CN115523948B - Interferometer absolute displacement demodulation system and method using gas absorption spectrum reference - Google Patents
Interferometer absolute displacement demodulation system and method using gas absorption spectrum reference Download PDFInfo
- Publication number
- CN115523948B CN115523948B CN202211229340.2A CN202211229340A CN115523948B CN 115523948 B CN115523948 B CN 115523948B CN 202211229340 A CN202211229340 A CN 202211229340A CN 115523948 B CN115523948 B CN 115523948B
- Authority
- CN
- China
- Prior art keywords
- interference
- interferometer
- absorption spectrum
- optical fiber
- wavelength
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Active
Links
- 238000000862 absorption spectrum Methods 0.000 title claims abstract description 138
- 238000000034 method Methods 0.000 title claims abstract description 71
- 238000006073 displacement reaction Methods 0.000 title claims abstract description 45
- 239000013307 optical fiber Substances 0.000 claims abstract description 119
- 238000005259 measurement Methods 0.000 claims abstract description 59
- 238000010521 absorption reaction Methods 0.000 claims abstract description 56
- 230000008859 change Effects 0.000 claims description 52
- 239000000835 fiber Substances 0.000 claims description 24
- 238000006243 chemical reaction Methods 0.000 claims description 20
- 238000012545 processing Methods 0.000 claims description 19
- 238000010606 normalization Methods 0.000 claims description 18
- 230000003595 spectral effect Effects 0.000 claims description 18
- 230000003287 optical effect Effects 0.000 claims description 7
- 230000008569 process Effects 0.000 claims description 6
- 238000013519 translation Methods 0.000 claims description 5
- 238000005070 sampling Methods 0.000 claims 2
- 238000001228 spectrum Methods 0.000 abstract description 11
- 238000001514 detection method Methods 0.000 description 11
- 238000010586 diagram Methods 0.000 description 7
- 238000005516 engineering process Methods 0.000 description 7
- 238000005305 interferometry Methods 0.000 description 6
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 description 6
- 239000000523 sample Substances 0.000 description 4
- 230000009286 beneficial effect Effects 0.000 description 3
- 230000007774 longterm Effects 0.000 description 3
- 230000003068 static effect Effects 0.000 description 3
- 230000007547 defect Effects 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 238000012544 monitoring process Methods 0.000 description 2
- 238000002360 preparation method Methods 0.000 description 2
- 230000004075 alteration Effects 0.000 description 1
- 230000005540 biological transmission Effects 0.000 description 1
- 238000010276 construction Methods 0.000 description 1
- 238000012937 correction Methods 0.000 description 1
- 238000002790 cross-validation Methods 0.000 description 1
- 230000007123 defense Effects 0.000 description 1
- 238000012217 deletion Methods 0.000 description 1
- 230000037430 deletion Effects 0.000 description 1
- 230000001419 dependent effect Effects 0.000 description 1
- 238000013461 design Methods 0.000 description 1
- 238000009434 installation Methods 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 239000003129 oil well Substances 0.000 description 1
- 238000002310 reflectometry Methods 0.000 description 1
- 238000012827 research and development Methods 0.000 description 1
- 230000004044 response Effects 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
Classifications
-
- 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
Landscapes
- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Health & Medical Sciences (AREA)
- Spectroscopy & Molecular Physics (AREA)
- Life Sciences & Earth Sciences (AREA)
- Chemical & Material Sciences (AREA)
- Analytical Chemistry (AREA)
- Biochemistry (AREA)
- General Health & Medical Sciences (AREA)
- Immunology (AREA)
- Pathology (AREA)
- Optics & Photonics (AREA)
- Instruments For Measurement Of Length By Optical Means (AREA)
- Investigating Or Analysing Materials By Optical Means (AREA)
- Spectrometry And Color Measurement (AREA)
Abstract
The invention discloses an interferometer absolute displacement demodulation system and method using gas absorption spectrum reference, the demodulation system comprises a scanning laser, an optical fiber isolator, an optical fiber coupler, an interferometer, a signal detector, a reference detector, a signal amplifier, a microprocessor and a gas reference air chamber which are connected in a light path, wherein the gas reference air chamber is filled with reference gas with absorption peaks in the wavelength scanning range of the scanning laser; the invention uses the absorption spectrum of the reference gas with absorption peak in the wavelength scanning range of the scanning laser as the absolute spectrum reference position, combines the fixed wavelength and half width of the absorption spectrum, or the distance between the two absorption spectrum wavelengths to perform the calibration method of converting from the time axis to the wavelength axis or the phase axis, and is matched with the characteristic point of the interference fringe to complete the absolute value measurement of the cavity length of the interference cavity, thereby being applicable to various sensing devices based on the interference principle and realizing the interference demodulation with high efficiency, high precision, low power consumption and low cost.
Description
Technical Field
The invention relates to the technical field of photoelectric measuring instruments and meters and interference sensors, in particular to an interferometer absolute displacement demodulation system, method and application by utilizing gas spectrum reference.
Background
Based on the requirements of pressure monitoring applications in the fields of medical treatment, aerospace, bridge construction, high-temperature oil wells, industrial monitoring, national defense and the like, various micro-optical fiber F-P and optical fiber MEMS sensing technologies have been developed and applied to different application scenes. These interferometric sensors based on the F-P interference principle typically sense by being measured against the F-P cavity, causing a change in cavity length. The two mirrors of the interferometer are respectively a film inner surface positioned at one end and an optical fiber tip positioned at the other end to form a core sensing element of the F-P interferometer, when incident light forms reflection at the two end surfaces of the F-P cavity, the reflected light beam generates interference signals at the signal detector. The interference signal or the interference fringe changes along with the change of the F-P cavity length, and the measured parameter sensing and measuring can be realized by demodulating the change of the interference fringe.
Demodulation of the interferometer fringes refers to extracting the change value of the optical cavity length of the interferometer from the interference fringe information of the interferometer. The conventional interferometer cavity length is extracted by a plurality of demodulation methods, namely a light splitting intensity demodulation method, a spectrum demodulation method and a low coherence interference demodulation method. The system corresponding to the light intensity demodulation method has simple structure and high response speed, but has too high requirements on the control of cavity length precision and the stability of the light source. The spectrum demodulation method adopts a more complex spectrum acquisition system, and the wide application of the method is limited because the cost of a spectrometer is generally high. Based on the white light interference demodulation technology, the cavity length change of the sensing interferometer can be demodulated by utilizing the cross-correlation relation between different types of interferometers (reference interferometers) and the Fabry-Perot cavity (sensing interferometer). The low coherence interference technology can be divided into a time scanning type and a space scanning type, a reference interferometer generates a series of optical path differences on a time axis or a space axis respectively, the interference fringes can be demodulated by utilizing the zero-order fringe peak position of any fringe peak position relative to the central wavelength interference fringes, the demodulation method has a complex structure, and the cost of precise mechanical scanning is high. The wavelength scanning light source is used as a light source of the interferometer, and the wavelength readability of the wavelength scanning laser light source is utilized, and the wavelength value at the maximum value or the minimum value of the light intensity of the interference fringes is added, so that demodulation of the interference fringes can be realized, and the change of the interference cavity length is inverted. However, the wavelength scanning laser source has high power consumption and high cost, and particularly for a small sensor, the power consumption, the cost and the volume limit the method. In particular, wavelength-scanning laser sources require correction as a wavelength reading of a precision measurement over a large temperature variation range. How to realize small size, low power consumption, low cost and high-precision interference demodulation is a technical problem in designing optical fiber interferometer sensing.
The sensor demodulation principle for the example of the F-P interferometer is as follows:
According to the F-P principle, when an F-P sensor with a cavity length of L and equal and smaller reflectivity R of two end faces is irradiated by light with a light wave wavelength of lambda, the reflection output light intensity of a certain sensor fiber optical Fabry-Perot sensor with a specific cavity length of L is in a cosine function relation with the light frequency, and the distribution formula of the reflection light intensity I is as follows:
Wherein the method comprises the steps of Is an initial phase, is a constant; while the phase isI 0 is the intensity of incident light, and I 0 is a constant under the ideal light source condition that the intensity of each wavelength is equal; therefore, the output light intensity of the interferometer contains F-P cavity length information, and the demodulation method of the interferometer uses the change information of I to reflect the change amount of L.
It is well known that the phase change is caused by a change in the interference cavity length L and the wavelength λ, so that by changing the interference cavity length or changing the laser wavelength, the phase can be changed accordingly, that is:
wherein, Representing the phase variation caused by the interference cavity length variation and by the laser wavelength variation, respectively. When deltal=0,Remain unchanged, whileWhen the delta lambda changes to cause the phase change of 2 pi, the reflected light intensity of the corresponding interferometer changes for one period, and a pair of interference fringes with alternate brightness and darkness are formed. At this time, ifThe phase change caused by the change in Δl translates the fringe relative to the fringe when Δl=0, and can be used by measuring the amount of translation of the fringe, or the phase changeThe variation of DeltaL is inverted, so that the effect of demodulating the variation of the interference cavity length from the interference fringe information is achieved.
The demodulation method adopting the measurement interference fringe tracking method or the phase change tracking method has the advantages of simple signal processing, high measurement speed and the like, but the method has the problem of limited dynamic range, and in addition, the demodulation precision of the cavity length is greatly dependent on the original point value of the recorded delta L, namely the position of the interference fringe when the delta L=0, so that the value of the delta L can be determined by comparing the positions of different interference fringes. The method relies on accurate reading of interference fringes, and outputs an approximate sine wave of the interference fringes, so that the position of the maximum value of the interference fringes is not easy to accurately determine, and the interference fringe tracking method has the problem of low demodulation precision. In particular, when the interferometer is powered down and restarted, the system cannot determine whether any fringe position changes are due to changes in the interference cavity length L or due to changes in the laser wavelength λ.
Disclosure of Invention
In order to solve the technical problems in the prior art, one of the purposes of the present invention is to provide an interferometer absolute displacement demodulation system using gas spectrum reference, wherein a scanning laser is used as a light source of an interferometer sensor, an absorption spectrum of a reference gas having an absorption peak in a wavelength scanning range of the scanning laser is used as an absolute spectrum reference position, and a calibration method of time-to-phase conversion is performed by combining a fixed wavelength and a spectral line half width of an absorption spectral line, or two absorption spectral lines, so as to complete absolute value measurement of an interference cavity length; the invention can be applied to interference demodulation of various interference sensors, and has the advantages of high resolution, high accuracy and the like of measuring the absolute cavity length of an interference cavity;
in addition, the demodulation method of the interferometer absolute displacement demodulation system utilizing the gas absorption spectrum reference can be applied to various sensing devices based on the interference principle, and has a very wide application prospect; when the demodulation method is used in the interferometer sensing device, the power consumption and the volume of the sensor can be reduced, and in the interferometer sensor with low power consumption, miniaturization and portability, the cost of the demodulator of the existing interferometer sensor is reduced, and the structure of the whole detection device is simplified.
The second object of the present invention is to provide a demodulation method of an interferometer absolute displacement demodulation system using gas spectrum reference, in which the absorption spectrum of the reference gas having an absorption peak in the wavelength scanning range of the scanning laser is used as an absolute spectrum reference position, and a calibration method of time-to-phase conversion is performed by combining a fixed wavelength and a spectral line half-width of the absorption spectrum, or two absorption spectrum lines, so as to complete absolute value measurement of the cavity length of the interference cavity, and compared with the prior art such as a sensing technology based on monochromatic light interferometry (contrary to white light interferometry), only the relative change Δl (relative to any initial value) can be measured, and the defect of the actual cavity length of the interference cavity cannot be determined, and the measured cavity length of the present invention is called absolute length because the measurement process is based on the fixed wavelength and spectral line half-width of the absorption spectrum, and is a physical quantity which does not change under normal temperature and normal pressure conditions; therefore, the characteristic of the absolute interferometric cavity length measurement overcomes the problems of the traditional interferometric fringe tracking method, and is of great importance for all applications requiring long-term static measurement.
The third objective of the present invention is to provide an interferometer absolute displacement demodulation device using gas absorption spectrum reference, which uses an adjustable laser as a light source and uses gas absorption spectrum as reference, and calculates the absolute measurement value of the interference cavity length L of the interferometer and the measurement value of the variation delta L thereof through a pre-calibrated time-phase relationship, so as to realize high-efficiency, high-precision, low-power consumption and low-cost interference demodulation.
One of the purposes of the invention is achieved by the following technical scheme:
An interferometer absolute displacement demodulation system utilizing a gas absorption spectrum reference, the demodulation system for measuring an absolute cavity length of an interferometer interference cavity; the demodulation system comprises a scanning laser, an optical fiber isolator, an optical fiber coupler, an interferometer, a detector, a signal amplifier and a microprocessor which are connected in an optical path; the detector comprises a signal detector and a reference detector; the fiber coupler comprises a2 x 2 fiber coupler; the laser scanning device further comprises a gas reference gas chamber, wherein the reference gas chamber is connected with the reference detector and is filled with reference gas with absorption peaks in the wavelength scanning range of the scanning laser; the scanning laser is driven by a sawtooth driver and generates a wavelength scanning beam;
The laser beam emitted by the scanning laser is coupled to a first connecting end of a 2X 2 optical fiber coupler after passing through the optical fiber isolator, the laser beam is output from a second connecting end of the 2X 2 optical fiber coupler and enters the interferometer, and interference reflected light generated by the interferometer returns to the third connecting end after passing through the 2X 2 optical fiber coupler and is absorbed by the signal detector to generate interference fringes; the interference reflected light is output to the gas reference gas chamber from the fourth connecting end of the 2x 2 optical fiber coupler, and the light beam transmitted by the reference gas is connected to a reference detector and generates an absorption spectrum line in the reference detector; the interference fringe signals acquired by the signal detector and the absorption spectrum line signals acquired 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 the variation delta L of the absolute measurement value through a pre-calibrated time-phase relation.
Further, the interferometer absolute displacement demodulation system also comprises 1 scanning laser, an optical fiber isolator, 1 XN optical fiber branching device, N-1 2X 1 optical fiber couplers, N-1 signal detectors, N-1 interferometers, a reference air chamber and a reference detector, wherein N is more than or equal to 2;
The laser beam emitted by the scanning laser is coupled to the 1 XN optical fiber splitter after passing through the optical fiber isolator, 1 path of the laser beam is output to the reference air chamber from the 1 path connecting end of the 1 XN optical fiber splitter after being split into N paths, and the beam transmitted by the reference air is connected to a corresponding reference detector and generates an absorption spectrum line in the reference detector; the other beams are respectively connected to the first connecting ends of the corresponding N-1 2X1 optical fiber couplers from the other N-1 paths of output ends of the 1X N optical fiber splitters, and output the corresponding N-1 interferometers from the corresponding second connecting ends of the 2X1 optical fiber couplers, and interference reflected light generated by the interferometers returns to enter the corresponding signal detectors through the third connecting ends of the 2X1 optical fiber couplers and generates interference fringes; the corresponding signal detector is used for collecting interference fringe signals, the corresponding reference detector is used for collecting absorption spectrum line signals, the absorption spectrum line signals are amplified by the signal amplifier respectively, and the signals 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 the variation delta L of the absolute measurement value through a pre-calibrated time-phase relation.
Further, the demodulation system comprises a scanning laser, an optical fiber isolator, a2×1 optical fiber coupler, an interferometer, a detector with a reference air chamber inside, a signal amplifier and a microprocessor, wherein the scanning laser, the optical fiber isolator, the 2×1 optical fiber coupler, the interferometer, the detector with the reference air chamber inside, the signal amplifier and the microprocessor are connected in an optical path;
The laser beam emitted by the scanning laser is coupled to the first connecting end of the 2X 1 optical fiber coupler after passing through the optical fiber isolator, the laser beam is output from the second connecting end of the 2X 1 optical fiber coupler and enters the interferometer, and interference reflected light generated by the interferometer returns to the detector provided with the reference air chamber inside after passing through the third connecting end of the 2X 1 optical fiber coupler to generate interference fringes and absorption spectrum lines; the interference fringe signal and the absorption spectrum line signal are collected by the detector and amplified by the signal amplifier, 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 the variation delta L of the absolute measurement value through a pre-calibrated time-phase relation.
Further, the interferometer absolute displacement demodulation system also comprises 1 scanning laser, an optical fiber isolator, 1X N optical fiber branching device, N2X 1 optical fiber couplers, N signal detectors, N interferometers and N detectors with the reference air chamber inside, wherein N is more than or equal to 2;
The laser beam emitted by the scanning laser is coupled to the 1 XN optical fiber splitter after passing through the optical fiber isolator, the laser beam is split into N beams by the 1 XN optical fiber splitter, the N paths of the laser beam are output from the N paths of connecting ends of the 1 XN optical fiber splitter and are respectively connected to the first connecting ends of N2X 1 optical fiber couplers, the corresponding N interferometers are output from the corresponding second connecting ends of the 2X 1 optical fiber couplers and are incident, and interference reflection light generated by the interferometers returns to the corresponding N detectors internally provided with reference air chambers through the third connecting ends of the 2X 1 optical fiber couplers to generate interference fringes and absorption spectrum lines; the detector collects interference fringe signals and absorption spectrum line signals, the interference fringe signals and the absorption spectrum line signals are amplified by the signal amplifier respectively, and the interference fringe signals and the absorption spectrum line signals 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 the variation delta L of the absolute measurement value through a pre-calibrated time-phase relation.
The output end of the microprocessor is connected with a D/A analog-to-digital converter, and the D/A analog-to-digital converter is used for controlling the scanning laser current driving circuit so as to realize the tuning of the scanning laser.
The second purpose of the invention can be realized by the following technical scheme:
scheme 1: separating the signal detector and the reference air chamber
A demodulation method of the interferometer absolute displacement demodulation system using gas absorption spectrum reference, comprising the following steps:
S1: under the control of a sawtooth wave driving circuit, a scanning laser light source outputs a laser beam with the wavelength changing along with time in a scanning period range;
s2: the laser beam in S1 is coupled to the optical fiber coupler after passing through the optical fiber isolator and respectively outputs the laser beam to be incident to the interferometer and the gas reference gas chamber, and interference reflection light generated by the interferometer returns to enter the corresponding signal detector after passing through the optical fiber coupler in the same wavelength scanning range, wherein interference fringes are generated in the signal detector by the interference reflection light; the light beam transmitted from the gas reference gas chamber is absorbed by the corresponding reference detector and synchronously generates an absorption spectrum line in the reference detector;
s3: the signal detector and the reference detector collect interference fringe signals and absorption spectrum line signals generated in the step S2, amplify the interference fringe signals and the absorption spectrum line signals through the signal amplifier respectively, and send the interference fringe signals and the absorption spectrum line signals to the microprocessor for signal intensity normalization processing after analog-to-digital conversion;
s4: and the microprocessor receives the interference fringe signal and the absorption spectrum line signal in the step S3, and calculates the interference cavity length and the change value of the interference cavity length of the interferometer through a pre-calibrated time-phase relation.
Scheme 2: a reference air chamber is arranged in the detector
A demodulation method of the interferometer absolute displacement demodulation system using gas absorption spectrum reference, comprising the following steps:
S1: under the control of a sawtooth wave driving circuit, a scanning laser light source outputs a laser beam with the wavelength changing along with time in a scanning period range;
S2: the laser beams in the S1 are coupled to the optical fiber coupler after passing through the optical fiber isolator and respectively output and are incident to the interferometer, interference reflection light generated by the interferometer returns to a detector provided with the gas reference gas chamber inside through the optical fiber coupler in the same wavelength scanning range, interference fringes are generated in the detector by the interference reflection light, and absorption spectral lines are synchronously generated;
s3: the detector acquires interference fringe signals and absorption spectrum line signals generated in the step S2, amplifies the interference fringe signals and the absorption spectrum line signals through the signal amplifier, and sends the interference fringe signals and the absorption spectrum line signals to the microprocessor for signal intensity normalization processing after analog-to-digital conversion;
s4: and the microprocessor receives the interference fringe signal and the absorption spectrum line signal in the step S3, and calculates the interference cavity length and the change value of the interference cavity length of the interferometer through a pre-calibrated time-phase relation.
Further, the method for calculating the demodulation interference cavity length value and the variation value thereof based on the time-phase calibration comprises the following steps:
1) Under the control of a sawtooth wave driving circuit, a scanning laser light source outputs a laser beam with the wavelength changing along with time in an actual scanning wavelength range;
2) When only one absorption peak exists in one scanning period of the scanning laser, the detector of the interferometer synchronously generates interference fringes and absorption spectrum lines, and an intensity curve of the corresponding interference fringes and absorption spectrum lines changing along with time is obtained; calibrating a time axis by utilizing the half width of an absorption spectrum line, so that the proportional relation of converting the time axis value into the wavelength value can be obtained;
Or when two absorption peaks exist in one scanning period, the relative position of the central wavelengths of the two absorption spectral lines on the time axis is measured, and the time axis is calibrated by utilizing the characteristic that the central wavelengths of the two spectral lines are fixed, so that the proportional relation of converting the time axis value into the wavelength value can be obtained; because the measurement error is relatively smaller when two absorption peaks are adopted for calibration, the calibration accuracy is higher;
3) And measuring the time difference of the Q point with the maximum light intensity change slope of one interference fringe relative to the wavelength center of the absorption spectrum line, and obtaining the measured value of the wavelength difference of the interference fringe at the Q point relative to the wavelength center of the absorption spectrum line by utilizing the proportional relation of the time axis value obtained in the calibration process to the wavelength value. And obtaining an absolute wavelength value lambda corresponding to the interference fringe Q point by utilizing the known wavelength value of the absorption spectrum line and the measured wavelength difference value.
4) Measuring the time difference of the Q point with the maximum light intensity change slope of one interference fringe relative to the central wavelength point of the absorption spectrum line, obtaining the measured value of the wavelength difference delta lambda corresponding to the phase value difference of the two Q points of the interference fringe or the corresponding wavelength difference when the half width of the interference fringe by utilizing the proportional relation of the time axis numerical value to the wavelength value, and reusingThe absolute value of the interference cavity length L can be obtained.
5) When the interference fringe generates translation due to the change of the length of the interference cavity, measuring the time difference of the Q point with the maximum light intensity change slope of the interference fringe relative to the central point of the absorption spectrum line, converting the time axis value into the proportional relation of the wavelength value to obtain the phase change value of the Q point of the interference fringe, and utilizingThe amount of change in Δl is inverted.
Further, in the 1), the minimum wavelength scanning range of the scanning laser can cover one or two absorption lines simultaneously in one scanning period; in the step 2), after corresponding interference fringes and intensity curves of absorption spectrum lines changing along with time are respectively obtained, measuring the numerical value of half width of the absorption spectrum lines relative to a time axis; or measuring the difference value of the relative positions of the central wavelengths of the two absorption lines on a time axis, and obtaining the proportional relation of the time axis numerical value to the wavelength value by using the known half width of the absorption lines or the known difference value of the central wavelengths of the two absorption lines to finish the system calibration; measuring the time difference of the Q point with the maximum light intensity change slope of one interference fringe relative to the wavelength center of the absorption spectrum line during the measurement of the 3), and converting the time difference into the wavelength difference of the Q point relative to the wavelength center of the absorption spectrum line, and adding or subtracting the wavelength difference from the known center wavelength of the absorption spectrum line to obtain an absolute wavelength value lambda corresponding to the Q point of the interference fringe; in said 4), it is described how the absolute value of the interference cavity length L is obtained by measuring the time difference between the two Q points with the largest slope of the light intensity variation of one interference fringe; 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 by only the phase difference of the Q point with respect to the center point of the absorption line.
The third object of the invention is achieved by the following technical scheme: the interferometer absolute displacement demodulation device using the gas absorption spectrum reference comprises the interferometer absolute displacement demodulation system and the interferometer absolute displacement demodulation method using the gas absorption spectrum reference, wherein an adjustable laser is used as a light source, the gas absorption spectrum is used as a reference, and the absolute measurement value of the interference cavity length L of the interferometer and the measurement value of the variation delta L of the interference cavity length L of the interferometer are calculated through a pre-calibrated time-phase relation, so that the interference demodulation with high efficiency, high precision, low power consumption and low cost is realized.
Compared with the prior art, the invention has at least the following beneficial effects:
1. For most of the application of the interference sensor, high resolution, high demodulation accuracy and quick demodulation are critical indexes for ensuring the measurement accuracy capability of a sensor system, a scanning laser is adopted as a light source of the interferometer sensor, under the condition that the wavelength scanning range of the scanning laser contains an absorption peak of reference gas, the absorption spectrum of the reference gas is used as an absolute spectrum reference position, and the fixed wavelength and spectral line half width of an absorption spectral line or the scanning time difference between two absorption spectral lines are combined, so that the scanning time value is converted into a phase, or a calibration method of the wavelength value is matched, and the absolute value measurement of the cavity length of an interference cavity is completed by measuring the wavelength difference of the half period of the interference fringes; meanwhile, the variable quantity of the interference cavity length is obtained by measuring the variable quantity of the interference fringe Q point relative to the absorption peak wavelength, so that the purpose of demodulating the interferometer is achieved; the invention is applied to the interference sensor, and has the advantages of high resolution, high accuracy and the like, and the absolute cavity length of the interference cavity can be measured;
2. Compared with the prior art such as the sensing technology based on monochromatic light interferometry (contrary to white light interferometry), the method can only measure the relative change delta L (relative to any initial value) of the length of the interference cavity, and cannot determine the defect of the absolute cavity length of the interference cavity, and the measured cavity length is called absolute length because the measuring process is based on the fixed wavelength and half width of the absorption spectrum line and is a physical quantity which cannot be changed under the condition of normal temperature and normal pressure; therefore, the characteristic of absolute interference cavity length measurement overcomes the problems of the traditional interference fringe tracking method, and is of great importance for all applications requiring long-term static measurement;
3. The demodulation method of the interferometer absolute displacement demodulation system using the gas absorption spectrum reference can be used for various sensing devices based on the interference principle, and has a very wide application prospect; when the demodulation method is used in the interferometer sensing device, the power consumption and the volume of the sensor can be reduced, and in the interferometer sensor with low power consumption, miniaturization and portability, the cost of the demodulator of the existing interferometer sensor is reduced, and the structure of the whole detection device is simplified;
4. the interferometer absolute displacement demodulation system using gas absorption spectrum reference can be a single detection channel, and a plurality of detection channels can be multiplexed with a laser light source; the invention can further simplify the interferometer demodulation device by utilizing the detector with the reference air chamber, is convenient for increasing the number of detection channels and has strong practicability;
5. Taking an F-P interferometer as an example, the demodulation method of the invention can measure the amplitude change and the vibration frequency of one mirror surface of the interferometer caused by mechanical vibration by continuously measuring the cavity length of the F-P interference cavity because the demodulation method of the invention has high speed which can reach microsecond;
6. The demodulation system has strong universality, can be suitable for various sensing devices based on the interference principle, and realizes interference demodulation with high efficiency, high precision, low power consumption and low cost.
Drawings
FIG. 1 is a schematic diagram showing the connection of an interferometer absolute displacement demodulation system using gas absorption spectrum reference according to embodiment 1 of the present invention;
FIG. 2 is a schematic diagram showing an absolute displacement demodulation system of an interferometer using gas absorption spectrum reference in embodiments 1-3 of the present invention, wherein the system can generate interference fringes and reference gas absorption peaks simultaneously in one scanning wavelength period;
FIG. 3 is a schematic diagram of calculating the phase value difference Deltaλ between two points of interference fringes by using the point Q with the largest slope of two light intensity changes of one interference fringe in the calibration principle of the interferometer absolute displacement demodulation system of the gas absorption spectrum reference in the embodiment 1-3 of the present invention;
FIG. 4 is a schematic diagram of calibration of the calibration principle of the interferometer absolute displacement demodulation system according to the embodiment 1-3 of the present invention, in which two absorption peaks are used to perform time-to-phase conversion;
FIG. 5 is a schematic diagram showing the connection of an interferometer absolute displacement demodulation system using gas absorption spectrum reference according to embodiment 2 of the present invention;
FIG. 6 is a schematic diagram showing 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 showing the connection of 16 detection channels of an interferometer absolute displacement demodulation system using gas absorption spectrum reference according to embodiment 3 of the present invention.
In the figure: 1. scanning a laser; 2. an optical fiber isolator; 3. an optical fiber coupler; 31. a2 x 2 fiber coupler; 311. a first connection end; 312. a second connection end; 313. a third connection end; 314. a fourth connection end; 32. a2 x 1 fiber coupler; 321. a first connection end; 322. a second connection end; 323. a third connection end; 33. a1 x 2 fiber coupler; 331. a first connection end; 332. a second connection end; 333. a third connection end; 4. an interferometer; 5. a detector; 51. a signal detector; 52. a reference detector; 6. a reference air chamber; 7. 1 x 8 fiber optic splitters.
Detailed Description
In order to facilitate understanding of the present invention, the following technical solutions and advantages of the present invention will be described in further detail with reference to the accompanying drawings and examples. The specific structure and features of the present invention are described below by way of example and should not be construed to limit the invention in any way. Also, any feature mentioned (including implicit or explicit) below, as well as any feature shown directly or implicit in the drawings, may be continued to be any combination or deletion of such features among themselves, to form still other embodiments that may not be directly or indirectly mentioned in the present invention. The drawings illustrate preferred embodiments of the invention. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete.
Example 1
1-4, An interferometer absolute displacement demodulation system utilizing a gas absorption spectrum reference for measuring an absolute cavity length of an interferometer interferometric cavity; the demodulation system comprises a scanning laser 1, an optical fiber isolator 2, an optical fiber coupler 3, an interferometer 4, a detector 5, a signal amplifier (not shown in the drawing) and a microprocessor (not shown in the drawing) which are connected to form a passage;
The detector 5 is a conventional C-band photoelectric detector; specifically, the detector 5 includes a signal detector 51, a reference detector 52; the optical fiber coupler 3 includes a2×2 optical fiber coupler 31; the demodulation system further comprises a gas reference gas chamber 6, the reference gas chamber 6 being connected to the reference detector 52; the gas reference gas chamber 6 is filled with a reference gas containing an absorption peak in the wavelength scanning range of the scanning laser 1; the output end of the microprocessor is connected with a D/A analog-to-digital converter, and the D/A analog-to-digital converter is used for controlling the scanning laser current driving circuit so as to realize wavelength tuning of the scanning laser 1; the scanning laser 1 is driven by a sawtooth driver (not shown in the drawings) and generates a wavelength scanning beam;
The laser beam emitted by the scanning laser 1 is coupled to the first connection end 311 of the 2×2 optical fiber coupler after passing through the optical fiber isolator 2, one path of laser beam is output from the second connection end 312 of the 2×2 optical fiber coupler 31 and enters the interferometer 4, and the interference reflected light generated by the interferometer 4 returns to the corresponding signal detector 51 after passing through the 2×2 optical fiber coupler 31 and enters the third connection end 313; the other path of interference reflected light is output from the fourth connection end 314 of the 2×2 fiber coupler 31 to the gas reference gas chamber 6 and then enters the corresponding reference detector 52; the interference reflected light generates interference fringes in the signal detector 51, and the light beam transmitted by the reference gas is absorbed by the corresponding reference detector 52 and synchronously generates absorption lines;
The signal detector 51 and the reference detector 52 collect interference fringe signals and absorption spectrum line signals, amplify the interference fringe signals and the absorption spectrum line signals respectively through the signal amplifier, send the interference fringe signals and the absorption spectrum line signals to the microprocessor for signal intensity normalization processing after analog-to-digital conversion, and calculate absolute measurement values of the interference cavity length L of the interferometer and measurement values of the variation delta L of the interference cavity length L of the interferometer through a pre-calibrated time-phase relation by the microprocessor.
Further refinement, the microprocessor drives the scanning laser 1 to emit a wavelength scanning signal; the output end of the microprocessor is connected with a D/A analog-to-digital converter (not shown in the drawing), and the D/A analog-to-digital converter (not shown in the drawing) is used for controlling the scanning laser current driving circuit so as to realize the tuning of the scanning laser; and the interference fringe signals and the absorption spectrum line signals acquired 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.
In this embodiment, the interferometer 4 adopts an F-P interferometer, the scanning laser 1 adopts a VCSEL laser, and by tuning the VCSEL laser by using a driving current of a sawtooth wave, an output wavelength of the VCSEL laser can be changed correspondingly, so as to form a scanning wavelength range; at the same time, a gas having a characteristic absorption peak, such as methane gas, is selected to be injected into the reference gas cell in the scanning wavelength range of the VCSEL laser. During one scanning period of the VCSEL laser, the laser light wave is synchronously received by the signal detector 51 and the reference detector 52; the F-P interferometer produces interference fringes in the signal detector 51 and the reference gas cell simultaneously produces absorption lines in the reference detector 52, as shown in fig. 2.
In other embodiments, the scanning laser 1 may be any other type of scanning laser, as long as the corresponding gas can be selected as the reference of the absorption spectrum in the scanning band range, which can achieve the beneficial effects of the present invention, and is not described herein.
The interferometer demodulation system of the embodiment can be also applied to other interferometers with the same working principle as the F-P interferometer, such as a Sagnac interferometer, a Michelson interferometer and the like.
In this embodiment, the optical fiber isolator, the optical fiber coupler, the interferometer, the detector, the linear transimpedance amplifier (not shown in the drawing), the a/D analog-to-digital converter, the D/a analog-to-digital converter, the microprocessor (not shown in the drawing), and the sawtooth driver are all suitable for the interference cavity length demodulation system of the present invention, and the installation mode, the control mode, the working principle, and the setting parameters thereof can refer to the prior art, so long as the beneficial effects of the present invention can be achieved.
Embodiment 1 also provides a demodulation method of an interferometer absolute displacement demodulation system using gas absorption spectrum reference, comprising the following steps:
S1: under the control of a sawtooth wave driving circuit, a scanning laser light source outputs a laser beam with the wavelength changing along with time in a scanning period range;
s2: the laser beam in the S1 is coupled to the optical fiber coupler after passing through the optical fiber isolator and is respectively output to the interferometer and the gas reference gas chamber, and interference reflected light generated by the interferometer returns to enter the signal detector through the optical fiber coupler; interference reflected light produces interference fringes in the signal detector; the light beam transmitted by the gas reference gas chamber is connected to a reference detector and synchronously generates an absorption spectrum line in the reference detector;
s3: the detector acquires interference fringe signals and absorption spectrum line signals generated in the step S2, amplifies the interference fringe signals and the absorption spectrum line signals through the signal amplifier respectively, and sends the interference fringe signals and the absorption spectrum line signals to the microprocessor for signal intensity normalization processing after analog-to-digital conversion;
s4: and the microprocessor receives the interference fringe signal and the absorption spectrum line signal in the step S3, and calculates the interference cavity length and the change value of the interference cavity length of the interferometer through a pre-calibrated time-phase relation.
The demodulation method of the embodiment uses a scanning laser as a light source of an interferometer sensor, uses an absorption spectrum of reference gas with an absorption peak in a wavelength scanning range of the scanning laser as an absolute spectrum reference position, combines a fixed wavelength and a half width of a spectral line of the absorption spectrum, or performs a calibration method of converting a time value into a phase value by two absorption spectrum lines, and completes absolute value measurement of the cavity length of an interference cavity by matching with the interference fringes; the invention is applied to the interference sensor and has the advantages of high resolution, high accuracy and the like of measuring the absolute cavity length of the interference cavity.
The calibration method of the pre-calibrated time-phase relation and the method for demodulating the interference cavity length value and the variation value thereof are as follows:
1) Under the control of a sawtooth wave driving circuit, a scanning laser light source outputs a laser beam with the wavelength changing along with time in an actual scanning wavelength range;
2) In one scanning period of the scanning laser, the detector of the interferometer synchronously generates interference fringes and absorption lines, and acquires intensity curves of the corresponding interference fringes and absorption lines changing along with time; calibrating a time axis by utilizing the half width of an absorption spectrum line, so that the proportional relation of converting the time axis value into the wavelength value can be obtained;
or by measuring the relative position of the central wavelengths of the two absorption spectral lines on the time axis and calibrating the time axis by utilizing the characteristic that the central wavelengths of the two spectral lines are fixed, the proportional relation of converting the time axis value into the wavelength value can be obtained;
3) And measuring the time difference of the Q point with the maximum light intensity change slope of one interference fringe relative to the wavelength center of the absorption spectrum line, and obtaining the measured value of the wavelength difference of the interference fringe at the Q point relative to the wavelength center of the absorption spectrum line by utilizing the proportional relation of the time axis value obtained in the calibration process to the wavelength value. And obtaining an absolute wavelength value lambda corresponding to the interference fringe Q point by utilizing the known wavelength value of the absorption spectrum line and the measured wavelength difference value.
4) Measuring the time difference of the Q point with the maximum light intensity change slope of one interference fringe relative to the central wavelength point of the absorption spectrum line, obtaining the measured value of the wavelength difference delta lambda corresponding to the phase value difference of the two Q points of the interference fringe or the corresponding wavelength difference when the half width of the interference fringe by utilizing the proportional relation of the time axis numerical value to the wavelength value, and reusingThe absolute value of the interference cavity length L can be obtained.
5) When the interference fringe generates translation due to the change of the length of the interference cavity, measuring the time difference of the Q point with the maximum light intensity change slope of the interference fringe relative to the central point of the absorption spectrum line, converting the time axis value into the proportional relation of the wavelength value to obtain the phase change value of the Q point of the interference fringe, and utilizingThe amount of change in Δl is inverted.
In the calibration method 1), the minimum wavelength scanning range of the scanning laser can cover one or two absorption spectrum lines simultaneously in one scanning period; in the step 2), after corresponding interference fringes and intensity curves of absorption lines changing along with time are respectively obtained, measuring the numerical value of half width of the absorption lines relative to a time axis, or measuring the difference value of the relative positions of the central wavelengths of the two absorption lines on the time axis, and obtaining the proportional relation of the numerical value of the time axis to the wavelength value by using the known half width of the absorption lines or the known difference value of the central wavelengths of the two absorption lines so as to finish the calibration of the system; measuring the time difference of the Q point with the maximum light intensity change slope of one interference fringe relative to the wavelength center of the absorption spectrum line during the measurement of the 3), and converting the time difference into the wavelength difference of the Q point relative to the wavelength center of the absorption spectrum line, and adding or subtracting the wavelength difference from the known center wavelength of the absorption spectrum line to obtain an absolute wavelength value lambda corresponding to the Q point of the interference fringe; in said 4), it is described how the absolute value of the interference cavity length L is obtained by measuring the time difference between the two Q points with the largest slope of the light intensity variation of one interference fringe; 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 by only the phase difference of the Q point with respect to the center point of the absorption line.
In this embodiment, in a scanning period range, the calibration principle of the time-phase relationship is as follows:
since the interference fringes and the absorption lines occur in the same wavelength scanning period, the wavelength value corresponding to each point of the interference fringes and the center wavelength value of the absorption line are relatively fixed in the corresponding position on the time axis and are unchanged, and the half width of the absorption line is also fixed on the time axis. Therefore, absolute wavelength values can be obtained by utilizing the absorption spectrum line, and the time axis is calibrated by utilizing the half width of the absorption spectrum line, so that the time axis value can be converted into the wavelength value. For an F-P interferometer with a fixed interference cavity length, when the variation of the output scanning wavelength of the VCSEL laser reaches a certain value, so that the phase variation of the interference cavity of the interferometer reaches 2 pi or N2 pi, one or N interference fringes with light intensity variation are generated at the output end of the interferometer, as shown in FIG. 2. By measuring the time difference between the two Q points (shown in FIG. 3) with the maximum slope of light intensity variation of one interference fringe and the central wavelength point of the absorption spectrum, the measured value of the wavelength difference Deltalambda corresponding to the phase value difference of the two Q points of the interference fringe or the corresponding wavelength difference when the half width of the interference fringe is obtained, and then the time difference is utilized Thereby further obtaining an absolute measurement of the interference cavity length L.
When the interference fringe generates translation due to the change of the interference cavity length, the phase change value of the interference fringe Q point can be calculated by measuring the time difference of the Q point (shown in figure 3) with the maximum light intensity change slope of the interference fringe relative to the central point of the absorption spectrum and then using the calibration relation of the time relative to the phase, and the method is utilizedThe measurement of the variation delta L of the cavity length of the interference cavity can be achieved, so that the effect of demodulating the variation of the cavity length of the interference from the interference fringe information is achieved.
Optionally, in 1) of the calibration method, the minimum wavelength scanning range of the scanning laser may cover two absorption lines simultaneously in one scanning period; and 3) respectively acquiring intensity curves of corresponding interference fringes and absorption spectrum lines changing along with time, performing normalization processing on data of a signal detector and a reference detector, and measuring time difference of two Q points with the largest light intensity change slope of one interference fringe relative to the central wavelength of the absorption spectrum line to obtain a measured value of a wavelength difference delta lambda corresponding to the phase value difference of two Q points of the interference fringe or a wavelength difference corresponding to the half width of the interference fringe.
In this embodiment, the wavelength scanning range of the VCSEL laser is extended to about 2.73nm, so as to ensure that two absorption lines are covered simultaneously in one scanning period; as shown in fig. 4, by measuring the relative positions of two absorption spectrum lines on the time axis, the time axis can be calibrated by utilizing the characteristic that the central wavelength of the two absorption spectrum lines is fixed, and the time axis value can be converted into the wavelength value.
The absolute cavity length of the interference cavity can be measured by using one of the two calibration methods, and the cavity length is called as the absolute length because the measurement process is based on the fixed wavelength and the half width of the spectral line of the absorption spectral line and is a physical quantity which cannot be changed under the condition of normal temperature and normal pressure. Two calibration methods can be used simultaneously, and the measurement accuracy is improved by using the method in a cross-validation mode. In contrast, prior art sensing techniques based on monochromatic interferometry (as opposed to white light interferometry) can only measure the relative change in length Δl (relative to an arbitrary initial value), and cannot determine the actual cavity length of the interferometric cavity. The characteristics of the absolute interferometric cavity length measurement of the present invention are critical for all applications requiring long-term static measurements.
Example 2
As shown in fig. 5, the present embodiment 2 differs from embodiment 1 in that the reference air chamber 6 is provided inside the probe 5; the fiber coupler includes a 2x1 fiber coupler 32; the laser beam emitted by the scanning laser 1 is coupled to the first connection end 321 of the 2X1 optical fiber coupler 32 after passing through the optical fiber isolator 2, and is output from the second connection end 322 of the 2X1 optical fiber coupler 32 to be incident on the interferometer 4, the interference reflected light generated by the interferometer 4 returns to the detector 5 provided with the reference air chamber 6 inside after passing through the third connection end 323 of the 2X1 optical fiber coupler 32, interference fringe signals and absorption spectrum signals are collected by the detector 5 and amplified by the signal amplifier respectively, and are sent to the microprocessor for signal intensity normalization processing after analog-digital conversion.
That is, in the demodulation method of the demodulation system of embodiment 2, since the detector 5 having the reference air chamber 6 inside is used, the interference fringe signal and the absorption line signal are collected at the same time by the detector 5, amplified and converted, and transmitted.
In this embodiment, the autonomous research and development detector technology with a reference air chamber (chinese invention patent CN201810036930.0, a photoelectric detector with a reference air chamber and a preparation method thereof) is used to design the interferometer absolute displacement demodulation system using gas absorption spectrum reference, and the reference air chamber is integrated into the detector, so that the interferometer demodulation device can be further simplified, and the practicability is stronger; in addition, the demodulator cost of the existing interferometer sensor can be reduced in the low-power-consumption miniaturized portable interferometer sensor, and the structure of the whole detection device is simplified.
The method for demodulating the interference cavity length value and the variation value thereof according to the pre-calibrated time-phase relation is just to refer to the embodiment 1.
Example 3
As shown in fig. 2-4 and fig. 6-7, in order to further expand the application scope of the present invention, embodiment 3 provides an interferometer absolute displacement demodulation system multi-probe sensor multiplexing system using gas absorption spectrum reference based on the above embodiment 1-2, and multi-channel detection is performed, so as to meet different requirements.
The method comprises the following steps: the interferometer absolute displacement demodulation system also comprises a 1X 8 optical fiber branching device 7; the fiber coupler 3 further comprises a1×2 fiber coupler 33;
In this embodiment, the 1×n optical fiber splitter is a1×8 optical fiber splitter 7, as shown in fig. 5, and is composed of 11×2 optical fiber couplers 33 and 21×8 optical fiber splitters 7, as shown in fig. 6; the laser beam emitted by the scanning laser 1 is coupled to the first connection end 331,1 ×2 of one 1×2 optical fiber coupler 33 through the optical fiber isolator 2, and the second connection end 332 and the third connection end 333 of the one 1×2 optical fiber coupler 33 are respectively connected to 1×8 optical fiber splitters 7; the 15 connection ends of the 21×8 optical fiber splitters 7 are respectively connected to the first connection ends 321 of the 15 2×1 optical fiber couplers 32; the second connection ends 322 of the 15 2×1 fiber couplers 32 are respectively connected with 15F-P interferometers 4, and the third connection ends 323 of the 15 2×1 fiber couplers 32 are respectively connected with 15 signal detectors; the 16 th path of the 1 x8 optical fiber splitter 7 is connected to a reference gas chamber 6 filled with methane, and the light beam transmitted by the reference gas is connected to a corresponding reference detector 52; the interference reflected light generated by the interferometer is respectively output from the other 15 paths of connection ends of the 21×8 optical fiber splitters to the third connection end 323 corresponding to the 2×1 optical fiber coupler, enters the signal detector 51 and generates interference fringes; the transmission of the reference gas results in the simultaneous generation of absorption lines in the reference detector 52; the signal detector 51 collects interference fringe signals, the reference detector 52 collects absorption spectrum signals, signals measured by all detectors are amplified by linear transimpedance amplifiers respectively, and are digitized by analog-to-digital converters (A/D) and then output to the microprocessor for signal intensity normalization processing, and absolute measurement values of the interference cavity length L of the interferometer and measurement values of the variation delta L of the interference cavity length L are calculated through a pre-calibrated time-phase relation. The output end of the microprocessor is connected with a digital-to-analog converter (D/A) for controlling a laser current driving circuit to realize the tuning of the VCSEL.
For system simplification, as a further preferred embodiment, the reference air chamber may be provided inside the detector; by using the detector with the reference air chamber, namely, the mediation system omits to separately divide 1 path of light to be connected to one reference air chamber filled with methane, and 16 paths of light are all connected to the corresponding detector, one path of detection is added compared with the embodiment of separately arranging the reference air chamber to be connected with the reference detector, so that the multiplexing number of the multi-probe sensor of the whole system reaches 16 paths. By utilizing the independently developed detector technology with a reference air chamber (a photoelectric detector with the reference air chamber and a preparation method thereof disclosed in Chinese patent No. 201810036930.0), designing the interferometer absolute displacement demodulation system utilizing gas absorption spectrum reference, integrating the reference air chamber into the detector can further simplify an interferometer demodulation device, and has stronger practicability; in addition, the demodulator cost of the existing interferometer sensor can be reduced in the low-power-consumption miniaturized portable interferometer sensor, and the whole detection device is simplified.
Further, the multiplexing number of the multiple probe sensors of the system can be further increased under the condition that the VCSEL light intensity is sufficient, so as to meet the requirements of different applications.
The method for demodulating the interference cavity length value and the variation value thereof according to the pre-calibrated time-phase relation is just to refer to the embodiment 1.
The 1×8 optical fiber splitter may be another optical fiber splitter with a splitting path not less than 2 paths, so long as the technical scheme of the present invention is satisfied.
The invention also provides a demodulation device of the interferometer absolute displacement demodulation system and method by utilizing the gas absorption spectrum reference, which takes the adjustable laser as a light source and uses the 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 the variation delta L thereof through a pre-calibrated time-phase relation, thereby realizing high-efficiency, high-precision, low-power consumption and low-cost interference demodulation.
The above-described embodiments are only preferred embodiments of the present invention and should not be construed as limiting the scope of the invention, it being understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the spirit and scope of the invention as defined by the appended claims and their equivalents.
Claims (10)
1. An interferometer absolute displacement demodulation system utilizing a gas absorption spectrum reference, the demodulation system for measuring an absolute cavity length of an interferometer interference cavity; the demodulation system comprises a scanning laser, an optical fiber isolator, an optical fiber coupler, an interferometer, a detector, a signal amplifier and a microprocessor which are connected in an optical path; the detector comprises a signal detector and a reference detector; the fiber coupler comprises a 2 x 2 fiber coupler; the laser scanning device is characterized by further comprising a gas reference gas chamber filled with reference gas having an absorption peak in the wavelength scanning range of the scanning laser; the output end of the microprocessor is connected with a D/A analog-to-digital converter, and the D/A analog-to-digital converter is used for controlling the scanning laser current driving circuit so as to realize wavelength tuning of the scanning laser; the scanning laser is driven by a sawtooth driver and generates a wavelength scanning beam;
The laser beam emitted by the scanning laser is coupled to a first connecting end of a 2X 2 optical fiber coupler after passing through the optical fiber isolator, the laser beam is output from a second connecting end of the 2X 2 optical fiber coupler and enters the interferometer, and interference reflected light generated by the interferometer returns to the third connecting end after passing through the 2X 2 optical fiber coupler and is absorbed by the signal detector to generate interference fringes; the interference reflected light is output to the gas reference gas chamber from the fourth connecting end of the 2x 2 optical fiber coupler, and the light beam transmitted by the reference gas is connected to a reference detector and generates an absorption spectrum line in the reference detector; the interference fringe signals acquired by the signal detector and the absorption spectrum line signals acquired 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 the variation delta L of the absolute measurement value through a pre-calibrated time-phase relation.
2. The interferometer absolute displacement demodulation system of claim 1, wherein the interferometer absolute displacement demodulation system comprises 1 scanning laser, 1 fiber isolator, 1 1xn fiber splitter, N-1 2 x1 fiber coupler, N-1 signal detector, N-1 interferometer, 1 reference gas cell, and 1 reference detector, wherein N is ≡2;
The laser beam emitted by the scanning laser is coupled to the 1 XN optical fiber splitter after passing through the optical fiber isolator, the laser beam is output to the reference air chamber from the 1-path connecting end of the 1 XN optical fiber splitter after being split into N paths, and the beam transmitted by the reference air is connected to a corresponding reference detector and generates an absorption spectrum line in the reference detector; the other beams are respectively output to the first connecting ends of the corresponding N-1 2X 1 optical fiber couplers from the other N-1 paths of connecting ends of the 1X N optical fiber splitters, and are output to the corresponding N-1 interferometers from the corresponding second connecting ends of the 2X 1 optical fiber couplers, and interference reflected light generated by the interferometers returns to enter the corresponding signal detectors through the third connecting ends of the 2X 1 optical fiber couplers and generates interference fringes; the corresponding signal detector is used for collecting interference fringe signals, the reference detector is used for collecting absorption spectrum line signals, the absorption spectrum line signals are amplified by the signal amplifier respectively, and the signals 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 the variation delta L of the absolute measurement value through a pre-calibrated time-phase relation.
3. A demodulation method of an interferometer absolute displacement demodulation system using a gas absorption spectrum reference as claimed in claim 1 or 2 comprising the steps of:
S1: under the control of a sawtooth wave driving circuit, a scanning laser light source outputs a laser beam with the wavelength changing along with time in a scanning period range;
S2: the laser beam in S1 is coupled to the optical fiber coupler and the interferometer after passing through the optical fiber isolator, or the 1 XN optical fiber splitter and the N-1 optical fiber couplers are respectively output to the N-1 interferometers and the gas reference gas chamber, interference reflection light generated by the interferometers returns to the corresponding signal detectors after passing through the optical fiber coupler in the same wavelength scanning range, and interference reflection light generates interference fringes in the signal detectors; the light beam transmitted from the gas reference gas chamber is absorbed by the corresponding reference detector and synchronously generates an absorption spectrum line in the reference detector;
S3: the signal detector and the reference detector respectively acquire interference fringe signals and absorption spectrum line signals generated in the step S2, amplify the interference fringe signals and the absorption spectrum line signals respectively through the signal amplifier, and send the interference fringe signals and the absorption spectrum line signals to the microprocessor for signal intensity normalization processing after analog-to-digital conversion;
s4: and the microprocessor receives the interference fringe signal and the absorption spectrum line signal in the step S3, and calculates the interference cavity length and the change value of the interference cavity length of the interferometer through a pre-calibrated time-phase relation.
4. An interferometer absolute displacement demodulation system utilizing a gas absorption spectrum reference, the demodulation system for measuring an absolute cavity length of an interferometer interference cavity; the demodulation system is characterized by comprising a scanning laser, an optical fiber isolator, an optical fiber coupler, an interferometer, a detector, a signal amplifier and a microprocessor, wherein the scanning laser, the optical fiber isolator, the optical fiber coupler, the interferometer, the detector, the signal amplifier and the microprocessor are connected in an optical path; the fiber coupler comprises a 2x 1 fiber coupler;
The laser beam emitted by the scanning laser is coupled to the first connecting end of the 2X 1 optical fiber coupler after passing through the optical fiber isolator, the laser beam is output from the second connecting end of the 2X 1 optical fiber coupler and enters the interferometer, and interference reflected light generated by the interferometer returns to the detector provided with the reference air chamber inside after passing through the third connecting end of the 2X 1 optical fiber coupler to generate interference fringes and absorption spectrum lines; the interference fringe signal and the absorption spectrum line signal are collected by the detector and amplified by the signal amplifier, 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 the variation delta L of the absolute measurement value through a pre-calibrated time-phase relation.
5. The interferometer absolute displacement demodulation system using gas absorption spectrum reference of claim 4, wherein the interferometer absolute displacement demodulation system comprises 1 fiber isolator, 1 x N fiber optic splitter, N2 x1 fiber optic couplers, N detectors with reference gas cells inside and N interferometers, wherein N is greater than or equal to 2;
The laser beam emitted by the scanning laser is coupled to the 1 XN optical fiber splitter after passing through the optical fiber isolator, the laser beam is respectively output to the first connecting ends of the corresponding N2X 1 optical fiber couplers after being divided into N paths, the corresponding N interferometers are output from the corresponding second connecting ends of the 2X 1 optical fiber couplers and are incident, interference reflection light generated by the interferometers returns to the corresponding N detectors internally provided with the reference air chamber through the third connecting ends of the 2X 1 optical fiber couplers to generate interference fringes and absorption spectrum lines; the interference fringe signal and the absorption spectrum line signal are collected by the detector and amplified by the signal amplifier, 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 the variation delta L of the absolute measurement value through a pre-calibrated time-phase relation.
6. A demodulation method of an interferometer absolute displacement demodulation system using a gas absorption spectrum reference as claimed in claim 4 or 5 comprising the steps of:
S1: under the control of a sawtooth wave driving circuit, a scanning laser light source outputs a laser beam with the wavelength changing along with time in a scanning period range;
S2: the laser beam in S1 is coupled to the optical fiber coupler and the interferometer after passing through the optical fiber isolator, or the 1 XN optical fiber splitter and the corresponding N optical fiber couplers and output to the N interferometers, interference reflection light generated by the interferometers returns to the corresponding detector with the reference air chamber inside after passing through the optical fiber coupler in the same wavelength scanning range, and interference reflection light generates interference fringes and absorption spectral lines in the detector with the reference air chamber inside;
s3: the detector acquires interference fringe signals and absorption spectrum line signals generated in the step S2, amplifies the interference fringe signals and the absorption spectrum line signals through the signal amplifier respectively, and sends the interference fringe signals and the absorption spectrum line signals to the microprocessor for signal intensity normalization processing after analog-to-digital conversion;
s4: and the microprocessor receives the interference fringe signal and the absorption spectrum line signal in the step S3, and calculates the interference cavity length and the change value of the interference cavity length of the interferometer through a pre-calibrated time-phase relation.
7. The demodulation method of an interferometer absolute displacement demodulation system using gas absorption spectrum reference of claim 3 or 6, wherein the calibration method of the pre-calibrated time-phase relationship comprises the steps of:
S1: under the control of a sawtooth wave driving circuit, a scanning laser light source outputs a laser beam with the wavelength changing along with time in a scanning period range;
s2: in one scanning period of the scanning laser, interference reflection light of the interferometer synchronously generates interference fringes and absorption spectrum lines in the corresponding detector by arranging a gas reference gas chamber;
s3: and respectively acquiring corresponding interference fringes and working curves of absorption spectral lines changing along with time, measuring a time difference corresponding to half width of an absorption peak when only one absorption peak exists in one scanning period, obtaining a conversion relation of time-value phase wavelength values by utilizing a fixed half width value of the absorption peak under the same temperature and pressure environment condition, and determining a wavelength value corresponding to each sampling point by utilizing the central wavelength of the absorption peak to finish calibration.
8. The method for demodulating an absolute displacement demodulation system of an interferometer using a gas absorption spectrum reference as claimed in claim 7, wherein in S1 of said calibration method, a minimum wavelength scanning range of said scanning laser is such that it can cover two absorption lines simultaneously in one scanning period; in the step S3 of the calibration method, the time difference corresponding to the central wavelength of the two absorption peaks is measured, then the fixed wavelength difference of the two absorption peaks is utilized to obtain the conversion relation of the time value phase wavelength values, and then the wavelength value corresponding to each sampling point can be determined by utilizing the central wavelength of one absorption peak, so that the calibration is completed.
9. Demodulation method of an interferometer absolute displacement demodulation system using gas absorption spectrum reference as claimed in claim 3 or 6 characterised in that the method of demodulating the interferometric cavity length values and their variations is as follows:
1) Measuring the time difference of the Q point with the maximum light intensity change slope of one interference fringe relative to the wavelength center of the absorption spectrum line, obtaining a measured value of the wavelength difference of the interference fringe at the Q point relative to the wavelength center of the absorption spectrum line by utilizing the proportional relation of the time axis value obtained in the calibration process to the wavelength value, and obtaining an absolute wavelength value lambda corresponding to the Q point of the interference fringe by utilizing the known wavelength value of the absorption spectrum line and the measured wavelength difference;
2) Measuring the time difference of the Q point with the maximum light intensity change slope of one interference fringe relative to the central wavelength point of the absorption spectrum line, obtaining the measured value of the wavelength difference delta lambda corresponding to the phase value difference of the two Q points of the interference fringe or the corresponding wavelength difference when the half width of the interference fringe by utilizing the proportional relation of the time axis numerical value to the wavelength value, and reusing The absolute value of the interference cavity length L can be obtained;
3) When the interference fringe generates translation due to the change of the length of the interference cavity, measuring the time difference of the Q point with the maximum light intensity change slope of the interference fringe relative to the central point of the absorption spectrum line, converting the time axis value into the proportional relation of the wavelength value to obtain the phase change value of the Q point of the interference fringe, and utilizing The amount of change in Δl is inverted.
10. An interferometer absolute displacement demodulation device using gas absorption spectrum reference is characterized by comprising the interferometer absolute displacement demodulation system using gas absorption spectrum reference as claimed in claim 1,2, 4 or 5, wherein an adjustable laser is used as a light source, the gas absorption spectrum is used as a reference, and the absolute measurement value of the interference cavity length L of the interferometer and the measurement value of the variation delta L of the interference cavity length L are calculated through a pre-calibrated time-phase relation.
Priority Applications (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202211229340.2A CN115523948B (en) | 2022-10-09 | 2022-10-09 | Interferometer absolute displacement demodulation system and method using gas absorption spectrum reference |
| PCT/CN2022/124758 WO2024077503A1 (en) | 2022-10-09 | 2022-10-12 | Interferometer absolute-displacement demodulation system and method using gas absorption spectrum as reference |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202211229340.2A CN115523948B (en) | 2022-10-09 | 2022-10-09 | Interferometer absolute displacement demodulation system and method using gas absorption spectrum reference |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN115523948A CN115523948A (en) | 2022-12-27 |
| CN115523948B true CN115523948B (en) | 2024-08-02 |
Family
ID=84701551
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202211229340.2A Active CN115523948B (en) | 2022-10-09 | 2022-10-09 | Interferometer absolute displacement demodulation system and method using gas absorption spectrum reference |
Country Status (2)
| Country | Link |
|---|---|
| CN (1) | CN115523948B (en) |
| WO (1) | WO2024077503A1 (en) |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN118464839B (en) * | 2024-07-12 | 2024-09-17 | 安徽岑锋科技有限公司 | Multi-component gas on-line monitoring laser modulation and false alarm removing method |
Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103928834A (en) * | 2014-04-25 | 2014-07-16 | 北京交通大学 | Ultra-narrow line-width FDML ring-shaped laser based on SOA |
| AU2020103491A4 (en) * | 2020-11-17 | 2021-01-28 | Harbin Engineering University | A twin array Michelson fiber optic white light interferometry strain gauge |
Family Cites Families (13)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103181753B (en) * | 2003-10-27 | 2016-12-28 | 通用医疗公司 | For the method and apparatus using frequency-domain interferometry to carry out optical imagery |
| CN101718942B (en) * | 2009-11-25 | 2011-10-26 | 北京航空航天大学 | Multi-channel fiber Bragg grating (FBG) demodulator |
| CN102235968A (en) * | 2010-04-27 | 2011-11-09 | 清华大学 | Heterodyne interference-based optical fiber hydrogen sensing device and method |
| CN102494874B (en) * | 2011-12-08 | 2014-07-16 | 兖矿集团有限公司 | Tunable laser type fiber Bragg grating wavelength demodulation device |
| CN104931081B (en) * | 2015-06-10 | 2017-08-11 | 天津大学 | The fiber grating sensing demodulation apparatus and method referred to based on composite wavelength |
| CN105424605B (en) * | 2015-11-18 | 2018-05-01 | 安徽大学 | Photoacoustic spectrum measuring device and method based on low-coherence fiber differential interference non-contact vibration measurement |
| CN108204827A (en) * | 2016-12-16 | 2018-06-26 | 中国电子科技集团公司电子科学研究院 | A kind of phase-shifted fiber grating demodulating system |
| CN110657947B (en) * | 2019-09-03 | 2021-01-12 | 天津大学 | Optical fiber calibration method for signal splicing based on gas absorption cell |
| CN111442716B (en) * | 2020-05-19 | 2021-04-16 | 宝宇(武汉)激光技术有限公司 | Interferometric measuring device and method for introducing reference light |
| DE102020208869A1 (en) * | 2020-07-16 | 2022-01-20 | Robert Bosch Gesellschaft mit beschränkter Haftung | Sensor device, sensor system and method for operating a sensor device |
| AU2020103626A4 (en) * | 2020-11-24 | 2021-02-04 | Harbin Engineering University | An optical path autocorrelator used for distributed fiber strain sensing measurement |
| CN113791036A (en) * | 2021-07-23 | 2021-12-14 | 桂林电子科技大学 | High-speed spectral domain optical coherence tomography system based on Michelson interferometer |
| CN114062275B (en) * | 2021-11-18 | 2024-04-30 | 国网安徽省电力有限公司电力科学研究院 | Spatial domain multiplexing demodulation instrument and method for optical fiber photoacoustic sensor |
-
2022
- 2022-10-09 CN CN202211229340.2A patent/CN115523948B/en active Active
- 2022-10-12 WO PCT/CN2022/124758 patent/WO2024077503A1/en unknown
Patent Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103928834A (en) * | 2014-04-25 | 2014-07-16 | 北京交通大学 | Ultra-narrow line-width FDML ring-shaped laser based on SOA |
| AU2020103491A4 (en) * | 2020-11-17 | 2021-01-28 | Harbin Engineering University | A twin array Michelson fiber optic white light interferometry strain gauge |
Also Published As
| Publication number | Publication date |
|---|---|
| CN115523948A (en) | 2022-12-27 |
| WO2024077503A1 (en) | 2024-04-18 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| US7561276B2 (en) | Demodulation method and apparatus for fiber optic sensors | |
| CN107024236B (en) | F-P/FBG optical fiber sensor demodulation system | |
| JP3549153B2 (en) | Optical fiber interference sensor, signal processing system for optical fiber interference sensor, signal processing method, and recording medium | |
| US20040119981A1 (en) | Active Q-point stabilization for linear interferometric sensors | |
| CN109099943A (en) | Self-calibration and self-compensation type white light path matching differential interference phase demodulation system and method thereof | |
| CN105737733A (en) | Air refractive index correction method in large-range absolute distance measurement | |
| CN106940220B (en) | A kind of laser wavelength real-time measurement device of Simple low-cost | |
| CN110617875B (en) | Wavelength phase-shifting type optical fiber acoustic sensing array demodulation system and method | |
| CN115523948B (en) | Interferometer absolute displacement demodulation system and method using gas absorption spectrum reference | |
| CN104501731A (en) | Low-coherence multiplexing quasi-distribution optical fiber strain measurement system | |
| CN103697922A (en) | High-speed demodulation system of optical fiber F-P cavity sensor | |
| US4974961A (en) | Optical fibre measuring system | |
| Downs et al. | Bi-directional fringe counting interference refractometer | |
| CN116105776A (en) | Method and device for high-precision in-situ calibration and high-speed real-time demodulation of cavity length of optical fiber Fabry-Perot sensor | |
| CN204405012U (en) | The multiplexed accurate profile fiber strain measurement system of a kind of Low coherence | |
| CN105953919B (en) | A kind of all -fiber Fourier spectrum analyzer | |
| CN110118532B (en) | Dual-wavelength nonlinear displacement demodulation method and system of fiber Fabry-Perot displacement sensor | |
| AU2020103491A4 (en) | A twin array Michelson fiber optic white light interferometry strain gauge | |
| Zhang et al. | A novel digital phase detection method for frequency-modulated continuous-wave interferometric fiber-optic displacement sensor | |
| CN101592526A (en) | A kind of measuring method of average light wavelength and device | |
| AU2020103490A4 (en) | A multiplexing optical fiber interferometer and its nesting construction method | |
| Zhang et al. | A Wide Frequency Response Fabry–Pérot Acoustic Sensor Based on the Self-Stabilization System | |
| Zhan et al. | A linearity interrogation technique with enlarged dynamic range for fiber Bragg grating sensing | |
| CN205642638U (en) | Simple and easy low -cost real -time measuring device of wavelength | |
| CN110657947B (en) | Optical fiber calibration method for signal splicing based on gas absorption cell |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PB01 | Publication | ||
| PB01 | Publication | ||
| SE01 | Entry into force of request for substantive examination | ||
| SE01 | Entry into force of request for substantive examination | ||
| GR01 | Patent grant | ||
| GR01 | Patent grant |