CN103743391A - Full-depolarized optical fiber gyroscope of unicoupler - Google Patents

Abstract

The present invention provides a fully depolarized fiber optic gyroscope with a single coupler, which includes a wide-spectrum light source, a depolarizer before the ring, a coupler, two depolarizers in the ring, a single-mode fiber ring, and a photodetector, wherein the broadband The output end of the spectrum light source is connected to the depolarizer before the ring through a single-mode fiber, the other end of the depolarizer before the ring is coupled to the first port of the coupler, the third port and the fourth port of the coupler are connected to the two ports through a single-mode fiber The other ends of the two ring depolarizers are respectively coupled with the two ports of the polarization maintaining fiber ring, and the second port of the coupler is coupled with the input end of the photodetector through a single-mode fiber. The gyroscope structure saves the polarizer and one of the couplers in the minimum reciprocal structure of the gyroscope, and eliminates the non-reciprocal error through decoherence and interference light intensity compensation between the two polarization states, thereby greatly reducing the cost , with lower noise and better bias stability.

Description

The complete depolarized fibre optic gyroscope of a kind of unicoupler

Technical field

The invention belongs to gyroscope technical field, be specifically related to the complete depolarized fibre optic gyroscope of a kind of unicoupler.

Background technology

Gyroscope is a kind of rotation sensor, for measuring the rotational angular velocity of its place carrier.Gyroscope is widely used in the fields such as guidance, industry and military precision measurement of aircraft and weapon.Early stage gyroscope is mechanical gyroscope, and mechanical gyroscope is to utilize the turning axle of high-speed rotary body to have the orienting device that keeps the such physical principle of trend of its direction and produce.For example, because mechanical gyroscope comprises movable part (high speed rotor), therefore, its complex structure, technological requirement is high and precision has been subject to many-sided restriction.

In generation nineteen sixty, along with the appearance of laser, the research that utilizes laser to manufacture optical gyroscope develops rapidly.Optical gyroscope is based on Sagnac effect (Sagnac effect) and produced orienting device.Specifically, in the closed light path of rotating, the identical light of two bundle features being sent by same light source interferes respectively when (CW) direction is with counterclockwise (CCW) direction transmission clockwise, by detecting the phase differential of described two-beam or the variation of interference fringe, just can measure the rotational angular velocity of this closure light path.Above-mentioned phase differential is known as Sagnac phase shift φ _s, it is directly proportional to the rotational angular velocity Ω of closed light path:

${\mathrm{\φ}}_S=\frac{4\mathrm{\ωA}}{c^2}\mathrm{\Ω}$ Formula (1)

Wherein, ω is light frequency, and c is the light velocity in vacuum, and A is the area that closed light path is enclosed.

Optical gyroscope does not have movable part, and its compact conformation, highly sensitive, good reliability and life-span are long.Within 1963, first generation optical gyroscope-lasergyro is come out.The primary element of lasergyro is ring laser.For example, lasergyro can comprise the triangular closed light path of being made by quartz, is provided with a he-ne laser tube, two catoptrons and a semitransparent mirror in this light path.The laser of the contrary transmission of two bundles of sending from he-ne laser tube reflects through two catoptrons respectively, then derives loop by semitransparent mirror, by measuring the phase differential of this two-beam, just can obtain the rotational angular velocity of closed light path.

Within 1976, second generation optical gyroscope-fibre optic gyroscope occurs.Sensitivity and the degree of stability of fibre optic gyroscope are higher, cost and power consumption is lower and small volume.Fibre optic gyroscope is roughly divided into interferometric fiber optic gyroscope and resonant mode fibre optic gyroscope, at present, and being most widely used of interferometric fiber optic gyroscope.

In interferometric fiber optic gyroscope, the longer optical fiber of normal employing turns to multiturn coil to form closed light path.Adopt multiturn coil can strengthen Sagnac effect.In this case, Sagnac phase shift φ _sexpression formula be:

${\mathrm{\φ}}_S=2\mathrm{\π}\frac{\mathrm{LD}}{\mathrm{\λc}}\mathrm{\Ω}$ Formula (2)

Wherein, the length that L is optical fiber, D is fiber optic coils diameter, the wavelength that λ is light wave.

In order accurately to measure Sagnac effect, (be Sagnac phase shift φ _s), guarantee that described closed light path has reciprocity, guarantee that the light (calling CW light in the following text) transmitting along the clockwise direction of described closed light path and the light (calling CCW light in the following text) transmitting along the counter clockwise direction of described closed light path have identical pattern, polarization and phase delay, make the phase differential of CW light and CCW light only relevant with the rotational angular velocity of this closure light path, and irrelevant with transmission, thereby improve the accuracy of measuring.

Fig. 1 shows the minimum reciprocal structure of interferometric fiber optic gyroscope.As shown in Figure 1, this minimum reciprocal structure comprises light source, source ends coupling mechanism, the polarizer, ring end coupling mechanism, fiber optic loop and photodetector.Above-mentioned coupling mechanism can be realized the beam splitting of light beam and again converge.Light beam of light source is after passing through the polarizer, through encircling, end coupling mechanism is divided into CW light and CCW light transmits in fiber optic loop, this CW light and CCW light are held coupling mechanism again to converge by ring again after transmitting in fiber optic loop and are formed interference wave, and this interference wave enters photodetector finally by crossing source ends coupling mechanism.Ring end coupling mechanism has reciprocity, and the phase delay that it causes CW light and CCW light is identical.In addition, the polarizer is used for light wave to carry out polarization filtering, to guarantee that CW light and CCW light have identical polarization, thereby realizes polarization reciprocity.In fibre optic gyroscope, can adopt polarization maintaining optical fibre to guarantee polarization reciprocity.

Due to fiber optic loop when static the phase place of CW light and CCW light identical with amplitude, so power P of interference light ₀for maximum.When fiber optic loop has rotation, interference light power P is for rotating the phase difference of caused CW light and CCW light _sfunction P (φ _s)=P ₀(1+cos φ _s).In order to obtain high sensitivity, should give φ _sapply a biasing △ φ, make system works near the non-vanishing point of luminous power slope: P (φ _s)=P ₀[1+cos (φ _s+ △ φ)].For this reason, need to add in one end of fiber optic loop phase-modulator (for example, PZT phase-modulator), to the CW light transmitting in fiber optic loop and CCW light are carried out to phase-modulation, thereby make it when fiber optic loop is static, produce phase differential △ φ.

Interferometric fiber optic gyroscope need to have been divided different precision grades according to its application, and table 1 shows the technical requirement of each precision grade.

The technical requirement of each precision grade of table 1.

Wherein, zero bias stability is to weigh the most important technical indicator of interferometric fiber optic gyroscope precision.Zero partial correlation noise comprises quantizing noise, angle random walk, speed random walk, rate ramp etc.

As mentioned above, in fibre optic gyroscope, the structural principle of two coupling mechanisms and a polarizer can be eliminated the nonreciprocal noise component causing of polarization, guarantees good zero bias stability, but has also caused the raising of cost.

Summary of the invention

The object of the invention is to, provide a kind of unicoupler complete depolarized fibre optic gyroscope, the complete depolarized fibre optic gyroscope of this unicoupler has very low complexity, lower cost and higher precision and zero bias stability.

To achieve these goals, the invention provides the complete depolarized fibre optic gyroscope of a kind of unicoupler, it comprises wide spectrum light source, depolarizer before ring, coupling mechanism, depolarizer in two rings, single-mode fiber ring, and photodetector, wherein, the output terminal of wide spectrum light source is connected with depolarizer before ring by single-mode fiber, the first port coupling of the other end of depolarizer and coupling mechanism before ring, the 3rd port of coupling mechanism and the 4th port are coupled by depolarizer in single-mode fiber and two rings, in two rings, the other end of depolarizer is coupled with two ports of single-mode fiber ring respectively, the second port of coupling mechanism is coupled by the input end of single-mode fiber and photodetector.

Preferably, described coupling mechanism is 3dB single-mode optical-fibre coupler.

Preferably, in described single-mode fiber ring, be inserted with phase-modulator.Further preferably, described phase-modulator is PZT phase-modulator.

Preferably, before described ring, in depolarizer, ring, depolarizer is the two-part Lyot depolarizer that polarization maintaining optical fibre is made.

The length of the two-part Lyot depolarizer that preferably, wherein the front depolarizer of ring adopts is (L ₀, 16L), the length of the two-part Lyot depolarizer that in two rings, depolarizer adopts is (1L, 2L), (4L, 8L), wherein, L ₀with L be constant.

Preferably, length L ₀meet L ₀=L _d/ △ n, the refringence between the x axle of the birefringece crystal that Δ n is this polarization maintaining optical fibre and y axle or between x ' axle and y ' axle,

for the decoherence length of described wide spectrum light source, λ ₀for the centre wavelength of described wide spectrum light source, the spectrum width that Δ λ is described wide spectrum light source.

Preferably, length L meets Δ nL=Δ n ₀l _sMF+ L ₀, Δ n is the x axle of the polarization maintaining optical fibre that uses of the described depolarizer of making and the refringence between y axle, Δ n ₀for the specific refractivity of the birefringece crystal of described single-mode fiber ring, L _sMFfor the fiber lengths of described single-mode fiber ring, and L ₀for the first paragraph length of described two-part light source depolarizer, and

${\mathrm{\Δn}}_0=0.25n_{\mathrm{eff}}^2(P_{11}-P_{12})(1+v){(a/r)}^2=0.0927{(a/r)}^2,$

Wherein, n _efffor the equivalent refractive index of the optical fiber in described single-mode fiber ring, P ₁₁and P ₁₂for the elasto-optical coefficient of the optical fiber in described single-mode fiber ring, ν is the Poisson's coefficient of the optical fiber in described single-mode fiber ring, and a and r are respectively the bending radius of core diameter and the described single-mode fiber ring of the optical fiber in described single-mode fiber ring.

As mentioned above, the principle that the present invention is based on polarization error compensation has broken through the restriction of optical fibre gyro minimum reciprocal structure, the complete depolarized fibre optic gyroscope of unicoupler of the present invention does not need the polarizer, only need a coupling mechanism, greatly reduce the cost of structure, the cost of its structure is lower than the current optical fibre gyro structure of main flow on the market.The condition that meets dual-polarization error compensation by encircling depolarized light that front Lyot depolarizer produces, can reach good nonreciprocal error compensation effect, realizes higher Gyro Precision and degree of stability.

Accompanying drawing explanation

Fig. 1 is the schematic diagram of the minimum reciprocal structure of interferometric fiber optic gyroscope;

Fig. 2 is the schematic diagram of the structure of the complete depolarized fibre optic gyroscope of unicoupler described in one embodiment of the present of invention;

Fig. 3 is the schematic diagram of the two-part Lyot depolarizer based on polarization maintaining optical fibre;

Fig. 4 is the time domain data figure of the gyroscope Output speed value in Fig. 2; And

Fig. 5 is the error analysis figure of the gyroscope Output speed data in Fig. 2.

Embodiment

In the following description, for purposes of illustration, for the complete understanding to one or more embodiment is provided, many details have been set forth.Yet, clearly, also can in the situation that there is no these details, realize these embodiment.In other example, one or more embodiment for convenience of description, known structure and equipment illustrate with the form of block scheme.

Below with reference to accompanying drawings each embodiment of the present invention is described in detail.

Fig. 2 is the schematic diagram of the structure of the complete depolarized fibre optic gyroscope of unicoupler described in one embodiment of the present of invention.As shown in Figure 2, the complete depolarized fibre optic gyroscope of unicoupler of the present invention comprises: comprise depolarizer, phase-modulator, single-mode fiber ring and photodetectors in wide spectrum light source, the front depolarizer of ring, coupling mechanism, two rings.Wide spectrum light source can adopt the wide spectrum light source generally adopting in interference type optical fiber gyroscope, for example, can adopt ASE wide spectrum light source, and its centre wavelength is 1550nm, and spectrum width is 40nm.The output terminal of wide spectrum light source is connected with depolarizer before ring by single-mode fiber.Preferably, before ring, depolarizer is used the two-part Lyot depolarizer based on polarization maintaining optical fibre.

Before described ring, the other end of depolarizer and the first port of coupling mechanism are connected, and preferably, use the single-mode optical-fibre coupler that splitting ratio is 50:50, i.e. 3dB single-mode optical-fibre coupler.The 3rd port of coupling mechanism and the 4th port are coupled by depolarizer in single-mode fiber and two rings, and in two rings, the other end of depolarizer is coupled with two ports of single-mode fiber ring respectively.Preferably, in ring, depolarizer is used the two-part Lyot depolarizer based on polarization maintaining optical fibre.

Fig. 3 is the principle schematic of described two-part Lyot depolarizer.As shown in Figure 3, Lyot depolarizer comprises two sections of polarization maintaining optical fibres of the same race, and its length is respectively L ₁and L ₂, its main shaft x and x ' angle at 45 °.If the refringence (that is to say between x ' axle and y ' axle) between the x axle of this polarization maintaining optical fibre and y axle is Δ n, the decoherence length L of light source _dbe less than Δ nL, light wave train A is divided into unevenly two bundles vertical and mutual incoherent wave train B mutually after by first crystal.Every Shu Bolie B is decomposed equably after by second crystal again, finally at output terminal, forms four wave train C, and the light intensity of these wave trains on two polarization directions equates and be irrelevant mutually, form depolarized light.

Preferably, the depolarizer adopting in the present invention can be the two-part Lyot depolarizer of making of polarization maintaining optical fibre.The cost of this depolarizer is only the cost of same length polarization maintaining optical fibre, well below the polarizer in traditional fiber gyro with protect the cost of inclined to one side device.The length of the two-part Lyot depolarizer that preferably, wherein the front depolarizer of ring adopts is (L ₀, 16L), the length of the two-part Lyot depolarizer that in two rings, depolarizer adopts is (1L, 2L), (4L, 8L).

The expression formula of the specific refractivity of the birefringece crystal of the single-mode fiber ring using in embodiments of the invention is ${\mathrm{\Δn}}_0=0.25n_{\mathrm{eff}}^2(P_{11}-P_{12})(1+v){(a/r)}^2=0.0927{(a/r)}^2,$ Wherein, n _effequivalent refractive index (n for silica fibre _eff=0.146), P11 and P12 are quartzy elasto-optical coefficient (P11=0.12, P12=0.27), and ν is Poisson's coefficient (ν=0.16), and a is optical fiber core diameter, the bending radius that r is fiber optic loop.In this example, the fiber lengths L of single-mode fiber ring _sMF=2100m, optical fiber core diameter is a=1253 μ m, the bending radius of ring is r=7cm.

In addition, the second port of described coupling mechanism is coupled by the input end of single-mode fiber and photodetector.Preferably, photodetector can adopt for example semiconductor PIN optical diode.

As mentioned above, the present invention utilizes complete depolarized light path to avoid using the polarizer in existing fiber gyroscope, and has realized the compensation effect (will describe in detail) of phase error below.In addition the said fibre optic gyroscope of the present invention only need to use a coupling mechanism, and unlike using two coupling mechanisms in existing fiber gyro, therefore the cost of fibre optic gyroscope of the present invention has reduced widely.

The front depolarizer of ring can produce light intensity and equate and two separate polarization states, and it has nonreciprocity, but can eliminate the impact that nonreciprocity brings by error compensation.Below by theoretical analysis, this point is described.

Definition C point place, before ring, between depolarizer and coupling mechanism, the polarization degree at some place is d, the normalization light field of inputting like this single-mode fiber ring is:

$E_C=\left[\begin{array}{c}\sqrt{(1+d)/2}{e}^{-\mathrm{j\Δ\βL}}\\ \sqrt{(1-d)/2}\end{array}\right]e^{j{\mathrm{\ω}}_{0}t}$ Formula (3)

Wherein, △ β is the poor of the propagation constant between polarization maintaining optical fibre diaxon in Lyot depolarizer, and length L has been eliminated the coherence between two polarization states.The degree of polarization of light wave is that d span is ﹣ 1～1.D=﹣ 1 represents y direction linear polarization, and d=0 represents the sizes such as amplitude of x direction and y direction, and d=1 represents x direction linear polarization.

Use symbol M _cWrepresent that the light wave of transmission clockwise passes total transmission matrix of coupling mechanism and fiber optic loop, uses symbol M _cCWrepresent that the light wave of transmission counterclockwise, through total transmission matrix of coupling mechanism and fiber optic loop, has:

$M_{\mathrm{CW}}=\left[\begin{array}{cc}{C}_1& C_2\\ C_3& C_4\end{array}\right]$ Formula (4)

$M_{\mathrm{CCW}}=\left[\begin{array}{cc}{C}_1& C_3\\ C_2& C_4\end{array}\right]$ Formula (5)

Can calculate thus the interference light wave that close echo forms:

$E_{\mathrm{CW}}+E_{\mathrm{CCW}}=M_{\mathrm{CW}}{E}_C{e}^{\mathrm{i\φ}}+M_{\mathrm{CCW}}{E}_C$ Formula (6)

Non-reciprocal phase φ=φ wherein _s+ △ φ (t) has comprised Sagnac phase difference _sphase bias △ φ (t) with modulator introducing.In formula, the concrete form of each is as follows

$E_{\mathrm{CW}}=M_{\mathrm{CW}}{E}_C{e}^{\mathrm{j\φ}}=\left[\begin{array}{c}{C}_1\sqrt{(1+d)/2}{e}^{-\mathrm{j\Δ\βL}}+C_2\sqrt{(1-d)/2}\\ C_3\sqrt{(1+d)/2}{e}^{-\mathrm{j\Δ\βL}}+C_4\sqrt{(1-d)/2}\end{array}\right]e^{j{\mathrm{\ω}}_{0}t}{e}^{\mathrm{j\φ}}$ Formula (7)

$E_{\mathrm{CCW}}=M_{\mathrm{CCW}}{E}_C=\left[\begin{array}{c}{C}_1\sqrt{(1+d)/2}{e}^{-\mathrm{j\Δ\β}{L}_0}+C_3\sqrt{(1-d)/2}\\ C_2\sqrt{(1+d)/2}{e}^{-\mathrm{j\Δ\β}{L}_0}+C_4\sqrt{(1-d)/2}\end{array}\right]e^{j{\mathrm{\ω}}_{0}t}$ Formula (8)

For the clear principle that obtains interpretation errors compensation, we calculate respectively x polarized component and y polarized component in resulting interference light wave.Wherein the interference light intensity of x polarized component is

I _x=<|E _CWx+E _CCWx| ²>

=I _x0+ | C ₁| ²(1+d) cos φ+(1-d) | C ₂c ₃| Γ (z ₂₃) cos φ cos φ ₂₃formula (9)

-(1-d)|C ₂C ₃|Γ(z ₂₃)sinφsinφ ₂₃

Write one with the DC component of phase-independent and weak coherent term in this step and be incorporated to I _x0, cast out high-order in a small amount.φ wherein ₂₃and z ₂₃respectively C ₂

phase place and birefringence time delay, Γ (z) is the coherence degree function of light source.

In order to analyze the error of resulting signal, we can be write as the result of formula (9) form of following equivalence

$I_x=I_{x0}+q_x\cos \mathrm{\&phi;}+p_x\sin \mathrm{\&phi;}=I_{x0}+\sqrt{p_x^2+q_x^2}\cos (\mathrm{\&phi;}-{\mathrm{\&phi;}}_{\mathrm{err}}^x)$ Formula (10)

P _x=-(1-d) | C ₂c ₃| Γ (z ₂₃) sin φ ₂₃formula (11)

Q _x=(1+d) | C ₁| ²+ (1-d) | C ₂c ₃| Γ (z ₂₃) cos φ ₂₃formula (12)

Wherein represented the size of the phase error of the nonreciprocal introducing of x direction polarization.

Similarly, we can obtain the interference light intensity I of y direction _ywith the phase error in signal ${\mathrm{\&phi;}}_{\mathrm{err}}^y=\arctan (p_y/q_y)$

$I_y=I_{y0}+q_y\cos \mathrm{\&phi;}+p_y\sin \mathrm{\&phi;}=I_{y0}+\sqrt{p_y^2+q_y^2}\cos (\mathrm{\&phi;}-{\mathrm{\&phi;}}_{\mathrm{err}}^y)$ Formula (10)

P _y=(1+d) | C ₂c ₃| Γ (z ₂₃) sin φ ₂₃formula (11)

Q _y=(1-d) | C ₄| ²+ (1+d) | C ₂c ₃| Γ (z ₂₃) cos φ ₂₃formula (12)

Finally, two composition I _x, I _ythe form of the total light intensity of interference light obtaining after stack can be expressed as DC component (DC) and add interference correlated components:

I _x+I _y=I _x0+I _y0+(q _x+q _y)cosφ _S+(p _x+p _y)sinφ _S

=I ₀+ cos (φ-φ _err) formula (13)

The error that polarization nonreciprocity is introduced is:

${\mathrm{\&phi;}}_{\mathrm{err}}=\arctan \left(\frac{p_x+p_y}{q_x+q_y}\right)$

$=\arctan \frac{2d\left|C_2{C}_3\right|\mathrm{\&Gamma;}\left(z_{23}\right)\sin {\mathrm{\&phi;}}_{23}}{{\left|C_1\right|}^2(1+d)+{\left|C_4\right|}^2(1-d)+2\left|C_2{C}_3\right|\mathrm{\&Gamma;}\left(z_{23}\right)\cos {\mathrm{\&phi;}}_{23}}$ Formula (14)

Visible, when light splitting is uniform (d=0), I _xand I _yin the phase error large opposite sign such as just, now final phase error is zero.While being d=0, φ _err=0.This has just illustrated that the optical fibre gyro structure in the present invention can effectively reduce the error of the nonreciprocal introducing of polarization, thereby does not need two coupling mechanisms to carry out strict guarantee reciprocity, only with a coupling mechanism, also can obtain stable angular velocity detection result.

Fig. 4 shows the time domain data figure of the gyrostatic Output speed value in Fig. 2.Wherein, experiment measuring to as if rotational-angular velocity of the earth, on the surface level of laboratory dimension (north latitude 40.0 degree), theoretical value to be measured be 9.67 degree/hour, data output gap is about 0.35 second, test duration length 2 hours.Visual data stable output, migration and drift are all very very little.Wherein input and output have a fixing deviation to be about 38 °/h.This deviation is introduced by coupling mechanism nonreciprocity, is individual not temporal evolution droop, can eliminate by simply doing poor mode, does not affect the precision and stability of gyro.

Fig. 5 shows the error analysis figure of gyrostatic Output speed data in Fig. 2.According to this figure, the error parameter of resulting gyro is: quantizing noise coefficient Q=8.6 * 10 ^-8rad, angle random walk zero bias stability B=1.8 * 10 ^-2°/h, speed random walk K=1.1 * 10 ^-1°/h ^3/2, rate ramp R=1.6 * 10 ^-1°/h ².

In the inclined to one side gyro of traditional guarantor and De-FOG, if remove the polarizer, its zero inclined to one side instability can reach tens～up to a hundred °/h.For the described complete depolarized fibre optic gyroscope of unicoupler of the present invention, the noise and the drift that can the nonreciprocal problem of almost Perfect ground compensation cause, its result and have the gyroscope structure of the polarizer suitable.In addition, the complete depolarized fibre optic gyroscope of unicoupler of the present invention only needs a coupling mechanism, and lower than the inclined to one side gyro of traditional guarantor and De-FOG structure complexity, cost is lower.

Although disclosed content shows exemplary embodiment of the present invention above, it should be noted that under the prerequisite of scope of the present invention that does not deviate from claim restriction, can carry out multiple change and modification.According to the structure of inventive embodiments described herein, the element of claim can substitute with the element of any function equivalent.Therefore, protection scope of the present invention should be determined by the content of appending claims.

Claims (10)

1. the complete depolarized fibre optic gyroscope of unicoupler, it is characterized in that, comprise wide spectrum light source, depolarizer before ring, coupling mechanism, depolarizer in two rings, single-mode fiber ring, and photodetector, wherein, the output terminal of wide spectrum light source is connected with depolarizer before ring by single-mode fiber, the first port coupling of the other end of depolarizer and coupling mechanism before ring, the 3rd port of coupling mechanism and the 4th port are coupled by depolarizer in single-mode fiber and two rings, in two rings, the other end of depolarizer is coupled with two ports of single-mode fiber ring respectively, the second port of coupling mechanism is coupled by the input end of single-mode fiber and photodetector.

2. the complete depolarized fibre optic gyroscope of unicoupler according to claim 1, is characterized in that, described coupling mechanism is 3dB single-mode optical-fibre coupler.

3. the complete depolarized fibre optic gyroscope of unicoupler according to claim 1, is characterized in that, in described single-mode fiber ring, is inserted with phase-modulator.

4. the complete depolarized fibre optic gyroscope of unicoupler according to claim 3, is characterized in that, described phase-modulator is PZT phase-modulator.

5. the complete depolarized fibre optic gyroscope of unicoupler according to claim 1, is characterized in that, before described ring, in depolarizer, ring, depolarizer is the two-part Lyot depolarizer that polarization maintaining optical fibre is made.

6. the complete depolarized fibre optic gyroscope of unicoupler according to claim 1 or 5, the length of the two-part Lyot depolarizer that wherein before ring, depolarizer adopts is (L ₀, 16L), the length of the two-part Lyot depolarizer that in two rings, depolarizer adopts is (1L, 2L), (4L, 8L), wherein L ₀with L be constant.

7. the complete depolarized fibre optic gyroscope of unicoupler according to claim 6, is characterized in that length L ₀meet L ₀=L _d/ △ n, the refringence between the x axle of the birefringece crystal that Δ n is this polarization maintaining optical fibre and y axle or between x ' axle and y ' axle, for the decoherence length of described wide spectrum light source, λ ₀for the centre wavelength of described wide spectrum light source, the spectrum width that Δ λ is described wide spectrum light source.

8. the complete depolarized fibre optic gyroscope of unicoupler according to claim 6, is characterized in that, length L meets Δ nL=Δ n ₀l _sMF+ L ₀, Δ n is the x axle of the polarization maintaining optical fibre that uses of the described depolarizer of making and the refringence between y axle, Δ n ₀for the specific refractivity of the birefringece crystal of described single-mode fiber ring, L _sMFfor the fiber lengths of described single-mode fiber ring, and L ₀for the first paragraph length of described two-part light source depolarizer, and

${\mathrm{\&Delta;n}}_0=0.25n_{\mathrm{eff}}^2(P_{11}-P_{12})(1+v){\left(\frac{a}{r}\right)}^2=0.0927{\left(\frac{a}{r}\right)}^2,$

Wherein, n _efffor the equivalent refractive index of the optical fiber in described single-mode fiber ring, P ₁₁and P ₁₂for the elasto-optical coefficient of the optical fiber in described single-mode fiber ring, ν is the Poisson's coefficient of the optical fiber in described single-mode fiber ring, and a and r are respectively the bending radius of core diameter and the described single-mode fiber ring of the optical fiber in described single-mode fiber ring.

9. the complete depolarized fibre optic gyroscope of unicoupler according to claim 1, is characterized in that, described wide spectrum light source adopts ASE wide spectrum light source.

10. the complete depolarized fibre optic gyroscope of unicoupler according to claim 1, is characterized in that, described photodetector adopts semiconductor PIN optical diode.

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