CN102183866B - Imbalanced-Mach-Zehnder-based demodulation device for multiplexing optical fiber interferometer - Google Patents

Abstract

The invention provides an imbalanced-Mach-Zehnder-based demodulation device for a multiplexing optical fiber interferometer. The device consists of a broadband light source, an optical circulator, an optical divider, a sensor array switching and transmitting optical fiber, an optical fiber sensor array, an imbalanced-Mach-Zehnder optical autocorrelator and an interference signal detecting unit in connection, wherein the imbalanced-Mach-Zehnder interferometer forms an optical path correlator, narrow linewidth laser complexed in the correlator evaluates scanning amplitude and uniformity of the optical path, the optical path scanning error is compensated, and the measuring accuracy of the sensor is improved; the interference beating noise of the interferometer can be reduced, and multiplexing number of interferometers is improved; the optical autocorrelator demodulates signals of a multiplexing optical fiber sensor; and the unique optical path matching condition suppresses interference noise of secondary optical path matching. The device can be applied in the fields of real-time monitoring and measuring of multi-point stress or temperature and other physical quantities, monitoring of large-scale intelligent structures and the like.

Description

Demodulating equipment based on the multiplex fibre optic interferometer of non-equilibrium Mach-Zehnder

Technical field

The present invention relates to a kind of demodulating equipment of fibre optic interferometer, specifically a kind of demodulating equipment of the multiplex fibre optic interferometer based on non-equilibrium Mach-Zehnder optics autocorrelator.

Background technology

Adopt low relevant, broad spectrum light source, for example the fibre optic interferometer of light emitting diode (LED), ultra spontaneous radiation light source (ASE) or superradiance laser diode (SLD) driving is commonly called the white light fibre optic interferometer.Typical its structure of optical fiber white light interference appearance is as shown in Figure 1; Adopt wide spectrum light source LED or ASE as light source in the Michelson formula interferometer of building by single-mode fiber, realize measurement measured physical quantity through the white-light fringe that detector detected.Its principle of work is following; After the wide range light that is sent by low relevant wide spectrum light source 11 gets into single-mode fiber; Be divided into two bundles by 3dB single-mode fiber 2 * 2 coupling mechanisms 13, a branch of light gets into the single-mode fiber 14 that is used as gage beam, is returned along former road by the optical reflection face 15 reflection backs of its rear end; Arrive photodetector 12 through single-mode fiber 14, coupling mechanism 13, this Shu Guang is called measuring-signal light; Send light by light source 11 and be coupled device 13 other a branch of light along separate routes; Getting into as a reference, the single mode of arm connects optical fiber 16, GRIN Lens 17; Arrive photodetector 12 through same returning along former road after the reflection of mobile mirror 18, this Shu Guang is called as reference signal light.Measuring-signal light and reference signal light are in detector surface generation coherence stack; Because the coherent length of wide spectrum light source is very short; Be approximately several microns to tens microns; Have only when reference signal light and measuring-signal optical path difference during, just can produce coherence stack, output white light interference pattern (referring to accompanying drawing 2) less than the coherent length of light source.

As shown in Figure 2, the characteristic of white-light fringe is that a principal maximum is arranged, and is called the center striped, and it is corresponding for it with zero optical path difference, and during promptly corresponding to reference beam and measuring beam equivalent optical path, the light path that is called reference beam and measuring beam is complementary.When the gage beam change in optical path length, through changing the retardation of fibre delay line, the light path of reference signal is changed, can obtain the center interference fringe.The position of center striped provides a reliable absolute position reference for measuring; When its light path changes under the influence of measuring beam at extraneous measured physical quantity; The change in location of the white-light fringe that only needs can to obtain through the adjustment of reference arm light path, thus the absolute change value of measured physics amount obtained.Compare with other fibre optic interferometers, optical fiber white light interference is except having advantages such as high sensitivity, essential safety, anti-electromagnetic field interference, and maximum characteristics are to carry out absolute measurement to pressure, strain, temperature etc. are to be measured.Therefore white light interference property fibre optic interferometer is widely used in the measurement of physical quantity, mechanical quantity, environment parameter, chemistry amount, biomedical amount.

Be to solve the multiplexed problem of Fibre Optical Sensor, nineteen ninety-five U.S. H-P Wayne V.Sorin of company and Douglas M.Baney disclose a kind of multiplexing method (United States Patent (USP): the patent No. 5557400) of the white light interference sensor based on the optics autocorrelator.As shown in Figure 3; It is based on non-equilibrium Michelson interferometer structure; Utilize the coupling of light signal between the optical path difference of former and later two end face reflection light signals of optical path difference that forms between Michlson interferometer fixed arm and the variable sweep arm and multiplexing fiber-optic sensor to realize the optics auto-correlation; Obtain the white light interference signal peak of sensor; Utilize to change light path extent between scan arm and the fixed arm again, mate one by one, accomplish the multiplexed of Fibre Optical Sensor with the length of each sensor in a plurality of end to end serial fibre optic sensor arras.Though said structure is the multiplexed classical architecture of white light interference optical fiber sensing device, its shortcoming mainly contains two: first light source power efficient is low, and it is in 1/4 the optical power sensor that equivalence is only arranged; It two is that being sent in the flashlight feedback meeting light source by light source of a half-power arranged, for the light source of ASE as not isolating the stability that can influence system works.

Except that said structure, the applicant in 2007 and 2008 disclosed low relevant strand turn round formula class Sagnac optical-fiber deformation sensor (one Chinese patent application number: 200710072350.9) with space division multiplexing Mach-Zehnder cascade type optical fiber interferometer and measuring method (one Chinese patent application number: 200810136824.6) mainly use the problem that solves the anti-breaking-up in the fibre optic sensor arra laying process; The applicant in the composite instrument of disclosed optical fiber Mach-Zehnder in 2008 and Michelson interferometer array (one Chinese patent application number: 200810136819.5) and twin array Michelson optical fiber white light interference strain gage (the Chinese patent application number: 200810136820.8) be mainly used in solve the white light fibre optic interferometer multiplexed in temperature disturb and temperature and strain while problems of measurement to measuring; The applicant is disclosed a kind of simplifying type multiplexing white light interference optical fiber sensing demodulating equipment (one Chinese patent application number: 200810136826.5) with based on the distributed optical fiber white light interference sensor array of adjustable Fabry-Perot resonant cavity (one Chinese patent application number: 200810136833.5) in 2008; The introducing of ring cavity, F-P chamber light path autocorrelator; Be mainly used in the structure of simplifying multiplexed interferometer; Structure is light channel structure altogether, improves temperature stability; The applicant in 2008 disclosed a kind of double-datum length low coherent optical fiber ring network apparatus for sensing demodulating (one Chinese patent application number: 200810136821.2) based on the introducing of 4 * 4 fiber coupler light path autocorrelators, purpose is problems of measurement when solving many reference sensors.In the above-mentioned interferometer structure based on space division multiplexing; The light path autocorrelator adopts structures such as Michelson interferometer, Mach-Zehnder interferometer, Fabry-Perot interferometer mostly; In order to form the signal beams with certain optical path difference (more than at least two bundles) that can be complementary with Fibre Optical Sensor front/rear end reflected signal optical path difference, at least one N * M fiber coupler in the light path autocorrelator (for example: 2 * 2,3 * 3 or 4 * 4 fiber couplers).Because the dichroism and the light path symmetry characteristic of N * M fiber coupler, there are three problems without exception in above-mentioned optics autocorrelator: first light path topological structure is big to the light source power decay, the light source utilization factor is low.To adopt 2 * 2 fiber couplers is example, and the light signal that is taken place by light source only has half to reach sensor array, by the light signal of its reflection; Half is arranged through overdamping again; With the disclosed light channel structure of W.V.Sorin shown in Figure 3, have only 1/4 light source power participation optical correlation process in theory at most, other power all have been attenuated; If adopt 3 * 3 or 4 * 4 fiber couplers, then its power attenuation is (1/3) ²Perhaps (1/4) ², then even more serious; It two is some light channel structure; Twice (perhaps repeatedly) is through the light path autocorrelator before and after the light signal; Like: one Chinese patent application numbers 200810136826.5,200810136833.5 and a kind of double-datum length low coherent optical fiber ring network apparatus for sensing demodulating (one Chinese patent application number: the technical scheme in the patent document 200810136821.2); Make that light signal between Fibre Optical Sensor and the light path autocorrelator is relevant to exist plural light path matching relationship; Cause to have secondary (perhaps repeatedly) light path coupling noise in the white light interference signal, make sensor auto-correlation peak value no longer unique on the locus, its identification and sensor measurement are caused difficulty; It three is to have symmetry on the light path topological structure, and light source and detector are symmetry and reciprocity in light path, have at least in theory to feed back in the light source again with the light signal of the identical numerical value of detector received power; Though the type of light source is a wide range light, compare with LASER Light Source, very inresponsive to feedback; But excessive signal power feedback; Can cause the resonance (as based on the light source ASE of the spontaneous superradiance type of optical fiber etc.) of light source, can cause the power of light source generation light signal to reduce, particularly when white light interference; Bigger interference signal power swing can cause extremely adverse influence to the use of light source, reduces the measuring accuracy of optics from relevant peak amplitude.

Summary of the invention

The purpose of this invention is to provide and a kind ofly can improve the light source power utilization factor, suppress to interfere clap noise, eliminate the problems such as distortion and heterogeneity of light path scanning in the optics autocorrelator, improve the demodulating equipment based on the multiplex fibre optic interferometer of non-equilibrium Mach-Zehnder of the demodulation accuracy of the fine interferometer of low-coherent light and the multiplexing number that increases interferometer.

The objective of the invention is to realize like this:

It switches Transmission Fibers 3, fibre optic sensor arra 4, non-equilibrium Mach-Zehnder optics autocorrelator 5 and interference signal probe unit 6 wide range (ASE) light source 1, optical circulator 2, optical branching device 7, sensor array and is formed by connecting;

The first input end a of said optical circulator 2 connects wide spectrum light source 1, the second output terminal b and connects fibre optic sensor arra 4 through Transmission Fibers 3, and reflection end c connects non-equilibrium Mach-Zehnder optics autocorrelator 5;

Said non-equilibrium Mach-Zehnder optics autocorrelator 5 is made up of first fiber coupler 51, three port photocirculators 52, optical fiber collimator 53, removable optical mirror 54, second fiber coupler 55 and narrow linewidth laser 56; The input port of first fiber coupler 51 connects the reflector port c and the narrow linewidth laser 56 of circulator 2 respectively; Two optics output terminals of first fiber coupler 51 are connected with the input end d of second optical circulator 52 and the input end h of second coupling mechanism 55 respectively; The output terminal e of second optical circulator 52 is connected with optical fiber collimator 53; An optics input port of the reflector port g of second optical circulator 52 and second coupling mechanism 26 links;

Said interference signal probe unit 6 is by two wavelength division multiplexer 61a, 61b, four photodetector 62a, 62b, 63a, 63b, and two differential amplifier 64a, 64b and data acquisition system (DAS)s 65 and signal Processing computing machine 66 connect to form.

The present invention can also comprise:

Described three port photocirculators 2 or 52 have an optics input end a or d, optics output terminal b or e and optical reflection end c or g; Has the optical-unidirectional transfer function; Inject light signal only by output terminal b or e output by input end a or d; Inject light signal by output terminal b or e, then only by reflection end c or g output;

Described optical branching device 7 is characterized in that a section single-mould fiber, or the fiber coupler divided equally of 1 * N, or 1 * N fiber switch;

Described first fiber coupler 51 and second fiber coupler 55 have two optical input signals ends and two optical output signal ends at least, and optimum splitting ratio is 50: 50;

The work spectral range of described first fiber coupler 51, second fiber coupler 55 and three port photocirculators 52 can cover the emission spectrum of wide spectrum light source 1 and narrow bandwidth laser instrument 56 simultaneously;

Two of described non-equilibrium Mach-Zehnder optics autocorrelator 5 interferes the sweep limit of arm optical path difference can cover the light path value that comprehensive Fibre Optical Sensor front/rear end is produced, the size of the change in optical path length that is produced when comprising sensor measurement;

Described narrow linewidth laser 56 is characterized in that spectral range and wide spectrum light source 1 are not overlapping, and the coherent length of light source 56 is greater than more than 10 times of two arm optical path differences of non-equilibrium Mach-Zehnder optics autocorrelator 5.

The wavelength division multiplexer 61a of described interference signal probe unit 6,61b have an input end, link to each other with two outputs of second coupling mechanism 55 respectively; With two output terminals that spectral response range is different, corresponding with the spectral range of wide spectrum light source 1 and narrow-linewidth laser light source 56 respectively; The photodetector 62a and 63a, 62b and the 63b that are connected on the output terminal of same spectra response realize the differential type balance detection in twos.

In described non-equilibrium Mach-Zehnder optics autocorrelator 5 and the interference signal probe unit 6; When removable optical mirror 54 moves the light path scanning of realization; The flashlight that is sent by narrow-linewidth laser light source 56 is converted into light path scan calibration signal through forming interference fringe behind two arm h of optics autocorrelator 5 and the d-＞e-＞f-＞e-＞g by two photodetector 62a in the interference signal probe unit 6 and 63a or 62b and 63b, realizes optical mirror 54 light paths are scanned accuracy and the inhomogeneity assessment of moving.

Described Optical Fiber Sensing Array 4 is made up of several head and the tail Fibre Optical Sensor 41 of serial connection successively; And Fibre Optical Sensor 41 is any by a segment length, and two ends have the single-mode fiber of fiber stub and form a series of end to end serial array of single-mode fiber sections formation that are uneven in length.

Optical fibre device all is operated in the single mode state in the demodulating equipment of described multiplex fibre optic interferometer based on non-equilibrium Mach-Zehnder optics autocorrelator.

The ultimate principle of the inventive method is based on hangs down principle of interference and space division multiplexing principle relevant, wide range light (white light).Demodulating equipment based on the multiplex fibre optic interferometer of non-equilibrium Mach-Zehnder optics autocorrelator is as shown in Figure 4, promptly only connects the situation of a sensor 41 in the sensor array.

Input end a through circulator 2 exports from output terminal b by the outgoing flashlight that hangs down relevant wide spectrum light source 1, reaches Fibre Optical Sensor 41 through after the Transmission Fibers 3, by R ₁₀And R ₁₁End face reflection forms two bundle reflected light signals, and Yan Yuanlu returns behind Transmission Fibers 3 and optical circulator 2, gets into non-equilibrium Mach-Zehnder optics autocorrelator 5 from delivery outlet c.They are divided into four bundles through first fiber coupler 51, and wherein two bundle flashlights are through the fixed arm 55 of Mach-Zehnder interferometer, directly output to the interference signal probe unit 6 from the output port of second fiber coupler 56; Other two bundle flashlights get into the input port d of optical circulator 52 through the output port of first fiber coupler 51; Arrive delivery outlet e via input port d end, get into optical fiber collimator 53, and after mirror 54 reflections that are reflected; Once more by the incident of e port; From reflector port g output, the light path that outputs to interference signal probe unit 6, four bundle flashlights through second fiber coupler is following:

1) through sensor end face R ₁₀Transmitted light beam with the fixed arm of nonequilibrium Mach-Zehnder interferometer:

a-＞b-＞R ₁₀-＞b-＞c-＞h-＞i；

2) through sensor end face R ₁₁Transmitted light beam with the fixed arm of nonequilibrium Mach-Zehnder interferometer:

a-＞b-＞R ₁₀-＞R ₁₁-＞b-＞c-＞h-＞i；

3) through sensor end face R ₁₀Transmitted light beam with the scan arm of nonequilibrium Mach-Zehnder interferometer:

a-＞b-＞R ₁₀-＞b-＞c-＞d-＞e-＞f-＞e-＞g-＞i；

4) through sensor end face R ₁₁Transmitted light beam with the scan arm of nonequilibrium Mach-Zehnder interferometer:

a-＞b-＞R ₁₀-＞R ₁₁-＞b-＞c-＞d-＞e-＞f-＞e-＞g-＞i；

After four bundle light evenly are divided into two parts by second coupling mechanism 56, received by the photodetector device in the arrival interference signal probe unit 6.

Be without loss of generality, suppose that the fixing of non-equilibrium Mach-Zehnder optics autocorrelator 5 is shorter than d-＞e-＞f-＞e-＞g, 1 than h)～4) four bundle flashlights, 1) the shortest, 4) the longest, 2) and 3) and sensor length R ₁₀-＞R ₁₁(d-＞e-＞f-＞e-＞g-h) optical path difference is relevant with M-Z two arms.When accurately certain scanning reflection mirror 54, make d-＞e-＞f-＞e-＞g-h and R ₁₀-＞R ₁₁The two is equal fully, promptly restraints the optical path differences that flashlight had by two of Fibre Optical Sensor 41 left and right sides end face reflections, fully by 5 compensation of non-equilibrium Mach-Zehnder optics autocorrelator.At this moment; The reflected signal of two end faces produces and interferes about Fibre Optical Sensor, in detector surface generation coherence stack, because the coherent length of wide range low-coherence light source is very short; Be approximately several microns to tens microns; Have only when the optical path difference of interference signal during, just can produce coherence stack, output white light interference pattern less than the coherent length of light source.Two interference amplitudes that detector obtained in the interference signal probe unit 6 are:

$I_{\mathrm{<figure-callout\; id="1"\; label="PD"\; filenames="HDA0000059982990000012.png,HDA0000059982990000021.png"\; state="\{\{state\}\}">PD</figure-callout>}1}=I_1+{\mathrm{<figure-callout\; id="2"\; label="I"\; filenames="HDA0000059982990000021.png,HDA0000059982990000022.png"\; state="\{\{state\}\}">I</figure-callout>}}_2+2\sqrt{I_1{\mathrm{<figure-callout\; id="2"\; label="I"\; filenames="HDA0000059982990000021.png,HDA0000059982990000022.png"\; state="\{\{state\}\}">I</figure-callout>}}_2}\left|\mathrm{\&gamma;}\left(x\right)\right|\cos (k_{1}x+{\mathrm{\&phi;}}_1)$ (1)

$I_{\mathrm{<figure-callout\; id="2"\; label="PD"\; filenames="HDA0000059982990000021.png,HDA0000059982990000022.png"\; state="\{\{state\}\}">PD</figure-callout>}2}=I_1+I_2-2\sqrt{I_1{\mathrm{<figure-callout\; id="2"\; label="I"\; filenames="HDA0000059982990000021.png,HDA0000059982990000022.png"\; state="\{\{state\}\}">I</figure-callout>}}_2}\left|\mathrm{\&gamma;}\left(x\right)\right|\cos (k_{1}x+{\mathrm{\&phi;}}_1)$

In the formula: I ₁, I ₂Be the signal intensity of the reference beam and the measuring beam of wide range light, k ₁Be the wave number of wide spectrum light source, x is two interference signal optical path differences,

Be initial phase, γ (x) is the light source autocorrelation function.Differential amplifier in the process interference signal probe unit 6 is handled and is obtained:

$I_{\mathrm{PD}1}-{\mathrm{<figure-callout\; id="2"\; label="I\; PD"\; filenames="HDA0000059982990000021.png,HDA0000059982990000022.png"\; state="\{\{state\}\}">I</figure-callout>}}_{\mathrm{PD}}=4\sqrt{I_1{\mathrm{<figure-callout\; id="2"\; label="I"\; filenames="HDA0000059982990000021.png,HDA0000059982990000022.png"\; state="\{\{state\}\}">I</figure-callout>}}_2}\left|\mathrm{\&gamma;}\left(x\right)\right|\cos (k_{1}x+{\mathrm{\&phi;}}_1)---\left(2\right)$

Its white light interference signal is as shown in Figure 2.Specific to the optical fiber measurement system of Fig. 4, be measuring-signal and equate in the optical path difference of introducing between annular multiple beam maker catoptron 54 and the optical fiber collimator in light path that sensor 41 left and right sides end face reflections are accumulated and reference signal.

(nL ₁+2X)-nL ₂-＝2nl (3)

Wherein, l is the length of the Fibre Optical Sensor between the reflecting surface of the left and right sides, and n is the refractive index of fiber core, and X represents optical fiber collimator 53 to the distance between the catoptron 54, nL ₁Be the light path of d-＞e+e-＞f, nL ₂Light path for h.

By the coherent light that laser of narrowband light source 55 sends, pass through two arms of non-equilibrium Mach-Zehnder optics autocorrelator 5 equally after, arrive in the interference signal probe unit 6.Because the spectrum of light source 55 is extremely narrow; Its coherent length is much larger than the optical path difference of 5 liang of arms of optics autocorrelator; Therefore in the light path of catoptron 54 motion realization light paths scanning; The flashlight that comes from light source 55 can be realized interfering after through 55 liang of arms of light path scan arm all the time, is surveyed by other two detectors in the interference signal probe unit 6 equally.Can be expressed as:

$I_{\mathrm{<figure-callout\; id="3"\; label="PD"\; filenames="HDA0000059982990000021.png,HDA0000059982990000031.png"\; state="\{\{state\}\}">PD</figure-callout>}3}=I_3+{\mathrm{<figure-callout\; id="4"\; label="I"\; filenames="HDA0000059982990000022.png"\; state="\{\{state\}\}">I</figure-callout>}}_4+2\sqrt{I_3{\mathrm{<figure-callout\; id="4"\; label="I"\; filenames="HDA0000059982990000022.png"\; state="\{\{state\}\}">I</figure-callout>}}_4}\&CenterDot;\cos (k_{2}x+{\mathrm{\&phi;}}_2)$ (4)

$I_{\mathrm{<figure-callout\; id="4"\; label="PD"\; filenames="HDA0000059982990000022.png"\; state="\{\{state\}\}">PD</figure-callout>}4}=I_3+I_4-2\sqrt{I_3{I}_4}\&CenterDot;\cos (k_{2}x+{\mathrm{\&phi;}}_2)$

In the formula: I ₃, I ₄Be the signal intensity of the reference beam and the measuring beam of laser of narrowband, k ₂Be the wave number of wide spectrum light source, x is two interference signal optical path differences,

Be initial phase.

Processing through the another one differential amplifier in the interference signal probe unit 6 obtains:

$I_{\mathrm{PD}3}-{\mathrm{<figure-callout\; id="4"\; label="I\; PD"\; filenames="HDA0000059982990000022.png"\; state="\{\{state\}\}">I</figure-callout>}}_{\mathrm{PD}}=4\sqrt{I_1{I}_2}\cos (k_{2}x+{\mathrm{\&phi;}}_2)---\left(5\right)$

Its narrow band light interference signal is as shown in Figure 4, and is wherein corresponding among light path scanning position X and Fig. 2.

Wide range light is separated by wavelength division multiplexer 61a, 61b in the interference signal probe unit 6 with narrow band light; Wavelength division multiplexer has two spectral response ranges can be with wide spectrum light source 1 and narrow-linewidth laser light source 56 good making a distinction in the optical frequency territory, thus make the photodetector 62a that connects on it and 63a, 62b and 63b realize respectively to the detection of broadband and narrow-band light source interference fringe with separate.

Can know by (2) and (5) formula; The difference that wide range light and laser of narrowband are interfered is; Catoptron 54 carries out light path when scanning, has only when d-＞e-＞f-＞e-＞g-h and R10-＞R11 are approaching when equating, white light interference (as shown in Figure 2) could take place wide range light; And in the overall process of light path scanning, laser of narrowband has interference fringe output (as shown in Figure 5) all the time.And if catoptron 55 carries out the light path scanning of high precision, high uniformity, the interference fringe of laser of narrowband is constant amplitude, equifrequent sinusoidal signal; Otherwise then it will produce distortion.When reality scans light path; Because scan table precision, motion control precision, light path degree of regulation etc. are limited; Produce the light path scanning errors inevitably; Utilization can be proofreaied and correct the light path scanning process the processing and the assessment of laser of narrowband output interference signal characteristic, improves the precision of signal measurement.

Have the M-Z light path autocorrelator structure of optical circulator among the present invention, and the laser of narrowband light source that connects on it makes it have following significant advantage and characteristics:

The detection of the high coherent interference signal that (1) produces after utilizing narrow-linewidth laser through non-equilibrium Mach-Zehnder light path correlator; Obtain the light path scanning accuracy of sub-wavelength level; Utilize characteristics such as interference signal single-frequency constant amplitude simultaneously, can realize, suppressed the kinematic error of light path scanning light path scan amplitude and homogeneity fine compensation; The white light interference accuracy of detection is brought up to sub-micrometer scale, realized the high-acruracy survey of Fibre Optical Sensor;

(2) be utilized in and connect complementary double detector behind the non-equilibrium Mach-Zehnder light path correlator; Can realize the detection of the differential white light interference signal of balanced type; Suppressed to come from the interference bat noise that the non-white light interference signal of sensor produces; Improve the detection signal-to-noise ratio of light path correlator, improved the multiplexing number of interferometer equivalently;

(3) introducing of optical circulator between light source and the sensor array and in the non-equilibrium M-Z optics autocorrelator; Make the light signal that sends by light source only have the characteristic of fl transmission; Its advantage is: light signal can't be got back in the light source, has avoided the light beam feedback, increases the stability of light-source system; Avoided twice (perhaps repeatedly) through the light path autocorrelator, suppressed secondary (repeatedly) the light path coupling interaction noise that causes; The power of light source all reaches detection array; And the signal power by the sensor array reflection also all arrives detector, when using same light source, even consider the decay of optical circulator; Also be that the power that reaches detector doubles at least, greatly improved the utilization factor of light source.Light path topological structure disclosed by the invention is the present known the highest a kind of light path of light source utilization ratio.

The demodulating equipment of the multiplex fibre optic interferometer based on non-equilibrium Mach-Zehnder optics autocorrelator disclosed by the invention.It adopts non-equilibrium M-Z interferometer and circulator to constitute the light path correlator; Realized the signal demodulation of multiplexing fiber-optic sensor; The light path matching condition of unique existence has suppressed the interaction noise that the secondary light path matees; The reflected light signal of sensor is all participated in interventional procedures, is the highest a kind of light channel structure of light source utilization ratio; No light signal feeds back in the light source, has increased the stability of system.The narrow-linewidth laser light source that employing is compound in the light path correlator is estimated light path scan amplitude and homogeneity, has compensated the light path scanning errors, has improved the sensor measurement precision.Adopt balanced differential double detector detection method, reduce the interference of interferometer and clap noise, improved the multiplexing number of interferometer.But the present invention can be used for the real-time monitoring and the measurement of physical quantitys such as multiple spot strain or temperature, fields such as large-sized intelligence structure monitoring.

Description of drawings

Fig. 1 is typical white light interference Michelson interferometer structure synoptic diagram.

Fig. 2 is typical white-light fringe signal schematic representation.

Fig. 3 is based on the multiplexed light channel structure synoptic diagram of Fibre Optical Sensor of non-equilibrium Michelson interferometer structure light path autocorrelator.

Fig. 4 is based on the light channel structure synoptic diagram of the fibre optic interferometer connection single-sensor of non-equilibrium Mach-Zehnder interferometer structure light path autocorrelator.

The interference signal that narrow-band light source produced through the light path autocorrelator when Fig. 5 was light path scanning ideal.

Fig. 6 is based on non-equilibrium Mach-Zehnder light path autocorrelator and utilizes optical branching device to realize the multiplexed light path synoptic diagram of fibre optic interferometer.

Embodiment

Below in conjunction with embodiment and accompanying drawing the present invention is described further, but should limit protection scope of the present invention with this.

Embodiment: utilize optical branching device to realize the scheme of a kind of distributing optical fiber sensing measuring system that fibre optic interferometer is multiplexed based on non-equilibrium Mach-Zehnder light path autocorrelator, as shown in Figure 6.Can know by Fig. 6, wideband light source 1 and narrow-band light source 55 respectively by centre wavelength 1550nm, half spectral width greater than SLD light source and the centre wavelength 1310nm of 30nm, partly spectrum width constitutes less than the DFB light source of 1pm.Optical branching device is made up of the 1 * N fiber switch that works in the 1550nm wave band.In the fibre optic sensor arra 4, S ₁₁～S _NNLength approximately be 1 meter, and length each is unequal, difference in length is more than 1mm; Transmission Fibers 3 is the single-mode fiber formation of 50km for maximum length; First coupling mechanism 51 and second coupling mechanism 56 are the equal branch/coupler of the dual wavelength 3dB that can be operated in 1310nm and 1550nm and constitute; Three port photocirculators also can be operated in 1310nm and two windows of 1550nm. and the initial light path difference of 5 liang of arms of non-equilibrium Mach-Zehnder optics autocorrelator is about 1m; Light path scanning distance between optical fiber collimator 53 and the removable catoptron 54 (reflectivity is more than 90%) changes between 0～400mm greatly, and the insertion loss is 1.5dB.Wavelength division multiplexer 61a in the interference signal probe unit 6,61b are respectively the 1310nm/1550nm Coarse Wave Division Multiplexer; Photodetector 62a, 62b, 63a, 63b are the InGaAs photodetector; The photodetection scope is 1100～1700nm; Can cover the spectrum of wide spectrum light source and laser of narrowband simultaneously, as adopting the Nirvana of New Focus company ^TMSeries 2017 type balance detection devices.

Only occur near the light path coupling several microns between tens microns based on the interference fringe of the fibre optic interferometer of white light interference principle.Utilize this characteristics, need not to utilize complicated time-division or frequency multiplexing technique, can realize the multiplexing of sensor, as shown in Figure 6.With Fibre Optical Sensor S ₁₁～S _1NEnd to end composition serial array 4.The end face of each sensor all has certain reflectivity R ₁₀～R _1NIf the length of each sensor is greater than the coherent length of light source, then only there is single white light interference signal in interference fringe in coherent length separately, and promptly interference fringe is not disturbed mutually, and is separate; But through adjusting implementation space light path scanning to the scanning reflection mirror 54 in the non-equilibrium Mach-Zehnder optics autocorrelator 5; If the length of each sensor is not simultaneously; Just can distinguish a plurality of sensors; Thereby realize to the inquiry of a plurality of external physical quantity with inquire, can realize very easily that distributed sensing measures.

By above-mentioned visible; Distributed optical fiber white light interference sensor array multiplexed with basic thought demodulation be when being compensated by the variable light path difference that produces in the non-equilibrium Mach-Zehnder optics autocorrelator 5 by the optical path difference that sensor is introduced; Light path coupling one to one takes place; Make the white-light fringe of generation separate on the light path scanning space, do not disturb mutually, thereby realize the distributed sensing measurement.

As sensor S _KjWhen receiving extraneous factor effect generation deformation such as strain, regulate variable parameter X _Kj, make the light path coupling, that is:

ΔX _kj＝Δnl _kj k，j＝1，2，3，...N (6)

Suppose that first Fibre Optical Sensor length in the first via array is by l ₁₁Change to l ₁₁+ Δ l ₁₁, second sensor is by l ₁₂Change to l ₁₂+ Δ l ₁₂, N sensor is by l _NChange to l _1N+ Δ l _1NIn like manner,, equally also like this for the sensor in the N road through switches light shunt 7.Then, then can obtain the strain of each sensor institute perception through the variable quantity of survey sensor length

$\begin{array}{c}{\mathrm{\&epsiv;}}_{11}=\frac{\mathrm{\&Delta;}{l}_{11}}{{\mathrm{<figure-callout\; id="11"\; label="l"\; filenames="HDA0000059982990000011.png"\; state="\{\{state\}\}">l</figure-callout>}}_{11}},{\mathrm{\&epsiv;}}_{12}=\frac{\mathrm{\&Delta;}{l}_{12}}{{\mathrm{<figure-callout\; id="12"\; label="l"\; filenames="HDA0000059982990000011.png"\; state="\{\{state\}\}">l</figure-callout>}}_{12}},......{\mathrm{\&epsiv;}}_N=\frac{\mathrm{\&Delta;}{l}_{1N}}{l_{1N}}\\ \&CenterDot;\&CenterDot;\end{array}---\left(7\right).$

${\mathrm{\&epsiv;}}_{\mathrm{<figure-callout\; id="1"\; label="N"\; filenames="HDA0000059982990000012.png,HDA0000059982990000021.png"\; state="\{\{state\}\}">N</figure-callout>}1}=\frac{\mathrm{\&Delta;}{l}_{N1}}{{\mathrm{<figure-callout\; id="1"\; label="l\; N"\; filenames="HDA0000059982990000012.png,HDA0000059982990000021.png"\; state="\{\{state\}\}">l</figure-callout>}}_N},{\mathrm{\&epsiv;}}_{12}=\frac{\mathrm{\&Delta;}{L}_{N2}}{{\mathrm{<figure-callout\; id="2"\; label="l\; N"\; filenames="HDA0000059982990000021.png,HDA0000059982990000022.png"\; state="\{\{state\}\}">l</figure-callout>}}_N},......{\mathrm{\&epsiv;}}_{\mathrm{NN}}=\frac{\mathrm{\&Delta;}{L}_{\mathrm{NN}}}{l_{\mathrm{NN}}}$

Claims (9)

1. the demodulating equipment based on the multiplex fibre optic interferometer of non-equilibrium Mach-Zehnder switches Transmission Fibers (3), fibre optic sensor arra (4), non-equilibrium Mach-Zehnder optics autocorrelator (5) and interference signal probe unit (6) wide spectrum light source (1), optical circulator (2), optical branching device (7), sensor array and is formed by connecting; It is characterized in that:

The first input end (a) of said optical circulator (2) connects wide spectrum light source (1), and second output terminal (b) connects fibre optic sensor arra (4) through Transmission Fibers (3), and reflection end (c) connects non-equilibrium Mach-Zehnder optics autocorrelator (5);

Said non-equilibrium Mach-Zehnder optics autocorrelator (5) is made up of first fiber coupler (51), second optical circulator (52), optical fiber collimator (53), removable optical mirror (54), second fiber coupler (55) and narrow linewidth laser (56); The input port of first fiber coupler (51) connects the reflector port (c) and the narrow linewidth laser (56) of optical circulator (2) respectively; Two optics output terminals of first fiber coupler (51) are connected with the input end (d) of second optical circulator (52) and the input end (h) of second coupling mechanism (55) respectively; The output terminal (e) of second optical circulator (52) is connected with optical fiber collimator (53); The reflector port (g) of second optical circulator (52) links with an optics input port of second coupling mechanism (26);

Said interference signal probe unit (6) is by two wavelength division multiplexers (61a, 61b), four photodetectors (62a, 62b, 63a, 63b), and two differential amplifiers (64a, 64b) and data acquisition system (DAS) (65) and signal Processing computing machine (66) connect to form.

2. the demodulating equipment of the multiplex fibre optic interferometer based on non-equilibrium Mach-Zehnder according to claim 1; It is characterized in that: described optical circulator (2) and second optical circulator (52) are to have an optics input end, an optics output terminal and an optical reflection end; Has the optical-unidirectional transfer function; Inject light signal only by output terminal output by input end, inject light signal by output terminal, the optical circulator of then only exporting by reflection end.

3. the demodulating equipment of the multiplex fibre optic interferometer based on non-equilibrium Mach-Zehnder according to claim 2; It is characterized in that: described optical branching device (7) is a section single-mould fiber; Or the fiber coupler divided equally of 1 * N, or 1 * N fiber switch.

4. the demodulating equipment of the multiplex fibre optic interferometer based on non-equilibrium Mach-Zehnder according to claim 3; It is characterized in that: described first fiber coupler (51) and second fiber coupler (55) have two optical input signals ends and two optical output signal ends at least, and splitting ratio is 50: 50.

5. the demodulating equipment of the multiplex fibre optic interferometer based on non-equilibrium Mach-Zehnder according to claim 4, it is characterized in that: the work spectral range of described first fiber coupler (51), second fiber coupler (55) and second optical circulator (52) covers the emission spectrum of wide spectrum light source (1) and narrow linewidth laser (56) simultaneously.

6. the demodulating equipment of the multiplex fibre optic interferometer based on non-equilibrium Mach-Zehnder according to claim 5; It is characterized in that: two of described non-equilibrium Mach-Zehnder optics autocorrelator (5) interferes the sweep limit of arm optical path difference to cover the light path value that the Fibre Optical Sensor front/rear end is produced, the size of the change in optical path length that is produced when comprising fiber sensor measuring comprehensively.

7. the demodulating equipment of the multiplex fibre optic interferometer based on non-equilibrium Mach-Zehnder according to claim 6; It is characterized in that: the spectral range of described narrow linewidth laser (56) and wide spectrum light source (1) are not overlapping, and the coherent length of narrow linewidth laser (56) is greater than more than 10 times of two arm optical path differences of non-equilibrium Mach-Zehnder optics autocorrelator (5).

8. the demodulating equipment of the multiplex fibre optic interferometer based on non-equilibrium Mach-Zehnder according to claim 7; It is characterized in that: the wavelength division multiplexer of described interference signal probe unit (6) (61a, 61b) has an input end, links to each other with two outputs of second coupling mechanism (55) respectively; Two output terminals that spectral response range is different, corresponding with the spectral range of wide spectrum light source (1) and narrow-linewidth laser light source (56) respectively; The photodetector (62a and 63a, 62b and 63b) that is connected on the output terminal of same spectra response is realized the differential type balance detection in twos.

9. the demodulating equipment of the multiplex fibre optic interferometer based on non-equilibrium Mach-Zehnder according to claim 8 is characterized in that: described Optical Fiber Sensing Array (4) is made up of several head and the tail Fibre Optical Sensor (41) of serial connection successively; And Fibre Optical Sensor (41) by a segment length arbitrarily, the two ends single-mode fiber that has a fiber stub forms a series of single-mode fiber sections that are uneven in length and constitutes end to end serial array.

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