1×N光纤分路器的1路连接端输出至所述参考气室，经参考气体透射的光束连接到对应的参考探测器，并在参考探测器中产生吸收谱线；其余光束从1×N光纤分路器的其他N-1路输出端分别连接至对应的N-1个2×1光纤耦合器的第一连接端，并从2×1光纤耦合器的对应的第二连接端输出入射对应的N-1个干涉仪，所述干涉仪产生 的干涉反射光返回经过所述2×1光纤耦合器的第三连接端进入对应的信号探测器，并产生干涉条纹；由对应的所述信号探测器采集干涉条纹信号，由对应的所述参考探测器采集吸收谱线信号并分别经过所述信号放大器放大，通过模数转换后发送至所述微处理器进行信号强度归一化处理；所述微处理器通过预先标定的时间-位相关系计算出所述干涉仪的干涉腔长L的绝对测量值及其变化量ΔL的测量值。
进一步地，所述解调***包括连接在光路中的扫描激光器、光纤隔离器、2×1光纤耦合器、干涉仪、内部设有参考气室的探测器、信号放大器、微处理器；
所述扫描激光器发出的激光光束经过所述光纤隔离器后耦合到所述2×1光纤耦合器的第一连接端，并从2×1光纤耦合器的第二连接端输出入射所述干涉仪，所述干涉仪产生的干涉反射光返回经过所述2×1光纤耦合器的第三连接端进入内部设有所述参考气室的探测器中产生干涉条纹和吸收谱线；由所述探测器采集干涉条纹信号及吸收谱线信号并经过所述信号放大器放大，通过模数转换后发送至所述微处理器进行信号强度归一化处理；所述微处理器通过预先标定的时间-位相关系计算出所述干涉仪的干涉腔长L的绝对测量值及其变化量ΔL的测量值。
进一步地，所述干涉仪绝对位移解调***还包括1个扫描激光器、一个光纤隔离器、1个1×N光纤分路器、N个2×1光纤耦合器、N个信号探测器、N个干涉仪、N个内部设有所述参考气室的探测器，其中N≥2；
所述扫描激光器发出的激光光束经过所述光纤隔离器后耦合到所述1×N光纤分路器，激光光束经1×N光纤分路器分成N束后，从1×N光纤分路器的N路连接端输出分别接入N个2×1光纤耦合器的第一连接端，并从2×1光纤 耦合器的对应的第二连接端输出入射对应的N个干涉仪，所述干涉仪产生的干涉反射光返回经过所述2×1光纤耦合器的第三连接端进入对应的N个内部设有参考气室的探测器中产生干涉条纹和吸收谱线；由所述探测器采集干涉条纹信号及吸收谱线信号并分别经过所述信号放大器放大，通过模数转换后发送至所述微处理器进行信号强度归一化处理；所述微处理器通过预先标定的时间-位相关系计算出所述干涉仪的干涉腔长L的绝对测量值及其变化量ΔL的测量值。
其中，所述微处理器的输出端连接有D/A模数转换器，所述D/A模数转换器用于控制所述扫描激光器电流驱动电路，以实现对所述扫描激光器的调谐。
本发明的目的之二可以通过以下技术方案实现：
方案1：分离所述信号探测器和所述参考气室
一种如上述的利用气体吸收光谱参考的干涉仪绝对位移解调***的解调方法，包括以下步骤：
S1：扫描激光器光源在锯齿波驱动电路的控制下，在一个扫描周期范围内，输出波长随时间变化的激光光束；
S2：S1中的激光光束经所述光纤隔离器后耦合到所述光纤耦合器并分别输出入射到所述干涉仪和所述气体参考气室，在同一个波长扫描范围内，所述干涉仪产生的干涉反射光返回经过所述光纤耦合器后进入对应的所述信号探测器，干涉反射光在所述信号探测器中产生干涉条纹；从气体参考气室透射的光束被对应的参考探测器吸收并在参考探测器中同步产生吸收谱线；
S3：所述信号探测器、参考探测器采集S2中产生的干涉条纹信号及吸收谱线信号并分别经过所述信号放大器放大，通过模数转换后发送至所述微处理器进行信号强度归一化处理；
S4：所述微处理器接收S3中的干涉条纹信号及吸收谱线信号，并通过预先标定的时间-位相关系计算出所述干涉仪的干涉腔长及其变化数值。
方案2：在所述探测器内部设有参考气室
一种如上述的利用气体吸收光谱参考的干涉仪绝对位移解调***的解调方法，包括以下步骤：
S1：扫描激光器光源在锯齿波驱动电路的控制下，在一个扫描周期范围内，输出波长随时间变化的激光光束；
S2：S1中的激光光束经所述光纤隔离器后耦合到所述光纤耦合器并分别输出入射到所述干涉仪，在同一个波长扫描范围内，干涉仪产生的干涉反射光返回经过所述光纤耦合器进入内部设有所述气体参考气室的探测器中，干涉反射光在所述探测器中产生干涉条纹并同步产生吸收谱线；
S3：所述探测器采集S2中产生的干涉条纹信号及吸收谱线信号经过所述信号放大器放大，通过模数转换后发送至所述微处理器进行信号强度归一化处理；
S4：所述微处理器接收S3中的干涉条纹信号及吸收谱线信号，并通过预先标定的时间-位相关系计算出所述干涉仪的干涉腔长及其变化数值。
进一步地，所述预先标定的时间-位相关系的标定及基于该时间-位相标定计算解调干涉腔长值和其变化值的方法如下：
1)扫描激光器光源在锯齿波驱动电路的控制下，在实际扫描波长范围，输出波长随时间变化的激光光束；
2)在扫描激光器的一个扫描周期内只有一个吸收峰时，干涉仪的探测器同步产生干涉条纹及吸收谱线,并获取对应的干涉条纹、吸收谱线随时间变化的强度曲线；利用吸收谱线的半宽度对时间轴标定，从而可以得到将时间轴数 值转变成波长值的比例关系；
或者，在一个扫描周期中有两个吸收峰时，通过测量两个吸收谱线中心波长在时间轴的相对位置，利用两谱线中心波长固定的特性，对时间轴进行标定，也可以得到将时间轴数值转变成波长值的比例关系；由于采用两个吸收峰进行标定时的测量误差相对较小，因此标定的精度就更高；
3)测量一个干涉条纹的光强变化斜率最大的Q点相对于吸收谱线的波长中心的时间差，利用标定过程中得到的时间轴数值转变成波长值的比例关系，得到干涉条纹在Q点相对于吸收谱线的波长中心的波长差的测量值。再利用已知的吸收谱线的波长值和测量到的波长差值，就可以得到干涉条纹Q点所对应的绝对波长值λ。
4)测量一个干涉条纹的两个光强变化斜率最大的Q点相对于吸收谱线的中心波长点的时间差，利用时间轴数值转变成波长值的比例关系，得到干涉条纹两个Q点的位相值差对应的波长差Δλ的测量值，或干涉条纹半宽度时对应的波长差，再利用
Figure PCTCN2022124758-appb-000010
就可以得到干涉腔长度L的绝对值。
5)当干涉条纹因干涉腔长变化而产生平移时，测量干涉条纹的光强变化斜率最大的Q点相对于吸收谱线的中心点的时间差，再利用时间轴数值转变成波长值的比例关系，得到干涉条纹Q点的位相变化值，利用
Figure PCTCN2022124758-appb-000011
反演出ΔL的变化量。
进一步地，所述1)中，所述扫描激光器的最小波长扫描范围可使其一个扫描周期内同时覆盖一个或两个吸收谱线；所述2)中，分别获取对应的干涉条纹和吸收谱线随时间变化的强度曲线后，测量吸收谱线的半宽度相对时间轴的数值；或者，测量两个吸收谱线中心波长在时间轴的相对位置的差值，利用已知的吸收谱线的半宽度，或已知的两个吸收谱线中心波长差值，得到时间轴 数值转变成波长值的比例关系，完成***标定；在所述3)的测量时，测量一个干涉条纹的光强变化斜率最大的Q点相对于吸收谱线的波长中心的时间差，并转换成Q点相对于吸收谱线的波长中心的波长差，已知的吸收谱线的中心波长加上或减去这个波长差，得到干涉条纹Q点所对应的绝对波长值λ；所述4)中，描述怎样通过测量一个干涉条纹的两个光强变化斜率最大的Q点的时间差，来得到干涉腔长度L的绝对值；所述5)中，如果干涉条纹因干涉腔长变化而产生平移时，只要Q点相对于吸收谱线的中心点的位相差，就可以得到干涉腔长的变化值。
本发明的目的之三通过以下技术方案实现：一种利用气体吸收光谱参考的干涉仪绝对位移解调装置，包括上述的利用气体吸收光谱参考的干涉仪绝对位移解调***及方法，其以可调激光器为光源、用气体吸收光谱做参考，通过预先标定的时间-位相关系计算出所述干涉仪的干涉腔长L的绝对测量值及其变化量ΔL的测量值，实现高效率、高精度、低功耗、低成本的干涉解调。
相比现有技术，本发明至少具备以下有益效果：
1、对于大多数干涉传感器的应用而言，高分辨率、高解调准确度和快速解调是保证传感器***的测量准确度能力的至关重要的指标，本发明采用扫描激光器作为干涉仪传感器的光源，在保证所述扫描激光器的波长扫描范围内包含有参考气体的吸收峰的条件下，利用参考气体的吸收光谱作为绝对光谱参考位置，以及结合吸收谱线的固定波长和谱线半宽度，或两个吸收谱线之间的扫描时间差值，将扫描时间数值转换成位相，或波长值的标定方法，配合测量干涉条纹半周期的波长差完成干涉腔腔长的绝对值测量；同时，利用测量干涉条纹Q点相对吸收峰波长的变化量，得到干涉腔长的变化量，达到对干涉仪的解调目的；本发明应用于干涉传感器中，具备可以测量干涉腔绝对腔长的高分辨 和高准确度等优势；
2、相对于现有技术中如基于单色光干涉术(与白光干涉术相反)的传感技术，仅能测量干涉腔长度相对变化ΔL(相对于任意的初始值)，无法确定干涉腔的绝对腔长的缺陷，本发明的测量到的空腔长度之所以被称为绝对长度，是因为测量过程是基于吸收谱线的固定波长和谱线半宽度，在常温常压条件下是不会改变的物理量；因此本发明的绝对干涉腔长测量的特性，克服了传统的干涉条纹追踪法存在的上述问题，对于要求长期静态测量的所有应用都是至关重要的；
3、本发明的利用气体吸收光谱参考的干涉仪绝对位移解调***的解调方法可以用于到各种基于干涉原理的传感装置，应用前景十分广阔；当这种解调方法用在干涉仪传感装置时，不但可以减少传感器的功耗和体积，而且可以在低功耗、微型化、轻便式干涉仪传感器中，降低了现有干涉仪传感器的解调仪成本，简化了整个检测装置的结构；
4、本发明的利用气体吸收光谱参考的干涉仪绝对位移解调***可以是单个检测通道，也可以使多个检测通道复用一个激光器光源；本发明利用自带参考气室的探测器可以进一步简化干涉仪解调装置，便于增加检测通道个数，实用性强；
5、以F-P干涉仪为例，由于本发明的解调方法测量F-P干涉腔腔长的速度很快，可达微秒级，因此，通过对F-P干涉腔腔长的的连续测量，也可以采用这种解调方法测量由于机械振动引起干涉仪的一个镜面的幅值变化和振动频率；
6、本发明的解调***的通用性强，可适用于各种基于干涉原理的传感装置中，实现高效率、高精度、低功耗、低成本的干涉解调。
附图说明
图1为本发明实施例1的利用气体吸收光谱参考的干涉仪绝对位移解调***连接示意图；
图2为本发明实施例1-3的利用气体吸收光谱参考的干涉仪绝对位移解调***在一个扫波长描周期内，***可以同时产生干涉条纹和参考气体吸收峰的示意图；
图3为本发明实施例1-3利用气体吸收光谱参考的干涉仪绝对位移解调***标定原理中一个干涉条纹的两个光强变化斜率最大的Q点，算出干涉条纹两个Q点的位相值差Δλ的示意图；
图4为本发明实施例1-3利用气体吸收光谱参考的干涉仪绝对位移解调***标定原理中用两个吸收峰可以做时间转换成位相的转换关系标定示意图；
图5本发明实施例2利用气体吸收光谱参考的干涉仪绝对位移解调***的连接示意图；
图6本发明实施例3利用气体吸收光谱参考的干涉仪绝对位移解调***的15路检测通道连接示意图；
图7本发明实施例3利用气体吸收光谱参考的干涉仪绝对位移解调***的16路检测通道连接示意图。
图中：1、扫描激光器；2、光纤隔离器；3、光纤耦合器；31、2×2光纤耦合器；311、第一连接端；312、第二连接端；313、第三连接端；314、第四连接端；32、2×1光纤耦合器；321、第一连接端；322、第二连接端；323、第三连接端；33、1×2光纤耦合器；331、第一连接端；332、第二连接端；333、第三连接端；4、干涉仪；5、探测器；51、信号探测器；52、参考探测器；6、参考气室；7、1×8光纤分路器。
具体实施方式
为了便于理解本发明，以下结合附图及实施例，对本发明的技术方案及优点进行进一步详细说明。以下以示例的方式对本发明具体结构及特点进行说明，不应将构成对本发明的任何限制。同时，有关下列所提及(包括隐含或公开)的任何一个技术特征，以及被直接显示或隐含在图中的任何一个技术特征，均可以在这些技术特征之间继续进行任意组合或删减，从而形成可能没有在本发明中直接或间接提到的更多其他实施例。附图中给出了本发明的较佳实施方式。但是，本发明可以以许多不同的形式来实现，并不限于本文所描述的实施方式。相反地，提供这些实施方式的目的是使对本发明的公开内容理解的更加透彻全面。
实施例1
如图1-4所示，一种利用气体吸收光谱参考的干涉仪绝对位移解调***，所述解调***用于测量干涉仪干涉腔的绝对空腔长度；解调***包括连接形成通路的扫描激光器1、光纤隔离器2、光纤耦合器3、干涉仪4、探测器5、信号放大器(附图未示意)、微处理器(附图未示意)；
所述探测器5为常规的C波段光电探测器；具体地，所述探测器5包括信号探测器51、参考探测器52；所述光纤耦合器3包括2×2光纤耦合器31；所述解调***还包括气体参考气室6，参考气室6与所述参考探测器52连接；所述气体参考气室6充满在所述扫描激光器1的波长扫描范围内含有吸收峰的参考气体；所述微处理器的输出端连接有D/A模数转换器，所述D/A模数转换器用于控制所述扫描激光器电流驱动电路，以实现对所述扫描激光器1的波长调谐；所述扫描激光器1通过锯齿波驱动器(附图未示意)驱动并产生波长扫描光束；
所述扫描激光器1发出的激光光束经过所述光纤隔离器2后耦合到所述2×2光纤耦合器的第一连接端311，其中一路从所述2×2光纤耦合器31的第二连接端312输出入射所述干涉仪4，所述干涉仪4产生的干涉反射光返回经过所述2×2光纤耦合器31后由第三连接端313进入对应的所述信号探测器51；干涉反射光另一路从所述2×2光纤耦合器31的第四连接端314输出至所述气体参考气室6后进入对应的所述参考探测器52；干涉反射光在所述信号探测器51中产生干涉条纹，经参考气体透射的光束被对应的参考探测器52吸收并同步产生吸收谱线；
所述信号探测器51和参考探测器52采集干涉条纹信号及吸收谱线信号并分别经过所述信号放大器放大，通过模数转换后发送至所述微处理器进行信号强度归一化处理，由所述微处理器通过预先标定的时间-位相关系计算出所述干涉仪的干涉腔长L的绝对测量值及其变化量ΔL的测量值。
进一步细化，所述微处理器向扫描激光器1驱动发出波长扫描信号；所述微处理器的输出端连接有D/A模数转换器(附图未示意)，所述D/A模数转换器(附图未示意)用于控制所述扫描激光器电流驱动电路，以实现对所述扫描激光器的调谐；以及，所述信号探测器、参考探测器采集的干涉条纹信号及吸收谱线信号经过线性跨阻放大器放大，并由A/D模数转换器数字化再输出到所述微处理器进行信号强度归一化处理。
在本实施例中，所述干涉仪4采用F-P干涉仪，所述扫描激光器1采用VCSEL激光器，通过采用锯齿波的驱动电流调谐VCSEL激光器，就可以使VCSEL激光器的输出波长做相应的变化，形成一个扫描波长范围；同时，在VCSEL激光器的扫描波长范围内选择一种具有特征吸收峰的气体，例如甲烷气体，注入到参考气室中。在VCSEL激光器的一个扫描周期内，激光光波同步被 信号探测器51和参考探测器52接收；F-P干涉仪在信号探测器51中产生干涉条纹，参考气室在参考探测器52中同步产生吸收谱线，如图2所示。
在其他实施例中，所述扫描激光器1还可以是其他类型的扫描激光器，只要在其扫描波段范围内可以选取到对应的气体作为吸收光谱参考，能达成本发明的有益效果即可，此处不赘述。
本实施例的干涉仪解调***同样可以适用于与F-P干涉仪工作原理相同的其他干涉仪中，如Sagnac干涉仪、Michelson干涉仪等。
需要说明的是，在本实施例中，所述光纤隔离器、光纤耦合器、干涉仪、探测器、线性跨阻放大器(附图未示意)、A/D模数转换器、D/A模数转换器、微处理器(附图未示意)、锯齿波驱动器均适用于本发明的干涉腔长解调***，其安装方式、控制方式、工作原理、设置参数均可参考现有技术，只要能够达成本发明的有益效果的均可进行实施。
本实施例1还提供一种利用气体吸收光谱参考的干涉仪绝对位移解调***的解调方法，包括以下步骤：
S1：扫描激光器光源在锯齿波驱动电路的控制下，在一个扫描周期范围内，输出波长随时间变化的激光光束；
S2：S1中的激光光束经所述光纤隔离器后耦合到所述光纤耦合器并分别输出至所述干涉仪和气体参考气室，干涉仪产生的干涉反射光返回经过所述光纤耦合器进入所述信号探测器；干涉反射光在所述信号探测器中产生干涉条纹；经气体参考气室透射的光束连接到参考探测器并在参考探测器中同步产生吸收谱线；
S3：所述探测器采集S2中产生的干涉条纹信号及吸收谱线信号并分别经过所述信号放大器放大，通过模数转换后发送至所述微处理器进行信号强度归 一化处理；
S4：所述微处理器接收S3中的干涉条纹信号及吸收谱线信号，并通过预先标定的时间-位相关系计算出所述干涉仪的干涉腔长及其变化数值。
本实施例的解调方法通过采用扫描激光器作为干涉仪传感器的光源，利用在所述扫描激光器的波长扫描范围内具有吸收峰的参考气体的吸收光谱作为绝对光谱参考位置，以及结合吸收谱线的固定波长和谱线半宽度，或两个吸收谱线进行时间值向位相值转换的标定方法，配合利用干涉条纹自身完成干涉腔腔长的绝对值测量；本发明应用于干涉传感器中，具备可以测量干涉腔绝对腔长的高分辨和高准确度等优势。
其中，所述预先标定的时间-位相关系的标定方法及解调干涉腔长值和其变化值的方法如下：
1)扫描激光器光源在锯齿波驱动电路的控制下，在实际扫描波长范围，输出波长随时间变化的激光光束；
2)在扫描激光器的一个扫描周期内，干涉仪的探测器同步产生干涉条纹及吸收谱线,并获取对应的干涉条纹和吸收谱线随时间变化的强度曲线；利用吸收谱线的半宽度对时间轴标定，从而可以得到将时间轴数值转变成波长值的比例关系；
或者，通过测量两个吸收谱线中心波长在时间轴的相对位置，利用两谱线中心波长固定的特性，对时间轴进行标定，也可以得到将时间轴数值转变成波长值的比例关系；
3)测量一个干涉条纹的光强变化斜率最大的Q点相对于吸收谱线的波长中心的时间差，利用标定过程中得到的时间轴数值转变成波长值的比例关系，得到干涉条纹在Q点相对于吸收谱线的波长中心的波长差的测量值。再利用已 知的吸收谱线的波长值和测量到的波长差值，就可以得到干涉条纹Q点所对应的绝对波长值λ。
4)测量一个干涉条纹的两个光强变化斜率最大的Q点相对于吸收谱线的中心波长点的时间差，利用时间轴数值转变成波长值的比例关系，得到干涉条纹两个Q点的位相值差对应的波长差Δλ的测量值，或干涉条纹半宽度时对应的波长差，再利用
Figure PCTCN2022124758-appb-000012
就可以得到干涉腔长度L的绝对值。
5)当干涉条纹因干涉腔长变化而产生平移时，测量干涉条纹的光强变化斜率最大的Q点相对于吸收谱线的中心点的时间差，再利用时间轴数值转变成波长值的比例关系，得到干涉条纹Q点的位相变化值，利用
Figure PCTCN2022124758-appb-000013
反演出ΔL的变化量。
所述标定方法的1)中，所述扫描激光器的最小波长扫描范围可使其一个扫描周期内同时覆盖一个或两个吸收谱线；所述2)中，分别获取对应的干涉条纹和吸收谱线随时间变化的强度曲线后，测量吸收谱线的半宽度相对时间轴的数值，或者，测量两个吸收谱线中心波长在时间轴的相对位置的差值，利用已知的吸收谱线的半宽度，或已知的两个吸收谱线中心波长差值，得到时间轴数值转变成波长值的比例关系，完成***标定；在所述3)的测量时，测量一个干涉条纹的光强变化斜率最大的Q点相对于吸收谱线的波长中心的时间差，并转换成Q点相对于吸收谱线的波长中心的波长差，已知的吸收谱线的中心波长加上或减去这个波长差，得到干涉条纹Q点所对应的绝对波长值λ；所述4)中，描述怎样通过测量一个干涉条纹的两个光强变化斜率最大的Q点的时间差，来得到干涉腔长度L的绝对值；所述5)中，如果干涉条纹因干涉腔长变化而产生平移时，只要Q点相对于吸收谱线的中心点的位相差，就可以得到干涉腔长的变化值。
在本实施例中，在一个扫描周期范围内，所述时间-位相关系的标定原理如下：
由于干涉条纹和吸收谱线是在同一个波长扫描周期中出现，干涉条纹的每一点对应的波长值和吸收谱线的中心波长值在时间轴上对应位置是相对固定的，并且是不会改变的，同时吸收谱线的半宽度在时间轴上也是固定的。这样，就可以利用吸收谱线得到绝对的波长值，利用吸收谱线的半宽度对时间轴标定，从而可以将时间轴数值转变成波长值。对于具有一个固定的干涉腔长的F-P干涉仪，当VCSEL激光器的输出扫描波长的变化到达一定值，使得干涉仪干涉腔位相变化到达2π或N个2π时，就会在干涉仪输出端产生一个或N个光强变化的干涉条纹，如图2所示。通过测量一个干涉条纹的两个光强变化斜率最大的Q点(如图3所示)相对于吸收谱线的中心波长点的时间差，就可以得到干涉条纹两个Q点的位相值差对应的波长差Δλ的测量值，或干涉条纹半宽度时对应的波长差，然后利用
Figure PCTCN2022124758-appb-000014
从而进一步得到干涉腔腔长L的绝对测量值。
当干涉条纹因干涉腔长变化而产生平移时，通过测量干涉条纹的光强变化斜率最大的Q点(如图3所示)相对于吸收谱线的中心点的时间差，再利用时间相对于位相的标定关系，就可以算出干涉条纹Q点的位相变化值，利用
Figure PCTCN2022124758-appb-000015
就可以到的干涉腔腔长的变化量ΔL的测量值，从而达到从干涉条纹信息解调出干涉腔长的变化量的效果。
可选地，所述标定方法的1)中，所述扫描激光器的最小波长扫描范围可使其一个扫描周期内同时覆盖两个吸收谱线；所述3)中，分别获取对应的干涉条纹和吸收谱线随时间变化的强度曲线后，对从信号探测器和参考探测器的数据做归一化处理，测量一个干涉条纹的两个光强变化斜率最大的Q点相对于 吸收谱线的中心波长的时间差，得到干涉条纹两个Q点的位相值差对应的波长差Δλ的测量值，或干涉条纹半宽度时对应的波长差。
在本实施例中，所述VCSEL激光器波长扫描范围扩大到大约2.73nm即可确保其一个扫描周期内同时覆盖两个吸收谱线；如图4所示，通过测量两个吸收谱线在时间轴的相对位置，利用两谱线中心波长固定的特性，对时间轴进行标定，也可以将时间轴数值转变成波长值，由于采用两个吸收峰进行标定时的测量误差相对较小，这种标定方式的精度更高。
本发明利用上述两种标定方法中的一种方法就可以测量到干涉腔的绝对空腔长度，空腔长度之所以被称为绝对长度，是因为测量过程是基于吸收谱线的固定波长和谱线半宽度，在常温常压条件下是不会改变的物理量。也可以同时使用两种标定方法，通过交叉验证地使用，来提高测量精度。相比之下，现有技术中基于单色光干涉术(与白光干涉术相反)的传感技术，仅能测量长度相对变化ΔL(相对于任意的初始值)，无法确定干涉腔的实际腔长。本发明的绝对干涉腔长测量的特性，对于要求长期静态测量的所有应用都是至关重要的。
实施例2
如图5所示，本实施例2与实施例1的区别在于，所述探测器5内部设有所述参考气室6；所述光纤耦合器包括2×1光纤耦合器32；所述扫描激光器1发出的激光光束经过所述光纤隔离器2后耦合到所述2X1光纤耦合器32的第一连接端321，并从2×1光纤耦合器32的第二连接端322输出入射所述干涉仪4，所述干涉仪4产生的干涉反射光返回经过所述2×1光纤耦合器32的第三连接端323进入内部设有参考气室6的探测器5中，由所述探测器5采集干涉条纹信号及吸收谱线信号并分别经过所述信号放大器放大，通过模数转换后发送至所述微处理器进行信号强度归一化处理。
即，本实施例2的所述解调***的解调方法中，由于采用了内部设有参考气室6的探测器5，由探测器5同时采集干涉条纹信号及吸收谱线信号并经过信号放大、转换后发送。
在本实施例中，利用自主研发的自带参考气室的探测器技术(中国发明专利CN201810036930.0一种自带参考气室的光电探测器及其制备方法)，设计所述利用气体吸收光谱参考的干涉仪绝对位移解调***，将所述参考气室集成到探测器内部，可以进一步简化干涉仪解调装置，实用性更强；而且可以在低功耗、微型化、轻便式干涉仪传感器中，降低了现有干涉仪传感器的解调仪成本，简化了整个检测装置的结构。
其中，所述预先标定的时间-位相关系及解调干涉腔长值和其变化值的方法参照实施例1即可。
实施例3
如图2-4，图6-7所示，为进一步扩大本发明的应用范围，本实施例3在上述实施例1-2的基础上提供一种利用气体吸收光谱参考的干涉仪绝对位移解调***多探头传感器复用***，多通道检测，以便满足不同的需求。
具体如下：述干涉仪绝对位移解调***还包括1×8光纤分路器7；所述光纤耦合器3还包括1×2光纤耦合器33；
在本实施方式中，所述1×N光纤分路器为1×8光纤分路器7，如图5所示，由1个1×2光纤耦合器33和2个1×8光纤分路器7组成，如图6所示；所述扫描激光器1发出的激光光束经过所述光纤隔离器2耦合到一个1×2光纤耦合器33的第一连接端331，1×2光纤耦合器33的第二连接端332、第三连接端333分别与1个所述1×8光纤分路器7连接；2个1×8光纤分路器7的15个连接端分别连接15个2×1光纤耦合器32的第一连接端321；15个2 ×1光纤耦合器32的第二连接端322分别连接15个F-P干涉仪4，15个2×1光纤耦合器32的第三连接端323分别连接15个信号探测器；所述1×8光纤分路器7的第16路连接到一个充满甲烷的参考气室6，经参考气体透射的光束再连接到对应的参考探测器52；所述干涉仪产生的干涉反射光从2个1×8光纤分路器的其他15路连接端分别输出至对应所述2×1光纤耦合器的第三连接端323进入所述信号探测器51中并产生干涉条纹；经参考气体透射后在所述参考探测器52中同步产生吸收谱线；由所述信号探测器51采集干涉条纹信号，所述参考探测器52采集吸收谱线信号，所有探测器测量的的信号都分别经过线性跨阻放大器放大，由模数转换器(A/D)数字化再输出到所述微处理器进行信号强度归一化处理，通过预先标定的时间-位相关系计算出所述干涉仪的干涉腔长L的绝对测量值及其变化量ΔL的测量值。所述微处理器的输出端连接一个数模转换器(D/A)，用来控制激光器电流驱动电路，实现对VCSEL的调谐。
为实现***简化，作为进一步优选的实施方案，可在所述探测器内部设有所述参考气室；利用自带参考气室的探测器，即所述调解***中省去了单独分1路光连接到一个充满甲烷的参考气室，而是16路均连接到对应的探测器中，相比单独设置参考气室连接参考探测器的实施方式增加了一路检测，使整个***的多探头传感器复用数达到16路。利用自主研发的自带参考气室的探测器技术(中国发明专利CN201810036930.0一种自带参考气室的光电探测器及其制备方法)，设计所述利用气体吸收光谱参考的干涉仪绝对位移解调***，将所述参考气室集成到探测器内部，可以进一步简化干涉仪解调装置，实用性更强；而且可以在低功耗、微型化、轻便式干涉仪传感器中，降低了现有干涉仪传感器的解调仪成本，简化了整个检测装置。
进一步地，在VCSEL光强度充足的条件下，这种***的多探头传感器复用数量还可以进一步增加，以便满足不同应用的需求。
其中，所述预先标定的时间-位相关系及解调干涉腔长值和其变化值的方法参照实施例1即可。
其中，所述1×8光纤分路器还可以为分路不小于2路的其他光纤分路器，只要其满足本发明的技术方案即可实施。
本发明还提供一种利用气体吸收光谱参考的干涉仪绝对位移解调***及方法的解调装置，其以可调激光器为光源、用气体吸收光谱做参考，通过预先标定的时间-位相关系计算出所述干涉仪的干涉腔长L的绝对测量值及其变化量ΔL的测量值，实现高效率、高精度、低功耗、低成本的干涉解调。
上述实施方式仅为本发明的优选实施方式，不能以此来限定本发明保护的范围，当对于本领域的普通技术人员而言，可以理解在不脱离本发明的原理和精神的情况下可以对这些实施例进行多种变化、修改、替换和变型，本发明的范围由所附权利要求及其等同物限定。

Claims (10)

  1. 一种利用气体吸收光谱参考的干涉仪绝对位移解调***，所述解调***用于测量干涉仪干涉腔的绝对空腔长度；解调***包括连接在光路中的扫描激光器、光纤隔离器、光纤耦合器、干涉仪、探测器、信号放大器、微处理器；所述探测器包括信号探测器、参考探测器；所述光纤耦合器包括2×2光纤耦合器；其特征在于，还包括气体参考气室，所述气体参考气室充满在所述扫描激光器的波长扫描范围内具有吸收峰的参考气体；所述微处理器的输出端连接有D/A模数转换器，所述D/A模数转换器用于控制所述扫描激光器电流驱动电路，以实现对所述扫描激光器的波长调谐；所述扫描激光器通过锯齿波驱动器驱动并产生波长扫描光束；
    所述扫描激光器发出的激光光束经过所述光纤隔离器后耦合到2×2光纤耦合器的第一连接端，从所述2×2光纤耦合器的第二连接端输出入射所述干涉仪，所述干涉仪产生的干涉反射光返回经过所述2×2光纤耦合器后由第三连接端由所述信号探测器吸收并产生干涉条纹；干涉反射光从所述2×2光纤耦合器的第四连接端输出至所述气体参考气室，经参考气体透射的光束连接到参考探测器并在参考探测器中产生吸收谱线；由所述信号探测器采集干涉条纹信号和参考探测器采集吸收谱线信号分别经过所述信号放大器放大，通过模数转换后发送至所述微处理器进行信号强度归一化处理；所述微处理器通过预先标定的时间-位相关系计算出所述干涉仪的干涉腔长L的绝对测量值及其变化量ΔL的测量值。
  2. 如权利要求1所述的利用气体吸收光谱参考的干涉仪绝对位移解调***，其特征在于，所述干涉仪绝对位移解调***包括1个扫描激光器、1个光纤隔离器、1个1×N光纤分路器、N-1个2×1光纤耦合器、N-1个信号探测器、N-1个干涉仪、1个参考气室和1个参考探测器，其中N≥2；
    所述扫描激光器发出的激光光束经过所述光纤隔离器后耦合到所述1×N光纤分路器，激光光束在分成N路后，从1×N光纤分路器的1路连接端输出至所述参考气室，经参考气体透射的光束连接到对应的参考探测器，并在参考探测器中产生吸收谱线；其余光束从1×N光纤分路器的其他N-1路连接端分别输出至对应的N-1个2×1光纤耦合器的第一连接端，并从2×1光纤耦合器的对应的第二连接端输出入射对应的N-1个干涉仪，所述干涉仪产生的干涉反射光返回经过所述2×1光纤耦合器的第三连接端进入对应的信号探测器，并产生干涉条纹；由对应的所述信号探测器采集干涉条纹信号，由参考探测器采集吸收谱线信号并分别经过所述信号放大器放大，通过模数转换后发送至所述微处理器进行信号强度归一化处理；所述微处理器通过预先标定的时间-位相关系计算出所述干涉仪的干涉腔长L的绝对测量值及其变化量ΔL的测量值。
  3. 一种如权利要求1或2所述的利用气体吸收光谱参考的干涉仪绝对位移解调***的解调方法，其特征在于，包括以下步骤：
    S1：扫描激光器光源在锯齿波驱动电路的控制下，在一个扫描周期范围内，输出波长随时间变化的激光光束；
    S2：S1中的激光光束经所述光纤隔离器后耦合到所述光纤耦合器和干涉仪，或1×N光纤分路器和N-1个光纤耦合器并分别输出到N-1个所述干涉仪和所述气体参考气室，在同一个波长扫描范围内，所述干涉仪产生的干涉反射光返回经过所述光纤耦合器后进入对应的所述信号探测器，干涉反射光在所述信号探测器中产生干涉条纹；从气体参考气室透射的光束被对应的参考探测器吸收并在参考探测器中同步产生吸收谱线；
    S3：所述信号探测器和参考探测器分别采集S2中产生的干涉条纹信号及吸收谱线信号，并分别经过所述信号放大器放大，通过模数转换后发送至所述 微处理器进行信号强度归一化处理；
    S4：所述微处理器接收S3中的干涉条纹信号及吸收谱线信号，并通过预先标定的时间-位相关系计算出所述干涉仪的干涉腔长及其变化数值。
  4. 一种利用气体吸收光谱参考的干涉仪绝对位移解调***，所述解调***用于测量干涉仪干涉腔的绝对空腔长度；其特征在于，所述解调***包括连接在光路中的扫描激光器、光纤隔离器、光纤耦合器、干涉仪、内部设有参考气室的探测器、信号放大器、微处理器；所述光纤耦合器包括2×1光纤耦合器；
    所述扫描激光器发出的激光光束经过所述光纤隔离器后耦合到所述2×1光纤耦合器的第一连接端，并从2×1光纤耦合器的第二连接端输出入射所述干涉仪，所述干涉仪产生的干涉反射光返回经过所述2×1光纤耦合器的第三连接端进入内部设有所述参考气室的探测器中产生干涉条纹和吸收谱线；由所述探测器采集干涉条纹信号及吸收谱线信号并经过所述信号放大器放大，通过模数转换后发送至所述微处理器进行信号强度归一化处理；所述微处理器通过预先标定的时间-位相关系计算出所述干涉仪的干涉腔长L的绝对测量值及其变化量ΔL的测量值。
  5. 如权利要求4所述的利用气体吸收光谱参考的干涉仪绝对位移解调***，其特征在于，所述干涉仪绝对位移解调***包括1个光纤隔离器、1个1×N光纤分路器、N个2×1光纤耦合器、N个内部设有参考气室的探测器和N个干涉仪，其中N≥2；
    所述扫描激光器发出的激光光束经过所述光纤隔离器后耦合到所述1×N光纤分路器，激光光束在分成N路后分别输出至对应的N个2×1光纤耦合器的第一连接端，并从2×1光纤耦合器的对应的第二连接端输出入射对应的N个干涉仪，所述干涉仪产生的干涉反射光返回经过所述2×1光纤耦合器的第三 连接端进入对应的N个内部设有所述参考气室的探测器中产生干涉条纹和吸收谱线；由所述探测器采集干涉条纹信号及吸收谱线信号并经过所述信号放大器放大，通过模数转换后发送至所述微处理器进行信号强度归一化处理；所述微处理器通过预先标定的时间-位相关系计算出所述干涉仪的干涉腔长L的绝对测量值及其变化量ΔL的测量值。
  6. 一种如权利要求4或5所述的利用气体吸收光谱参考的干涉仪绝对位移解调***的解调方法，其特征在于，包括以下步骤：
    S1：扫描激光器光源在锯齿波驱动电路的控制下，在一个扫描周期范围内，输出波长随时间变化的激光光束；
    S2：S1中的激光光束经所述光纤隔离器后耦合到所述光纤耦合器和干涉仪，或1×N光纤分路器和对应的N个光纤耦合器并输出到N个所述干涉仪，在同一个波长扫描范围内，所述干涉仪产生的干涉反射光返回经过所述光纤耦合器后进入对应的所述内部设有参考气室的探测器，干涉反射光在所述内部设有参考气室的探测器中产生干涉条纹和吸收谱线；
    S3：所述探测器采集S2中产生的干涉条纹信号及吸收谱线信号并分别经过所述信号放大器放大，通过模数转换后发送至所述微处理器进行信号强度归一化处理；
    S4：所述微处理器接收S3中的干涉条纹信号及吸收谱线信号，并通过预先标定的时间-位相关系计算出所述干涉仪的干涉腔长及其变化数值。
  7. 如权利要求3或6所述的利用气体吸收光谱参考的干涉仪绝对位移解调方法，其特征在于，所述预先标定的时间-位相关系的标定方法包括如下步骤：
    S1：扫描激光器光源在锯齿波驱动电路的控制下，在一个扫描周期范围内，输出波长随时间变化的激光光束；
    S2：在扫描激光器的一个扫描周期内，通过设置气体参考气室，干涉仪的干涉反射光在对应的探测器中同步产生干涉条纹及吸收谱线；
    S3：分别获取对应的干涉条纹、吸收谱线随时间变化的工作曲线，在一个扫描周期中只有一个吸收峰时，测量吸收峰半宽度对应的时间差，再利用在同一温度和压力环境条件下的固定吸收峰半宽度值，得到时间值相波长值的转换关系，再利用吸收峰中心波长，就可以确定每一个采样点对应的波长值，完成标定。
  8. 如权利要求7所述的利用气体吸收光谱参考的干涉仪绝对位移解调方法的时间-位相关系标定方法，其特征在于，所述标定方法的S1中，所述扫描激光器的最小波长扫描范围可使其一个扫描周期内同时覆盖两个吸收谱线；所述标定方法的S3中，测量两吸收峰中心波长对应的时间差，再利用两吸收峰的固定波长差值，得到时间值相波长值的转换关系，再利用一个吸收峰中心波长，就可以确定每一个采样点所对应的波长值，完成标定。
  9. 如权利要求3或6所述的利用气体吸收光谱参考的干涉仪绝对位移解调方法，其特征在于，解调所述干涉腔长值和其变化值的方法如下：
    1)测量一个干涉条纹的光强变化斜率最大的Q点相对于吸收谱线的波长中心的时间差，利用标定过程中得到的时间轴数值转变成波长值的比例关系，得到干涉条纹在Q点相对于吸收谱线的波长中心的波长差的测量值，再利用已知的吸收谱线的波长值和测量到的波长差值，就可以得到干涉条纹Q点所对应的绝对波长值λ；
    2)测量一个干涉条纹的两个光强变化斜率最大的Q点相对于吸收谱线的中心波长点的时间差，利用时间轴数值转变成波长值的比例关系，得到干涉条纹两个Q点的位相值差对应的波长差Δλ的测量值，或干涉条纹半宽度时对应 的波长差，再利用
    Figure PCTCN2022124758-appb-100001
    就可以得到干涉腔长度L的绝对值；
    3)当干涉条纹因干涉腔长变化而产生平移时，测量干涉条纹的光强变化斜率最大的Q点相对于吸收谱线的中心点的时间差，再利用时间轴数值转变成波长值的比例关系，得到干涉条纹Q点的位相变化值，利用
    Figure PCTCN2022124758-appb-100002
    反演出ΔL的变化量。
  10. 一种利用气体吸收光谱参考的干涉仪绝对位移解调装置，其特征在于，包括权利要求1-9任一项所述的利用气体吸收光谱参考的干涉仪绝对位移解调***及方法，其以可调激光器为光源、用气体吸收光谱做参考，通过预先标定的时间-位相关系计算出所述干涉仪的干涉腔长L的绝对测量值及其变化量ΔL的测量值。
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