CN103868507B - The double; two interference type optical fiber gyroscope of difference based on tail optical fiber coupling polarizes nonreciprocal error inhibition method - Google Patents

Abstract

The invention discloses a method for suppressing polarization non-reciprocity errors of a differential double-interference optical fiber gyroscope based on pigtail matching. In this method, the optical fiber fusion splicing point and the coupler are used as nodes, and the pigtail and optical fiber on the optical path of the differential double-interference optical fiber gyroscope are segmented and identified, and the decoherence length of the broadband light source is obtained; secondly, the main wave train of the two-way gyroscope, The amplitude and phase of the primary and secondary polarization cross-coupled wave trains; then subtract the phases of the wave trains with the same polarization state at the output of the gyroscope to obtain the phase difference; finally convert the phase difference into an optical path difference, Construct the inequality group so that the coherence condition is satisfied between the main wave, the decoherence condition is satisfied between the main wave and the coupled wave train, and between the coupled wave train and the coupled wave train, and the length of each segment of fiber and pigtail is adjusted according to the inequality group. The invention realizes the effective suppression of the polarization non-reciprocity error of the differential double-interference fiber optic gyroscope, and improves the detection accuracy of the differential double-interference fiber optic gyroscope.

Description

Differential dual-interference fiber optic gyroscope polarization non-reciprocal error suppression method based on pigtail matching

technical field

The invention belongs to the technical field of fiber optic gyroscopes, and relates to a method for suppressing polarization non-reciprocity errors of fiber optic gyroscopes with differential double interference based on pigtail matching.

Background technique

As a new type of inertial angular velocity sensor that is developing extremely rapidly, fiber optic gyroscope has its unique technical and performance advantages, such as all-solid-state structure, high reliability, long life; fast start-up speed, short response time; large measurement range and wide dynamic range ; Anti-shock, vibration, chemical corrosion resistance; small size, light weight, low cost; suitable for mass production, etc., have been widely used in various fields.

The internationally accepted form of fiber optic gyroscope is the single interferometric type, that is, the fast axis or slow axis of a set of optical paths (a polarization-maintaining fiber ring) is used to realize the SAGNAC interferometer, through clockwise (CW) and counterclockwise (CCW) propagation The interference between the two main wave trains of , is used to solve the SAGNAC phase shift caused by the carrier rotation. Although the structure of this kind of interferometer is simple, with the continuous expansion of the application field of fiber optic gyro, the contradiction between its volume, weight and precision has become increasingly prominent. It is difficult to achieve a breakthrough with small volume and weight, and vice versa.

The differential double-interference fiber optic gyro implements a SAGNAC interferometer using its fast axis and slow axis in a set of optical paths (a polarization-maintaining fiber ring). The output of the two interferometers is in a differential form. After differential calculation , the SAGNAC effect is doubled. Since there is no polarizer in the optical system and the two polarization states of the polarization-maintaining fiber are used at the same time, the polarization states of the two interferometers affect each other. The complexity of the polarization non-reciprocal error is increased, and its generation mechanism is different from that of the traditional fiber optic gyroscope. Due to the fluctuation of polarization non-reciprocal error with temperature, it seriously affects the practical application of gyroscopes.

Contents of the invention

The purpose of the present invention is to solve the problem that the above-mentioned polarization non-reciprocity error fluctuates with temperature changes, thereby affecting the practical application of the gyroscope, and proposes a method for suppressing the polarization non-reciprocity error of the fiber optic gyroscope based on the matching of the differential double interference .

The method for suppressing the polarization non-reciprocity error of the differential dual-interference fiber optic gyroscope based on pigtail matching of the present invention comprises the following steps:

Step 1: Use the fiber splicing point and the coupler as nodes, mark the pigtails and optical fibers on the optical path of the differential double interference fiber optic gyroscope, and make a mark for a section of pigtail or optical fiber between two adjacent nodes; Obtain the decoherence length L _dc of the broadband light source;

Step 2: Obtain the amplitude and phase of the main wave trains of the two gyroscopes, and obtain the amplitude and phase of the primary and secondary polarization cross-coupled wave trains generated by the two gyroscopes;

Step 3: Subtract the phases of the wave trains with the same polarization state at the output end of the gyroscope to obtain the phase difference;

For a gyroscope, the main wave train of the gyroscope, the secondary polarization cross-coupling wave train generated, and the primary polarization cross-coupling wave train generated by another gyro have the same polarization state, and any two wave trains with the same polarization state Phase subtraction to obtain the phase difference, and obtain a set of phase differences of the gyroscope;

Step 4: converting the phase difference obtained in step 3 into an optical path difference;

Step 5: Construct the inequality group so that the coherence condition is satisfied between the main wave, the decoherence condition is satisfied between the main wave and the coupled wave train, and between the coupled wave train and the coupled wave train, and the lengths of each segment of fiber and pigtail are adjusted according to the inequality group.

The set of inequalities described is as follows:

|ΔOPD _1,2 |<L _dc ;

|ΔOPD _p,q |>L _dc, , 1≤p≤n, 1≤q≤n, and p≠q, p=1 when q≠2, p=2 when q≠1;

Among them, ΔOPD _p,q represents the optical path difference between the pth wave train and the qth wave train, and ΔOPD _1,2 represents the optical path difference between the two main waves.

In the above step 3, it is assumed that a certain gyroscope has n (n is a positive integer) wave trains with the same polarization state at the output end, then the phase difference between the pth wave train and the qth wave train for:

1≤p≤n, 1≤q≤n, and p≠q

and denote the phases of the p-th wave train and the q-th wave train, respectively.

In the described step 4, according to the following formula, the phase difference Convert to optical path difference ΔOPD _p,q :

where λ is the wavelength of the incident light wave.

The present invention provides a method for suppressing polarization non-reciprocal errors of differential dual-interference fiber optic gyroscopes, which has the following advantages and positive effects compared with the prior art:

(1) It can reduce the requirements on the parameters of optical fiber fusion points, couplers and other components in the optical system;

(2) The method is simple and easy to implement, and the suppression effect of polarization non-reciprocity error is remarkable.

Description of drawings

Figure 1 is a schematic block diagram of a differential double-interference optical fiber gyroscope optical system;

Fig. 2 schematic diagram of polarization cross-coupling point and each pigtail;

Fig. 3 is a schematic diagram of light wave transmission at melting point ₀₁ ;

Figure 4 is a schematic diagram of optical fiber on-axis fusion;

Fig. 5 is a schematic diagram of generation of primary and secondary polarization coupled wave trains;

Fig. 6 is a schematic flow chart of a method for suppressing polarization non-reciprocal errors of differential double interference fiber optic gyroscopes of the present invention;

Fig. 7 is the gyro output waveform before the pigtail is matched;

Figure 8 is the output waveform of the gyroscope after the pigtail is matched;

In the picture:

1-light source 2- First coupler 3-waveguide 4- Second coupler 5- Birefringent phase modulator 6-fiber ring 7- Polarization Beam Splitter 8- Input wave train 9- Primary coupled wave train 10-Secondary coupled wave train 11 - main wave train

detailed description

The technical solutions of the present invention will be further described in detail below in conjunction with the accompanying drawings.

The present invention is a method for suppressing polarization non-reciprocity errors based on differential double-interference optical fiber gyroscope.

The light source 1 and the end A of the first coupler 2 are welded at the melting point O1 at 45°, the C end of the first coupler 2 and one end of the waveguide 3 are welded at the melting point _O2 at 0°, and the other end of the waveguide 3 is connected to the second coupling The A end of the coupler 4 is welded to the melting point O ₃ at 0°, the C end of the second coupler 4 and the A end of the birefringent phase modulator 5 are welded to the melting point O ₄ at 0°, and the B end of the birefringent phase modulator 5 One end of the optical fiber ring 6 is fused at the melting point O ₇ at 0°, the midpoint O ₈ of the optical fiber ring 6 is 90° axially fused, and the other end of the optical fiber ring 6 is fused with the D end of the second coupler 4 at 0° At the melting point O ₉ , the B end of the first coupler 2 and the input end of the polarization beam splitter 7 are welded at 0° at the melting point O ₁₀ . End A of the birefringent phase modulator 5 and the pigtail are welded at the melting point O5, and end B of the birefringent phase modulator 5 and the pigtail are welded at the melting point _O6 . The fiber splicing point and the coupler are used as nodes, and a section of pigtail or optical fiber between two adjacent nodes is used as a mark. After simplifying the optical path shown in FIG. 1 , a schematic diagram of the polarization cross-coupling point and each pigtail is obtained as shown in FIG. 2 . _C1 and C2 in FIG. ₂ represent the first coupler 2 and the second coupler 4, respectively.

In the optical path system, 10 optical fiber splicing points O ₁ ~ O ₁₀ and 2 couplers C ₁ , C ₂ divide the optical fiber and tail fiber of the entire optical path into 11 parts L ₁ ~ L ₁₁ , including 9 sections of pigtail and 2 sections fiber optic ring. As shown in Fig. ₃ , light waves travel along the fast and slow axes at O1, respectively. Fig. 4 is a schematic diagram of splicing optical fibers at different angles. Assume that the incident light wave of the first gyroscope passes through the 45° fusion point O ₁ and then transmits along the fast axis of the polarization-maintaining fiber. If there is an angle error in the fiber fusion point and polarization crosstalk in the coupler, the fusion point O ₁ is a polarization crossover Coupling point, when the light wave is transmitted to the cross-coupling point, part of the light wave will be coupled to the slow axis orthogonal to the main wave for transmission, and the resulting wave train is the primary coupled wave train; the primary coupled wave train passes through the 90° melting point After O ₈ , it enters the fast axis of the polarization-maintaining fiber and transmits, while the main wave passes through the 90° melting point O ₈ and then enters the slow axis of the polarization-maintaining fiber for transmission. After that, the cross-coupling point will generate a coupled wave train transmitted in the fast axis. These primary coupling wave trains of the first gyro have the same polarization state as the main wave of the second gyro, so they may interfere with the main wave of the second gyro, and their interference phase difference is different from that of the main wave, resulting in Polarization non-reciprocal error. As shown in Fig. 5, it is a schematic diagram of primary and secondary polarization coupled wave trains.

If the light wave is coupled back to the original polarization state at the next polarization cross-coupling point after one coupling, it may interfere with the main wave of its own gyroscope, and a polarization non-reciprocal error will also occur. Because the amplitude of the primary coupled wave train is greater than that of the secondary coupled wave train, the interaction of the polarization states between the two gyroscopes is the main factor of the polarization non-reciprocal error of the differential dual interference fiber optic gyroscope.

As shown in FIG. 6 , it is a schematic flow chart of the method for suppressing the polarization non-reciprocity error of the fiber optic gyroscope based on the differential dual-interference fiber optic gyro matching provided by the present invention, and will be specifically described below with examples.

Step 1: Use the fiber splicing point and the coupler as nodes, mark the pigtails and optical fibers on the optical path of the differential double interference fiber optic gyroscope, and make a mark for a section of pigtail or optical fiber between two adjacent nodes; Obtain the decoherence length L _dc of the broadband light source. In the embodiment of the present invention, as shown in FIG. 2 , 11 sections of optical fibers and pigtails L ₁ -L ₁₁ are identified.

Step 2: Obtain the amplitude and phase of the two gyroscope main wave trains, primary and secondary polarization cross-coupled wave trains.

Taking the first gyroscope as an example, the main waves A ₁ and A ₂ propagating clockwise and counterclockwise can be expressed as

Among them, k ₁ and k ₂ represent the amplitude coefficients of the main wave train propagating clockwise and counterclockwise respectively; E ₀ represents the amplitude of the incident light wave; Respectively represent the phase of the main wave train propagating clockwise and counterclockwise; ω represents the angular frequency of light wave vibration; is the initial phase of the light wave; are the phase delays of the main wave train propagating clockwise and counterclockwise after passing through the waveguide; Indicates the modulation phase of the fast-axis light wave at time t, Indicates the modulation phase of the slow-axis light wave at time t-τ; Turn the Sagnac phase shift for the FOG.

Amplitude coefficient of main wave train

${\mathrm{<span\; class="notranslate">\; k</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; k</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; cos</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; \&theta;</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; cos</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; \&theta;</span>}}_{\mathrm{<span\; class="notranslate">\; 3</span>}}\mathrm{<span\; class="notranslate">\; cos</span>}{\mathrm{<span\; class="notranslate">\; \&theta;</span>}}_{\mathrm{<span\; class="notranslate">\; 4</span>}}\mathrm{<span\; class="notranslate">\; cos</span>}{\mathrm{<span\; class="notranslate">\; \&theta;</span>}}_{\mathrm{<span\; class="notranslate">\; 5</span>}}\mathrm{<span\; class="notranslate">\; cos</span>}{\mathrm{<span\; class="notranslate">\; \&theta;</span>}}_{\mathrm{<span\; class="notranslate">\; 6</span>}}\mathrm{<span\; class="notranslate">\; cos</span>}{\mathrm{<span\; class="notranslate">\; \&theta;</span>}}_{\mathrm{<span\; class="notranslate">\; 7</span>}}\mathrm{<span\; class="notranslate">\; sin</span>}{\mathrm{<span\; class="notranslate">\; \&theta;</span>}}_{\mathrm{<span\; class="notranslate">\; 8</span>}}{\mathrm{<span\; class="notranslate">\; \&theta;</span>}}_{\mathrm{<span\; class="notranslate">\; 9</span>}}{\sqrt{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; r</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; )</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}{\sqrt{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; r</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; )</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}$

Among them, θ ₂ , θ ₃ ,..., θ ₉ are the welding angles of welding points O ₂ , O ₃ ..., O ₉ respectively, r ₁ is the cross-coupling ratio of the first coupler 2, r ₂ is the second coupler 4 cross-coupling rate.

Taking the primary coupled wave train of the first gyroscope as an example, the amplitude coefficients k ₃ , k ₄ ... of the primary coupled wave train are expressed as:

${\mathrm{<span\; class="notranslate">\; k</span>}}_{\mathrm{<span\; class="notranslate">\; 3</span>}}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; cos</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; \&theta;</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; cos</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; \&theta;</span>}}_{\mathrm{<span\; class="notranslate">\; 3</span>}}\mathrm{<span\; class="notranslate">\; cos</span>}{\mathrm{<span\; class="notranslate">\; \&theta;</span>}}_{\mathrm{<span\; class="notranslate">\; 4</span>}}\mathrm{<span\; class="notranslate">\; cos</span>}{\mathrm{<span\; class="notranslate">\; \&theta;</span>}}_{\mathrm{<span\; class="notranslate">\; 5</span>}}\mathrm{<span\; class="notranslate">\; cos</span>}{\mathrm{<span\; class="notranslate">\; \&theta;</span>}}_{\mathrm{<span\; class="notranslate">\; 6</span>}}\mathrm{<span\; class="notranslate">\; cos</span>}{\mathrm{<span\; class="notranslate">\; \&theta;</span>}}_{\mathrm{<span\; class="notranslate">\; 7</span>}}\mathrm{<span\; class="notranslate">\; sin</span>}{\mathrm{<span\; class="notranslate">\; \&theta;</span>}}_{\mathrm{<span\; class="notranslate">\; 8</span>}}{\mathrm{<span\; class="notranslate">\; \&theta;</span>}}_{\mathrm{<span\; class="notranslate">\; 9</span>}}{\sqrt{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; r</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; )</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}{\sqrt{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; r</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; )</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}$

${\mathrm{<span\; class="notranslate">\; k</span>}}_{\mathrm{<span\; class="notranslate">\; 4</span>}}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; sin</span>}{\mathrm{<span\; class="notranslate">\; \&theta;</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}\mathrm{<span\; class="notranslate">\; cos</span>}{\mathrm{<span\; class="notranslate">\; \&theta;</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; cos</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; \&theta;</span>}}_{\mathrm{<span\; class="notranslate">\; 3</span>}}\mathrm{<span\; class="notranslate">\; cos</span>}{\mathrm{<span\; class="notranslate">\; \&theta;</span>}}_{\mathrm{<span\; class="notranslate">\; 4</span>}}\mathrm{<span\; class="notranslate">\; cos</span>}{\mathrm{<span\; class="notranslate">\; \&theta;</span>}}_{\mathrm{<span\; class="notranslate">\; 5</span>}}\mathrm{<span\; class="notranslate">\; cos</span>}{\mathrm{<span\; class="notranslate">\; \&theta;</span>}}_{\mathrm{<span\; class="notranslate">\; 6</span>}}\mathrm{<span\; class="notranslate">\; cos</span>}{\mathrm{<span\; class="notranslate">\; \&theta;</span>}}_{\mathrm{<span\; class="notranslate">\; 7</span>}}\mathrm{<span\; class="notranslate">\; sin</span>}{\mathrm{<span\; class="notranslate">\; \&theta;</span>}}_{\mathrm{<span\; class="notranslate">\; 8</span>}}{\mathrm{<span\; class="notranslate">\; \&theta;</span>}}_{\mathrm{<span\; class="notranslate">\; 9</span>}}{\sqrt{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; r</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; )</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}{\sqrt{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; r</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; )</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}$

…

After obtaining the phase and amplitude of all the wave trains of the two gyroscopes, the primary polarization cross-coupling wave train generated by the main wave of the first gyro and the secondary polarization cross-coupling wave train generated by the main wave of the second gyro will be obtained at the output end have the same polarization state. A coupled wave train A iCW propagating clockwise and a coupled wave train A _iCCW propagating _{counterclockwise} can be expressed as follows:

Among them, i is a positive integer used to identify a certain coupled wave train; k _i1 is the amplitude coefficient of the coupled wave train transmitted clockwise, and k _i2 is the amplitude coefficient of the coupled wave train transmitted counterclockwise; is the phase of the coupled wave train propagating clockwise, is the phase of the coupled wave train propagating counterclockwise; is the phase delay of the coupled wave train propagating clockwise after passing through the waveguide, is the phase delay of the coupled wave train propagating counterclockwise after passing through the waveguide; Indicates the modulation phase of the fast-axis and slow-axis light waves at time t, Indicates the modulation phase of the fast-axis and slow-axis light waves at time t-τ.

It can be seen from the above that the size of the polarization non-reciprocal error is related to the angle error of the fiber fusion point and the cross-coupling rate of the coupler. By reducing the fusion error of the fusion point and the cross-coupling rate of the coupler, the polarization non-reciprocal error can be effectively reduced. However, the parameter accuracy requirements of the welding point and the coupler are very high, which is difficult to achieve in practice. Therefore, under the condition that the coupled wave train exists, if the decoherence between the coupled wave train and the main wave is satisfied, the generation of polarization non-reciprocity error can be effectively reduced.

Step 3: Subtract the phases of the wave trains with the same polarization state at the gyroscope output two by two to obtain the phase difference.

For the first gyro, the main wave train of the first gyro, the secondary polarization cross-coupling wave train generated by the first gyro, and the primary polarization cross-coupling wave train generated by the second gyro have the same polarization state. The phase difference is obtained by subtracting the phases of any two wave trains in the column.

Similarly, for the second gyro, the primary polarization cross-coupling wave train generated by the first gyro, the main wave train of the second gyro, and the secondary polarization cross-coupling wave train generated by the second gyro have the same polarization state. These wave trains are used as a group, and the phases of any two of them are subtracted to obtain the phase difference.

Because the two gyroscope light waves experience the symmetry of the fast and slow axis optical paths when they are transmitted in the optical path, it is only necessary to obtain the phase difference of one set of polarization state wave trains.

Assuming that there are n (n is a positive integer) wave trains of the same polarization state at the output of a certain gyroscope, the phase difference between the pth wave train and the qth wave train for:

1≤p≤n, 1≤q≤n, and p≠q

and denote the phases of the p-th wave train and the q-th wave train, respectively.

Step 4: Convert the phase difference obtained in step 3 into an optical path difference.

The formula for converting phase difference to optical path difference is:

where λ is the wavelength of the incident light wave.

In the embodiment shown in Figure 1, the optical path difference ΔOPD ₁₂ between the two main waves is:

ΔOPD _1,2 = (L ₆ +L ₇ +L ₈ +L ₉ -L ₁₀ -L ₁₁ )(n _s -n _f )

Among them, n _s represents the refractive index of the fast axis of the fiber, and n _f represents the refractive index of the slow axis of the fiber.

The optical path difference between the main wave and the coupled wave train is as follows:

$\left\{\begin{array}{c}\mathrm{<span\; class="notranslate">\; \&Delta;</span>}{\mathrm{<span\; class="notranslate">\; OPD</span>}}_{\mathrm{<span\; class="notranslate">\; 1,3</span>}}<span\; class="notranslate">\; =</span><span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; 10</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; 11</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; 6</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; 7</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; 8</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; 9</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; the\; s</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; f</span>}}<span\; class="notranslate">\; )</span>\\ \mathrm{<span\; class="notranslate">\; \&Delta;</span>}{\mathrm{<span\; class="notranslate">\; OPD</span>}}_{\mathrm{<span\; class="notranslate">\; 1,4</span>}}<span\; class="notranslate">\; =</span><span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; 3</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; 10</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; 11</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; 6</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; 7</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; 8</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; 9</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; the\; s</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; f</span>}}<span\; class="notranslate">\; )</span>\\ \mathrm{<span\; class="notranslate">\; \&Delta;</span>}{\mathrm{<span\; class="notranslate">\; OPD</span>}}_{\mathrm{<span\; class="notranslate">\; 1,5</span>}}<span\; class="notranslate">\; =</span><span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}{<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; 3</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; 4</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; 10</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; 11</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; 6</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; 7</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; 8</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; 9</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; the\; s</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; f</span>}}<span\; class="notranslate">\; )</span>\\ \mathrm{<span\; class="notranslate">\; \&Delta;</span>}{\mathrm{<span\; class="notranslate">\; OPD</span>}}_{\mathrm{<span\; class="notranslate">\; 1,6</span>}}<span\; class="notranslate">\; =</span><span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; 3</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; 4</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; 5</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; 10</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; 11</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; 6</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; 7</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; 8</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; 9</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; the\; s</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; f</span>}}<span\; class="notranslate">\; )</span>\\ \mathrm{<span\; class="notranslate">\; \&Delta;</span>}{\mathrm{<span\; class="notranslate">\; OPD</span>}}_{\mathrm{<span\; class="notranslate">\; 1,7</span>}}<span\; class="notranslate">\; =</span><span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; 3</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; 4</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; 5</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; 10</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; 11</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; 7</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; 8</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; 9</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; the\; s</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; f</span>}}<span\; class="notranslate">\; )</span>\\ \mathrm{<span\; class="notranslate">\; \&Delta;</span>}{\mathrm{<span\; class="notranslate">\; OPD</span>}}_{\mathrm{<span\; class="notranslate">\; 1,8</span>}}<span\; class="notranslate">\; =</span><span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; 3</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; 4</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; 5</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; 10</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; 11</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; 8</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; 9</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; the\; s</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; f</span>}}<span\; class="notranslate">\; )</span>\\ \mathrm{<span\; class="notranslate">\; \&Delta;</span>}{\mathrm{<span\; class="notranslate">\; OPD</span>}}_{\mathrm{<span\; class="notranslate">\; 1,9</span>}}<span\; class="notranslate">\; =</span><span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; 3</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; 4</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; 5</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; 10</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; 11</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; 9</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; the\; s</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; f</span>}}<span\; class="notranslate">\; )</span>\\ \mathrm{<span\; class="notranslate">\; \&Delta;</span>}{\mathrm{<span\; class="notranslate">\; OPD</span>}}_{\mathrm{<span\; class="notranslate">\; 1,10</span>}}<span\; class="notranslate">\; =</span><span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; 3</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; 4</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; 5</span>}}{<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; 10</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; 11</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; the\; s</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; f</span>}}<span\; class="notranslate">\; )</span>\\ <span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span>\end{array}\right.$

The above mainly lists the optical path difference between the main wave 1 and the clockwise coupled wave train. Since there are many coupled wave trains, they can be sorted and numbered according to different rules. The above listed formula is just an example.

Step 5: Construct the inequality group so that the coherence condition is satisfied between the main wave, the decoherence condition is satisfied between the main wave and the coupled wave train, and between the coupled wave train and the coupled wave train, and the lengths of each segment of fiber and pigtail are adjusted according to the inequality group.

For a gyroscope, construct the following inequality group:

ΔOPD _1,2 < L _dc ;

ΔOPD _p,q >L _dc ,, 1≤p≤n, 1≤q≤n, and p≠q, p=1 when q≠2, p=2 when q≠1;

Make the optical path difference between the main waves smaller than the decoherence length, that is, ΔOPD _1,2 <L _dc , so that the coherence condition is satisfied between the main waves; let the main wave and the primary coupling wave train, the main wave and the secondary coupling wave train, and the primary coupling wave The optical path difference between the column and the secondary coupling wave train is greater than the decoherence length, that is, ΔOPD _p,q >L _dc (p≠q, q≠2 when p=1, q≠1 when p=2), so that the main wave and The decoherence condition is satisfied between coupled wave trains, and the decoherence condition is satisfied between coupled wave trains. Simplify the set of inequalities formed, and obtain a set of inequalities that the lengths of all pigtails and optical fibers should satisfy. Length matching is completed by adjusting the lengths of optical fibers and pigtails. By matching the length of pigtails, the double-interference fiber optic gyroscope can be effectively reduced. Polarization non-reciprocal error.

In the embodiment of the present invention, by adjusting the lengths of the pigtails L ₁ to L ₁₁ to satisfy the above inequality, the influence of the coupling secondary wave on the intensity of the main interference light can be effectively reduced, that is, the reduction of the differential double interference fiber optic gyroscope can be realized. Purpose of polarization non-reciprocity error.

The effect of the polarization non-reciprocal error suppression method of the present invention is illustrated below through the static experiment of the differential double interference fiber optic gyroscope before and after the length of the pigtail is matched.

As shown in Figure 1, the differential double interference fiber optic gyroscope test system is placed in a laboratory room temperature environment for static output testing. The light source adopts an ASE light source with a central wavelength of 1550nm and a spectral width of 7nm; the coupler adopts a polarization maintaining coupler, and the model is PMC-X-2*2-1550-50/50-0-4X type polarization maintaining of Shenzhen Langguang Company Coupler; polarization maintaining optical fiber ring is used for fiber ring; polarization beam splitter is PBS-1*2-1550-S-N polarization beam splitter of Tianjin Junfeng Technology Co., Ltd.; detector is PFTM901-001 of Wuhan Telecom Devices Co., Ltd. Type photodetector; the birefringent phase modulator is a Ti diffusion integrated optical modulator. The lengths of each pigtail and optical fiber ring before and after matching the pigtail length are:

(1) Before pigtail length matching: L ₁ =0.4m, L ₂ =0.6m, L ₃ =2m, L ₄ =0.5m, L ₅ =0.8m, L ₆ =0.7m, L ₇ =1.5m, L ₈ =297m, L ₉ =299m, L ₁₀ =1m, L ₁₁ =0.9m.

(2) After pigtail length matching: L ₁ =0.4m, L ₂ =0.8m, L ₃ =51.2m, L ₄ =12.8m, L ₅ =25.6m, L ₆ =1.6m, L ₇ =3.2m , L ₈ =269.6m, L ₉ =293.6m, L ₁₀ =6.4m, L ₁₁ =1m.

Figure 7 shows the static output of the differential double-interference fiber optic gyroscope before the length of the pigtail is matched. The output fluctuation amplitude is relatively large. Because the polarization non-reciprocity error will fluctuate with the temperature, the polarization non-reciprocity error of the gyro is very large at this time; 8 is the static output of the differential dual-interference fiber optic gyroscope after the length of the pigtail is matched, and the output waveform is relatively stable. At this time, the polarization non-reciprocal error of the gyroscope is effectively suppressed, and the accuracy of the gyroscope is higher.

The experimental results show that the matching of pigtail lengths with a specific relationship can effectively suppress the polarization non-reciprocity error of the differential double interference fiber optic gyroscope, thereby improving the detection accuracy of the differential double interference fiber optic gyroscope.

Claims (2)

1. the double; two interference type optical fiber gyroscope of the difference based on tail optical fiber coupling polarizes nonreciprocal error inhibition method, it is characterised in that comprise the steps:

Step 1: using optical fiber fusion welding point and bonder as node, the tail optical fiber in the double; two interference type optical fiber gyroscope light path of difference is carried out segment identification with optical fiber, often one section of tail optical fiber between adjacent two nodes or optical fiber do a mark; Obtain wide spectrum light source decoherence length L_dc;

Step 2: obtain the amplitude of the main wave train of two-way gyro and phase place, obtain that two-way gyro produces once and the amplitude of the secondary polarization cross coupling wave train and phase place;

If the A end of light source and the first bonder is fused to fusing point O with 45 ��₁, the C end of the first bonder and one end of waveguide are fused to fusing point O with 0 ��₂, the other end of waveguide and the A end of the second bonder are fused to fusing point O with 0 ��₃, the C end of the second bonder and the A end of birefringent phase manipulator are fused to fusing point O with 0 ��₄, the B end of birefringent phase manipulator and one end of fiber optic loop are fused to fusing point O with 0 ��₇, the midpoint O of fiber optic loop₈Being 90 �� of countershaft weldings, the other end of fiber optic loop and the D end of the second bonder are fused to fusing point O with 0 �� simultaneously₉, the B end of the first bonder and the input of polarization beam apparatus are fused to fusing point O with 0 ��₁₀; The A end of birefringent phase manipulator and tail optical fiber are fused to fusing point O₅, the B end of birefringent phase manipulator and tail optical fiber are fused to fusing point O₆;

For first via gyro, along the main ripple A propagated clockwise, counterclockwise₁And A₂It is expressed as

Wherein, k₁��k₂Represent the amplitude coefficient of the main wave train propagated clockwise, counterclockwise respectively; E₀Represent the amplitude of incident light wave;Represent the phase place of the main wave train propagated clockwise, counterclockwise respectively; �� represents light wave vibrations angular frequency;For light wave initial phase;The main wave train respectively propagated clockwise, counterclockwise Phase delay after waveguide;Represent that t is to fast axial light wave modulation phase place,Represent that the t-�� moment is to slow axial light wave modulation phase place;Sagnac phase shift is rotated for optical fibre gyro;

The amplitude coefficient of the main wave train

$k_1=k_2={\cos }^2{\mathrm{\&theta;}}_2{\cos }^2{\mathrm{\&theta;}}_3{\mathrm{cos\&theta;}}_4{\mathrm{cos\&theta;}}_5{\mathrm{cos\&theta;}}_6{\mathrm{cos\&theta;}}_7{\mathrm{sin\&theta;}}_8{\mathrm{cos\&theta;}}_9{\sqrt{(1-r_1)}}^2{\sqrt{(1-r_2)}}^2$

Wherein, ��₂,��₃,��,��₉Respectively fusion point O₂,O₃��,O₉Welding angle, r₁It is the cross-couplings rate of the first bonder, r₂It it is the cross-couplings rate of the second bonder;

Arrange for first via gyro coupled wave, once couple the amplitude coefficient k of the wave train₃��k₄... it is expressed as:

$k_3={\cos }^2{\mathrm{\&theta;}}_2{\cos }^2{\mathrm{\&theta;}}_3{\mathrm{cos\&theta;}}_4{\mathrm{cos\&theta;}}_5{\mathrm{cos\&theta;}}_6{\mathrm{cos\&theta;}}_7{\mathrm{sin\&theta;}}_7{\mathrm{sin\&theta;}}_8{\mathrm{cos\&theta;}}_9\sqrt{r_1}\sqrt{(1-r_1)}{\sqrt{(1-r_2)}}^2$

$k_4={\mathrm{sin\&theta;}}_2{\mathrm{cos\&theta;}}_2{\cos }^2{\mathrm{\&theta;}}_3{\mathrm{cos\&theta;}}_4{\mathrm{cos\&theta;}}_5{\mathrm{cos\&theta;}}_6{\mathrm{cos\&theta;}}_7{\mathrm{sin\&theta;}}_8{\mathrm{cos\&theta;}}_9{\sqrt{(1-r_1)}}^2{\sqrt{(1-r_2)}}^2$

��

After the phase and amplitude obtaining all wave trains of two-way gyro, the secondary polarization cross coupled wave that the polarization cross coupling wave train and the main ripple of No. second gyro that obtain the generation of first via gyro main ripple produce is listed in outfan there is identical polarization state; Certain coupling wave train A along clockwise transmission_iCWWith certain coupling wave train A along counterclockwise transmission_iCCWIt is expressed as:

Wherein, i is positive integer, is used for identifying a certain coupling wave train; k_i1For the amplitude coefficient of the coupling wave train along clockwise transmission, k_i2Amplitude coefficient for the coupling wave train along counterclockwise transmission;For along clockwise transmission coupling the wave train phase place,Phase place for the coupling wave train along counterclockwise transmission;For along clockwise transmission coupling wave train Phase delay after waveguide,For the coupling wave train Phase delay after waveguide along counterclockwise transmission;Represent that t is to fast axle, slow axial light wave modulation phase place,Represent that the t-�� moment is to fast axle, slow axial light wave modulation phase place;

Step 3: the phase place at gyro outfan with the wave train of identical polarization state subtracted each other between two, obtains phase contrast;

For certain road gyro, the main wave train of gyro, the secondary polarization cross coupling wave train of generation and the polarization cross coupling wave train of another road gyro generation have identical polarization state, and the phase place wherein with any two train waves row of identical polarization state is subtracted each other acquisition phase contrast;

Step 4: phase contrast is converted to optical path difference;

Step 6: structure inequality group so that meet coherent condition between main ripple, main ripple with couple between the wave train, couple the wave train and meet decoherence condition between the wave train with coupling, adjust the length of each section of optical fiber and tail optical fiber according to inequality group;

Described inequality group is expressed as follows:

|��OPD_1,2|<L_dc;

|��OPD_p,q|>L_dc, 1��p��n, 1��q��n, and q �� 2 when p �� q, p=1, q �� 1 during p=2;

Wherein, �� OPD_p,qRepresent the optical path difference of pth the wave train and the q-th wave train, �� OPD_1,2Represent the optical path difference of two main ripples.

2. the double; two interference type optical fiber gyroscope of the difference based on tail optical fiber coupling according to claim 1 polarizes nonreciprocal error inhibition method, it is characterised in that in described step 4, according to formula below, phase contrast is converted to optical path difference:

Wherein, �� is the wavelength of incident light wave,It is pth the wave train and the phase contrast of the q-th wave train, �� OPD_p,qIt is willThe optical path difference of conversion.