CN102706340A - Interference optical fiber gyroscope - Google Patents

Abstract

The invention relates to an interference optical fiber gyroscope which comprises a wide-spectrum light source, a light source end coupler, a depolarizer on the front portion of a ring, a coupler at the end of the ring, a single-mode fiber ring and a photoelectric detector. The output end of the wide-spectrum light source is coupled with a first port of the light source end coupler through single-mode fiber, a third port of the light source end coupler is coupled with one end of the depolarizer on the front portion of the ring through the single-mode fiber, the other end of the depolarizer on the front portion of the ring is coupled with a first port of the coupler at the end of the ring through the single-mode fiber, a third port and a fourth port of the coupler at the end of the ring are coupled with two ports of the single-mode fiber ring through the single-mode fiber respectively, and a second port of the light source end coupler is coupled with the input end of a photoelectric detector through the single-mode fiber. The gyroscope structure omits a polarizer in a minimum reciprocity structure of a gyroscope, non-reciprocal errors are removed through decoherence and interference light intensity compensation between two polarization states, cost is greatly reduced, simultaneously noise is low, and bias stability is good.

Description

A kind of interferometric fiber optic gyroscope

Technical field

The present invention relates to the gyroscope field, specifically, relate to a kind of interferometric fiber optic gyroscope.

Background technology

Gyroscope is a kind of rotation sensor, is used to measure 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 a mechanical gyroscope, and mechanical gyroscope is to utilize the turning axle of high-speed rotary body to have the such physical principle of trend that keeps its direction and the orienting device that produces.Because mechanical gyroscope comprises movable part (for example high speed rotor), therefore, its complex structure, technological requirement height and precision have received many-sided restriction.

In generation nineteen sixty, along with the appearance of laser, the research that utilizes laser to make 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 characteristics that is sent by same light source interferes during with (CCW) direction transmission counterclockwise along (CW) direction clockwise respectively; Through phase differential or the change of interference fringes that detects said two-beam, just can measure the rotational angular velocity of this closure light path.Above-mentioned phase differential is known as Sagnac phase shift φ S, and it is directly proportional with the rotational angular velocity Ω of closed light path:

${\mathrm{\&phi;}}_S=\frac{4\mathrm{\&omega;\; <figure-callout\; id="2"\; label="A\; c"\; filenames="HDA00001636857400021.png,HDA00001636857400022.png"\; state="\{\{state\}\}">A</figure-callout>}}{c^{}}\mathrm{\&Omega;}$ Formula (1)

Wherein, ω is a light frequency, and c is the light velocity in the 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.First generation optical gyroscope-lasergyro was come out in 1963.The primary element of lasergyro is a ring laser.For example, lasergyro can comprise the triangular closed light path of being processed by quartz, in this light path, is provided with a he-ne laser tube, two catoptrons and a semitransparent mirror.The laser that two bundles that send from he-ne laser tube transmit is on the contrary derived the loop by semitransparent mirror more respectively through two mirror reflects, just can obtain the rotational angular velocity of closed light path through the phase differential of measuring this two-beam.

Second generation optical gyroscope-fibre optic gyroscope occurred in 1976.The sensitivity and the degree of stability of fibre optic gyroscope is higher, cost and power consumption is lower and volume is less.Fibre optic gyroscope roughly is divided into interferometric fiber optic gyroscope resonant formula fibre optic gyroscope, and at present, the application of interferometric fiber optic gyroscope is the most extensive.

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

${\mathrm{\&phi;}}_S=2\mathrm{\&pi;}\frac{\mathrm{LD}}{\mathrm{\&lambda;\; c}}\mathrm{\&Omega;}$ Formula (2)

Wherein, L is a length of fiber, and D is the fiber optic coils diameter, and λ is the wavelength of light wave.

In order accurately to measure the Sagnac effect (is Sagnac phase shift φ _S); Guarantee that said closed light path has reciprocity; I.e. assurance has identical pattern, polarization and phase delay along the light (calling CW light in the following text) of the CW transmission of said closed light path and the light (calling CCW light in the following text) that transmits along the counter clockwise direction of said closed light path; Make that the phase differential of CW light and CCW light is only relevant with the rotational angular velocity of this closure light path, and irrelevant with transmission, thus improve the accuracy of measuring.

Fig. 1 shows the minimum reciprocal property structure of interferometric fiber optic gyroscope.As shown in Figure 1, this minimum reciprocal property structure comprises light source 10, source ends coupling mechanism 20, the polarizer 30, ring end coupling mechanism 40, fiber optic loop 50 and photodetector 60.Source ends coupling mechanism 20 can be X-coupler (i.e. four port coupler) or Y type coupling mechanism (i.e. three port coupler) with ring end coupling mechanism 40.Fig. 2 shows an exemplary configurations of X type source ends coupling mechanism 20.As shown in Figure 2, X type source ends coupling mechanism 20 comprises two optical fiber (first optical fiber 21 and second optical fiber 22) that lean on very closely.When light wave from an end 21a of first optical fiber 21 during to the other end 21b of this optical fiber transmission; Coupled zone at two optical fiber; The fadout afterbody 11a of the bell basic mode 11 of this light wave extends to the fibre core of the second adjacent optical fiber 22, and in second optical fiber 22, inspires optical mode, so; Stiffness of coupling (distance of fibre core-fibre core) and coupling length according to said two optical fiber; The luminous power of one end 21a of first optical fiber 21 just can be distributed between the other end 22b of the other end 21b of first optical fiber 21 and second optical fiber 22, and preferably, can make said distribution ratio is 50:50 (being 3dB).Likewise, the light wave that returns from the other end 21b of first optical fiber 21, also can beam split to an end 21a of first optical fiber 21 and an end 22a of second optical fiber 22.This shows that above-mentioned coupling mechanism can be realized the beam splitting of light beam and converge again.

When a port of X-coupler was free end, it just was equivalent to Y type coupling mechanism.Fig. 3 a shows four ports of X-coupler, and Fig. 3 b and 3c show three ports that close road type Y type coupling mechanism and shunt type Y type coupling mechanism respectively.Followingly the port of coupling mechanism is unified name so that censure with reference to figure 3a-3c.

Shown in Fig. 3 a; First port one and the 3rd port 3 that one end and the other end of first optical fiber in the X-coupler is called this coupling mechanism respectively, second port 2 and the 4th port 4 that an end and the other end of second optical fiber in the X-coupler is called this coupling mechanism respectively.Shown in Fig. 3 b, the left end two-port of closing road type Y type coupling mechanism is called first port one and second port 2 of this coupling mechanism respectively, the port of right-hand member that closes road type Y type coupling mechanism is called the 3rd port 3 of this coupling mechanism.Shown in Fig. 3 c, port of left end of shunt type Y type coupling mechanism is called first port one of this coupling mechanism, two ports of right-hand member of shunt type Y type coupling mechanism are called the 3rd port 3 and the 4th port 4 of this coupling mechanism respectively.

Referring again to Fig. 1; Light beam of light source is after passing through the polarizer 30; End coupling mechanism 40 is divided into CW light and CCW light transmits in fiber optic loop 50 through encircling; Again converge through ring end coupling mechanism 40 again after this CW light and CCW light transmit in fiber optic loop 50 and forms interference wave, this interference wave is at last through source ends coupling mechanism 20 entering photodetectors 60.Ring end coupling mechanism 40 has reciprocity, and it is identical to the phase delay that CW light and CCW light cause.In addition, the polarizer 30 is used for light wave is carried out polarization filtering, has identical polarization to guarantee CW light with CCW light, thereby realizes the polarization reciprocity.In fibre optic gyroscope, can adopt polarization maintaining optical fibre to guarantee the polarization reciprocity.

Because the phase place and the amplitude of CW light and CCW light were identical when fiber optic loop was static, so the power P of interference light ₀Be maximum.When fiber optic loop had rotation, the interference light power P was 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 bias φ, make system works near the non-vanishing point of luminous power slope: P (φ _S)=P ₀[1+cos (φ _S+ Δ φ)].For this reason, need add phase-modulator (for example, the PZT phase-modulator),, thereby make its generation phase difference φ when fiber optic loop 50 is static so that CW light and the CCW light of transmission in the fiber optic loop 50 is carried out phase modulation (PM) at an end of fiber optic loop 50.Fig. 4 is the interferometric fiber optic gyroscope with reciprocity phase modulation (PM)-demodulating equipment.In fibre optic gyroscope shown in Figure 4; Except comprising minimum reciprocal property structure shown in Figure 1, locking multiplying arrangement 80 that also be included in phase-modulator 70 that fiber optic loop 50 1 ends increase, increases at photodetector 60 1 ends and the signal generator 90 that same modulation-demodulation signal is provided for phase-modulator 70 and locking multiplying arrangement 80.

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

Table 1

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

As stated, in fibre optic gyroscope, the polarizer has perhaps had partially can eliminate the nonreciprocal noise component that causes of polarization with the device of protecting the bias ability, guarantees good zero stability partially, but has also caused the raising of cost.In addition, adopting polarization maintaining optical fibre is an effective means that guarantees the polarization reciprocity of optical fibre gyro structure, but in practical applications, the polarization maintaining optical fibre gyro still exists cost height, polarization maintaining optical fibre to crooked responsive to problems such as magnetic-field-sensitives.Therefore, people have proposed depolarized scheme again, the optical fibre gyro structure that adopts depolarizer and single-mode fiber to build lower cost.But, in existing polarization maintaining optical fibre gyro and depolarized optical fibre gyro, all the polarizer to be set before the fiber optic loop, perhaps be provided with the Y waveguide integrated optical circuit of inclined to one side function, these have all caused the raising of cost.Be example for example with present market price, the price of the polarizer be about 3000 yuan/individual, the price of Y waveguide integrated optical circuit be about 6000 yuan/individual; The price of polarization maintaining optical fibre is about 20 yuan/meter (and the length of fiber optic loop is 100 ~ 2000 meters in the actual gyro); The price of polarization-maintaining coupler is about 1000 ~ 2000 yuan, and therefore, the cost of polarization maintaining optical fibre gyro is wanted tens thousand of units/individual; And depolarized optical fibre gyro is owing to use device such as Y waveguide, cost is also up to ten thousand/and individual.

Summary of the invention

The objective of the invention is to, a kind of interferometric fiber optic gyroscope is provided, this interferometric fiber optic gyroscope has very low cost and higher precision and zero stability partially.

To achieve these goals; The present invention provides a kind of interferometric fiber optic gyroscope; It comprises wide spectrum light source, source ends coupling mechanism, the preceding depolarizer of ring, ring end coupling mechanism, single-mode fiber ring and photodetector; Wherein, The output terminal of wide spectrum light source is coupled through first port of single-mode fiber and source ends coupling mechanism, and an end of the 3rd port of source ends coupling mechanism depolarizer through single-mode fiber and before encircling is coupled, and the other end of the preceding depolarizer of ring passes through single-mode fiber and is coupled with first port that encircles the end coupling mechanism; The 3rd port of ring end coupling mechanism and the 4th port through single-mode fiber respectively with two ports couplings of single-mode fiber ring, second port of source ends coupling mechanism is coupled through the input end of single-mode fiber with photodetector.

Preferably, said source ends coupling mechanism and/or said ring end coupling mechanism can be the 3dB fiber coupler.

Preferably, in said single-mode fiber ring, can be inserted with the PZT phase-modulator.

Preferably, the output terminal at above-mentioned wide spectrum light source can be inserted with the light source depolarizer.Further preferably, said light source depolarizer can be the two-part Lyot depolarizer of polarization maintaining optical fibre making.Especially, the segment length of said two-part Lyot depolarizer can be (L ₀, 2L ₀), wherein, L ₀=L _d/ Δ n, Δ n are between x axle and the y axle of birefringece crystal of this polarization maintaining optical fibre or the refringence between x ' axle and the y ' axle, Be the decoherence length of said wide spectrum light source, λ ₀Be the centre wavelength of said wide spectrum light source, Δ λ is the spectrum width of said wide spectrum light source.

In addition, preferably, depolarizer in the 3rd port of said ring end coupling mechanism can be inserted with first ring, and/or the 4th port of said ring end coupling mechanism can be inserted with second encircle in depolarizer.Further preferably, depolarizer can be the two-part Lyot depolarizer of being made by polarization maintaining optical fibre in depolarizer and/or said second encircled in depolarizer and/or said first ring before the said ring.

Preferably, be inserted with the light source depolarizer, be inserted with depolarizer in first ring at the 3rd port of said ring end coupling mechanism at the output terminal of said wide spectrum light source, and the 4th port of said ring end coupling mechanism be inserted with second encircle in depolarizer.Depolarizer was the two-part Lyot depolarizer of being made by polarization maintaining optical fibre in depolarizer and said second encircled in depolarizer, said first ring before said light source depolarizer, the said ring.The segment length of said light source depolarizer is (L ₀, 2L ₀), before the said ring in depolarizer, said first ring in depolarizer and said second ring segment length of depolarizer be taken as respectively (1L, 2L), (4L, 8L), (16L, 32L) } a kind of arrangement, L ₀With L be constant.Especially, length L satisfies Δ nL=Δ n ₀L _SMF+ L ₀, Δ n is between the x axle of the birefringece crystal of the polarization maintaining optical fibre of making said depolarizer and the y axle or the refringence between x ' axle and the y ' axle, Δ n ₀Poor for the refractive index of the birefringece crystal of said single-mode fiber ring, L _SMFBe the fiber lengths of this single-mode fiber ring, and L ₀Be first segment length of said two-part light source depolarizer, and

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

n _EffEquivalent refractive index for the optical fiber in the said single-mode fiber ring; P11 and P12 are the elasto-optical coefficient of the optical fiber in the said single-mode fiber ring; V is the Poisson's coefficient of the optical fiber in the said single-mode fiber ring, and a and r are respectively the bending radius of the core diameter and the said single-mode fiber ring of the optical fiber in the said single-mode fiber ring.

As stated; The principle that the present invention is based on the polarization error compensation has broken through the restriction of optical fibre gyro minimum reciprocal structure; Interferometric fiber optic gyroscope of the present invention does not need the polarizer and the inclined to one side device of any guarantor; Greatly reduce the cost of structure, the cost of its structure is lower than all on the market optical fibre gyro structures at present.Good nonreciprocal error compensation effect be can reach through depolarizer in depolarizer, the ring before light source depolarizer, the ring, higher Gyro Precision and degree of stability realized.

In order to realize above-mentioned and relevant purpose, one or more aspects of the present invention comprise the characteristic that the back will specify and in claim, particularly point out.Following explanation and accompanying drawing have specified some illustrative aspects of the present invention.Yet, the indication of these aspects only be some modes that can use in the variety of way of principle of the present invention.In addition, the present invention is intended to comprise all these aspects and their equivalent.

Description of drawings

Through with reference to below in conjunction with the explanation of accompanying drawing and the content of claims, and along with to more complete understanding of the present invention, other purpose of the present invention and result will understand more and reach easy to understand.In the accompanying drawings:

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

Fig. 2 is the synoptic diagram of an exemplary configurations of X type source ends coupling mechanism;

Fig. 3 a is the synoptic diagram of four ports of X-coupler;

Fig. 3 b is the synoptic diagram that closes three ports of road type Y type coupling mechanism;

Fig. 3 c is the synoptic diagram of three ports of shunt type Y type coupling mechanism;

Fig. 4 is the synoptic diagram with interferometric fiber optic gyroscope of reciprocity phase modulation (PM)-demodulating equipment;

Fig. 5 is the synoptic diagram of the structure of the described interferometric fiber optic gyroscope of one embodiment of the present of invention;

Fig. 6 is the principle schematic of Lyot depolarizer;

Fig. 7 is the structural representation by the Lyot depolarizer of polarization maintaining optical fibre making;

Fig. 8 is the synoptic diagram of the approximate model structure of the interferometric fiber optic gyroscope among Fig. 5;

Fig. 9 is the synoptic diagram of the structure of the described interferometric fiber optic gyroscope of an alternative embodiment of the invention;

Figure 10 is the time domain data figure of the gyroscope output angle velocity amplitude among Fig. 9; And

Figure 11 is the error analysis figure of the gyroscope output angle speed data among Fig. 9.

Embodiment

In the following description, for purposes of illustration,, many details have been set forth for the complete understanding to one or more embodiment is provided.Yet, clearly, can not have to realize these embodiment under the situation of these details yet.In other example, for the ease of describing one or more embodiment, 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. 5 is the synoptic diagram of the structure of the described interferometric fiber optic gyroscope of one embodiment of the present of invention.As shown in Figure 5, interferometric fiber optic gyroscope of the present invention comprises: depolarizer 35, ring end coupling mechanism 40, single-mode fiber ring 50 and photodetector 60 before wide spectrum light source 10, source ends coupling mechanism 20, the ring.Wide spectrum light source 10 can adopt the wide spectrum light source that generally adopts in the interference type optical fiber gyroscope, for example can adopt the ASE wide spectrum light source, and its centre wavelength is 1550nm, and spectrum width is 40nm.The output terminal of wide spectrum light source 10 is through first port one coupling of single-mode fiber and source ends coupling mechanism 20.Source ends coupling mechanism 20 can be X-coupler or Y type coupling mechanism, preferably, uses the fiber coupler of splitting ratio as 50:50, i.e. the 3dB fiber coupler.

The 3rd port 3 of source ends coupling mechanism 20 is through the end coupling of single-mode fiber with the preceding depolarizer 35 of ring, and the other end of depolarizer 35 is through first port one coupling of single-mode fiber and ring end coupling mechanism 40 before the ring.Depolarizer is a kind of polarized light to be become the device of nonpolarized light, and specifically, depolarizer is used for a branch of linearly polarized light is become the linearly polarized light that intensity is identical, direction of vibration is vertical each other and incoherent mutually two bundles are superimposed.That is to say that the light that comes out from depolarizer can equivalence be the result of the two bunch polarized light non-coherent addition that leach from two orthogonal polarizers respectively.Depolarizer has a lot of types, the principle of the Lyot depolarizer that makes a brief explanation below.

Fig. 6 is the principle schematic of Lyot depolarizer.As shown in Figure 6, the Lyot depolarizer comprises two birefringece crystals of the same race, and its thickness is respectively L and 2L, and its main shaft x becomes 45 ° of angles with x '.If the refringence that (that is to say between x ' axle and the y ' axle) between the x axle and y axle of this birefringece crystal is Δ n, the decoherence length L of light source _dLess than Δ nL, then light wave train A is divided into two bundles vertical and mutual incoherent wave train B each other unevenly after through first crystal.Every Shu Bolie B is decomposed after through second crystal more equably, finally forms four wave train C at output terminal, and the light intensity of these wave trains on two polarization directions equates and be irrelevant mutually, promptly form depolarized light.

Utilize the birefringence effect of polarization maintaining optical fibre, can make the Lyot depolarizer through two sections polarization maintaining optical fibres.Fig. 7 shows the structure of the Lyot depolarizer of being made by polarization maintaining optical fibre.As shown in Figure 7, main shaft x becomes two sections polarization maintaining optical fibres of 45 to form the Lyot depolarizer through welding with x ', and the depolarized mechanism of its depolarized mechanism and birefringece crystal is identical.Preferably, the depolarizer that is adopted among the present invention can be the Lyot depolarizer made from polarization maintaining optical fibre.The cost of this depolarizer only is the cost with the length polarization maintaining optical fibre, the polarizer in the traditional fiber gyro with protect inclined to one side device cost.

Referring again to Fig. 5, the 3rd port 3 of ring end coupling mechanism 40 and the 4th port 4 are coupled with two ports of single-mode fiber ring 50 respectively through single-mode fiber.Ring end coupling mechanism 40 can be X-coupler or Y type coupling mechanism, and preferably, the splitting ratio of ring end coupling mechanism 40 is 50:50, and promptly ring end coupling mechanism 40 is the 3dB fiber coupler.

The expression formula of the difference of the refractive index of the birefringece crystal of employed single-mode fiber ring 50 is following in the embodiments of the invention:

${\mathrm{\&Delta;\; n}}_0=0.25n_{\mathrm{Eff}}^2(P_{11}-P_{12})(1+v){\left(\frac{a}{r}\right)}^2=0.0927{\left(\frac{a}{r}\right)}^2$ Formula (3)

Wherein, n _EffEquivalent refractive index (n for silica fibre _Eff=0.146), P11 and P12 be quartzy elasto-optical coefficient (P11=0.12, P12=0.27), v is Poisson's coefficient (v=0.16), a is the optical fiber core diameter, r is the bending radius of fiber optic loop.In this example, the fiber lengths L of single-mode fiber ring _SMF=2100m, optical fiber core diameter are a=1253 μ m, and the bending radius of ring is r=7cm.

In addition, second port 2 of source ends coupling mechanism 20 is through the input end coupling of single-mode fiber and photodetector 60.Preferably, photodetector 60 can adopt for example semiconductor PIN optical diode.

As stated, depolarizer 35 replaced the polarizer 30 in the existing interferometric fiber optic gyroscope before the present invention utilized ring, and had realized the compensation effect (back will be described in detail) of phase error, and therefore the cost of fibre optic gyroscope of the present invention has reduced widely.

Fig. 8 is the synoptic diagram of the approximate model structure of the interferometric fiber optic gyroscope among Fig. 5.Wherein, Circulator 351 and circulator 352 make the incident light wave that belongs to separately in the light path branch and return light wave and transmit along different paths; The function of polarization branch/bundling device (PBS/C) 353 is: realize that from left to right polarization closes bundle, the incident light wave in two light path branches of promptly transmitting is from left to right exported after being risen respectively and being biased to x axle and y axle and mutual superposition; Realize polarization beam splitting from right to left; The x component that returns in the light wave of i.e. transmission is from right to left exported by a port (being that the x axle plays inclined to one side port) of PBS/C 353 left ends, and the y component in this light wave is by another port (being that the y axle plays inclined to one side port) output of PBS/C 353 left ends.The function of depolarizer 35 just is equivalent to two-way light wave among Fig. 8 and rises respectively through PBS/C and stack up after being biased to x axle and y axle before the ring among Fig. 5, but the preceding depolarizer 35 of ring does not have Insertion Loss, and PBS/C has Insertion Loss.Delay line 354 among Fig. 8 is used for the decoherence function of depolarizer 35 before the equivalence ring; In addition; All comprise nonreciprocal error in the testing result of photodetector 355 and photodetector 356; But the result of its summation cancels out each other error, thereby obtains the stable output of low noise, and this summed result is equivalent to the direct output result of the photodetector 60 among Fig. 5.The result of experiment test shows that above equivalent model can be simulated actual fibre optic gyroscope fully, and its zero inclined to one side stability has all reached 10 ^-2The degree/hour magnitude, promptly reached the requirement of inert stage and tactics level.

Depolarizer 35 can produce equal and two the separate polarization states of light intensity before the ring, and it has nonreciprocity, but can eliminate the influence that nonreciprocity brings through error compensation.Through theoretical analysis this point is described below.

The x direction of depolarizer 35 and the Jones matrix that the y direction plays two inclined to one side equivalent polarizers are before the ring:

$P_x=\left[\begin{array}{cc}1& 0\\ 0& {\mathrm{\&epsiv;}}_1\end{array}\right]$ Formula (4)

$P_y=\left[\begin{array}{cc}{\mathrm{\&epsiv;}}_2& 0\\ 0& 1\end{array}\right]$ Formula (5)

Wherein, playing inclined to one side imperfection equivalence is the imperfection of depolarizer decoherence.When desirable, ε ₁=ε ₂=0.

The degree of polarization that gets into the light wave of the preceding depolarizer 35 of ring is d, and its span is ﹣ 1 ~ 1.D=﹣ 1 expression y directional ray polarization, d=0 representes the sizes such as amplitude of x direction and y direction, d=1 representes x directional ray polarization.The normalization amplitude that import light wave this moment does

$E_{\mathrm{IN}}=\left[\begin{array}{c}\sqrt{(1+d)/2}\\ \sqrt{(1-d)/2}\end{array}\right]$ Formula (6)

Use symbol T _CwThe total transmission matrix that encircles preceding coupling mechanism 35 is passed in the expression light wave of transmission clockwise, uses symbol T _CcwThe total transmission matrix that encircles preceding coupling mechanism 35 is passed in the expression light wave of transmission counterclockwise, then has:

$T_{\mathrm{Cw}}=\left[\begin{array}{cc}{C}_1& -C_2\\ C_3& {\mathrm{<figure-callout\; id="4"\; label="C"\; filenames="HDA00001636857400021.png,HDA00001636857400023.png"\; state="\{\{state\}\}">C</figure-callout>}}_4\end{array}\right]$ Formula (7)

$T_{\mathrm{Ccw}}=\left[\begin{array}{cc}{C}_1& -C_3\\ C_2& {\mathrm{<figure-callout\; id="4"\; label="C"\; filenames="HDA00001636857400021.png,HDA00001636857400023.png"\; state="\{\{state\}\}">C</figure-callout>}}_4\end{array}\right]$ Formula (8)

Each matrix element of above-mentioned transmission matrix has following relation:

＜C ₁C ₂ ^*＞=＜C ₃C ₄ ^*The C of＞≠＜ ₁C ₃ ^*＞=＜C ₂C ₄ ^*＞formula (9)

| C ₁C ₂|=| C ₃C ₄| ≠ | C ₁C ₃|=| C ₂C ₄| formula (10)

φ ₁₂=φ ₃₄≠ φ ₁₃=φ ₂₄, φ ₂₃≠ O formula (11)

Wherein, φ ₁₂, φ ₃₄, φ ₁₃, φ ₂₄, φ ₂₃Be respectively＜C ₁C ₂ ^*＞phase place,＜C ₃C ₄ ^*＞phase place,＜C ₁C ₃ ^*＞phase place,＜C ₂C ₄ ^*＞phase place,＜C ₂C ₃ ^*＞phase place.Can calculate the interference light wave that the close echo of incident wave and the x direction polarization of x direction polarization forms thus:

$E_{\mathrm{CWx}}+E_{\mathrm{CCWx}}=P_x{T}_{\mathrm{Cw}}{P}_x{E}_{\mathrm{IN}}{e}^{{\mathrm{I\&phi;}}_S}+P_x{T}_{\mathrm{Ccw}}{P}_x{E}_{\mathrm{IN}}$ Formula (12)

Further can obtain the light intensity I of the interference wave that the close echo of incident wave and the x direction polarization of x direction polarization forms _Xx=| E _CWx+ E _CCWx| ², cast out wherein with the DC component of phase-independent and high-order in a small amount, obtain after only keeping the component relevant with interference:

$\begin{array}{c}{I}_{\mathrm{Xx}}=2{\left|{\mathrm{<figure-callout\; id="1"\; label="C"\; filenames="HDA00001636857400021.png,HDA00001636857400022.png"\; state="\{\{state\}\}">C</figure-callout>}}_1\right|}^2(1+d){\mathrm{Cos}\mathrm{\&phi;}}_S+{2\mathrm{\&epsiv;}}_1\sqrt{1-d^2}\left[\right|C_1{\mathrm{<figure-callout\; id="3"\; label="C"\; filenames="HDA00001636857400021.png,HDA00001636857400022.png"\; state="\{\{state\}\}">C</figure-callout>}}_3|(-{\mathrm{Cos}\mathrm{\&phi;}}_S{\mathrm{Cos}\mathrm{\&phi;}}_{13}+{\mathrm{Sin}\mathrm{\&phi;}}_S{\mathrm{Sin}\mathrm{\&phi;}}_{13})\\ +\left|C_2{\mathrm{<figure-callout\; id="1"\; label="C"\; filenames="HDA00001636857400021.png,HDA00001636857400022.png"\; state="\{\{state\}\}">C</figure-callout>}}_1\right|(-{\mathrm{Cos}\mathrm{\&phi;}}_S{\mathrm{Cos}\mathrm{\&phi;}}_{12}-{\mathrm{Sin}\mathrm{\&phi;}}_S{\mathrm{Sin}\mathrm{\&phi;}}_{12})]\end{array}$ Formula (13)

In like manner, can obtain the incident wave of y direction polarization and the close echo of x direction polarization (this is nonreciprocal composition, can bring than mistake) with interfering relevant light intensity component be:

$\begin{array}{c}{I}_{\mathrm{Yx}}=2(1-d)\left|C_2{\mathrm{<figure-callout\; id="3"\; label="C"\; filenames="HDA00001636857400021.png,HDA00001636857400022.png"\; state="\{\{state\}\}">C</figure-callout>}}_3\right|({\mathrm{Cos}\mathrm{\&phi;}}_S{\mathrm{Cos}\mathrm{\&phi;}}_{23}-{\mathrm{Sin}\mathrm{\&phi;}}_S{\mathrm{Sin}\mathrm{\&phi;}}_{23})+2{\mathrm{\&epsiv;}}_2\sqrt{1-d^2}\left[\right|C_1{\mathrm{<figure-callout\; id="3"\; label="C"\; filenames="HDA00001636857400021.png,HDA00001636857400022.png"\; state="\{\{state\}\}">C</figure-callout>}}_3|(-{\mathrm{Cos}\mathrm{\&phi;}}_S{\mathrm{Cos}\mathrm{\&phi;}}_{13}\\ +{\mathrm{Sin}\mathrm{\&phi;}}_S{\mathrm{Sin}\mathrm{\&phi;}}_{13})+|C_2{\mathrm{<figure-callout\; id="1"\; label="C"\; filenames="HDA00001636857400021.png,HDA00001636857400022.png"\; state="\{\{state\}\}">C</figure-callout>}}_1\left|(-{\mathrm{Cos}\mathrm{\&phi;}}_S{\mathrm{Cos}\mathrm{\&phi;}}_{12}-{\mathrm{Sin}\mathrm{\&phi;}}_S{\mathrm{Sin}\mathrm{\&phi;}}_{12})\right]\end{array}$ Formula (14)

Similarly; Being respectively of the close echo (this is nonreciprocal composition, can bring than mistake) of the light intensity component relevant of the close echo of the incident wave of y direction polarization and y direction polarization and the incident wave of x direction polarization and y direction polarization with interfering relevant light intensity component with interference:

$\begin{array}{c}{I}_{\mathrm{Yy}}=2{\left|{\mathrm{<figure-callout\; id="4"\; label="C"\; filenames="HDA00001636857400021.png,HDA00001636857400023.png"\; state="\{\{state\}\}">C</figure-callout>}}_4\right|}^2(1-d){\mathrm{Cos}\mathrm{\&phi;}}_S+{2\mathrm{\&epsiv;}}_2\sqrt{1-d^2}\left[\right|C_4{\mathrm{<figure-callout\; id="2"\; label="C"\; filenames="HDA00001636857400021.png,HDA00001636857400022.png"\; state="\{\{state\}\}">C</figure-callout>}}_2|({\mathrm{Cos}\mathrm{\&phi;}}_S{\mathrm{Cos}\mathrm{\&phi;}}_{24}+{\mathrm{Sin}\mathrm{\&phi;}}_S{\mathrm{Sin}\mathrm{\&phi;}}_{24})\\ +\left|C_3{\mathrm{<figure-callout\; id="4"\; label="C"\; filenames="HDA00001636857400021.png,HDA00001636857400023.png"\; state="\{\{state\}\}">C</figure-callout>}}_4\right|(-{\mathrm{Cos}\mathrm{\&phi;}}_S{\mathrm{Cos}\mathrm{\&phi;}}_{34}-{\mathrm{Sin}\mathrm{\&phi;}}_S{\mathrm{Sin}\mathrm{\&phi;}}_{34})]\end{array}$ Formula (15)

$\begin{array}{c}{I}_{\mathrm{Xy}}=2(1+d)\left|C_3{\mathrm{<figure-callout\; id="2"\; label="C"\; filenames="HDA00001636857400021.png,HDA00001636857400022.png"\; state="\{\{state\}\}">C</figure-callout>}}_2\right|({\mathrm{Cos}\mathrm{\&phi;}}_S{\mathrm{Cos}\mathrm{\&phi;}}_{23}-{\mathrm{Sin}\mathrm{\&phi;}}_S{\mathrm{Sin}\mathrm{\&phi;}}_{23})+2{\mathrm{\&epsiv;}}_1\sqrt{1-d^2}\left[\right|C_4{\mathrm{<figure-callout\; id="2"\; label="C"\; filenames="HDA00001636857400021.png,HDA00001636857400022.png"\; state="\{\{state\}\}">C</figure-callout>}}_2|({\mathrm{Cos}\mathrm{\&phi;}}_S{\mathrm{Cos}\mathrm{\&phi;}}_{24}\\ +{\mathrm{Sin}\mathrm{\&phi;}}_S{\mathrm{Sin}\mathrm{\&phi;}}_{24})+|C_3{\mathrm{<figure-callout\; id="4"\; label="C"\; filenames="HDA00001636857400021.png,HDA00001636857400023.png"\; state="\{\{state\}\}">C</figure-callout>}}_4\left|({\mathrm{Cos}\mathrm{\&phi;}}_S{\mathrm{Cos}\mathrm{\&phi;}}_{34}-{\mathrm{Sin}\mathrm{\&phi;}}_S{\mathrm{Sin}\mathrm{\&phi;}}_{34})\right]\end{array}$ Formula (16)

Finally, four composition I _Xx, I _Yx, I _XyAnd I _YyThe form of the total light intensity of interference light that obtains after the stack can be expressed as DC component (DC) and add the interference correlated components:

DC+qcos φ _S+ psin φ _S=DC+cos (φ _S-φ _Err) formula (17)

The error that the polarization nonreciprocity is introduced is:

${\mathrm{\&phi;}}_{\mathrm{Err}}=\mathrm{Arctan}\left(\frac{p}{q}\right)$ Formula (18)

Wherein, p=p _x+ p _yQ=q _x+ q _y

$P_x=-2(1-d)\left|C_2{\mathrm{<figure-callout\; id="3"\; label="C"\; filenames="HDA00001636857400021.png,HDA00001636857400022.png"\; state="\{\{state\}\}">C</figure-callout>}}_3\right|{\mathrm{Sin}\mathrm{\&phi;}}_{23}+{2\mathrm{\&epsiv;}}_1\sqrt{1-d^2}\left(\right|C_1{\mathrm{<figure-callout\; id="3"\; label="C"\; filenames="HDA00001636857400021.png,HDA00001636857400022.png"\; state="\{\{state\}\}">C</figure-callout>}}_3|{\mathrm{Sin}\mathrm{\&phi;}}_{13}-|C_1{\mathrm{<figure-callout\; id="2"\; label="C"\; filenames="HDA00001636857400021.png,HDA00001636857400022.png"\; state="\{\{state\}\}">C</figure-callout>}}_2\left|{\mathrm{Sin}\mathrm{\&phi;}}_{12}\right)$ Formula (19)

$+{2\mathrm{\&epsiv;}}_2\sqrt{1-d^2}\left[\right|C_1{\mathrm{<figure-callout\; id="3"\; label="C"\; filenames="HDA00001636857400021.png,HDA00001636857400022.png"\; state="\{\{state\}\}">C</figure-callout>}}_3|{\sin \mathrm{\&phi;}}_{13}-|C_1{\mathrm{<figure-callout\; id="2"\; label="C"\; filenames="HDA00001636857400021.png,HDA00001636857400022.png"\; state="\{\{state\}\}">C</figure-callout>}}_2\left|{\sin \mathrm{\&phi;}}_{12}\right)]$

$P_y=2(1+d)\left|C_3{\mathrm{<figure-callout\; id="2"\; label="C"\; filenames="HDA00001636857400021.png,HDA00001636857400022.png"\; state="\{\{state\}\}">C</figure-callout>}}_2\right|{\mathrm{Sin}\mathrm{\&phi;}}_{23}+{2\mathrm{\&epsiv;}}_2\sqrt{1-d^2}\left(\right|C_2{\mathrm{<figure-callout\; id="4"\; label="C"\; filenames="HDA00001636857400021.png,HDA00001636857400023.png"\; state="\{\{state\}\}">C</figure-callout>}}_4|{\mathrm{Sin}\mathrm{\&phi;}}_{24}-|C_3{\mathrm{<figure-callout\; id="4"\; label="C"\; filenames="HDA00001636857400021.png,HDA00001636857400023.png"\; state="\{\{state\}\}">C</figure-callout>}}_4\left|{\mathrm{Sin}\mathrm{\&phi;}}_{34}\right)$ Formula (20)

$+{2\mathrm{\&epsiv;}}_1\sqrt{1-d^2}\left(\right|C_2{\mathrm{<figure-callout\; id="4"\; label="C"\; filenames="HDA00001636857400021.png,HDA00001636857400023.png"\; state="\{\{state\}\}">C</figure-callout>}}_4|{\sin \mathrm{\&phi;}}_{24}-|C_3{\mathrm{<figure-callout\; id="4"\; label="C"\; filenames="HDA00001636857400021.png,HDA00001636857400023.png"\; state="\{\{state\}\}">C</figure-callout>}}_4\left|{\sin \mathrm{\&phi;}}_{34}\right)$

$q_x=2\left|{{\mathrm{<figure-callout\; id="1"\; label="C"\; filenames="HDA00001636857400021.png,HDA00001636857400022.png"\; state="\{\{state\}\}">C</figure-callout>}}_1|}^2(1+d){-2\mathrm{\&epsiv;}}_1\sqrt{1-d^2}\right[\left(\right|C_1{\mathrm{<figure-callout\; id="3"\; label="C"\; filenames="HDA00001636857400021.png,HDA00001636857400022.png"\; state="\{\{state\}\}">C</figure-callout>}}_3|{\mathrm{Sin}\mathrm{\&phi;}}_{13}+|C_2{\mathrm{<figure-callout\; id="1"\; label="C"\; filenames="HDA00001636857400021.png,HDA00001636857400022.png"\; state="\{\{state\}\}">C</figure-callout>}}_1\left|{\mathrm{Sin}\mathrm{\&phi;}}_{12}\right)$ Formula (21)

$+2(1-d)\left|C_2{\mathrm{<figure-callout\; id="3"\; label="C"\; filenames="HDA00001636857400021.png,HDA00001636857400022.png"\; state="\{\{state\}\}">C</figure-callout>}}_3\right|{\cos \mathrm{\&phi;}}_{23}-{2\mathrm{\&epsiv;}}_2\sqrt{1-d^2}\left(\right|C_1{\mathrm{<figure-callout\; id="3"\; label="C"\; filenames="HDA00001636857400021.png,HDA00001636857400022.png"\; state="\{\{state\}\}">C</figure-callout>}}_3|{\cos \mathrm{\&phi;}}_{13}+|C_2{\mathrm{<figure-callout\; id="1"\; label="C"\; filenames="HDA00001636857400021.png,HDA00001636857400022.png"\; state="\{\{state\}\}">C</figure-callout>}}_1\left|{\cos \mathrm{\&phi;}}_{12}\right)$

$q_y=2\left|{{\mathrm{<figure-callout\; id="4"\; label="C"\; filenames="HDA00001636857400021.png,HDA00001636857400023.png"\; state="\{\{state\}\}">C</figure-callout>}}_4|}^2(1-d){+2\mathrm{\&epsiv;}}_2\sqrt{1-d^2}\right[\left(\right|C_4{\mathrm{<figure-callout\; id="2"\; label="C"\; filenames="HDA00001636857400021.png,HDA00001636857400022.png"\; state="\{\{state\}\}">C</figure-callout>}}_2|{\mathrm{Sin}\mathrm{\&phi;}}_{24}+|C_3{\mathrm{<figure-callout\; id="4"\; label="C"\; filenames="HDA00001636857400021.png,HDA00001636857400023.png"\; state="\{\{state\}\}">C</figure-callout>}}_4\left|{\mathrm{Sin}\mathrm{\&phi;}}_{34}\right)$ Formula (22)

$+2(1+d)\left|C_2{\mathrm{<figure-callout\; id="2"\; label="C"\; filenames="HDA00001636857400021.png,HDA00001636857400022.png"\; state="\{\{state\}\}">C</figure-callout>}}_2\right|{\cos \mathrm{\&phi;}}_{23}+{2\mathrm{\&epsiv;}}_1\sqrt{1-d^2}\left(\right|C_4{\mathrm{<figure-callout\; id="2"\; label="C"\; filenames="HDA00001636857400021.png,HDA00001636857400022.png"\; state="\{\{state\}\}">C</figure-callout>}}_2|{\cos \mathrm{\&phi;}}_{24}+|C_3{\mathrm{<figure-callout\; id="4"\; label="C"\; filenames="HDA00001636857400021.png,HDA00001636857400023.png"\; state="\{\{state\}\}">C</figure-callout>}}_4\left|{\cos \mathrm{\&phi;}}_{34}\right)$

Obviously, p=p _x+ p _yBe bordering on zero more, then error is more little.p _xAnd p _yFirst be the main source of error, the item of back be the single order a small amount of of error.Visible according to formula (19) and formula (20), when the miter angle of depolarizer 35 before the ring is desirable, d=0, first main error can be offset fully, has promptly eliminated the influence that nonreciprocity brings through the method for error compensation.Like this, can save the polarizer and protect inclined to one side device, and can use depolarizer but can eliminate the error that nonreciprocity causes.

Fig. 9 is the synoptic diagram of the structure of the described interferometric fiber optic gyroscope of an alternative embodiment of the invention.As shown in Figure 9, interferometric fiber optic gyroscope of the present invention can also comprise the phase-modulator 70 that is inserted in the single-mode fiber ring 50.An example of phase-modulator 70 is PZT phase-modulators.Phase-modulator 70 helps to improve the sensitivity of measurement, and the existing in front narration of its principle here just no longer repeats.

In addition; As shown in Figure 9, interferometric fiber optic gyroscope of the present invention can also comprise: be inserted in wide spectrum light source 10 output terminal light source depolarizer 36 and/or be inserted in depolarizer 37 in first ring of the 3rd port 3 of ring end coupling mechanism 40 and/or be inserted in depolarizer 38 in second ring of the 4th port 4 of ring end coupling mechanism 40.

Light source depolarizer 36 is used for wide spectrum light source 10 is carried out depolarized, in other words, when the miter angle of depolarizer 35 before the ring is undesirable, can carry out depolarized to realize d=0 through 36 pairs of wide spectrum light sources of light source depolarizer 10.Light source depolarizer 36 is preferably the two-part Lyot depolarizer made from polarization maintaining optical fibre, referring to Fig. 7.The segment length of this Lyot depolarizer is designated as (L ₀, 2L ₀), the first segment length L ₀Need to guarantee Δ nL ₀Decoherence length L more than or equal to light source _d, second segment length is 2L ₀For example, L can be arranged ₀=L _d/ Δ n, wherein, the refringence that (that is to say between x ' axle and the y ' axle) between the x axle and y axle of Δ n for the birefringece crystal of this polarization maintaining optical fibre,

Be the decoherence length of wide spectrum light source 10, here, λ ₀Be the centre wavelength of wide spectrum light source 10, Δ λ is the spectrum width of wide spectrum light source 10.For example, preferably used the ASE wide spectrum light source in the instance, its centre wavelength 1550nm, spectrum width 40nm, the decoherence length that therefore can calculate light source is 34.3 μ m, the first segment length L of light source depolarizer ₀Be 6.86cm.In order to guarantee depolarized effect, can get L ₀=10cm, so the total length of the employed optical fiber of light source depolarizer is L ₀+ 2L ₀=30cm.

The effect of depolarizer 37 and/or the interior depolarizer 38 of second ring is to change coefficient C in the above-mentioned transmission matrix in first ring ₁, C ₂, C ₃, C ₄Thereby the coherence who reduces nonreciprocal composition promptly reduces the amplitude of interfering time error.Error compensation and error span reduce to work in coordination can realize best effect.If depolarizer 35 is fully desirable before the ring, so, even without the interior depolarizer of ring, nonreciprocal error also can be eliminated through the method for compensation fully.Preferably, depolarizer 38 can be the two-part Lyot depolarizer of being made by polarization maintaining optical fibre in depolarizer 37 and/or said second encircled in depolarizer 35 and/or said first ring before the ring.

In one embodiment of the invention; As shown in Figure 9; Output terminal at wide spectrum light source 10 is inserted with light source depolarizer 36, holds the 3rd port 3 of coupling mechanism 40 to be inserted with depolarizer 37 in first ring at ring, and is inserted with depolarizer 38 in second ring at the 4th port 4 of ring end coupling mechanism 40.Depolarizer 38 can be the two-part Lyot depolarizer of being made by polarization maintaining optical fibre in depolarizer 37 and second encircled in depolarizer 35, first ring before light source depolarizer 36, the ring.The segment length of light source depolarizer 36 is (L ₀, 2L ₀), L ₀Be constant.Depolarized fully in order to guarantee, the length of six sections polarization maintaining optical fibres in depolarizer 37 and second encircles in depolarizer 35, first ring before the ring in depolarizer 38 these three depolarizers need satisfy the relation of length multiplication.Preferably, the segment length of said three depolarizers be respectively (1L, 2L), (4L, 8L), (16L, 32L) } a kind of arrangement, wherein, L is a constant.That is to say that the segment length of these three depolarizers can be respectively that (1L, 2L), (4L, 8L), (16L, 32L), and the position of these three depolarizers can exchange in twos.

In the above embodiments, length L need guarantee that Δ nL can offset the parasitic birefringence in the single-mode fiber ring 50 fully, promptly has: Δ nL>=Δ n ₀L _SMF+ L ₀, for example, Δ nL=Δ n ₀L _SMF+ L ₀, wherein, the refringence that (that is to say between x ' axle and the y ' axle) between the x axle and y axle of Δ n for the birefringece crystal of the employed polarization maintaining optical fibre of the said depolarizer of making, Δ n ₀Poor for the refractive index of the birefringece crystal of single-mode fiber ring 50 calculated L by formula (3) _SMFBe the length of single-mode fiber ring 50, L ₀First segment length for light source depolarizer 36.For example, in an example, the length L of single-mode fiber ring 50 _SMF=2100m, core diameter are 1253 μ m, and the bending radius of ring is 7cm, calculates length L=1.25+0.1=1.35m thus.In order to guarantee depolarized effect, can adopt L=1.5m.The optical fiber total length of depolarizer 38 was respectively L+2L=4.5m, 4L+8L=18m, 16L+32L=72m in depolarizer 37, the second encircled in depolarizer 35, the first rings before the ring like this.For the long L of shorter fiber optic loop _SMF, the proportional approx reduction of the optical fiber total length of said depolarizer.

Figure 10 shows the time domain data figure of the gyrostatic output angle velocity amplitude among Fig. 9.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, the data output gap is about 0.118 second, test duration length 1 hour.Visual data output is stable, and migration is all very very little with drift.

Figure 11 shows the error analysis figure of gyrostatic output angle speed data among Fig. 9.According to this figure, the error parameter of resultant gyro is: quantizing noise coefficient Q=8.6 * 10 ^-8Rad, the angle random migration

Zero stable partially B=2.1 * 10 ^-2°/h, speed random walk K=4.9 * 10 ^-2°/h ^3/2, rate ramp B=4.5 * 10 ^-1°/h ²

In inclined to one side gyro of traditional guarantor and depolarized gyro, if remove the polarizer, its zero inclined to one side instability can reach tens ~ up to a hundred °/h.For described complete depolarized type interferometric fiber optic gyroscope of the present invention; Can reasonably design the parameter of four Lyot depolarizers according to the front theory; Thereby be close to and ideally compensate noise and the drift that nonreciprocal problem causes, its result with have the gyro structure of the polarizer suitable.In addition, owing to contain circular component hardly in the depolarized light, Faraday effect can reduce greatly.Because the drift meeting that Faraday effect causes reduces greatly, therefore, the present invention has extra advantage with respect to protecting inclined to one side structure.

For complete depolarized type interferometric fiber optic gyroscope provided by the invention; Four depolarizers use polarization maintaining optical fibre length only to need tens meters altogether; The price of single-mode optical-fibre coupler be lower than 50 yuan/individual; About 0.2 yuan/meter of single-mode fiber price, if add light source and detector, gyrostatic cost of the present invention altogether about 3000 ~ 5000 yuan/individual.This is with respect to existing optical fibre gyro on the market, and cost greatly reduces.

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

Claims (10)

1. interferometric fiber optic gyroscope; Comprise wide spectrum light source, source ends coupling mechanism, the preceding depolarizer of ring, ring end coupling mechanism, single-mode fiber ring and photodetector; Wherein, The output terminal of wide spectrum light source is through first port coupling of single-mode fiber and source ends coupling mechanism; The 3rd port of source ends coupling mechanism is through the end coupling of single-mode fiber with the preceding depolarizer of ring; The other end of depolarizer is through the first port coupling of single-mode fiber with ring end coupling mechanism before the ring, the 3rd port of ring end coupling mechanism and the 4th port through single-mode fiber respectively with two ports couplings of single-mode fiber ring, second port of source ends coupling mechanism is coupled through the input end of single-mode fiber with photodetector.

2. interferometric fiber optic gyroscope according to claim 1, wherein, said source ends coupling mechanism and/or said ring end coupling mechanism are the 3dB fiber coupler.

3. interferometric fiber optic gyroscope according to claim 1 wherein, is inserted with the PZT phase-modulator in said single-mode fiber ring.

4. according to claim 1 or 3 described interferometric fiber optic gyroscopes, wherein, be inserted with the light source depolarizer at the output terminal of said wide spectrum light source.

5. interferometric fiber optic gyroscope according to claim 4, wherein, said light source depolarizer is the two-part Lyot depolarizer that polarization maintaining optical fibre is made.

6. interferometric fiber optic gyroscope according to claim 5, wherein, the segment length of said two-part Lyot depolarizer is (L ₀, 2L ₀), wherein, L ₀=L _d/ Δ n, Δ n are between x axle and the y axle of birefringece crystal of this polarization maintaining optical fibre or the refringence between x ' axle and the y ' axle, Be the decoherence length of said wide spectrum light source, λ ₀Be the centre wavelength of said wide spectrum light source, Δ λ is the spectrum width of said wide spectrum light source.

7. according to claim 1 or 3 described interferometric fiber optic gyroscopes, wherein, be inserted with depolarizer in first ring at the 3rd port of said ring end coupling mechanism, and/or the 4th port of said ring end coupling mechanism be inserted with second encircle in depolarizer.

8. interferometric fiber optic gyroscope according to claim 7, wherein, depolarizer was the two-part Lyot depolarizer of being made by polarization maintaining optical fibre in depolarizer and/or said second encircled in depolarizer and/or said first ring before the said ring.

9. according to claim 1 or 3 described interferometric fiber optic gyroscopes; Wherein, Output terminal at said wide spectrum light source is inserted with the light source depolarizer; The 3rd port at said ring end coupling mechanism is inserted with depolarizer in first ring, and is inserted with depolarizer in second ring at the 4th port of said ring end coupling mechanism; Depolarizer was the two-part Lyot depolarizer of being made by polarization maintaining optical fibre in depolarizer and said second encircled in depolarizer, said first ring before said light source depolarizer, the said ring; And the segment length of said light source depolarizer is (L ₀, 2L ₀), before the said ring in depolarizer, said first ring in depolarizer and said second ring segment length of depolarizer be taken as respectively (1L, 2L), (4L, 8L), (16L, 32L) } a kind of arrangement, wherein, L ₀With L be constant.

10. interferometric fiber optic gyroscope according to claim 9, wherein, length L satisfies Δ nL=Δ n ₀L _SMF+ L ₀, Δ n is between the x axle of the birefringece crystal of making the employed polarization maintaining optical fibre of said depolarizer and the y axle or the refringence between x ' axle and the y ' axle, Δ n ₀Poor for the refractive index of the birefringece crystal of said single-mode fiber ring, L _SMFBe the fiber lengths of said single-mode fiber ring, and L ₀Be first segment length of said two-part light source depolarizer, and

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

n _EffEquivalent refractive index for the optical fiber in the said single-mode fiber ring; P11 and P12 are the elasto-optical coefficient of the optical fiber in the said single-mode fiber ring; V is the Poisson's coefficient of the optical fiber in the said single-mode fiber ring, and a and r are respectively the bending radius of the core diameter and the said single-mode fiber ring of the optical fiber in the said single-mode fiber ring.

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