CN103411599B - A kind of difference double-interference type optical fiber gyroscope based on light path difference - Google Patents
A kind of difference double-interference type optical fiber gyroscope based on light path difference Download PDFInfo
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- CN103411599B CN103411599B CN201310312232.6A CN201310312232A CN103411599B CN 103411599 B CN103411599 B CN 103411599B CN 201310312232 A CN201310312232 A CN 201310312232A CN 103411599 B CN103411599 B CN 103411599B
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Abstract
The invention discloses a kind of difference double-interference type optical fiber gyroscope based on light path difference, comprise light source, coupling mechanism, birefringence modulator, fiber optic loop, polarization beam apparatus, the first detector and the second detector; The A of light source and coupling mechanism holds and is fused to fusing point O with 45 °
1, the C end of coupling mechanism is held with the A of birefringence modulator and is fused to fusing point O with 0 °
2, B end and the C end of birefringence modulator are fused to fusing point O with the two ends of polarization-maintaining fiber coil with 0 ° respectively
3with fusing point O
4, the mid point O of fiber optic loop simultaneously
5be 90 ° to axle welding, the B of coupling mechanism end is fused to fusing point O with the input end of polarization beam apparatus with 0 °
5, two output terminals of polarization beam apparatus respectively with the first detector and the second detector welding.Present invention achieves the path difference offshoot program of the two interference type optical fiber gyroscope of difference, reduce the nonreciprocal error of gyro, have employed the wide spectrum light source that coherence is very weak simultaneously, avoid various stray waves that laser light source strength coherence causes and interfere and the very noisy that brings.
Description
Technical field
The present invention relates to a kind of difference double-interference type optical fiber gyroscope realizing the multiplication of SAGNAC effect and light path difference under fiber optic loop area and the constant condition of fiber lengths, belong to fiber-optics gyroscope field.
Background technology
Optical fibre gyro is as development a kind of novel inertia angular-rate sensor very rapidly, and with its distinctive technology and performance advantage, as structure of whole solid state, reliability is high, the life-span is long; Toggle speed is fast, and the response time is short; Measurement range is large, wide dynamic range; Shock resistance, vibration, resistance to chemical attack; Volume is little, lightweight, cost is low; Be applicable to producing in enormous quantities, be widely used in each field.
Optical fibre gyro form general is in the world for going alone interferometric, namely utilize the fast axle of a set of light path (polarization-maintaining fiber coil) or slow axis to realize SAGNAC interferometer, resolve by the interference between the main wave train of two bundles propagated according to clockwise (CW), counterclockwise (CCW) respectively the SAGNAC phase shift that carrier rotation causes.Although this interferometer structure is simple, but along with the continuous expansion of optical fibre gyro application, its volume, contradiction between weight and precision, with existing technology and technological level, under the prerequisite maintaining precision, further reduction volume, weight are difficult to realize breaking through, and vice versa.
Difference double-interference type optical fiber gyroscope is in a set of light path (polarization-maintaining fiber coil), its fast axle and slow axis is utilized to realize a SAGNAC interferometer respectively, the output of this two-way interferometer presents difference form, and after difference is resolved, SAGNAC effect is doubled.At present, what difference double-interference type optical fiber gyroscope adopted is circuit differential detection scheme, reciprocity due to difference double-interference type optical fiber gyroscope is based upon on the basis of accurate difference, so the reciprocity in order to ensure gyro, need the parameter consistency of guarantee two alignment detection circuit, and this is be difficult to realize in practice, the two interfere type gyro of difference can be made to suppress the ability of environmental perturbation to decline.What the two interference type optical fiber gyroscope of simultaneously existing difference adopted is narrow spectrum light source, and the coherent length of light wave is longer, causes the noises such as backscattering, back-reflection and cross-couplings to increase, also causes impact to the precision of gyro.
Summary of the invention
The object of the invention is to solve the problem, proposing a kind of difference double-interference type optical fiber gyroscope realizing the multiplication of SAGNAC effect and light path Differential Detection under fiber optic loop area and the constant condition of fiber lengths.
Based on a difference double-interference type optical fiber gyroscope for light path difference, comprise light source, coupling mechanism, birefringence modulator, fiber optic loop, polarization beam apparatus, the first detector and the second detector;
The A of light source and coupling mechanism holds and is fused to fusing point O with 45 °
1, the C end of coupling mechanism is held with the A of birefringence modulator and is fused to fusing point O with 0 °
2, B end and the C end of birefringence modulator are fused to fusing point O with the two ends of fiber optic loop with 0 ° respectively
3with fusing point O
4, the mid point O of fiber optic loop simultaneously
5be 90 ° to axle welding, the B of coupling mechanism end is fused to fusing point O with the input end of polarization beam apparatus with 0 °
6, two output terminals of polarization beam apparatus respectively with the first detector and the second detector welding.
Described light source is wide spectrum light source, and wide spectrum light source exports polarized lightwave and creates through 45 ° of cross-couplings that two amplitudes are equal, the orthogonal light wave in polarization direction exports.The birefringence modulator of placing at fiber optic loop input end allows the light wave of two polarization directions to pass through simultaneously, but has the different indexes of modulation to the light wave of two axles.Utilize birefringence formula modulator to the different modulating of different polarization states light wave, realize the closed loop detect of wherein first via gyro, the testing result of this first via gyro utilized birefringence modulator to feed back to No. second gyro simultaneously, the testing result of first via gyro deducted from the output signal of No. second gyro, now the calculation result of No. second gyro is and completes the differentiated final output of light path.By light path Differential Detection, proper phase difference and the environmental drift thereof of existence can be eliminated, simultaneously, by adopting 90 °, fiber optic loop mid point to axle welding, substantially reduce nonreciprocal phase shift, thus make the light source that spectrum width can be used in light path wider, reduce light path noise level to a certain extent.
The invention has the advantages that:
(1) achieve the path difference offshoot program of the two interference type optical fiber gyroscope of difference, improve the environmental suitability of gyrosystem;
(2) by adopting the 90 ° of weldings of fiber optic loop mid point, the intrinsic nonreciprocity of light path is reduced;
(3) adopt wide spectrum light source, reduce due to the coherence length of laser coherent noise next compared with long band;
Accompanying drawing explanation
Fig. 1 is the two interference type optical fiber gyroscope structured flowchart of difference based on optics difference;
Fig. 2 is fusing point O
1place's light wave schematic diagram;
Fig. 3 is that optical fiber is to axle welding schematic diagram;
Fig. 4 is light wave propagation schematic diagram in fiber optic loop;
Fig. 5 is wide spectrum light source coherence function;
Fig. 6 is the modulation waveform that modulator applies;
Fig. 7 is the first detector place interference light intensity and phase modulation relation (being responsible for closed loop);
Fig. 8 is the second detector place interference light intensity and phase modulation relation (being responsible for phase place to resolve).
In figure:
1-light source 2-coupling mechanism 3-birefringence modulator
4-fiber optic loop 5-polarization beam apparatus 6-first detector
7-second detector
Embodiment
Below in conjunction with accompanying drawing, the present invention is described in further detail.
The present invention is a kind of difference double-interference type optical fiber gyroscope based on light path difference, as shown in Figure 1, comprises light source 1, coupling mechanism 2, birefringence modulator 3, fiber optic loop 4, polarization beam apparatus 5, first detector 6 and the second detector 7.
Described coupling mechanism 2 is four port devices, and be respectively A end, B end, C end and D end, light source 1 is held with the A of coupling mechanism 2 and is fused to fusing point O with 45 °
1, the C end of coupling mechanism 2 is held with the A of birefringence modulator 3 and is fused to fusing point O with 0 °
2, B end and the C end of birefringence modulator 3 are fused to fusing point O with two input ends of polarization-maintaining fiber coil 4 with 0 ° respectively
3, O
4, fiber optic loop mid point O
5place's employing 90 ° is to axle welding, and the B end of coupling mechanism 2 is fused to fusing point O with the input end of polarization beam apparatus 5 with 0 °
6, two output terminals of polarization beam apparatus 5 respectively with the first detector 6 and the second detector 7 welding.Concrete optical fiber to axle welding as shown in Figure 3.
In the present invention, light source 1 selects the wide range ASE light source with high-polarization, and birefringence modulator 3 selects Ti to spread integrated optical modulator; Polarization-maintaining coupler selected by coupling mechanism 2, and model is the PMC-X-2*2-1550-50/50-0-4X type polarization-maintaining coupler of Shenzhen Lang Guang company; Fiber optic loop 4 selects polarization-maintaining fiber coil; Polarization beam apparatus 5 is the PBS-1*2-1550-S-N type polarization beam apparatus of Tianjin Jun Feng Science and Technology Ltd.; The PFTM901-001 type photodetector of detector (first detector 6 and the second detector 7) Wuhan Telecommunication Devices Co., Ltd.
Light source 1 polarization light output, at fusion point O
1place is because 45 ° to axle welding, input line polarized light creates that amplitude is equal, orthogonal two wave train X and Y in polarization direction, (wherein fast axle is the quick shaft direction of polarization maintaining optical fibre as shown in Figure 2, represent with Y, slow axis is the slow-axis direction of polarization maintaining optical fibre, represents with X), when wave train X and wave train Y enters fiber optic loop 4 through birefringence modulator 3, all there is the light wave of two polarization directions separately at the two ends of fiber optic loop 4, this four bundles light wave transmits in opposite directions.Because the fiber optic loop 4 in the present invention adopts mid point O
5locate 90 ° of weldings, so when optical transport is through fiber optic loop 4 mid point O
5time can change its transmission axle, concrete light wave transmissions path and the polarization state residing when birefringence modulator 3 of light wave are as shown in Figure 4, at the output terminal of fiber optic loop 4, coaxial light is only had to interfere, form fast axle, slow axis two gyros, the phase accumulation of the four bundle light waves transmitted in opposite directions in fiber optic loop 4 and interference output phase place (the wherein Δ n=n as shown in the table of each gyro
x-n
y, λ is optical wavelength,
rotate the SAGNAC phase shift caused, L
1o
3point is to mid point O
5fiber lengths, L
2o
4point is to mid point O
5fiber lengths, L
1≈ L
2).
The interference of table 1 gyro exports phase place
Owing to adopting fiber optic loop 4 mid point O
5locate 90 ° to axle welding, make intrinsic light path difference 2 π Δ n (L
1-L
2the two interference optical fiber gyro of the difference type that)/λ is more traditional is much little, and the ASE light source that therefore only spectrum width need be adopted wider can make the coaxial light wave propagated in opposite directions interfere, and its coherence function as shown in Figure 5.The light wave coherent length that wide spectrum light source sends is shorter, can suppress the correlation noises such as such as sharp keen scattering, backscattering, polarization cross coupling.
The birefringence modulator 3 used in the present invention is Ti diffusion integrated optical modulator, and it allows the light wave of X, Y two axles to pass through simultaneously, but has the different indexes of modulation to two axles.This birefringence modulator 3 introduces two kinds of modulation systems, and one is square-wave frequency modulation, and it is identical to the phase modulation of two gyros; Another kind is HVDC Modulation, and it is to the phase modulation equal and opposite in direction of two gyros, and direction is contrary.
Four bundle light waves transmit in opposite directions, the coaxial interference occurs at the output port B place of coupling mechanism 2, produces X-axis, Y-axis two optical interference circuit signals, enter the first detector 6 and the second detector 7 after polarization beam apparatus 5 beam splitting respectively, its interference light intensity I exported
1, I
2be shown below respectively:
I
1＝I
0cos(Φ
0+Φ
m1+Φ
m2+Φ
s)I
2＝I
0cos(Φ
0+Φ′
m1+Φ′
m2-Φ
s)
Wherein I
0for arriving the direct current light intensity of the first detector 6 and the second detector 7, Φ
0for proper phase is poor, Φ
m1with Φ '
m1for the phase modulation that square-wave frequency modulation is introduced, Φ
m2with Φ '
m2for the phase modulation that HVDC Modulation is introduced, Φ
sfor rotating the SAGNAC phase signal caused.
Conveniently resolve SAGNAC phase shift phi
s, utilize the output signal of the X-axis gyro i.e. output signal of the first detector 6 to realize closed loop, utilize the output signal of the Y-axis gyro i.e. output signal of the second detector 7 to realize SAGNAC phase shift demodulation.Use for reference the closed loop principle of traditional single interference type optical fiber gyroscope, by applying suitable modulation waveform in birefringence modulator 3, as shown in Figure 6, the gyro of mode to two mutual vertical axials superposing certain direct current biasing with periodic square wave is modulated, wherein phase modulation Φ
m1=± pi/2 realize as in classical spinning top ± pi/2 bias modulation; Phase modulation Φ
m2=-Φ
0-Φ
sfor realizing the closed loop of first via interferometer (interference signal namely on the first detector 6), its from No. second gyro exports (i.e. signal on the second detector 7) being deducted simultaneously, realizing light path difference.Now (what in figure, coordinate axis top represented is that first via interferometer interference light intensity changes by cosine rule to the interference waveform of first via interferometer as shown in Figure 7, bottom is additional phase-modulation waveform, by phase-modulation, the working point of interferometer is locked in ± pi/2, then the first actual detector 6 output waveform for the amplitude that there is spike such as shown in the upper right corner close to 0 waveform.), for No. second interferometer, its working point is at-2 Φ
s± pi/2, (what in figure, coordinate axis top represented is that No. second interferometer interference light intensity changes by cosine rule to its interference waveform, and bottom is additional phase-modulation waveform, by phase-modulation, the working point of interferometer is locked in-2 Φ as shown in Figure 8
s± pi/2, then the second actual detector 7 output waveform is the waveform that there is spike such as shown in the upper right corner.), by 2 Φ can be calculated to its demodulation
s, thus the multiplication of SAGNAC effect is achieved under fiber optic loop area and the constant condition of fiber lengths.
Claims (1)
1. based on a difference double-interference type optical fiber gyroscope for light path difference, it is characterized in that: comprise light source, coupling mechanism, birefringence modulator, fiber optic loop, polarization beam apparatus, the first detector and the second detector;
The A of light source and coupling mechanism holds and is fused to fusing point O with 45 °
1, the C end of coupling mechanism is held with the A of birefringence modulator and is fused to fusing point O with 0 °
2, B end and the C end of birefringence modulator are fused to fusing point O with the two ends of fiber optic loop with 0 ° respectively
3with fusing point O
4, the mid point O of fiber optic loop simultaneously
5be 90 ° to axle welding, the B of coupling mechanism end is fused to fusing point O with the input end of polarization beam apparatus with 0 °
6, two output terminals of polarization beam apparatus respectively with the first detector and the second detector welding;
Described light source exports polarized lightwave and creates through 45 ° of cross-couplings that two amplitudes are equal, the orthogonal light wave in polarization direction exports; Utilize birefringence formula modulator to the different modulating of different polarization states light wave, realize the closed loop detect of first via gyro, the testing result of this first via gyro utilized birefringence modulator to feed back to No. second gyro simultaneously, the testing result of first via gyro deducted from the output signal of No. second gyro, now the calculation result of No. second gyro is and completes the differentiated final output of light path;
Described light source is the wide range ASE light source with high-polarization; Birefringence modulator selects Ti to spread integrated optical modulator; Polarization-maintaining coupler selected by coupling mechanism; Fiber optic loop selects polarization-maintaining fiber coil;
The interference light intensity I that described first detector exports
1with the interference light intensity I that the second detector exports
2be shown below respectively:
I
1＝I
0cos(Φ
0+Φ
m1+Φ
m2+Φ
s)I
2＝I
0cos(Φ
0+Φ′
m1+Φ′
m2-Φ
s)
Wherein I
0for arriving the direct current light intensity of the first detector and the second detector, Φ
0for proper phase is poor, Φ
m1with Φ '
m1for the phase modulation that square-wave frequency modulation is introduced, Φ
m2with Φ '
m2for the phase modulation that HVDC Modulation is introduced, Φ
sfor rotating the SAGNAC phase signal caused;
Described phase modulation Φ
m1=± pi/2; Phase modulation Φ
m2=-Φ
0-Φ
s.
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| CN109883412A (en) * | 2019-03-12 | 2019-06-14 | 哈尔滨工程大学 | A kind of double path optical fiber gyroscopes |
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