CN106643835B - Optical fiber Fabry-Perot cavity demodulation method and device and optical fiber Fabry-Perot interferometer - Google Patents
Optical fiber Fabry-Perot cavity demodulation method and device and optical fiber Fabry-Perot interferometer Download PDFInfo
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- CN106643835B CN106643835B CN201510740349.3A CN201510740349A CN106643835B CN 106643835 B CN106643835 B CN 106643835B CN 201510740349 A CN201510740349 A CN 201510740349A CN 106643835 B CN106643835 B CN 106643835B
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- 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
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Abstract
The invention discloses a demodulation method and a device of an optical fiber Fabry-Perot cavity and an optical fiber Fabry-Perot interferometer, wherein the demodulation method of the optical fiber Fabry-Perot cavity comprises the following steps: acquiring a spectrum signal of an interference optical fiber Fabry-Perot cavity; performing first demodulation on the spectrum signal by adopting unequal distance Fourier transform to obtain a first cavity length value of the optical fiber Fabry-Perot cavity, wherein the precision of the first cavity length value is greater than a first threshold value, and half-wave jump cannot occur in cavity length demodulation of the optical fiber Fabry-Perot cavity when the precision of the first cavity length value is greater than the first threshold value; and carrying out second demodulation on the spectrum signal according to the first cavity length value to obtain a second cavity length value of the optical fiber Fabry-Perot cavity, wherein the precision of the second cavity length value is greater than that of the first cavity length value. The invention solves the problem of low cavity length demodulation precision of the optical fiber Fabry-Perot cavity in the related technology, and further achieves the effect of improving the cavity length demodulation precision of the optical fiber Fabry-Perot cavity.
Description
Technical field
The present invention relates to Fabry-perot optical fiber interferometer fields, in particular to a kind of Fabry-perot optical fiber chamber demodulation method and dress
It sets and Fabry-perot optical fiber interferometer.
Background technique
Fabry-perot optical fiber interferometer (i.e. Fiber-optical Fabry-Perot Interferometric Cavity, referred to as optical fiber FP interferometer), as a kind of light
Fiber sensor part, since the advantages that production is simple, and stability is good, and precision is high is widely used to various components or environment measuring.
According to the actual application, in conjunction with different encapsulation, optical fiber FP interferometer can become temperature sensor, pressure transducer, stress/answer
Become sensor and vibrating sensor etc..Since the change of respective environment parameter (such as temperature, pressure, strain) will lead to FP chamber chamber
Long variation, therefore it is long by interference spectrum to demodulate chamber, can obtain metrical information to be checked.
The major way of FP chamber demodulation has intensity demodulation and phase demodulating, and intensity demodulation is the technology used earliest, simply
Easy but error is larger, and what is be currently mainly used is the higher phase demodulating of precision.For wide range optical interface fiber FP chamber, commonly use
Spectral analysis method have Fringe-counting method, Wavelength-tracking method, the improvement of fourier transform method and approximating method and these methods
And combination.Fringe-counting method obtains the long absolute value of chamber according to the relationship of fringe period and wavelength, but precision is very low；Wave
Long tracing precision is relatively high, but the dynamic range of only half-wavelength, and there are half-wave jumps, wherein half-wave, which jumps, is
Refer to the deviation for causing the chamber long value demodulated and true value to have half wavelength due to algorithm factor；Fourier transform method will
Periodic signal transforms to its frequency domain, that is, corresponds to chamber long message, but its error is not also small.Approximating method passes through the accurate solution of building
Mode transfer type, scanning construction signal and actual signal, the long output of chamber when obtaining closest to actual signal, approximating method mainly have phase
Pass method and least square method etc., this kind of demodulation method can reach sub-nanometer precision, but the big speed of operand is slower, and can also go out
Existing half-wave hopping phenomenon, influences cavity length demodulating precision.
For the not high problem of Fabry-perot optical fiber chamber cavity length demodulating precision in the related technology, effective solution is not yet proposed at present
Scheme.
Summary of the invention
The main purpose of the present invention is to provide a kind of Fabry-perot optical fiber chamber demodulation method and device and Fabry-perot optical fiber interferometer,
To solve the problems, such as that Fabry-perot optical fiber chamber cavity length demodulating precision is not high in the related technology.
To achieve the goals above, according to an aspect of the invention, there is provided a kind of Fabry-perot optical fiber chamber demodulation method.
Fabry-perot optical fiber chamber demodulation method according to the present invention includes: the spectral signal for obtaining interference optical fiber Fa-Po cavity；Using
The discrete Fourier transform pairs spectral signal of Unequal distance carries out the first demodulation, obtains the first chamber long value of Fabry-perot optical fiber chamber, wherein the
The precision of one chamber long value is greater than first threshold, the long solution of the chamber of Fabry-perot optical fiber chamber when the precision of the first chamber long value is greater than first threshold
Tune is not in half-wave jump；And the second demodulation is carried out to spectral signal according to the first chamber long value, obtain Fabry-perot optical fiber chamber
Second chamber long value, wherein the precision of the second chamber long value is greater than the precision of the first chamber long value.
Further, the first demodulation is carried out to spectral signal, the first chamber long value for obtaining Fabry-perot optical fiber chamber includes: using not
Equidistant discrete Fourier transform pairs spectral signal carries out the first demodulation, obtains the first chamber long value of Fabry-perot optical fiber chamber.
Further, the first demodulation is being carried out using the discrete Fourier transform pairs spectral signal of Unequal distance, is obtaining Fiber Optic Sensor
Before first chamber long value of amber chamber, method further include: spectral signal is multiplied with window function, obtains the first spectral signal, uses
It includes: using the discrete Fourier transform pairs first of Unequal distance that the discrete Fourier transform pairs spectral signal of Unequal distance, which carries out the first demodulation,
Spectral signal carries out the first demodulation, obtains the first chamber long value of Fabry-perot optical fiber chamber.
Further, the second demodulation is carried out to spectral signal according to the first chamber long value, obtains the second chamber of Fabry-perot optical fiber chamber
Long value includes: the construction signal for obtaining spectral signal；Spectral signal is calculated according to the first chamber long value and constructs the minimum of signal
Estimate of variance；And the second chamber long value of Fabry-perot optical fiber chamber is determined according to nonlinear IEM model value.
Further, include: according to the nonlinear IEM model value that the first chamber long value calculates spectral signal and constructs signal
Obtain the first step-length；Scanning range is determined according to the first chamber long value and the first step-length；Obtain the second step-length, wherein the second step-length
Less than the first step-length；Every the long progress value of second step out of scanning range, multiple values are obtained；Respectively according to multiple value meters
It calculates spectral signal and constructs the mean square deviation estimated value of signal, obtain multiple mean square deviation estimated values；Obtain multiple mean square deviation estimated values
In the smallest mean square deviation estimated value as nonlinear IEM model value.
Further, method further include: judge whether the second step-length is greater than second threshold；It is greater than judging that second step is long
When second threshold, continue to obtain third step-length, wherein third step-length is less than the second step-length；According in multiple mean square deviation estimated values
The smallest mean square deviation estimated value determines the third chamber long value of Fabry-perot optical fiber chamber；And it is determined according to third chamber long value and the second step-length
Scanning range, wherein every the long progress value of third step out of scanning range.
To achieve the goals above, according to another aspect of the present invention, a kind of Fabry-perot optical fiber chamber demodulating equipment is provided.It should
Fabry-perot optical fiber chamber demodulating equipment includes: first acquisition unit, for obtaining the spectral signal of interference optical fiber Fa-Po cavity；First demodulation
Unit obtains the first of Fabry-perot optical fiber chamber for carrying out the first demodulation using the discrete Fourier transform pairs spectral signal of Unequal distance
Chamber long value, wherein the precision of the first chamber long value is greater than first threshold, the optical fiber when the precision of the first chamber long value is greater than first threshold
The cavity length demodulating of Fa-Po cavity is not in half-wave jump；And second demodulating unit, for being believed according to the first chamber long value spectrum
Number carry out second demodulation, obtain the second chamber long value of Fabry-perot optical fiber chamber, wherein the precision of the second chamber long value be greater than the first chamber long value
Precision.
Further, the first demodulating unit is used to carry out the first solution using the discrete Fourier transform pairs spectral signal of Unequal distance
It adjusts, obtains the first chamber long value of Fabry-perot optical fiber chamber.
Further, device further include: arithmetic element obtains the first spectrum for spectral signal to be multiplied with window function
Signal, the first demodulating unit are used to carry out the first demodulation using discrete the first spectral signal of Fourier transform pairs of Unequal distance, obtain
First chamber long value of Fabry-perot optical fiber chamber.
Further, the second demodulating unit includes: acquisition module, for obtaining the construction signal of spectral signal；Calculate mould
Block, for calculating spectral signal according to the first chamber long value and constructing the nonlinear IEM model value of signal；And determining module, it uses
In the second chamber long value for determining Fabry-perot optical fiber chamber according to nonlinear IEM model value.
Further, computing module includes: the first acquisition submodule, for obtaining the first step-length；First determines submodule,
For determining scanning range according to the first chamber long value and the first step-length；Second acquisition submodule, for obtaining the second step-length,
In, the second step-length is less than the first step-length；Value submodule, for, every the long progress value of second step, being obtained out of scanning range
Multiple values；Computational submodule, for respectively according to multiple exploitation spectral signals and construction signal mean square deviation estimated value,
Obtain multiple mean square deviation estimated values；The smallest mean square deviation estimated value in multiple mean square deviation estimated values is obtained to estimate as Minimum Mean Square Error
Evaluation.
Further, device further include: judging unit, for judging whether the second step-length is greater than second threshold；Second obtains
Unit is taken, for obtaining third step-length, wherein third step-length is less than second when judging that second step length is greater than second threshold
Step-length；First determination unit, for determining Fabry-perot optical fiber chamber according to mean square deviation estimated value the smallest in multiple mean square deviation estimated values
Third chamber long value；And second determination unit, for determining scanning range according to third chamber long value and the second step-length, wherein
Every the long progress value of third step out of scanning range.
According to a further aspect of the invention, a kind of Fabry-perot optical fiber interferometer is provided, Fabry-perot optical fiber interferometer includes upper
State any one Fabry-perot optical fiber chamber demodulating equipment.
Through the invention, using the spectral signal for obtaining interference optical fiber Fa-Po cavity；Using Unequal distance discrete Fourier transform
First demodulation is carried out to spectral signal, obtains the first chamber long value of Fabry-perot optical fiber chamber, wherein the precision of the first chamber long value is greater than the
One threshold value, when the precision of the first chamber long value is greater than first threshold, the cavity length demodulating of Fabry-perot optical fiber chamber is not in half-wave jump；
And the second demodulation is carried out to spectral signal according to the first chamber long value, obtain the second chamber long value of Fabry-perot optical fiber chamber, wherein second
The precision of chamber long value is greater than the precision of the first chamber long value, and it is not high to solve Fabry-perot optical fiber chamber cavity length demodulating precision in the related technology
Problem, and then achieved the effect that improve Fabry-perot optical fiber chamber cavity length demodulating precision.
Detailed description of the invention
The attached drawing constituted part of this application is used to provide further understanding of the present invention, schematic reality of the invention
It applies example and its explanation is used to explain the present invention, do not constitute improper limitations of the present invention.In the accompanying drawings:
Fig. 1 is the flow chart of Fabry-perot optical fiber chamber demodulation method according to an embodiment of the present invention；
Fig. 2 is the schematic diagram of three kinds of Fourier transform spectrums according to an embodiment of the present invention；
Fig. 3 is the test macro schematic diagram of Fabry-perot optical fiber cavity pressure sensor according to an embodiment of the present invention；
Fig. 4 is the calibration curve figure of Fabry-perot optical fiber cavity pressure sensor according to an embodiment of the present invention；And
Fig. 5 is the schematic diagram of Fabry-perot optical fiber chamber demodulating equipment according to an embodiment of the present invention.
Specific embodiment
It should be noted that in the absence of conflict, the features in the embodiments and the embodiments of the present application can phase
Mutually combination.The present invention will be described in detail below with reference to the accompanying drawings and embodiments.
In order to make those skilled in the art more fully understand application scheme, below in conjunction in the embodiment of the present application
Attached drawing, the technical scheme in the embodiment of the application is clearly and completely described, it is clear that described embodiment is only
The embodiment of the application a part, instead of all the embodiments.Based on the embodiment in the application, ordinary skill people
Member's every other embodiment obtained without making creative work, all should belong to the model of the application protection
It encloses.
It should be noted that the description and claims of this application and term " first " in above-mentioned attached drawing, "
Two " etc. be to be used to distinguish similar objects, without being used to describe a particular order or precedence order.It should be understood that using in this way
Data be interchangeable under appropriate circumstances, so as to embodiments herein described herein.In addition, term " includes " and " tool
Have " and their any deformation, it is intended that cover it is non-exclusive include, for example, containing a series of steps or units
Process, method, system, product or equipment those of are not necessarily limited to be clearly listed step or unit, but may include without clear
Other step or units listing to Chu or intrinsic for these process, methods, product or equipment.
The embodiment of the invention provides a kind of Fabry-perot optical fiber chamber demodulation method, Fig. 1 is optical fiber according to an embodiment of the present invention
The flow chart of Fa-Po cavity demodulation method.
As shown in Figure 1, this method includes the following steps, namely S102 to step S106:
Step S102: the spectral signal of interference optical fiber Fa-Po cavity is obtained.
After using wide range optical interface fiber Fa-Po cavity, the wide range interference of light can be obtained by spectrometer or (FBG) demodulator
The spectral signal that Fabry-perot optical fiber chamber obtains, specifically, spectral signal can be the interference that wide range optical interface fiber Fa-Po cavity obtains
Striped.The chamber of spectral signal and Fabry-perot optical fiber chamber is long, and there are one-to-one relationships, can be obtained by demodulating the spectral signal
Chamber to Fabry-perot optical fiber chamber is long.
Step S104: the first demodulation is carried out using the discrete Fourier transform pairs spectral signal of Unequal distance, obtains Fabry-perot optical fiber
First chamber long value of chamber, wherein the precision of the first chamber long value is greater than first threshold, is greater than the first threshold in the precision of the first chamber long value
The cavity length demodulating of Fabry-perot optical fiber chamber is not in half-wave jump when value.
Pre-demodulating (the i.e. first demodulation) is carried out to spectral signal, obtains estimating chamber long value (i.e. the first chamber long value).Pre-demodulating
Be in order to it is subsequent to spectral signal carry out essence demodulation prepare, it is therefore, not high to the required precision for estimating chamber long value, estimate chamber
The precision of long value need to only meet greater than first threshold, and first threshold is the accuracy value reached needed for half-wave can be inhibited to jump, tool
Body, first threshold can be set to quarter-wave.
Specifically, the embodiment of the present invention carries out the first demodulation using the discrete Fourier transform pairs spectral signal of Unequal distance, obtains
To the first chamber long value of Fabry-perot optical fiber chamber.
In field of signal processing, Fourier transformation is usually used in time-domain signal being transformed to frequency-region signal analyzing.In benefit
When carrying out spectral signal analysis with Fourier transformation, since the spectral signal obtained from spectrometer or (FBG) demodulator is generally directed to wave
Long equidistant (i.e. wave number perhaps frequency unequal spacing) and directly usually required between wave number or frequency etc. using Fourier transformation
Away from spectrum, the error of the chamber long value of the Fabry-perot optical fiber chamber otherwise measured is larger, is in the prior art usually by original spectrum signal
Difference to frequency it is equidistant after carry out Fourier transformation again, but error can be introduced because original spectrum signal is changed in this way, this
Outside, it when single frames spectral signature data point (i.e. the length of a frame spectrum number) is insufficient, is obtained using Fast Fourier Transform (FFT)
Characteristic peak points are less, and peak information error is big.The embodiment of the present invention is according to Fourier transformation original definition, by original acquisition
Spectral information and corresponding sine and cosine sequence carry out cross-correlation and obtain characteristic value to get Fourier transform spectrum, thus obtained spy is arrived
It is more to levy peak information point, peak error reduces.Preferably, the embodiment of the present invention is using the discrete Fourier transform pairs spectrum letter of Unequal distance
Number carry out first demodulation, wherein Unequal distance discrete Fourier transform refers to the spectrum directly to wave number or frequency unequal spacing
Signal carries out discrete Fourier transform, and the discrete Fourier transform formula of Unequal distance is as follows:
Wherein, d indicates that the chamber long value of Fabry-perot optical fiber chamber, N indicate that the spectral sequence columns of original spectral signal, λ indicate wave
Long, x (λ) indicates that original spectral signal, nDFT (d) indicate the spectral signal obtained by Unequal distance discrete Fourier transform,
The referred to as discrete Fourier transform spectrum of Unequal distance.
Preferably, in order to effectively inhibit the Unequal distance discrete fourier obtained through above-mentioned Unequal distance discrete Fourier transform become
The secondary lobe (other peaks i.e. by the discrete Fourier transform spectrum main peak of Unequal distance) exchanged cards with personal and family details when becoming sworn brothers, can be before above-mentioned discrete Fourier transform
To original spectral signal adding window.Preferably, the embodiment of the present invention is using the discrete Fourier transform pairs spectral signal of Unequal distance
Carry out the first demodulation, before obtaining the first chamber long value of Fabry-perot optical fiber chamber, this method further include: by spectral signal and window function phase
Multiply, obtain the first spectral signal, carrying out the first demodulation using the discrete Fourier transform pairs spectral signal of Unequal distance includes: using not
Equidistant discrete the first spectral signal of Fourier transform pairs carries out the first demodulation, obtains the first chamber long value of Fabry-perot optical fiber chamber.
Spectral signal is multiplied with window function Ji Wei original spectral signal adding window, it is preferable that the window function is Bu Laike
Graceful window function.Carrying out Unequal distance discrete Fourier transform to the spectral signal (i.e. the first spectral signal) after adding window can effectively obtain
More accurate peak information reduces pre-demodulating error.Fig. 2 is the signal of three kinds of Fourier transform spectrums according to an embodiment of the present invention
Figure, as shown in Fig. 2, abscissa indicate chamber it is long, unit be micron (um), ordinate indicate normalized intensity (i.e. relative intensity,
Each intensity value is divided by maximum intensity value, maximum value 1), FFT indicates Fast Fourier Transform (FFT) spectrum, and nDFT is indicated non-equally
Dissipate Fourier change spectrum, win-nDFT indicate adding window Unequal distance discrete fourier variation spectrum (i.e. to the spectral signal after adding window into
The spectral signal that row Unequal distance discrete fourier changes).Figure it is seen that adding window Unequal distance discrete fourier changes
Spectrum signature peak information is significantly more than Fast Fourier Transform (FFT) spectrum, and effectively inhibits secondary lobe information, thus obtain peak information compared with
It is accurate, reduction pre-demodulating error.
Step S106: the second demodulation is carried out to spectral signal according to the first chamber long value, obtains the second chamber of Fabry-perot optical fiber chamber
Long value, wherein the precision of the second chamber long value is greater than the precision of the first chamber long value.
The embodiment of the present invention carries out pre-demodulating to spectral signal through the above steps and obtains estimating chamber long value that (i.e. the first chamber is long
Value), it is based further on this and estimates chamber long value to the smart demodulation of spectral signal progress (the i.e. second demodulation), it is higher to obtain a precision
The chamber long value (i.e. the second chamber long value) of Fabry-perot optical fiber chamber, specifically, the embodiment of the present invention can be based on least square method to light
Spectrum signal carries out smart demodulation, is also possible to carry out smart demodulation to spectral signal based on cross-correlation method.The embodiment of the present invention by pair
Spectral signal carries out the first demodulation and obtains the first chamber long value, and guarantees that the precision of the first chamber long value is greater than first threshold, is based on
First chamber long value carries out the second demodulation to spectral signal to further increase the demodulation accuracy of the chamber long value of Fabry-perot optical fiber chamber.This hair
Bright embodiment improves Fabry-perot optical fiber chamber cavity length demodulating by combining the first demodulation second demodulation to demodulate spectral signal
Precision, and can effectively inhibit half-wave hopping phenomenon, it is not high to solve Fabry-perot optical fiber chamber cavity length demodulating precision in the related technology
The problem of.
Preferably, the second demodulation is carried out to spectral signal according to the first chamber long value, the second chamber for obtaining Fabry-perot optical fiber chamber is long
Value includes: the construction signal for obtaining spectral signal；Spectral signal is calculated according to the first chamber long value and constructs the lowest mean square of signal
Poor estimated value；And the second chamber long value of Fabry-perot optical fiber chamber is determined according to nonlinear IEM model value.
The embodiment of the present invention can establish the construction signal of above-mentioned spectral signal according to spectral model, can be by calculating light
The mean square deviation estimated value of spectrum signal and construction signal determines the second chamber long value of Fabry-perot optical fiber chamber, specifically, spectral signal and structure
The corresponding Fabry-perot optical fiber chamber chamber of nonlinear IEM model value for making signal is long, as the second chamber long value.Spectral signal and construction letter
Number mean square deviation estimated value calculation formula it is as follows:
Wherein, d, d0The Fabry-perot optical fiber chamber chamber for respectively indicating construction is long long with actual Fabry-perot optical fiber chamber chamber, x (n, d) table
Show construction signal, x (n, d0) indicate that spectral signal, N indicate that the spectral series columns of spectral signal, mse (d) indicate mean square deviation estimation
Value.
It optionally, can be in the hope of the lowest mean square of spectral signal and construction signal by least square method or cross-correlation method
Poor estimated value, so that it is long to obtain the corresponding Fabry-perot optical fiber chamber chamber of nonlinear IEM model value, i.e. the second chamber long value.But it uses
Least square method or cross-correlation method calculate spectral signal and construct computationally intensive speed when the nonlinear IEM model value of signal
Slowly, efficiency is lower.
In order to improve the efficiency for the nonlinear IEM model value for seeking spectral signal and construction signal, the embodiment of the present invention is adopted
Spectral signal is solved with the algorithm that one kind gradually refines and constructs the nonlinear IEM model value of signal, i.e., is swept by being gradually reduced
The mode for retouching step-length solves nonlinear IEM model value.Preferably, the embodiment of the present invention calculates spectrum letter according to the first chamber long value
Number and construction signal nonlinear IEM model value include: obtain the first step-length；It is determined according to the first chamber long value and the first step-length
Scanning range；Obtain the second step-length, wherein the second step-length is less than the first step-length；Every the long progress of second step out of scanning range
Value obtains multiple values；Respectively according to the mean square deviation estimated value of multiple exploitation spectral signals and construction signal, obtain more
A mean square deviation estimated value；The smallest mean square deviation estimated value is obtained in multiple mean square deviation estimated values as nonlinear IEM model value.
First step-length can be configured according to the error of the first chamber long value, for example, working as the first chamber that the first demodulation obtains
When the error of long value is 100nm, a length of 100nm of the first step can be set, also can be set slightly larger than 100nm, for example, setting
The a length of 150nm of the first step.In actual conditions, the error of the first chamber long value can be obtained by analyzing demodulating algorithm, be set same
The error of the chamber long value of the Fabry-perot optical fiber chamber obtained in standby or device with same demodulating algorithm is stable, for example, same
The error of the chamber long value demodulated in Fabry-perot optical fiber cavity pressure sensor using discrete Fourier transform is essentially identical.It is obtaining
To after the first step-length, scanning range is determined according to the first step-length and the first chamber long value, for example, a length of s1 of the first step, the first chamber are long
Value is d1, then scanning range can be set to [d1-s1, d1+s1].Second step-length be used for determine mean square deviation estimation scan across
Degree, the second step-length is less than the first step-length, specifically, 0.1 times of a length of first step-length of second step can be set, and also can be set the
Two step-lengths are other values less than the first step-length, for example, a length of 100nm of the first step, the second step-length can be set to 10nm, 20nm
Or 5nm etc..After determining the second step-length and scanning range, every the long progress value of second step out of scanning range, obtain more
A value, for example, scanning range is [d1-s1, d1+s1], a length of s2 of second step, since d1-s1, from scanning range [d1-
S1, d1+s1] it is interior every the second step-length s2 progress value, multiple values are obtained, each value in above-mentioned multiple values is distinguished
Chamber long value d as above-mentioned construction signal substitutes into above formula formula and calculates mean square deviation estimated value, and available multiple mean square deviations are estimated
Evaluation, more above-mentioned multiple mean square deviation estimated values, will wherein the smallest mean square deviation estimated value as nonlinear IEM model value.
Preferably, in order to further increase demodulation accuracy, this method further include: judge whether the second step-length is greater than the second threshold
Value；When judging that second step length is greater than second threshold, continue to obtain third step-length, wherein third step-length is less than the second step-length；
The third chamber long value of Fabry-perot optical fiber chamber is determined according to mean square deviation estimated value the smallest in multiple mean square deviation estimated values；And according to
Three chamber long values and the second step-length determine scanning range, wherein every the long progress value of third step out of scanning range.
The second threshold of the embodiment of the present invention is usually arranged as finally needing demodulation accuracy to be achieved, for example, setting second
Threshold value is 0.1nm.If second step is long to be greater than 0.1nm, illustrate that the chamber long value of currently available Fabry-perot optical fiber chamber is not up to pre-
If demodulation accuracy redefine scanning range and scanning step at this point, continuing to be demodulated using the above method, it is preferable that
Corresponding chamber long value (i.e. third chamber long value) is determined according to the smallest mean square deviation estimated value obtained above, and according to the second step-length
Scanning range is redefined with third chamber long value, and continues to obtain third step-length, wherein third step-length is less than the second step-length, example
Such as, 0.1 times of a length of second step-length of third step can be set.Each third step-length value out of this is redefined scanning range
It substitutes into above formula formula and calculates mean square deviation estimated value.Constantly proceed as described above, until scanning step reaches preset demodulation accuracy,
Then using the smallest mean square deviation estimated value of last time acquirement as final nonlinear IEM model value, and it is equal according to the minimum
Estimate of variance determines that the second chamber is long.The embodiment of the present invention solves nonlinear IEM model value by constantly reducing scanning step
Fabry-perot optical fiber chamber chamber long value is demodulated, nonlinear IEM model value is solved compared to existing least square method and demodulates Fiber Optic Sensor
Amber chamber chamber long value greatly improves demodulation efficiency under the conditions of guaranteeing higher demodulation accuracy.
The application of the Fabry-perot optical fiber chamber demodulation method of the embodiment of the present invention is illustrated with example below:
Fabry-perot optical fiber chamber cavity length demodulating is the important component of entire optical fiber pressure measuring system, directly affects demodulation
Resolution ratio, stability and the measurement accuracy of instrument.Fig. 3 is the survey of Fabry-perot optical fiber cavity pressure sensor according to an embodiment of the present invention
Test system schematic diagram.As shown in figure 3, spectrometer 3 acquires spectral signal, specifically, spectrum by 1 interference light circulator 2 of light source
Acquisition uses Bayspec demodulation module, and wave-length coverage is 1510~1590nm, and single frames spectral point is 512, and spectral signal passes
Computer 4 is given, the Fabry-perot optical fiber chamber demodulation method according to an embodiment of the present invention of computer 4 carries out the long solution of chamber according to spectral signal
It adjusts.During the experiment, the probe of Fabry-perot optical fiber cavity pressure sensor is placed in pressure chamber 5, using pressure pump 6 to pressure chamber
5 pressurizations, digital precision pressure meter 7 carry out survey pressure.Fig. 4 is determining for Fabry-perot optical fiber cavity pressure sensor according to an embodiment of the present invention
Curve graph is marked, in Fig. 4, abscissa indicates that actual pressure value, unit are megapascal (MPa), and ordinate indicates that demodulation chamber is long, unit
For micron (um), in 70MPa pressure limit, the curve linear fitting degree of correlation is up to 0.999999, pressure measurement accuracy
0.03%F.S.It can thus be seen that the Fabry-perot optical fiber chamber demodulation method demodulation accuracy with higher of the embodiment of the present invention.
It can be seen from the above description that the present invention realizes following technical effect:
The spectral signal that the embodiment of the present invention passes through acquisition interference optical fiber Fa-Po cavity；First demodulation is carried out to spectral signal,
Obtain the first chamber long value of Fabry-perot optical fiber chamber, wherein the precision of the first chamber long value is greater than first threshold；And it is long according to the first chamber
Value carries out the second demodulation to spectral signal, obtains the second chamber long value of Fabry-perot optical fiber chamber, wherein the precision of the second chamber long value is greater than
The precision of first chamber long value improves Fabry-perot optical fiber by combining the first demodulation second demodulation to demodulate spectral signal
The precision of chamber cavity length demodulating, and can effectively inhibit half-wave hopping phenomenon, solve the long solution of Fabry-perot optical fiber chamber chamber in the related technology
The problem for adjusting precision not high.In addition, carrying out pre-demodulating and combining gradually to refine using adding window Unequal distance discrete Fourier transform
Algorithm carry out smart demodulation, it can be achieved that wide range optical interface fiber Fa-Po cavity chamber is grown up long quick of dynamic range, high-precision, absolute chamber
Demodulation, and it is possible to prevente effectively from there is half-wave hopping phenomenon in demodulation result.
It should be noted that step shown in the flowchart of the accompanying drawings can be in such as a group of computer-executable instructions
It is executed in computer system, although also, logical order is shown in flow charts, and it in some cases, can be with not
The sequence being same as herein executes shown or described step.
According to another aspect of an embodiment of the present invention, a kind of Fabry-perot optical fiber chamber demodulating equipment is provided, the Fabry-perot optical fiber chamber
Demodulating equipment can be used for executing the Fabry-perot optical fiber chamber demodulation method of the embodiment of the present invention, the Fabry-perot optical fiber chamber of the embodiment of the present invention
Demodulation method can also Fabry-perot optical fiber chamber demodulating equipment through the embodiment of the present invention execute.
Fig. 5 is the schematic diagram of Fabry-perot optical fiber chamber demodulating equipment according to an embodiment of the present invention, as shown in figure 5, the device packet
It includes: first acquisition unit 10, the first demodulating unit 20 and the second demodulating unit 30.
First acquisition unit 10, for obtaining the spectral signal of interference optical fiber Fa-Po cavity.
After using wide range optical interface fiber Fa-Po cavity, the wide range interference of light can be obtained by spectrometer or (FBG) demodulator
The spectral signal that Fabry-perot optical fiber chamber obtains, specifically, spectral signal can be the interference that wide range optical interface fiber Fa-Po cavity obtains
Striped.The chamber of spectral signal and Fabry-perot optical fiber chamber is long, and there are one-to-one relationships, can be obtained by demodulating the spectral signal
Chamber to Fabry-perot optical fiber chamber is long.
First demodulating unit 20 is obtained for carrying out the first demodulation using the discrete Fourier transform pairs spectral signal of Unequal distance
To the first chamber long value of Fabry-perot optical fiber chamber, wherein the precision of the first chamber long value is greater than first threshold, in the precision of the first chamber long value
The cavity length demodulating of Fabry-perot optical fiber chamber is not in half-wave jump when greater than first threshold.
Pre-demodulating (the i.e. first demodulation) is carried out to spectral signal, obtains estimating chamber long value (i.e. the first chamber long value).Pre-demodulating
Be in order to it is subsequent to spectral signal carry out essence demodulation prepare, it is therefore, not high to the required precision for estimating chamber long value, estimate chamber
The precision of long value need to only meet greater than first threshold, and first threshold is the required accuracy value reached that half-wave can be inhibited to jump,
Specifically, first threshold can be set to quarter-wave.
The embodiment of the present invention is according to Fourier transformation original definition, by the spectral information of original acquisition and corresponding sine and cosine sequence
Column carry out cross-correlation and obtain characteristic value to get to Fourier transform spectrum, and thus obtained characteristic peak information point is more, and peak error subtracts
It is small.Above-mentioned Unequal distance discrete Fourier transform is directly to carry out direct computation of DFT to the spectral signal of wave number or frequency unequal spacing
Leaf transformation.
Preferably, device further include: arithmetic element obtains the first spectrum for spectral signal to be multiplied with window function
Signal, the first demodulating unit are used to carry out the first demodulation using discrete the first spectral signal of Fourier transform pairs of Unequal distance, obtain
First chamber long value of Fabry-perot optical fiber chamber.
Spectral signal is multiplied with window function Ji Wei original spectral signal adding window, it is preferable that the window function is Bu Laike
Graceful window function.Carrying out Unequal distance discrete Fourier transform to the spectral signal (i.e. the first spectral signal) after adding window can effectively obtain
More accurate peak information reduces pre-demodulating error.
Second demodulating unit 30 obtains Fabry-perot optical fiber for carrying out the second demodulation to spectral signal according to the first chamber long value
Second chamber long value of chamber, wherein the precision of the second chamber long value is greater than the precision of the first chamber long value.
Specifically, the embodiment of the present invention, which can be, carries out the second demodulation to spectral signal based on least square method, can also be with
It is that the second demodulation is carried out to spectral signal based on cross-correlation method.
The embodiment of the present invention obtains the spectral signal of interference optical fiber Fa-Po cavity by first acquisition unit 10；First demodulation is single
20 pairs of spectral signals of member carry out the first demodulation, obtain the first chamber long value of Fabry-perot optical fiber chamber, wherein the precision of the first chamber long value is big
In first threshold；And second demodulating unit 30 according to the first chamber long value to spectral signal carry out second demodulation, obtain Fiber Optic Sensor
Second chamber long value of amber chamber, wherein the precision of the second chamber long value is greater than the precision of the first chamber long value.By combining the first demodulation single
Member 20 and the second demodulating unit 30 demodulate spectral signal, improve the precision of Fabry-perot optical fiber chamber cavity length demodulating, and energy
Effectively inhibit half-wave hopping phenomenon, solves the problems, such as that Fabry-perot optical fiber chamber cavity length demodulating precision is not high in the related technology.
Preferably, the second demodulating unit 30 includes: acquisition module, for obtaining the construction signal of spectral signal；Calculate mould
Block, for calculating spectral signal according to the first chamber long value and constructing the nonlinear IEM model value of signal；And determining module, it uses
In the second chamber long value for determining Fabry-perot optical fiber chamber according to nonlinear IEM model value.
Preferably, of the invention in order to improve the efficiency for seeking spectral signal with the nonlinear IEM model value for constructing signal
The computing module of embodiment includes: the first acquisition submodule, for obtaining the first step-length；First determines submodule, is used for basis
First chamber long value and the first step-length determine scanning range；Second acquisition submodule, for obtaining the second step-length, wherein second step
Length is less than the first step-length；Value submodule, for, every the long progress value of second step, obtaining multiple values out of scanning range；
Computational submodule, for according to the mean square deviation estimated value of multiple exploitation spectral signals and construction signal, obtaining multiple respectively
Mean square deviation estimated value；The smallest mean square deviation estimated value is obtained in multiple mean square deviation estimated values as nonlinear IEM model value.
Preferably, the device further include: judging unit, for judging whether the second step-length is greater than second threshold；Second obtains
Unit is taken, for obtaining third step-length, wherein third step-length is less than second when judging that second step length is greater than second threshold
Step-length；First determination unit, for determining Fabry-perot optical fiber chamber according to mean square deviation estimated value the smallest in multiple mean square deviation estimated values
Third chamber long value；And second determination unit, for determining scanning range according to third chamber long value and the second step-length, wherein
Every the long progress value of third step out of scanning range.
The embodiment of the invention also provides a kind of Fabry-perot optical fiber interferometer, which includes above-mentioned any one
A Fabry-perot optical fiber chamber demodulating equipment.
Obviously, those skilled in the art should be understood that each module of the above invention or each step can be with general
Computing device realize that they can be concentrated on a single computing device, or be distributed in multiple computing devices and formed
Network on, optionally, they can be realized with the program code that computing device can perform, it is thus possible to which they are stored
Be performed by computing device in the storage device, perhaps they are fabricated to each integrated circuit modules or by they
In multiple modules or step be fabricated to single integrated circuit module to realize.In this way, the present invention is not limited to any specific
Hardware and software combines.
The foregoing is only a preferred embodiment of the present invention, is not intended to restrict the invention, for the skill of this field
For art personnel, the invention may be variously modified and varied.All within the spirits and principles of the present invention, made any to repair
Change, equivalent replacement, improvement etc., should all be included in the protection scope of the present invention.
Claims (7)
1. a kind of Fabry-perot optical fiber chamber demodulation method characterized by comprising
Obtain the spectral signal for interfering the Fabry-perot optical fiber chamber；
First demodulation is carried out using spectral signal described in the discrete Fourier transform pairs of Unequal distance, obtains the of the Fabry-perot optical fiber chamber
One chamber long value, wherein the precision of the first chamber long value is greater than first threshold, is greater than in the precision of the first chamber long value described
The cavity length demodulating of the Fabry-perot optical fiber chamber is not in half-wave jump when first threshold；And
The second demodulation is carried out to the spectral signal according to the first chamber long value, the second chamber for obtaining the Fabry-perot optical fiber chamber is long
Value, wherein the precision of the second chamber long value is greater than the precision of the first chamber long value；
Wherein, the Unequal distance discrete Fourier transform refers to and directly carries out to the spectral signal of wave number or frequency unequal spacing
The formula of discrete Fourier transform, the Unequal distance discrete Fourier transform is as follows:
Wherein, d indicates that the first chamber long value of the Fabry-perot optical fiber chamber, N indicate the spectral sequence columns of original spectral signal,
λ indicates that wavelength, x (λ) indicate that original spectral signal, nDFT (d) indicate the light obtained by Unequal distance discrete Fourier transform
The discrete Fourier transform spectrum of spectrum signal, referred to as Unequal distance；
Wherein, the second demodulation is carried out to the spectral signal according to the first chamber long value, obtains the of the Fabry-perot optical fiber chamber
Two chamber long values include:
Obtain the construction signal of the spectral signal；
The nonlinear IEM model value of the spectral signal and the construction signal is calculated according to the first chamber long value；And
The second chamber long value of the Fabry-perot optical fiber chamber is determined according to the nonlinear IEM model value；
Wherein, the nonlinear IEM model value packet of the spectral signal and the construction signal is calculated according to the first chamber long value
It includes:
Obtain the first step-length；
Scanning range is determined according to the first chamber long value and first step-length；
Obtain the second step-length, wherein second step-length is less than first step-length；
Every the long progress value of the second step out of described scanning range, multiple values are obtained；
The mean square deviation estimated value of the spectral signal according to the multiple exploitation and the construction signal respectively, obtains multiple
Mean square deviation estimated value；
The smallest mean square deviation estimated value is obtained in the multiple mean square deviation estimated value as nonlinear IEM model value.
2. Fabry-perot optical fiber chamber demodulation method according to claim 1, which is characterized in that
First demodulation is being carried out using spectral signal described in the discrete Fourier transform pairs of Unequal distance, is obtaining the Fabry-perot optical fiber chamber
Before first chamber long value, the method also includes: the spectral signal is multiplied with window function, obtains the first spectral signal,
Carrying out the first demodulation using spectral signal described in the discrete Fourier transform pairs of Unequal distance includes: using Unequal distance direct computation of DFT
Leaf transformation carries out the first demodulation to first spectral signal, obtains the first chamber long value of the Fabry-perot optical fiber chamber.
3. Fabry-perot optical fiber chamber demodulation method according to claim 1, which is characterized in that the method also includes:
Judge whether second step-length is greater than second threshold；
When judging that the second step length is greater than the second threshold, continue to obtain third step-length, wherein the third step-length
Less than second step-length；
Determine that the third chamber of the Fabry-perot optical fiber chamber is long according to mean square deviation estimated value the smallest in the multiple mean square deviation estimated value
Value；And
The scanning range is determined according to the third chamber long value and second step-length, wherein every out of described scanning range
Every the long progress value of the third step.
4. a kind of Fabry-perot optical fiber chamber demodulating equipment characterized by comprising
First acquisition unit, for obtaining the spectral signal for interfering the Fabry-perot optical fiber chamber；
First demodulating unit is obtained for carrying out the first demodulation using spectral signal described in the discrete Fourier transform pairs of Unequal distance
First chamber long value of the Fabry-perot optical fiber chamber, wherein the precision of the first chamber long value is greater than first threshold, in first chamber
The cavity length demodulating of the Fabry-perot optical fiber chamber is not in half-wave jump when the precision of long value is greater than the first threshold；And
Second demodulating unit obtains the light for carrying out the second demodulation to the spectral signal according to the first chamber long value
Second chamber long value of fine Fa-Po cavity, wherein the precision of the second chamber long value is greater than the precision of the first chamber long value；
Wherein, the Unequal distance discrete Fourier transform refers to and directly carries out to the spectral signal of wave number or frequency unequal spacing
The formula of discrete Fourier transform, the Unequal distance discrete Fourier transform is as follows:
Wherein, d indicates that the first chamber long value of the Fabry-perot optical fiber chamber, N indicate the spectral sequence columns of original spectral signal,
λ indicates that wavelength, x (λ) indicate that original spectral signal, nDFT (d) indicate the light obtained by Unequal distance discrete Fourier transform
The discrete Fourier transform spectrum of spectrum signal, referred to as Unequal distance；
Wherein, second demodulating unit includes:
Module is obtained, for obtaining the construction signal of the spectral signal；
Computing module, for calculating the Minimum Mean Square Error of the spectral signal and the construction signal according to the first chamber long value
Estimated value；And
Determining module, for determining the second chamber long value of the Fabry-perot optical fiber chamber according to the nonlinear IEM model value；
Wherein, the computing module includes:
First acquisition submodule, for obtaining the first step-length；
First determines submodule, for determining scanning range according to the first chamber long value and first step-length；
Second acquisition submodule, for obtaining the second step-length, wherein second step-length is less than first step-length；
Value submodule, for, every the long progress value of the second step, obtaining multiple values out of described scanning range；
Computational submodule, the mean square deviation for the spectral signal according to the multiple exploitation respectively and the construction signal
Estimated value obtains multiple mean square deviation estimated values；
The smallest mean square deviation estimated value is obtained in the multiple mean square deviation estimated value as nonlinear IEM model value.
5. Fabry-perot optical fiber chamber demodulating equipment according to claim 4, which is characterized in that
Described device further include: arithmetic element is used to for the spectral signal being multiplied with window function, obtains the first spectral signal,
First demodulating unit is used to carry out the first solution using the first spectral signal described in the discrete Fourier transform pairs of Unequal distance
It adjusts, obtains the first chamber long value of the Fabry-perot optical fiber chamber.
6. Fabry-perot optical fiber chamber demodulating equipment according to claim 4, which is characterized in that described device further include:
Judging unit, for judging whether second step-length is greater than second threshold；
Second acquisition unit, for obtaining third step-length when judging that the second step length is greater than the second threshold,
In, the third step-length is less than second step-length；
First determination unit, for determining the optical fiber according to mean square deviation estimated value the smallest in the multiple mean square deviation estimated value
The third chamber long value of Fa-Po cavity；And
Second determination unit, for determining the scanning range according to the third chamber long value and second step-length, wherein from
Every the long progress value of the third step in the scanning range.
7. a kind of Fabry-perot optical fiber interferometer, which is characterized in that including Fabry-perot optical fiber chamber described in any one of claim 4 to 6
Demodulating equipment.
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| CN108955734B (en) * | 2018-06-08 | 2020-05-05 | 武汉理工大学 | Cavity length demodulation method of optical fiber F-P temperature/pressure composite sensor |
| CN110595516B (en) * | 2019-09-18 | 2020-12-18 | 华中科技大学 | FPI cavity length demodulation method and system |
| CN111707303A (en) * | 2020-07-17 | 2020-09-25 | 武汉理工大学 | Variable-step-length rapid high-precision signal demodulation method for optical fiber F-P sensor |
| CN112050942B (en) * | 2020-07-30 | 2021-06-15 | 东北大学 | Optical fiber interference spectrum cavity length correction method based on phase compensation |
| CN112081587A (en) * | 2020-10-23 | 2020-12-15 | 西南石油大学 | Horizontal well output profile calculation method based on optical fiber noise data |
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