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CN108534811A - A kind of cavity length demodulating algorithm of short cavity optical fiber Fabry-Perot sensor - Google Patents

A kind of cavity length demodulating algorithm of short cavity optical fiber Fabry-Perot sensor Download PDF

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CN108534811A
CN108534811A CN201810333281.0A CN201810333281A CN108534811A CN 108534811 A CN108534811 A CN 108534811A CN 201810333281 A CN201810333281 A CN 201810333281A CN 108534811 A CN108534811 A CN 108534811A
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signal
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sensor
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CN108534811B (en
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王伟
唐瑛
张雄星
陈海滨
王可宁
高明
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Xian Technological University
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    • G01D5/00—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable
    • G01D5/26—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light
    • G01D5/32—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light
    • G01D5/34—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells
    • G01D5/353—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells influencing the transmission properties of an optical fibre
    • G01D5/35306—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
    • 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
    • G01D5/266—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 by interferometric means
    • 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
    • G01D5/268—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 using optical fibres
    • 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
    • G01D5/28—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 deflection of beams of light, e.g. for direct optical indication
    • G01D5/30—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 deflection of beams of light, e.g. for direct optical indication the beams of light being detected by photocells

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Abstract

本发明公开了一种短腔光纤法珀传感器的腔长解调算法，属于光纤传感技术领域。其特征为采用白光光源发射的宽带光照射短腔光纤法珀传感器，并采集短腔光纤法珀传感器的反射光谱，将原始反射光谱信号沿功率谱密度图横坐标方向移动一定距离，得到新增反射光谱信号，其移动距离小于反射光谱信号的周期长度，利用椭圆拟合方法对原始光谱信号与新增光谱信号求取相位差，根据法珀腔腔长计算公式得到实际绝对腔长值。本发明解决了短腔光纤法珀传感器解调系统在获取光谱不完整时的腔长解调问题，降低了系统对光源光谱范围的要求。

The invention discloses a cavity length demodulation algorithm of a short-cavity optical fiber F-P sensor, belonging to the technical field of optical fiber sensing. It is characterized in that the broadband light emitted by the white light source is used to irradiate the short-cavity fiber optic sensor, and the reflection spectrum of the short-cavity fiber sensor is collected, and the original reflection spectrum signal is moved for a certain distance along the abscissa direction of the power spectral density diagram to obtain a new The reflected spectral signal, whose moving distance is less than the period length of the reflected spectral signal, uses the ellipse fitting method to obtain the phase difference between the original spectral signal and the newly added spectral signal, and obtains the actual absolute cavity length value according to the formula for calculating the cavity length of the Farpert cavity. The invention solves the cavity length demodulation problem of the short-cavity optical fiber FAP sensor demodulation system when the acquired spectrum is incomplete, and reduces the requirement of the system on the spectrum range of the light source.

Description

A kind of cavity length demodulating algorithm of short cavity optical fiber Fabry-Perot sensor
Technical field
The invention belongs to technical field of optical fiber sensing, and in particular to a kind of cavity length demodulating calculation of short cavity optical fiber Fabry-Perot sensor Method.
Background technology
Optical fiber Fabry-Perot sensor is a kind of important type in phase type fibre optical sensor, outside this fiber optic transducer Shape is small and exquisite, is easy to make, and compared to homogeneous e sensor, has small, light-weight, high sensitivity, not by electromagnetic interference Influence, can remote sensing the advantages that.Due to the various selectable property of Fa-Po cavity material, fibre optical sensor is applicable to high temperature, height In the severe industry and military environments such as pressure, extensive chemical corrosion and strong electromagnetic, the measurement of such as deep oily down-hole pressure and temperature, Bridge, the health monitoring of dam, the health monitoring etc. of the sonic detection of nuclear blast experimental field, large-scale power and energy device, It can also be applied to the internal pressure measurement etc. of biomedical sector.
Fabry-perot optical fiber sensor-based system is divided into sensor and demodulating system two parts.Cavity length demodulating is the pass of entire demodulating system It builds, directly affects the performances such as demodulation accuracy, the stability of system.The demodulation method being currently mainly used has：Phase demodulating and strong Degree demodulation.Have the speed of response fast compared with the intensity demodulation method early used, it is simple in structure, it is at low cost the advantages that, but due to light The fluctuation of source luminous power and light have the influence compared with lossy in a fiber, cause demodulation accuracy low.
Currently, using it is relatively broad be Fourier transformation method in phase demodulating method.The method has dynamic range Greatly, not by effect of phase noise the advantages of.But due to itself existing fence effect in Fourier transformation method, block effective letter Point is ceased, frequency resolution is lowered.It improves frequency resolution and only increases sampling number, improve spectral measurement ranges and solve, It is not particularly suited for the cavity length demodulating of the relatively narrow method amber sensor-based system of light source light spectrum.Correlation method demodulation in phase method demodulation, is compared The requirement of spectral measurement ranges is reduced in Fourier transformation method, but requires the presence of complete week in surveyed spectral region simultaneously The signal of phase.Fabry-Perot sensor of the chamber length less than 30 μm belongs to the long Fabry-Perot sensor of short cavity, is sensed with the method amber of 20 μm of chamber length For device, when ASE light source center wavelength is 1550nm, it is computed to obtain spacing between the two neighboring peak of reflectance spectrum signal About 62nm, and ASE light source light spectrum width is commonly 40nm or so, is unable to get the spectral signal of complete cycle, cannot use Correlation method resolves.
In the related technology such as a kind of " cavity length demodulating algorithm of fibre-optical F-P sensor " (patent No.：1831485 A of CN) in, Propose a kind of quality evaluating method that mean square error is sub to F-P sensing head cavity length estimations.Make in the embodiment that patent is provided Light source range is 80nm, and spectral sequence length is 2000, a length of 303.9 μm of surveyed average cavity.It is computed, the light captured At least 1 complete spectral period in spectrum, and desired sampling number is more.In a kind of " extrinsic type optical fiber Fabry amber Sieve cavity length demodulating method " (patent No.：103697923 A of CN) in propose a kind of multi-wavelength intensity demodulation method, be directed to 100 μm or more of cavity length demodulating, and need the laser of multiple and different wavelength as the multiple return intensity values of light source measurement.From upper It states in known document, incomplete spectrum is demodulated using spectroscopic methodology to obtain the side of chamber length without being directed in solution demodulating system Method and the low scheme of cavity length demodulating precision in the case of this.
Invention content
The object of the present invention is to provide a kind of cavity length demodulating algorithms of short cavity optical fiber Fabry-Perot sensor, to overcome the prior art It is existing that spectroscopic methodology can not be used to be demodulated to obtain the problem that chamber is long and cavity length demodulating precision is low for incomplete spectrum, simultaneously It solves the problems, such as to require light source broader bandwidth.
The technical solution adopted in the present invention is：
A kind of cavity length demodulating algorithm of short cavity optical fiber Fabry-Perot sensor, it is characterised in that：
The algorithmic procedure is：
The reflectance spectrum for acquiring short cavity optical fiber Fabry-Perot sensor, by primary reflection spectral signal along the horizontal seat of power spectral density plot Mark direction moves a certain distance, and obtains newly-increased reflectance spectrum signal, and displacement distance is less than the cycle length of reflectance spectrum signal, Phase difference is sought to original spectrum signal and newly-increased spectral signal using ellipse fitting method, according to the long calculation formula of Fa-Po cavity chamber Obtain practical absolutely chamber long value.
A kind of cavity length demodulating algorithm of the short cavity optical fiber Fabry-Perot sensor, it is characterised in that：
Include the following steps：
Step 1：Wavelength-frequency-domain transform：It is anti-to the acquired short cavity optical fiber Fabry-Perot sensor of spectroanalysis instrument in demodulating system The spectroscopic data for penetrating spectrum carries out transformation of the wavelength domain to frequency domain, i.e., by power spectral density plot abscissa by formula f=c/ λ Frequency of light wave f is converted to by optical wavelength λ, obtains periodic frequency domain power spectrum density figure, in formula, c is vacuum light speed；
Step 2：Calculate the amount of bias m of spectral signalx, that is, calculate the maximum S (f) of spectral signal relative intensitymaxWith pole The S (f) of small valueminMean value；Formula is：
mx=(S (f)max-S(f)min)/2
Step 3：Simplified ellipse fitting equation is established in coordinate transform, by the way that reflectance spectrum signal S (f) is prolonged f axis directions Translation distance τ obtains amplitude, the identical two signal s (f) of angular frequency and s (f+ τ), and wherein τ is less than the period of s (f)；By two For the relative intensity value of signal respectively as the transverse and longitudinal coordinate axis of Lie groupoid figure, the Lie groupoid figure drawn is ellipse, ellipse Round long axis or short axle and XY coordinate system X-axis angles are always 45 °, and coordinate system is rotated to 45 ° counterclockwise and obtains new coordinate system For X'Y' coordinate systems, and ellipse is translated to the coordinate origin direction of X'Y'Elliptical focus F at this time1With F2On X' axis and about origin symmetry, it is (x to enable the coordinate of n point on ellipsei',yi'), elliptic equation is：
Step 4：Using least square solution overdetermination equation group, related coefficient is obtained；The elliptic equation obtained according to step 3 Establish system of linear equations AX=1；I.e. matrix form is as follows：
According to the algorithm of overdetermination solving equations, related coefficient a, b are acquired；
Step 5：Judge whether amount of bias is suitable：Ellipse fitting equation is obtained according to step 4 back substitution related coefficient a, b, it should The residual standard deviation of equation is S, judges whether S meets threshold value Sm (0<Sm<1)；If being unsatisfactory for requiring, calculated in above-mentioned steps 2 To mxOn the basis of new m is obtained as unit of step-length 0.1x, execute step 3 and step 4 execute step after meeting threshold value Sm 6 and step 7；
Step 6：By the ratio of related coefficient, phase difference and the signal period of signal are sought：Related coefficient a, b are elliptical Major semiaxis a and semi-minor axis b；Therefore phase differenceIt is represented by：
The signal period is obtained according to the relationship in phase difference and period：
Step 7：According to the long calculation formula of chamberObtain Fabry-Perot-type cavity chamber long value.
The present invention has the following advantages：
1, the present invention uses Lie groupoid innovatory algorithm, and Fa-Po cavity can be resolved by not needing the spectral signal of complete cycle Chamber long value.The present invention solves the fence effect occurred in Fourier transformation, reduces frequency resolution, shortens spectral measurement model It encloses.Long suitable for short cavity, spectral period is big, the period incomplete spectral signal demodulation in shorter spectral range, reduces pair The requirement of light source bandwidth.
2, present invention introduces coordinate conversion and two concepts of residual standard deviation, in two same frequencys with the signal fitting of amplitude It is elliptical Lie groupoid figure to go out figure, and long axis or the angle of short axle and abscissa are always specific 45 °.Utilize coordinate 45 ° of conversion rotation is judged and is searched using residual standard deviation concept unique suitable signal amount of bias, further converts ellipse At elliptical center in the positive ellipse of coordinate origin, it converts the elliptic equation of general 6 parameter to two-parameter elliptic equation, simplifies The foundation of elliptic equation obtains accurate related coefficient a, b.
3, by the chamber long value that Fa-Po cavity is calculated of phase, phase resolution changes more than frequency resolution in demodulation Soon, absolute chamber long value at this very moment can be more accurately reflected, using the present invention, demodulation accuracy is significantly improved, reachable To 1nm.
Description of the drawings
Fig. 1 is the structural schematic diagram of the embodiment of the present invention.
Fig. 2 is the operational flowchart of the embodiment of the present invention.
Fig. 3 is the signal graph for transforming to the biasing of frequency domain band.
Fig. 4 is the Lie groupoid figure of signal S (f) and signal S (f+ τ).
Fig. 5 is the Lie groupoid figure after coordinate transform and translation.
Specific implementation mode
The present invention will be described in detail With reference to embodiment.
To make the objectives, technical solutions, and advantages of the present invention clearer, below in conjunction with attached drawing to the present invention make into It is described in detail to one step, it is clear that described embodiments are only a part of the embodiments of the present invention, rather than whole implementation Example.Based on the embodiments of the present invention, obtained by those of ordinary skill in the art without making creative efforts All other embodiment, shall fall within the protection scope of the present invention.
A kind of cavity length demodulating algorithm of short cavity optical fiber Fabry-Perot sensor, using ellipse fitting method to the short of spectrometer collection Chamber optical fiber Fabry-Perot sensor reflectance spectrum carries out high-precision absolute chamber long value demodulation, it is characterised in that：Acquire short cavity Fiber Optic Sensor Reflectance spectrum signal S (f) is prolonged the spectral signal S after f axis direction translation distances τ is translated by the reflectance spectrum of amber sensor (f+ τ) seeks phase difference using ellipse fitting method to spectral signal S (f) and spectral signal S (f+ τ), long according to Fa-Po cavity chamber Calculation formula obtains practical absolutely chamber long value.The relatively narrow high-resolution cavity length demodulating of spectral region is realized, to obtain resolution ratio Higher measurand information.
A kind of the embodiment of the present invention is described below：
Fig. 1, which gives, is suitable for measuring the measuring system that Fa-Po cavity chamber is grown, the broadband light that ASE white light sources emit in system Short cavity optical fiber Fabry-Perot sensor is irradiated by optical circulators, reflected light is emitted by 3 port of optical circulators will by spectrometer Optical signal is converted to electric signal, then is acquired signal by demodulator circuit and grown into an actor's rendering of an operatic tune using the program that inventive algorithm is write and solved It calculates, host computer shows calculation result.Select ASE white lights wideband light source as system source, the spectral region of light source is 1524nm- 1570nm, centre wavelength：1550nm.By taking chamber grows 20 μm of short cavity optical fiber Fabry-Perot sensor as an example, the phase of reflectance spectrum signal It is spaced about 62nm between adjacent two peaks, with this systematic survey, cannot completely obtain a cycle.
Referring to Fig. 2, a kind of cavity length demodulating algorithm of short cavity optical fiber Fabry-Perot sensor, using ellipse fitting method to spectrometer The short cavity optical fiber Fabry-Perot sensor reflectance spectrum of acquisition carries out high-precision absolute chamber long value demodulation, it is characterised in that：It acquires short The reflectance spectrum of chamber optical fiber Fabry-Perot sensor moves primary reflection spectral signal centainly along power spectral density plot abscissa direction Distance, obtains newly-increased reflectance spectrum signal, and displacement distance is less than the cycle length of reflectance spectrum signal, utilizes ellipse fitting side Method seeks phase difference to original spectrum letter with newly-increased spectral signal, and it is long to obtain practical absolutely chamber according to the long calculation formula of Fa-Po cavity chamber Value.The relatively narrow high-resolution cavity length demodulating of spectral region is realized, to obtain the higher measurand information of resolution ratio.
It is as follows：
Step 1：Wavelength-frequency-domain transform, it is anti-to the acquired short cavity optical fiber Fabry-Perot sensor of spectroanalysis instrument in demodulating system The spectroscopic data of spectrum is penetrated, i.e., distribution relation of the power spectral density about optical wavelength in power spectral density plot passes through formula f= C/ λ carry out wavelength domain to the transformation of frequency domain, i.e., power spectral density plot abscissa are converted to frequency of light wave f by optical wavelength λ, obtained To periodic frequency domain power spectrum density figure, in formula, c is vacuum light speed.
Step 2：Calculate the amount of bias m of spectral signalx, that is, calculate the maximum S (f) of spectral signal relative intensitymaxWith pole The S (f) of small valueminMean value；Formula is：
mx=(S (f)max-S(f)min)/2
Step 3：Simplified ellipse fitting equation is established in coordinate transform, by the way that reflectance spectrum signal S (f) is prolonged f axis directions Translation distance τ obtains amplitude, the identical two signal s (f) of angular frequency and s (f+ τ), and wherein τ is less than the period of s (f).By two For the relative intensity value of signal respectively as the transverse and longitudinal coordinate axis of Lie groupoid figure, the Lie groupoid figure drawn is ellipse, Long axis and XY coordinate system X-axis angles are 45 °, and it is X'Y' coordinate systems, XY that coordinate system is rotated to 45 ° counterclockwise to obtain new coordinate system Coordinate transformation relation in coordinate system and X'Y' coordinate systems is：
Ellipse is translated to the coordinate origin direction of X'Y' simultaneouslyElliptical focus F at this time1And F2 On X' axis and about origin symmetry, it is (x to enable the coordinate of n point on ellipsei',yi'), elliptic equation is：
Step 4：Using least square solution overdetermination equation group, related coefficient is obtained.The elliptic equation obtained according to step 3 Establish system of linear equations AX=1；I.e. matrix form is as follows：
According to the algorithm of overdetermination solving equations, related coefficient a, b are acquired.
Step 5：Judge whether amount of bias is suitable：Ellipse fitting equation is obtained according to step 4 back substitution related coefficient a, b, it should The residual standard deviation of equation is S, and surplus standard deviation S is represented by：
Judge whether S meets threshold value Sm (0<Sm<1)；If being unsatisfactory for requiring, m is calculated in above-mentioned steps 2xOn the basis of New m is obtained as unit of step-length 0.1x, execute step 3 and step 4 execute step 6 and step 7 after meeting threshold value Sm；
Step 6：By the ratio of related coefficient, phase difference and the signal period of signal are sought：Related coefficient a, b are elliptical Major semiaxis a and semi-minor axis b, therefore phase differenceIt is represented by：
The signal period obtained according to the relationship of phase difference and period is represented by：
Step 7：According to the long calculation formula of chamberObtain Fabry-Perot-type cavity chamber long value.
Referring to Fig. 3, the original signal with biasing is given in figure, and amount of bias m is obtained by estimationxIt is 105.Original signal For S (f), the signal after translation is S (f+ τ), wherein τ=600GHz.Draw the Lie groupoid of signal S (f) and signal S (f+ τ) Figure (Fig. 4), is converted using coordinate, and figure is transformed into from XY coordinate systems under X'Y' coordinate systems, and flat to coordinate origin direction It movesIt obtains positive oval (Fig. 5).Coordinate conversion of the Lie groupoid figure from Fig. 4 to Fig. 5, realizes the letter for establishing elliptic equation Change, and establishes the elliptic equation containing 2 unknown quantitys：
It establishes super positive definite equation group and acquires a, b.It brings elliptic equation into, acquires surplus standard deviation S=0.172, be more than threshold value The requirement of Sm=0.05.As unit of step-length 0.1, increase the value of amount of bias, when being computed m=110, surplus standard deviation S= 0.0300, it is less than the requirement of threshold value 0.05.The bias of m=110 signals thus at this time.And then acquire phase differenceCycle T=7503, L=19.992 μm of chamber long value.
Present disclosure is not limited to cited by embodiment, and those of ordinary skill in the art are by reading description of the invention And to any equivalent transformation that technical solution of the present invention is taken, it is that claim of the invention is covered.

Claims (2)

1.一种短腔光纤法珀传感器的腔长解调算法，其特征在于：1. A cavity length demodulation algorithm of a short-cavity fiber optic sensor, characterized in that: 所述算法过程是：The algorithm process is: 采集短腔光纤法珀传感器的反射光谱，将原始反射光谱信号沿功率谱密度图横坐标方向移动一定距离，得到新增反射光谱信号，其移动距离小于反射光谱信号的周期长度，利用椭圆拟合方法对原始光谱信号与新增光谱信号求取相位差，根据法珀腔腔长计算公式得到实际绝对腔长值。Collect the reflection spectrum of the short-cavity fiber-optic F-P sensor, move the original reflection spectrum signal a certain distance along the abscissa direction of the power spectral density graph, and obtain a new reflection spectrum signal, whose moving distance is less than the period length of the reflection spectrum signal, and use ellipse fitting Methods The phase difference between the original spectral signal and the newly added spectral signal was obtained, and the actual absolute cavity length was obtained according to the formula for calculating the cavity length of the Faper cavity. 2.根据权利要求1所述的一种短腔光纤法珀传感器的腔长解调算法，其特征在于：2. the cavity length demodulation algorithm of a kind of short-cavity optical fiber Fabry sensor according to claim 1, is characterized in that: 包括如下步骤：Including the following steps: 步骤1：波长-频域变换：对解调系统中光谱分析仪所采集短腔光纤法珀传感器反射光谱的光谱数据，通过公式f＝c/λ进行波长域到频域的变换，即将功率谱密度图横坐标由光波波长λ转换为光波频率f，得到周期性的频域功率谱密度图，式中，c为真空光速；Step 1: Wavelength-frequency domain conversion: For the spectral data of the reflection spectrum of the short-cavity fiber optic F-P sensor collected by the spectrum analyzer in the demodulation system, the conversion from the wavelength domain to the frequency domain is performed by the formula f=c/λ, that is, the power spectrum The abscissa of the density diagram is converted from the light wave wavelength λ to the light wave frequency f to obtain a periodic frequency domain power spectral density map, where c is the speed of light in vacuum; 步骤2：计算光谱信号的偏置量mx，即计算光谱信号相对强度的极大值S(f)max与极小值的S(f)min均值；公式为：Step 2: Calculate the offset m x of the spectral signal, that is, calculate the mean value of the maximum value S(f) max and the minimum value S(f) min of the relative intensity of the spectral signal; the formula is: mx＝(S(f)max-S(f)min)/2m x ＝(S(f) max -S(f) min )/2 步骤3：坐标变换，建立简化的椭圆拟合方程，通过将反射光谱信号S(f)延f轴方向平移距离τ得到幅值，角频率相同的两个信号s(f)和s(f+τ)，其中τ小于s(f)的周期；将两个信号的相对强度值分别作为李萨如图图形的横纵坐标轴，绘出的李萨如图图形为椭圆，椭圆的长轴或短轴与XY坐标系X轴夹角始终为45°，将坐标系逆时针旋转45°得到新的坐标系为X'Y'坐标系，并将椭圆向X'Y'的坐标原点方向平移此时椭圆的焦点F1和F2在X'轴上且关于原点对称，令椭圆上的n个点的坐标为(x′i,y′i)，其椭圆方程为：Step 3: Coordinate transformation, establish a simplified ellipse fitting equation, obtain the amplitude by shifting the reflected spectral signal S(f) along the f-axis direction by a distance τ, and the two signals s(f) and s(f+ τ), where τ is less than the period of s(f); the relative intensity values of the two signals are respectively used as the horizontal and vertical coordinate axes of the Lissajous figure graph, and the drawn Lissajous figure graph is an ellipse, and the long axis of the ellipse or The angle between the minor axis and the X-axis of the XY coordinate system is always 45°. Rotate the coordinate system 45° counterclockwise to obtain a new coordinate system as the X'Y' coordinate system, and translate the ellipse toward the origin of the X'Y' coordinates At this time, the focal points F 1 and F 2 of the ellipse are on the X' axis and are symmetrical about the origin. Let the coordinates of n points on the ellipse be (x′ i , y′ i ), and the ellipse equation is: 步骤4：利用最小二乘法解超定性方程组，得相关系数；依据步骤3得到的椭圆方程建立线性方程组AX＝1；即矩阵形式如下：Step 4: Utilize the least squares method to solve the overdetermined equations to obtain correlation coefficients; establish the linear equations AX=1 according to the elliptic equation obtained in step 3; that is, the matrix form is as follows: 根据超定性方程组求解的算法，求得相关系数a,b；According to the algorithm for solving overdeterministic equations, the correlation coefficients a and b are obtained; 步骤5：判断偏置量是否合适：根据步骤4回代相关系数a、b得到椭圆拟合方程，该方程的剩余标准差为S，判断S是否满足阈值Sm(0<Sm<1)；若不满足要求，在上述步骤2计算得到mx的基础上以步长0.1为单位得到新的mx，执行步骤3和步骤4直到满足阈值Sm后执行步骤6和步骤7；Step 5: Judging whether the offset is appropriate: obtain the ellipse fitting equation according to step 4 by substituting the correlation coefficients a and b, the remaining standard deviation of the equation is S, and judging whether S satisfies the threshold Sm (0<Sm<1); If the requirements are not met, on the basis of the m x calculated in the above step 2, a new m x is obtained with a step size of 0.1, and step 3 and step 4 are performed until the threshold Sm is met, and then step 6 and step 7 are performed; 步骤6：由相关系数的比值，求取信号的相位差及信号周期：相关系数a,b为椭圆的长半轴a和短半轴b；因此相位差可表示为：Step 6: Calculate the phase difference and signal period of the signal from the ratio of the correlation coefficient: the correlation coefficient a and b are the major semi-axis a and the minor semi-axis b of the ellipse; therefore the phase difference Can be expressed as: 根据相位差和周期的关系得到信号周期：According to the relationship between the phase difference and the period, the signal period is obtained: 步骤7：依据腔长计算公式得到法布里-珀罗腔腔长值。Step 7: According to the cavity length calculation formula Get the Fabry-Perot cavity length value.
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