CN103558438B - A kind of system and method reducing the drift of reflection type optical fiber current meter - Google Patents

Abstract

The invention discloses a kind of system reducing the drift of reflection type optical fiber current meter, comprise SLD device, PINFET device, SLD device, PINFET device are connected by the mode of welding with lithium niobate Y waveguide integrated optical device, and lithium niobate Y waveguide integrated optical device swings to use.The invention also discloses a kind of method reducing the drift of reflection type optical fiber current meter, the polarization characteristic of each polarizer in light path is represented with Jones matrix, show that normalization scaling factor formula normalization scaling factor reflects the proportionate relationship of actual test result and desired result, show that extinction ratio is larger by analyzing, normalization factor of influence is more tending towards 1, namely the phase error introduced is less, and the drift of system is lower.The present invention uses lithium niobate Y waveguide integrated optical device to replace 3db coupling mechanism in existing system and the polarizer by swinging to, improve the polarization extinction ratio of system, obviously can reduce the impact of all-fiber current transformator polarization error, reduce drift, improve system zero bias stability.

Description

A kind of system and method reducing the drift of reflection type optical fiber current meter

Technical field

The invention belongs to full optical-fiber current field of sensing technologies, relate to a kind of system and method reducing the drift of reflection type optical fiber current meter.

Background technology

Reflection type optical fiber current meter because security is high, advantages of simple structure and simple large without hysteresis & saturation, measurement range, be subject to the attention of various countries researcher.At present, because the optical device in real system is not completely desirable, there is the crosstalk between polarized light in system, shows as other nonreciprocal phase shift introducing non-faraday's phase shift, and in no current situation, system exports non-vanishing, namely occurs zero drift phenomenon.For the galvanometer that drift is large, cannot judge that it exports is drift about or have less electric current, becomes problem demanding prompt solution in industrialization process.

Solve drift problem, key is the polarization error phenomenon eliminating all-fiber current transformator.For the polarization error problem of all-fiber current transformator, document [1] utilizes Jones matrix method, the error that each dominant polarization device of system brings is emulated, [2] the selective analysis impact of four/wave plate, [3] analyze nonreciprocal phase shift that its exterior environmental factor brings to the impact of test.But the above document of the polarization error for all-fiber current transformator does not all propose effective solution.

[1] Wang Xiaxiao, Zhang Chunxi. polarization error research [J] of all-fiber current transformator. photon journal, 2007,362:320-323

[2] JinhuiHao, PingHuang, XuyouLi.PolarizationErrorsAnalysisofWaveplateinSagnacOpt icalFiberCurrentSensor [J] .2011InternationalConferenceonElectronic & MechanicalEngineeringandInformationTechnology(Hao Jin brightness, polarization error analysis [J] the .2011 electronics of Huang Ping, Li Xu friend .Sagnac type fibre optic current sensor wave plate and mechanical engineering and infotech international conference .238-241)

[3] WeiWangn, XuefengWang, JunleiXia.TheNonreciprocalErrorsinFiberOpticCurrentSenso rs [J] .Optics & LaserTechnology, 2011,43:1470-1474(Wang Wei etc. the nonreciprocal error [J] of fibre optic current sensor. optics and laser technology, 2011,43:1470-1474.)

Summary of the invention

The object of this invention is to provide a kind of system and method reducing the drift of reflection type optical fiber current meter, solve the technical matters that in prior art, the drift of conventional reflector formula optical fibre amperemeter is larger.

The technical solution adopted in the present invention is, a kind of system reducing the drift of reflection type optical fiber current meter, comprise SLD device, PINFET device, SLD device, PINFET device is connected by the mode of welding with lithium niobate Y waveguide integrated optical device, lithium niobate Y waveguide integrated optical device swings to use, the light that SLD device sends becomes linearly polarized light through lithium niobate Y waveguide integrated optical device, by 45 ° of fusion points, a branch of linearly polarized light becomes the orthogonal linearly polarized light of two bundles, respectively along X-axis and the Y-axis propagation of polarization maintaining optical fibre, after quarter wave plate, two bunch polarized lights change left circularly polarized light and right-circularly polarized light respectively into, sensor fibre end is transferred to by sensor fibre, sensor fibre end is provided with catoptron.Upset is there is and returns by original optical path in left circularly polarized light and right-circularly polarized light by mirror polarization state, when left circularly polarized light and right-circularly polarized light are by sensor fibre, due to the Faraday effect of current induced magnetic field, make between the transmission phase place of left circularly polarized light and right-circularly polarized light, to produce faraday's difference; Simultaneously, the polarization state produced by catoptron overturns and the process returned by original optical path, the phase differential that Faraday effect is produced doubles, in time reaching quarter wave plate place, left circularly polarized light and right-circularly polarized light change mutually orthogonal linearly polarized light into, two bunch polarized lights interfere, and are measured by PINFET device.

The invention also discloses a kind of method reducing the drift of reflection type optical fiber current meter, its feature is: comprise,

When the polarizer is undesirable and in supposing the system, other devices are ideal component, available following Jones matrix represents the polarization characteristic of each polarizer in light path

(1) optical fiber polarizer P $G_p=\left[\begin{array}{cc}1& 0\\ 0& \mathrm{\ϵ}\end{array}\right]$

Wherein, ε represents the amplitude ratio that electric vector is respective in extinction axis and light transmission shaft direction, uses T=-10log ε ²represent extinction ratio

(2) 45 ° of fusion point S(3) phase-modulator Z

$G_s=\frac{1}{\sqrt{2}}\left[\begin{array}{cc}1& -1\\ 1& 1\end{array}\right]G_{\mathrm{Zin}}=\left[\begin{array}{cc}1& 0\\ 0& e^{\mathrm{i\ψ}(t-\mathrm{\τ})}\end{array}\right]G_{\mathrm{Zout}}=\left[\begin{array}{cc}1& 0\\ 0& e^{\mathrm{i\ψ}\left(t\right)}\end{array}\right]$

In formula, ψ (t-τ) represents the phase modulation of t-τ moment phase-modulator, and ψ (t) represents the phase modulation of t phase-modulation

(4) four/wave plate R(5) Faraday device

$G_{\mathrm{Rin}}=\frac{1}{\sqrt{2}}\left[\begin{array}{cc}1& i\\ i& 1\end{array}\right]G_{\mathrm{Rout}}=\frac{1}{\sqrt{2}}\left[\begin{array}{cc}1& -i\\ -i& 1\end{array}\right]G_{\mathrm{Fin}}=\left[\begin{array}{cc}\cos \mathrm{\θ}& \sin \mathrm{\θ}\\ -\sin \mathrm{\θ}& \cos \mathrm{\θ}\end{array}\right]G_{\mathrm{Fout}}=\left[\begin{array}{cc}\cos \mathrm{\θ}& -\sin \mathrm{\θ}\\ \sin \mathrm{\θ}& \cos \mathrm{\θ}\end{array}\right]$

Wherein, θ=VNI, V represent Verdet constant, and N is the sensor fibre number of turn, and I is tested electric current

(6) end reflector M $G_M=\left[\begin{array}{cc}1& 0\\ 0& -1\end{array}\right]$

Export the expression formula E of light vector _out=G _pg _sg _zoutg _routg _foutg _mg _fing _ring _zing _sg _pe _in

Wherein, E _infor input light, be expressed as $E_{\mathrm{in}}=\left[\begin{array}{c}1\\ 1\end{array}\right]$

Output intensity

I _out＝0.5[(1+ε ²) ²+(ε ²-1) ²cos(Δφ+4θ)]①

Wherein Δ φ=ψ (t-τ)-ψ (t), represents that the phase differential after demodulation is because the non-reciprocal phase difference of phase-modulation introducing is for open loop demodulation scheme:

Normalization scaling factor

Normalization scaling factor reflects the proportionate relationship of actual test result and desired result, and extinction ratio is larger, and normalization factor of influence is more tending towards 1, and the phase error namely introduced is less, and the drift of system is lower.

The invention has the beneficial effects as follows: reasonable in design of the present invention, lithium niobate Y waveguide integrated optical device is used to replace 3db coupling mechanism in existing system and the polarizer by swinging to, improve the polarization extinction ratio of system, obviously can reduce the impact of all-fiber current transformator polarization error, reduce drift, improve system zero bias stability.

Accompanying drawing explanation

Fig. 1 is reflection type optical fiber current meter systems block diagram in prior art;

Fig. 2 is that the present invention swings to use Y waveguide architecture system block diagram;

Fig. 3 is the relation schematic diagram of normalization scaling factor of the present invention and extinction ratio;

Fig. 4 is present system polarization coupled illustraton of model;

Fig. 5 is present system polarization state evolution;

Fig. 6 is the long-term drift test result figure of the present invention;

Wherein: SLD interface 1, PINFET interface 2, lithium niobate Y waveguide integrated optical device 3,45 ° of fusion points 4, phase-modulator 5, quarter wave plate 6, catoptron 7, the polarizer 8, Coupling point Q9, polarizer N10,3db coupling mechanism 11.

Embodiment

Below in conjunction with the drawings and specific embodiments, the present invention is described in detail.

As shown in Figure 1: this reflection type optical fiber current meter, comprise SLD device 1, PINFET device 2, the light that SLD device 1 sends is through 3db coupling mechanism 11, linearly polarized light is become again after the polarizer 8, by 45 ° of fusion points 4, through phase-modulator 5, a branch of linearly polarized light becomes the orthogonal linearly polarized light of two bundles, respectively along X-axis and the Y-axis propagation of polarization maintaining optical fibre, after quarter wave plate 6, two bunch polarized lights change left circularly polarized light and right-circularly polarized light respectively into, when left circularly polarized light and right-circularly polarized light are by sensor fibre, due to the Faraday effect of current induced magnetic field, faraday's difference is produced between left circularly polarized light and right-circularly polarized light, left circularly polarized light and right-circularly polarized light are transferred to sensor fibre end, sensor fibre end is provided with catoptron 7, due to the effect of catoptron 7, there is upset and return by original optical path in left circularly polarized light and right-hand circular polarization polarization state, again through sensor fibre, the phase differential produced due to Faraday effect doubles, reach quarter wave plate 6 place's left circularly polarized light and right-circularly polarized light changes mutually orthogonal linearly polarized light into, two bunch polarized lights interfere at the polarizer 8 place.

As shown in Figure 2: a kind of system reducing the drift of reflection type optical fiber current meter of the present invention, comprise SLD device 1, PINFET device 2, SLD device 1, PINFET device 2 is connected by the mode of welding with lithium niobate Y waveguide integrated optical device 3, lithium niobate Y waveguide integrated optical device 3 swings to use, the light that SLD device 1 sends becomes linearly polarized light through lithium niobate Y waveguide integrated optical device 3, by 45 ° of fusion points 4, a branch of linearly polarized light becomes the orthogonal linearly polarized light of two bundles, respectively along X-axis and the Y-axis propagation of polarization maintaining optical fibre, after quarter wave plate 6, two bunch polarized lights change left circularly polarized light and right-circularly polarized light respectively into, left circularly polarized light and right-circularly polarized light are transferred to sensor fibre end by sensor fibre, sensor fibre end is provided with catoptron 7.Upset is there is and returns by original optical path in left circularly polarized light and right-circularly polarized light by mirror polarization state, when left circularly polarized light and right-circularly polarized light are by sensor fibre, due to the Faraday effect of current induced magnetic field, make between the transmission phase place of left circularly polarized light and right-circularly polarized light, to produce faraday's difference; Simultaneously, the polarization state produced by catoptron overturns and the process returned by original optical path, the phase differential that Faraday effect is produced doubles, in time reaching quarter wave plate 6 place, left circularly polarized light and right-circularly polarized light change mutually orthogonal linearly polarized light into, two bunch polarized lights interfere, and are measured by PINFET device 2.

A kind of method reducing the drift of reflection type optical fiber current meter of the present invention, its feature is: comprise,

When the polarizer is undesirable and in supposing the system, other devices are ideal component, available following Jones matrix represents the polarization characteristic of each polarizer in light path

(1) optical fiber polarizer P $G_p=\left[\begin{array}{cc}1& 0\\ 0& \mathrm{\ϵ}\end{array}\right]$

Wherein, ε represents the amplitude ratio that electric vector is respective in extinction axis and light transmission shaft direction, uses T=-10log ε ²represent extinction ratio

(2) 45 ° of fusion point S(3) phase-modulator Z

$G_s=\frac{1}{\sqrt{2}}\left[\begin{array}{cc}1& -1\\ 1& 1\end{array}\right]G_{\mathrm{Zin}}=\left[\begin{array}{cc}1& 0\\ 0& e^{\mathrm{i\ψ}(t-\mathrm{\τ})}\end{array}\right]G_{\mathrm{Zout}}=\left[\begin{array}{cc}1& 0\\ 0& e^{\mathrm{i\ψ}\left(t\right)}\end{array}\right]$

In formula, ψ (t-τ) represents the phase modulation of t-τ moment phase-modulator, and ψ (t) represents the phase modulation of t phase-modulation

(4) four/wave plate R(5) Faraday device

$G_{\mathrm{Rin}}=\frac{1}{\sqrt{2}}\left[\begin{array}{cc}1& i\\ i& 1\end{array}\right]G_{\mathrm{Rout}}=\frac{1}{\sqrt{2}}\left[\begin{array}{cc}1& -i\\ -i& 1\end{array}\right]G_{\mathrm{Fin}}=\left[\begin{array}{cc}\cos \mathrm{\θ}& \sin \mathrm{\θ}\\ -\sin \mathrm{\θ}& \cos \mathrm{\θ}\end{array}\right]G_{\mathrm{Fout}}=\left[\begin{array}{cc}\cos \mathrm{\θ}& -\sin \mathrm{\θ}\\ \sin \mathrm{\θ}& \cos \mathrm{\θ}\end{array}\right]$

Wherein, θ=VNI, V represent Verdet constant, and N is the sensor fibre number of turn, and I is tested electric current

(6) end reflector M $G_M=\left[\begin{array}{cc}1& 0\\ 0& -1\end{array}\right]$

Export the expression formula E of light vector _out=G _pg _sg _zoutg _routg _foutg _mg _fing _ring _zing _sg _pe _in

Wherein, E _infor input light, be expressed as $E_{\mathrm{in}}=\left[\begin{array}{c}1\\ 1\end{array}\right]$

Output intensity

I _out＝0.5[(1+ε ²) ²+(ε ²-1) ²cos(Δφ+4θ)]①

Wherein Δ φ=ψ (t-τ)-ψ (t), represents that the phase differential after demodulation is because the non-reciprocal phase difference of phase-modulation introducing is for open loop demodulation scheme:

Normalization scaling factor

Normalization scaling factor reflects the proportionate relationship of actual test result and desired result, and extinction ratio is larger, and normalization factor of influence is more tending towards 1, and the phase error namely introduced is less, and the drift of system is lower.

As shown in Figure 3, transverse axis is extinction ratio, and simulation result shows that extinction ratio is larger, and normalization factor of influence is more tending towards 1, and the phase error namely introduced is less, and the drift of system is lower.

As shown in Figure 4: suppose at distance 45 ° of fusion point 4l ₁have a polarization coupled point Q9 after length, polarizer N10 regarded as by all devices after polarization coupled point Q9, and the rear section of polarization coupled point Q9, length is designated as l ₂.Because the polarizer 8 extinction ratio is undesirable, input light wave becomes along printing opacity axial light wave A1 with along the axial A of delustring after the polarizer 8 ₂, after 45 ° of fusion points 4, this two-beam wavelength-division is not decomposed into the vertical light wave A in polarization direction ₁₁, A ₁₂and A ₂₁, A ₂₂, this four bundles light wave continues to propagate, through polarization coupled point Q9 and polarizer N10.Process for simplifying the analysis, we only consider that light wave first time, the situation of polarization coupled occurred through polarization coupled point Q9, and do not consider the polarization coupled of return course.Can be divided three classes when light wave returns 45 ° of fusion points 4 again like this, be respectively there is not any coupling but polarization state upset key light ripple to A ₁₁, A ₁₂and A ₂₁, A ₂₂, by light wave A ₁₁, A ₁₂be coupled to the coupling light wave after orthogonal polarization axes respectively to A ₁₁₂, A ₁₂₁, by light wave A ₂₁, A ₂₂be coupled to the coupling light wave after orthogonal polarization axes respectively to A ₂₁₂, A ₂₂₁.These 4 pairs of light waves are decomposed into 16 bundle light waves after 45 ° of fusion points 4.

As shown in Figure 5: all light waves arrive polarizer place and interfere situation as follows:

By key light ripple to A ₁₁, A ₁₂and A ₂₁, A ₂₂the light wave that decomposition obtains is to A _1k1, A _2k1and A _1k2, A _2k2(k=1,2), produce main interference signal, and the non-reciprocal phase that interference phase difference is only the introducing of sensing head part is poor.

Coupling light wave is to A ₁₁₂, A ₁₂₁because experienced by a polarization coupled, after whole transmitting procedure, its light path is not identical, and the phase shift of this two-beam is respectively

β in formula _xfor polarization maintaining optical fibre X polarization axle propagation constant, β _yfor polarization maintaining optical fibre Y polarization axle propagation constant.Non-reciprocal phase difference between two-beam ripple is expressed as

6. known by formula, Coupling point distance 45 ° of fusing points are nearer, and the nonreciprocal difference of generation is less.Light wave A ₁₁₂, A ₁₂₁a is decomposed into after 45 ° of fusing points _1i1, A _1i2(i=12,21), light wave A _1i1with A _1k1polarization direction is identical, A _1i2with A _1k2polarization direction is identical, interferes between them, and total phase error is proportional to ε.In like manner, be coupled light wave A ₂₁₂, A ₂₂₁through 45 ° of fusing points, the interference of the light wave after decomposition and they be also proportional to ε with the phase error that corresponding main wave interference is introduced.

As shown in Figure 6: in experimentation, we use light source for 1310nmSLD, PINFET model is MFT915, and lock-in amplifier is SR830, is gathered the drift data of two cover systems by data collecting card respectively, every system testing 3 hours, Fig. 6 tests the long-term drift test result obtained, and can be obtained by experiment with computing data, system drift drops to 1.58A from 11.1A, utilize Y waveguide structure to significantly reduce drift, improve reflection type optical fiber current meter output stability.

For the drift problem of reflection type optical fiber current meter, first the present invention has derived the relational expression of reflection type optical fiber current meter systems polarizer extinction ratio and normalization scaling factor, then the impact of extinction ratio on polarization interference is analyzed, show that raising extinction ratio can lower drift on this basis, improved the conclusion of system stability.Finally built the experimental system of two kinds of structures, found through experiments, swing to and use after Y waveguide, system drift is reduced to 1.58A from 11.1A, the theoretical correctness of this result strong authentication.

Reasonable in design of the present invention, lithium niobate Y waveguide integrated optical device 3 is used to replace 3db coupling mechanism 11 in existing system and the polarizer 8 by swinging to, improve the polarization extinction ratio of system, obviously can reduce the impact of all-fiber current transformator polarization error, reduce drift, improve system zero bias stability.

Specific embodiment described herein is only to the explanation for example of the present invention's spirit.Those skilled in the art can make various amendment or supplement or adopt similar mode to substitute to described specific embodiment, but can't depart from spirit of the present invention or surmount the scope that appended claims defines.

Claims (2)

1. one kind is reduced the system of reflection type optical fiber current meter drift, comprise SLD device (1), PINFET device (2), it is characterized in that: described SLD device (1), PINFET device (2) is connected by the mode of welding with lithium niobate Y waveguide integrated optical device (3), lithium niobate Y waveguide integrated optical device (3) swings to use, the light that SLD device (1) sends becomes linearly polarized light through lithium niobate Y waveguide integrated optical device (3), by 45 ° of fusion points (4), a branch of linearly polarized light becomes the orthogonal linearly polarized light of two bundles, respectively along X-axis and the Y-axis propagation of polarization maintaining optical fibre, after quarter wave plate (6), two bunch polarized lights change left circularly polarized light and right-circularly polarized light respectively into, sensor fibre end is transferred to by sensor fibre, sensor fibre end is provided with catoptron.

2. reduce a method for reflection type optical fiber current meter drift, its feature is: comprise,

When the polarizer is undesirable and in supposing the system, other devices are ideal component, available following Jones matrix represents the polarization characteristic of each polarizer in light path

(1) optical fiber polarizer P $G_p=\left[\begin{array}{cc}1& 0\\ 0& \mathrm{\ϵ}\end{array}\right]$

Wherein, ε represents the amplitude ratio that electric vector is respective in extinction axis and light transmission shaft direction, uses T=-10log ε ²represent extinction ratio

(2) 45 ° of fusion point S(3) phase-modulator Z

$G_s=\frac{1}{\sqrt{2}}\left[\begin{array}{cc}1& -1\\ 1& 1\end{array}\right]G_{\mathrm{Zin}}=\left[\begin{array}{cc}1& 0\\ 0& e^{\mathrm{i\ψ}(t-\mathrm{\τ})}\end{array}\right]G_{\mathrm{Zout}}=\left[\begin{array}{cc}1& 0\\ 0& e^{\mathrm{i\ψ}\left(t\right)}\end{array}\right]$

In formula, ψ (t-τ) represents the phase modulation of t-τ moment phase-modulator, and ψ (t) represents the phase modulation of t phase-modulation

(4) four/wave plate R(5) Faraday device

$G_{\mathrm{Rin}}=\frac{1}{\sqrt{2}}\left[\begin{array}{cc}1& i\\ i& 1\end{array}\right]G_{\mathrm{Rout}}=\frac{1}{\sqrt{2}}\left[\begin{array}{cc}1& -i\\ -i& 1\end{array}\right]G_{\mathrm{Fin}}=\left[\begin{array}{cc}\cos \mathrm{\θ}& \sin \mathrm{\θ}\\ -\sin \mathrm{\θ}& \cos \mathrm{\θ}\end{array}\right]G_{\mathrm{Fout}}=\left[\begin{array}{cc}\cos \mathrm{\θ}& -\sin \mathrm{\θ}\\ \sin \mathrm{\θ}& \cos \mathrm{\θ}\end{array}\right]$

Wherein, θ=VNI, V represent Verdet constant, and N is the sensor fibre number of turn, and I is tested electric current

(6) end reflector M $G_M=\left[\begin{array}{cc}1& 0\\ 0& -1\end{array}\right]$

Export the expression formula E of light vector _out=G _pg _sg _zoutg _routg _foutg _mg _fing _ring _zing _sg _pe _in

Wherein, E _infor input light, be expressed as $E_{\mathrm{in}}=\left[\begin{array}{c}1\\ 1\end{array}\right]$

Output intensity

I _out＝0.5[(1+ε ²) ²+(ε ²-1) ²cos(Δφ+4θ)]①

Wherein Δ φ=ψ (t-τ)-ψ (t), represents that the phase differential after demodulation is because the non-reciprocal phase difference of phase-modulation introducing is for open loop demodulation scheme:

Normalization scaling factor

Normalization scaling factor reflects the proportionate relationship of actual test result and desired result, and extinction ratio is larger, and normalization factor of influence is more tending towards 1, and the phase error namely introduced is less, and the drift of system is lower.