JPH07128073A - Optical fiber gyro - Google Patents
Optical fiber gyroInfo
- Publication number
- JPH07128073A JPH07128073A JP27923293A JP27923293A JPH07128073A JP H07128073 A JPH07128073 A JP H07128073A JP 27923293 A JP27923293 A JP 27923293A JP 27923293 A JP27923293 A JP 27923293A JP H07128073 A JPH07128073 A JP H07128073A
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- optical
- optical fiber
- light
- polarization
- phase
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Abstract
Description
【0001】[0001]
【産業上の利用分野】この発明は光ファイバループに、
その軸心まわりに印加される角速度を、その光ファイバ
ループを伝搬する右、左回り光の位相差から検出する光
ファイバジャイロに関する。This invention relates to an optical fiber loop,
The present invention relates to an optical fiber gyro that detects an angular velocity applied around its axis from the phase difference between right-handed and left-handed light propagating in the optical fiber loop.
【0002】[0002]
【従来の技術】図3を参照して従来の光ファイバジャイ
ロを説明する。半導体レーザ光源11から出射した光は
光分岐手段としての光ファイバカプラ12を通じ、更に
偏光子13を通じて光分岐結合手段としての光ファイバ
カプラ14に入射される。光ファイバカプラ14にて2
分された光はそれぞれ偏波維持光ファイバ15,16を
通じて、光ファイバループ17に右回り光、左回り光と
して入射される。これら両光はその各偏光方向に対し
て、偏波維持光ファイバ15,16の偏波軸方向が45
°となるようにされ、かつ偏波維持光ファイバ15,1
6の長さが十分長くされてあって、光ファイバループ1
7に入射する光のx方向偏波成分とy方向偏波成分とが
互いに干渉しないように偏光度が低減される偏光解離手
段として偏波維持光ファイバ15,16はそれぞれ作用
する。2. Description of the Related Art A conventional optical fiber gyro will be described with reference to FIG. The light emitted from the semiconductor laser light source 11 is incident on the optical fiber coupler 12 as an optical branching means, and further through the polarizer 13 to the optical fiber coupler 14 as an optical branching / coupling means. 2 with optical fiber coupler 14
The split lights are incident on the optical fiber loop 17 as right-handed light and left-handed light through the polarization maintaining optical fibers 15 and 16, respectively. The polarization axes of the polarization-maintaining optical fibers 15 and 16 are 45 degrees with respect to the respective polarization directions of these two lights.
And the polarization maintaining optical fibers 15 and 1
The length of 6 is made sufficiently long, and the optical fiber loop 1
The polarization maintaining optical fibers 15 and 16 respectively act as polarization dissociation means for reducing the degree of polarization so that the x-direction polarization component and the y-direction polarization component of the light incident on 7 will not interfere with each other.
【0003】光ファイバカプラ14の片端と偏波維持光
ファイバ16との間に光位相変調器18が直列に挿入さ
れ、発振器19からの変調信号により光位相変調器18
が駆動され、光ファイバループ17を伝搬する左、右回
り光が周波数fm で位相変調される。光ファイバループ
17を伝搬した左、右回り光は光ファイバカプラ14で
結合され、その干渉光が偏光子13を通じ、更に光ファ
イバカプラ12を通じて受光器21に達して電気信号に
変換される。この電気信号は発振器19の出力で、同期
検波回路22において同期検波され、その検波出力がジ
ャイロ出力として出力端子23に出力される。An optical phase modulator 18 is inserted in series between one end of the optical fiber coupler 14 and the polarization maintaining optical fiber 16, and the optical phase modulator 18 is supplied with a modulation signal from an oscillator 19.
Is driven, and the left-handed and right-handed lights propagating through the optical fiber loop 17 are phase-modulated at the frequency f m . The left-handed and right-handed lights propagating through the optical fiber loop 17 are combined by the optical fiber coupler 14, and the interference light reaches the light receiver 21 through the polarizer 13 and further through the optical fiber coupler 12, and is converted into an electric signal. This electric signal is the output of the oscillator 19, is synchronously detected in the synchronous detection circuit 22, and the detected output is output to the output terminal 23 as a gyro output.
【0004】光ファイバコイル17にその軸心回りの角
速度が印加されると、サニヤック効果により両回り光に
位相差が生じる。この位相差φS は次式で表わされる。 φS =4πPLΩ/(cλ) (1) ここにR,Lはそれぞれ光ファイバループ17のループ
半径と全長、cは光速度、λは光波長、Ωは入力角速度
である。When the angular velocity around the axis of the optical fiber coil 17 is applied, a phase difference occurs between the two-direction light due to the Sannyak effect. This phase difference φ S is expressed by the following equation. φ S = 4πPLΩ / (cλ) (1) where R and L are the loop radius and the total length of the optical fiber loop 17, respectively, c is the optical velocity, λ is the optical wavelength, and Ω is the input angular velocity.
【0005】ところで干渉光強度の変化は(1)で決ま
るφS に対しcosφS に比例するためφS =0近傍で
感度がない。そこで光ファイバループ17の一端に光位
相変調器18を設置し、これを透過する光に対し、 φm sin(2πfm t) (2) なる光位相変調を印加する。ここにφm は光位相変調振
幅、fm は光位相変調周波数、tは時刻である。光ファ
イバループ17の光伝搬時間をτと書くと、干渉光の強
度を決める両回り光の位相差Δφ(t)は次式で表わせ
る。[0005] change in the interference light intensity has no sensitivity phi S = 0 near proportional to cos [phi S to determined phi S (1). Therefore, the optical phase modulator 18 is installed at one end of the optical fiber loop 17, and the optical phase modulation of φ m sin (2πf m t) (2) is applied to the light transmitted through the optical phase modulator 18. Here, φ m is the optical phase modulation amplitude, f m is the optical phase modulation frequency, and t is the time. If the light propagation time of the optical fiber loop 17 is written as τ, the phase difference Δφ (t) of the two-way light that determines the intensity of the interference light can be expressed by the following equation.
【0006】 Δφ(t)=φS +φm sin(2πfm (t−τ)) −φm sin(2πfm t) (3) このように位相差Δφ(t)は振動し、干渉光の強度変
化を与えるcosΔφ(t)は、次式で表わせる。 cosΔφ(t)=cosφS Σεn (−1)n cos2n(2πfm (t−(τ/2))J2n(x)−sinφS ・2Σ(−1)n cos(2n+1)(2πfm (t−(τ/2))J2n+1(x) (4) ε=1(n=0);ε=2(n≧1)、εはn=0から
無限大まで x=2φm sinπfm τ ここでJi は第1種第i次ベッセル関数である。(4)
式より干渉光の強度振動分から変調信号の奇数倍周波数
成分としてsinφS が検出できることがわかる。かく
てφS ≒0での感度を獲得するのが位相変調方式光ファ
イバジャイロであるが、通常は先に述べたように受光器
21の出力の基本波成分(n=0)を同期検波する。Δφ (t) = φ S + φ m sin (2πf m (t−τ)) −φ m sin (2πf m t) (3) Thus, the phase difference Δφ (t) oscillates and the interference light The cos Δφ (t) that gives the intensity change can be expressed by the following equation. cosΔφ (t) = cosφ S Σε n (-1) n cos2n (2πf m (t- (τ / 2)) J 2n (x) -sinφ S · 2Σ (-1) n cos (2n + 1) (2πf m ( t- (τ / 2)) J 2n + 1 (x) (4) ε = 1 (n = 0); ε = 2 (n ≧ 1), ε is from n = 0 to infinity x = 2φ m sin πf m τ where J i is the i-th order Bessel function of the first kind (4)
From the equation, it can be seen that sinφ S can be detected as an odd multiple frequency component of the modulation signal from the intensity vibration of the interference light. Thus, it is the phase modulation type optical fiber gyro that obtains the sensitivity at φ S ≈0, but normally, the fundamental wave component (n = 0) of the output of the light receiver 21 is synchronously detected as described above. .
【0007】さて特殊な例外を除いて光ファイバが伝送
する光のモードは通常単一ではなく、いわゆるシングル
モード光ファイバと呼ばれている光ファイバにおいても
HE 11 x ,HE11 y なる2つの直交する直線偏波モード
が縮退している。この縮退は応力等の作用で容易に解
け、偏波モード分散を生じる。しかもこれら分散したモ
ード間では応力攪乱等によりモード結合がしばしば起こ
る。これらの誤差要因を排除するため通常、光ファイバ
ループ17に接続する光分岐手段、つまり光ファイバカ
プラ14の前段に、モードフィルタとして直線偏光子1
3を挿入する。しかし、偏光子13の性能すなわち消光
比が現実のデバイスにおいて有限の値をもつため、光フ
ァイバジャイロとして十分な分解能を得るために通常次
の2つのいずれかの方法が取られる。すなわち第1の方
法は光ファイバループ17に偏波維持光ファイバを使用
して偏波モード間のモード結合を阻止する方法であり、
第2の方法は偏光解離手段、図4Aでは偏波維持光ファ
イバ15,16によって偏波モード間の光の振動の相関
をなくす方法である。上記モード分散による光ファイバ
ジャイロの誤差は位相差相当で次式で表わせる。Optical fibers are transmitted with special exceptions.
The light mode is usually not single, but so-called single
Even in optical fiber called mode optical fiber
HE 11 x, HE11 yTwo orthogonal linear polarization modes
Is degenerate. This degeneracy is easily solved by the action of stress.
However, polarization mode dispersion occurs. Moreover, these dispersed models
Mode coupling often occurs due to stress disturbance.
It Optical fiber is usually used to eliminate these error factors.
Optical branching means connected to the loop 17, that is, an optical fiber cable
In front of the plastic 14, a linear polarizer 1 is used as a mode filter.
Insert 3. However, the performance of the polarizer 13, that is, the extinction
Since the ratio has a finite value in a real device, the optical
In order to obtain sufficient resolution as a gyro,
One of two methods is adopted. That is, the first one
The method uses a polarization maintaining optical fiber for the optical fiber loop 17.
To prevent mode coupling between polarization modes,
The second method is polarization dissociation means, and in FIG.
Correlation of vibration of light between polarization modes by aver 15 and 16
Is a way to eliminate. Optical fiber with the above mode dispersion
The gyro error is equivalent to the phase difference and can be expressed by the following equation.
【0008】 Δφ<εγ(|Ey |/|Ex |)(|αxy|+|αyx|)/|αxx| (5) ここにεは偏光子13の消光比、γは偏波モード伝搬光
間の相関、Ex ,Eyは入射光の偏波主軸、複軸成分の
各振幅であり、αxx,αxy等は光ファイバループ17中
の各偏波モード間の振幅伝達係数、またεは十分小さい
としている。ここで前記第1の方法は(|αxy|+|α
yx|)/|αxx|を0とし、第2の方法はγを0とする
ものであり、前者を偏光系の、後者を非偏光系の光ファ
イバジャイロと呼ぶ。Δφ <εγ (| E y | / | E x |) (| α xy | + | α yx |) / | α xx | (5) where ε is the extinction ratio of the polarizer 13 and γ is the polarization Correlations between wave mode propagating lights, E x and E y are amplitudes of polarization main axis and multi-axis component of incident light, and α xx and α xy are amplitudes between polarization modes in the optical fiber loop 17. It is assumed that the transfer coefficient and ε are sufficiently small. Here, the first method is (| α xy | + | α
yx |) / | α xx | is 0, and the second method is to set γ to 0. The former is called a polarization system and the latter is called a non-polarization optical fiber gyro.
【0009】偏光解離は、特に直線偏光を対象とする場
合、先に述べたように比較的簡単に実現する。偏波維持
光ファイバなどの複屈折性媒質に、直線偏光を偏光方向
が複屈折軸に対し45°の方位で入射させると、伝搬距
離が大になるに従って両成分間の相関が減少し、偏光は
解離してゆく。このさい複屈折性伝送路が、偏波モード
間の光学距離差について光の可干渉距離に比べ十分な大
きさを有するだけの長さをもてばよい。The polarization dissociation is relatively easy to realize as described above, particularly when linearly polarized light is targeted. When linearly polarized light is incident on a birefringent medium such as a polarization-maintaining optical fiber at an angle of 45 ° with respect to the birefringence axis, the correlation between the two components decreases as the propagation distance increases, and Dissociates. In this case, the birefringent transmission line should be long enough to have a sufficient optical distance difference between the polarization modes as compared with the coherence length of light.
【0010】以上光ファイバジャイロ中の、位相変調方
式における非偏光系光ファイバジャイロについて、また
偏光解離手段について述べた。なお光位相変調器18と
しては光学結晶における電気光学効果を用いたものなど
もあるが、より簡便で多く用いられるものは、円筒形の
電歪振動子に偏波維持光ファイバを巻回し、その光ファ
イバを伸縮させるものである。また直線偏光子13とし
ては、副軸偏波モードについて曲げ損失の大きい特性を
持つ偏波維持光ファイバを、十分な小径に巻回して構成
するものが代表的である。The non-polarization type optical fiber gyro in the phase modulation system among the optical fiber gyros and the polarization dissociation means have been described above. As the optical phase modulator 18, there is a type that uses the electro-optic effect in an optical crystal, but the simpler and more widely used type is that a polarization maintaining optical fiber is wound around a cylindrical electrostrictive oscillator, It expands and contracts the optical fiber. The linear polarizer 13 is typically formed by winding a polarization-maintaining optical fiber having a large bending loss in the sub-axis polarization mode and winding the fiber with a sufficiently small diameter.
【0011】[0011]
【発明が解決しようとする課題】以上述べたように位相
変調方式光ファイバジャイロでは、受光器21に到達す
る光の光量の変調同期交流成分として、回転角速度起因
のサニヤック位相差を検出するものである。そこでそれ
以外の原因から受光器到達光量に変調同期交流成分が生
じることがあるとすれば、これはサニヤック位相差と分
離されないためジャイロのバイアス誤差となる。特に両
回り光の合波として干渉光を形成することによってでは
なく、すでに片回り光の段階でその伝送光量に位相変調
同期の振動変動が生じている場合、それによるジャイロ
誤差を光強度変調性バイアスと呼ぶ。かかる光強度変調
を生起する原因は、一つではないが、前述のような構成
の非偏光系の位相変調方式光ファイバジャイロにおいて
重要なのは、前記光位相変調器18で誘起する変調同期
光偏波状態変動である。以下これについて述べる。As described above, in the phase modulation type optical fiber gyro, the Sagnac phase difference due to the rotational angular velocity is detected as the modulation synchronous AC component of the light quantity of the light reaching the light receiver 21. is there. If there is a case where a modulation-synchronized AC component is generated in the amount of light reaching the light receiver due to other reasons, this is a bias error of the gyro because it is not separated from the Sagnac phase difference. In particular, not by forming interference light as a combination of double-sided light, but when the fluctuation of oscillation due to phase modulation synchronization has already occurred in the amount of transmitted light at the stage of single-sided light, the gyro error caused by the change in light intensity can be modulated. Called bias. Although there is no single cause for causing such light intensity modulation, what is important in the non-polarization type phase modulation type optical fiber gyro having the above-mentioned configuration is the modulation synchronous optical polarization induced by the optical phase modulator 18. It is a state change. This will be described below.
【0012】現実のデバイスとしての光ファイバ偏光子
13の消光比は〜20dB程度を典型とし、副軸偏波モ
ードが理想の如く消光しているわけではない。現実のデ
バイスとしての光ファイバカプラ14は、偏波維持性で
あっても若干のクロストーク即ち直交偏波モード間の結
合を有する。現実の光ファイバジャイロ製造過程で実行
される光ファイバの融着等による接続で、偏波維持性の
光ファイバについて偏波軸合せの方位誤差を完全になく
すことはできない。このような事情から例えば図4Aに
おける左回り光の伝送について、光源11から偏光子1
3、光ファイバカプラ14を経て光位相変調器18を通
過する光は零でない振幅をもつ偏波副軸励振があり、こ
の成分につき主軸とは相異なる変調振幅の光位相変調が
効果している。この場合主軸の光と副軸の光との相対的
な位相差が位相変調器18の駆動に同期して交流的に振
動することになる。The extinction ratio of the optical fiber polarizer 13 as an actual device is typically about 20 dB, and the sub-axis polarization mode does not extinct as ideal. The optical fiber coupler 14 as an actual device has some crosstalk, that is, coupling between orthogonal polarization modes even if it is polarization maintaining. In the actual optical fiber gyro manufacturing process, it is impossible to completely eliminate the azimuth error of polarization axis alignment in the polarization maintaining optical fiber by splicing the optical fibers. Under these circumstances, for example, for transmission of counterclockwise light in FIG.
3. The light passing through the optical phase modulator 18 via the optical fiber coupler 14 has a polarization sub-axis excitation having a non-zero amplitude, and the optical phase modulation of a modulation amplitude different from that of the main axis is effective for this component. . In this case, the relative phase difference between the light on the main axis and the light on the sub axis oscillates in an alternating current in synchronization with the driving of the phase modulator 18.
【0013】一方、非偏光系の光ファイバルジャイロに
おいては、光ファイバループ17を伝搬した光は完全に
偏光解離していることを建前とするが、偏光子13の消
光不足、光ファイバカプラ14のクロストーク、偏光解
離用の偏波維持光ファイバ15,16の45°接続角度
誤差、その他偏波維持光ファイバの接続箇所での複屈折
軸の接続角度誤差、光源11のスペクトラムに起因する
光可干渉性減衰特性の不単調等の現実の制約から、光フ
ァイバループ17を伝搬した光が零でない偏光度を有
し、わずかな部分偏光成分を持つことが避けられない。
かかる微少な部分偏光成分が、前記の光位相変調器18
の動作に起因し、これに同期してその偏波状態を変動さ
せることがあり、この位相変調と同期した偏波状態変動
がある光を、複屈折軸方位に対し角度差をもつ偏光子1
3を介して受光した場合、受光器21に到達する光は位
相変調と同期した強度変調が現われることになる。On the other hand, in the non-polarization type optical fiber regyro, it is assumed that the light propagating through the optical fiber loop 17 is completely polarization-dissociated, but the extinction of the polarizer 13 is insufficient, and the optical fiber coupler 14 is used. Crosstalk, a 45 ° connection angle error between polarization maintaining optical fibers 15 and 16 for polarization dissociation, a connection angle error between birefringence axes at other polarization maintaining optical fiber connection points, and light caused by the spectrum of the light source 11. Due to practical constraints such as non-monotonic coherence attenuation characteristics, it is inevitable that the light propagating through the optical fiber loop 17 has a non-zero degree of polarization and a slight partial polarization component.
Such a minute partial polarization component is the above-mentioned optical phase modulator 18
The polarization state may be changed in synchronism with the operation described above, and light having a polarization state change synchronized with this phase modulation is used for the polarizer 1 having an angle difference with respect to the birefringence axis direction.
When light is received via 3, the light reaching the light receiver 21 undergoes intensity modulation in synchronization with phase modulation.
【0014】上記の事情をごく一般的に記述すると、か
かる偏波状態変動にあずかる成分を規定する相関性のあ
る直交直線偏波成分をEx ,Ey 両者の位相差をδφと
書くと、この部分偏光の光が方位θを有する偏光子を透
過した光の強度Iθは次式で表わせる。 Iθ=Ix +Iy +2√Ix Iy cosδφ (6) Ix =|Ex |2 cos2 θ,Iy =|Ey |2 sinθ 位相差δφが光位相変調器18の動作により δφ=δφO (t)+δφm sin(2πfm t) (7) と変動すると、Iθは(8)式となる。To describe the above situation very generally, if the orthogonal linearly polarized wave component having correlation and defining the component involved in such polarization state fluctuation is written as E x and E y , the phase difference between them is expressed as δφ. The intensity Iθ of the partially polarized light transmitted through the polarizer having the azimuth θ can be expressed by the following equation. I θ = I x + I y + 2√I x I y cos δφ (6) I x = | E x | 2 cos 2 θ, I y = | E y | 2 sin θ The phase difference δφ is δφ due to the operation of the optical phase modulator 18. = Δφ O (t) + δφ m sin (2πf m t) (7), Iθ becomes the equation (8).
【0015】 Iθ=Ix +Iy +2√Ix Iy 〔cosδφO (t)Σεn cos2n(2πfm t )・J2n(δφm )−sinδφO (t)・2Σsin(2n+1) (2πfm t)・J2n+1(δφm )〕 ε=1(n=0);ε=2(n≧1) (8) Σはn=0から無限大まで、つまり、Iθには位相変調
の基本波と同期した成分を有し、その強度Iθ′は Iθ′=2|Ex ||Ey |sin2θ・sinδφO (t)J1 (δφm ) (9) となる。Iθ = I x + I y + 2√I x I y [cos δφ O (t) Σε n cos2n (2πf m t) · J 2n (δφ m ) −sin δφ O (t) · 2Σsin (2n + 1) (2πf m t) · J 2n + 1 (δφ m )] ε = 1 (n = 0); ε = 2 (n ≧ 1) (8) Σ is from n = 0 to infinity, that is, Iθ is a phase modulation It has a component synchronized with the fundamental wave, and its intensity Iθ ′ is Iθ ′ = 2 | E x || E y | sin2θ · sin δφ O (t) J 1 (δφ m ) (9).
【0016】[0016]
【課題を解決するための手段】非偏光系位相変調方式光
ファイバジャイロにおいて、請求項1の発明によれば光
位相変調器、またはこれに光偏波軸に関して方位を一致
させて接続された複屈折性偏波維持性光伝送路要素の全
路長において、2つの直交光偏波モードの光学距離差に
よる光位相差の直流成分がπラジアンの整数倍に設定さ
れている。According to a first aspect of the present invention, there is provided a non-polarization phase modulation type optical fiber gyro, or an optical phase modulator, or a compound phase gyro connected to the optical phase gyro with their directions aligned with respect to the optical polarization axis. In the entire path length of the refractive polarization maintaining optical transmission line element, the DC component of the optical phase difference due to the optical distance difference between the two orthogonal optical polarization modes is set to an integral multiple of π radian.
【0017】請求項2の発明によれば、請求項1の発明
において、光位相変調器に、光偏波軸に関して方位を一
致させて可変の複屈折性光位相補償器が直列に接続さ
れ、πラジアンの整数倍の設定が、複屈折性光位相補償
器を含めて設定されている。請求項3の発明によれば、
請求項2の発明において、同期検波器に対する参照信号
と位相がほぼ90°異なる参照信号により受光器の出力
が第2同期検波器で同期検波され、その検波出力により
複屈折性光位相補償器が負帰還制御される。According to the invention of claim 2, in the invention of claim 1, a birefringent optical phase compensator which is variable in direction and coincides with respect to the optical polarization axis is connected in series to the optical phase modulator. An integral multiple of π radian is set including the birefringent optical phase compensator. According to the invention of claim 3,
In the invention of claim 2, the output of the photodetector is synchronously detected by the second synchronous detector by the reference signal whose phase is different from the reference signal for the synchronous detector by approximately 90 °, and the birefringent optical phase compensator is obtained by the detected output. Negative feedback is controlled.
【0018】[0018]
【実施例】図1Aに請求項2の発明の実施例を示し、図
4と対応する部分に同一符号を付けてある。この実施例
では偏波維持光ファイバ16と光位相変調器18との間
に複屈折性光位相補償器25が直列に挿入される。複屈
折性位相補償器25は例えば機械的に径の可動なボビン
に十分尺長の複屈折性偏波維持光ファイバを巻回し、こ
の光ファイバを伸縮させるもの、または図1Bに示すよ
うなバビネ補償板やバビネ・ソレイユ補償板などが用い
られる。光位相変調器18として円筒状電歪振動子に偏
波維持光ファイバを巻回し、光ファイバを伸縮させるも
のが用いられる。この光位相変調器18の光ファイバ
と、複屈折性光位相補償器25とが光偏波軸に関して方
位が一致されている。つまり両者とも偏波維持光ファイ
バが用いられる場合は、その偏波維持方向が互いに一致
されて、互いに接続される。複屈折性光位相補償器25
と偏波維持光ファイバ16との接続も、両光偏波軸の方
向が一致するようにされる。DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1A shows an embodiment of the invention of claim 2 and the same reference numerals are attached to the portions corresponding to those of FIG. In this embodiment, a birefringent optical phase compensator 25 is inserted in series between the polarization maintaining optical fiber 16 and the optical phase modulator 18. The birefringent phase compensator 25 is, for example, a mechanically movable bobbin around which a sufficiently long birefringent polarization-maintaining optical fiber is wound, and the optical fiber is expanded or contracted, or a babinet as shown in FIG. 1B. Compensators and Babinet-Soleil compensators are used. As the optical phase modulator 18, used is a cylindrical electrostrictive oscillator in which a polarization maintaining optical fiber is wound and the optical fiber is expanded and contracted. The optical fiber of the optical phase modulator 18 and the birefringent optical phase compensator 25 have the same direction with respect to the optical polarization axis. That is, when polarization maintaining optical fibers are used for both, their polarization maintaining directions are matched with each other and are connected to each other. Birefringent optical phase compensator 25
The polarization maintaining optical fiber 16 is also connected so that the directions of both optical polarization axes coincide with each other.
【0019】光位相変調器18と複屈折性光位相補償器
25と、偏波維持光ファイバ16との全体における、2
つの直交偏波モードの光学距離差による光位相差の直流
成分がπラジアンの整数倍とされる。つまり、複屈折性
光位相補償器25に対する制御手段26を調整して、位
相補償器25における2つの直交光偏波モードの光位相
差を調整して、前記光学距離差による光位相差の直流成
分がπラジアンの整数倍になるようにする。The total of the optical phase modulator 18, the birefringent optical phase compensator 25, and the polarization maintaining optical fiber 16 is 2
The DC component of the optical phase difference due to the difference in optical distance between the two orthogonal polarization modes is an integral multiple of π radian. That is, the control means 26 for the birefringent optical phase compensator 25 is adjusted to adjust the optical phase difference between the two orthogonal optical polarization modes in the phase compensator 25, and the direct current of the optical phase difference due to the optical distance difference is adjusted. Make the component an integer multiple of π radians.
【0020】前述したように光位相変調にもとづく、光
強度変調は、同期検波器22の出力では(9)式に示し
たように、sinδφO (t)に比例している。δφO
(t)は(7)式に示したように、光位相変調器18を
含む複屈折性光伝送路要素が作る直交直線偏波成分(直
交光偏波モード)間の光位相差の直流成分であり、その
絶対量は前記伝送路要素の複屈折光路差、即ちリターデ
ーションであり、図1Aに示す実施例によれば、このδ
φO (t)がπラジアンの整数倍とされているため、s
inδφO (t)=0となり、従って同期検波器22の
出力には、光位相変調器18の位相変調に基づく、光強
度変調効果が現われず、バイアス誤差がゼロになる。As described above, the light intensity modulation based on the optical phase modulation is proportional to sin δφ O (t) at the output of the synchronous detector 22, as shown in the equation (9). δφ O
(T) is the DC component of the optical phase difference between orthogonal linear polarization components (orthogonal optical polarization mode) created by the birefringent optical transmission line element including the optical phase modulator 18, as shown in equation (7). And the absolute amount is the birefringence optical path difference of the transmission line element, that is, the retardation. According to the embodiment shown in FIG.
Since φ O (t) is an integral multiple of π radian, s
in δφ O (t) = 0, therefore, the output of the synchronous detector 22 does not show the optical intensity modulation effect based on the phase modulation of the optical phase modulator 18, and the bias error becomes zero.
【0021】複屈折性光位相補償器25を省略して、光
位相変調器18と偏波維持性光ファイバ16とでδφO
(t)がπラジアンの整数倍になるようにしてもよい。
これが請求項1の発明であり、この場合は偏波維持光フ
ァイバのビート長に鑑みて、尺長1mm未満の調整をす
る必要がある。その点光位相補償器25を用いると容易
にδφO (t)をπラジアンの整数倍にすることができ
る。By omitting the birefringent optical phase compensator 25, the optical phase modulator 18 and the polarization maintaining optical fiber 16 have δφ O.
(T) may be an integral multiple of π radian.
This is the invention of claim 1, and in this case, in consideration of the beat length of the polarization maintaining optical fiber, it is necessary to adjust the length to be less than 1 mm. By using the point optical phase compensator 25, δφ O (t) can be easily made an integral multiple of π radian.
【0022】図2Aに請求項3の発明の実施例を示し、
図1Aと対応する部分に同一符号を付けてある。同期検
波器27が設けられ、同期検波器27において受光器2
1の出力が、同期検波器22の参照信号と位相がほぼ9
0度異なる参照信号で同期検波される。つまり同期検波
器22に対する参照信号が移相器28により90度位相
がずらされて同期検波器27へ供給される。同期検波器
27の検波出力が駆動部29へ供給され、駆動部29に
より複屈折性光位相補償器25が駆動され、同期検波器
27の出力がゼロになるように負帰還制御される。FIG. 2A shows an embodiment of the invention of claim 3,
The same reference numerals are given to the portions corresponding to those in FIG. 1A. The synchronous detector 27 is provided, and in the synchronous detector 27, the light receiver 2
The output of 1 and the reference signal of the synchronous detector 22 have a phase of about 9
Synchronous detection is performed with reference signals that differ by 0 degrees. That is, the phase shifter 28 shifts the phase of the reference signal for the synchronous detector 22 by 90 degrees and supplies the reference signal to the synchronous detector 27. The detection output of the synchronous detector 27 is supplied to the driving unit 29, the birefringent optical phase compensator 25 is driven by the driving unit 29, and negative feedback control is performed so that the output of the synchronous detector 27 becomes zero.
【0023】受光器21の出力中のサニヤック位相差に
基づく、位相変調周波数成分は(4)式から次式で表わ
せる。 2sinφs J1 (x)・sin(2πfm t+((π/2)−πfm τ)) (10) 一方、位相変調にもとづく強度変調における位相変調周
波数成分は(8)式から次式で表わせる。The phase modulation frequency component based on the Sagnac phase difference in the output of the light receiver 21 can be expressed by the following equation from the equation (4). 2sinφ s J 1 (x) · sin (2πf m t + ((π / 2) −πf m τ)) (10) On the other hand, the phase modulation frequency component in the intensity modulation based on the phase modulation is expressed by the following formula from formula (8). Can be represented.
【0024】 2|Ex ||Ey |sin2θ・sinδφO (x)J1 (δφm )・sin (2πfm t) (11) 光ファイバループ17の長さLと、変調周波数fm とを
それぞれ特に大きな値にしなければ、(10)式中のπ
fm τはπ/2に比べてかなり小さい値となるため、
(10)式で表わされるジャイロ出力に対し、(11)
式で表わせる強度変調成分は図2Bに示すようにほぼ9
0度の位相差がある。従って同期検波器27から強度変
調成分を検出し、これがゼロになるように駆動部29を
通じて複屈折性光位相補償器25を制御することにより
バイアス誤差が除去される。2 | E x || E y | sin2θ · sin δφ O (x) J 1 (δφ m ) · sin (2πf m t) (11) The length L of the optical fiber loop 17 and the modulation frequency f m Π in equation (10) unless each is set to a particularly large value.
Since f m τ is a much smaller value than π / 2,
For the gyro output expressed by equation (10),
The intensity modulation component represented by the equation is approximately 9 as shown in FIG. 2B.
There is a phase difference of 0 degree. Therefore, the bias error is removed by detecting the intensity modulation component from the synchronous detector 27 and controlling the birefringent optical phase compensator 25 through the drive unit 29 so that the intensity modulation component becomes zero.
【0025】上述において光ファイバループ17には非
偏光系の光ファイバジャイロではシングルモード光ファ
イバを用いる。偏波維持光ファイバ15,16の代りに
他の偏光解離手段を用いてもよい。In the above description, a single-mode optical fiber is used for the optical fiber loop 17 in a non-polarization type optical fiber gyro. Instead of the polarization maintaining optical fibers 15 and 16, other polarization dissociation means may be used.
【0026】[0026]
【発明の効果】以上述べたようにこの発明によれば光位
相変調方式非偏光系光ファイバジャイロにおいて、光位
相変調により光偏波状態が変調周波数で変動することに
もとづく光強度変調成分が、2つの直交光偏波モードの
光学距離差による光位相差の直流成分δφO (t)がπ
ラジアンの整数倍とされているため、バイアス誤差がほ
ぼゼロとなる。請求項3の発明によれば、強度変調成分
が検出され、これにより2つの直流光偏波モードの位相
差が負帰還制御され、バイアス誤差がほぼゼロにされ
る。As described above, according to the present invention, in the optical phase modulation type non-polarization type optical fiber gyro, the optical intensity modulation component based on the optical polarization state changing at the modulation frequency due to the optical phase modulation is The DC component δφ O (t) of the optical phase difference due to the optical distance difference between the two orthogonal optical polarization modes is π
Since it is an integral multiple of radians, the bias error is almost zero. According to the third aspect of the invention, the intensity modulation component is detected, whereby the phase difference between the two DC optical polarization modes is subjected to negative feedback control, and the bias error is made substantially zero.
【図1】Aは請求項2の発明の実施例を示すブロック
図、Bはバビネ補償板を示す図である。FIG. 1A is a block diagram showing an embodiment of the invention of claim 2, and B is a diagram showing a Babinet compensating plate.
【図2】Aは請求項3の発明の実施例を示すブロック
図、Bはジャイロ出力の変調周波数成分と、強度変調の
変調周波数成分との角度関係を示す図である。2A is a block diagram showing an embodiment of the invention of claim 3, and FIG. 2B is a diagram showing an angular relationship between a modulation frequency component of a gyro output and a modulation frequency component of intensity modulation.
【図3】従来の光位相変調方式非偏光系光ファイバジャ
イロを示すブロック図。FIG. 3 is a block diagram showing a conventional optical phase modulation type non-polarization type optical fiber gyro.
Claims (3)
分されて光ファイバループの両端に右回り光及び左回り
光として入射され、 上記光ファイバループの少くとも一端と上記分岐結合手
段との間に、偏光解離手段が挿入されて、上記右回り光
及び左回り光の少くとも一方は十分偏光度の低い光とさ
れ、 上記光ファイバループの一端と上記分岐結合手段との間
に、偏波維持性光ファイバの伸縮によって動作する光位
相変調器が挿入されて、上記右回り光、左回り光が位相
変調され、 上記光ファイバループを伝搬した上記右回り光、左回り
光が上記分岐結合手段で合波した干渉光が受光器で電気
信号に変換され、 その電気信号が上記光位相変調器の変調信号を参照信号
として同期検波器で同期検波されてジャイロ出力を得る
光ファイバジャイロにおいて、 上記光位相変調器、またはこれに光偏波軸に関して方位
を一致させて接続された複屈折性偏波維持性光伝送路要
素の全路長において、2つの直交光偏波モードの光学距
離差による光位相差の直流成分がπラジアンの整数倍に
設定されていることを特徴とする光ファイバジャイロ。1. Light from a light source is converted into two by a branch coupling means.
The light is split into right and left lights at both ends of the optical fiber loop, and a polarization splitting means is inserted between at least one end of the optical fiber loop and the branch coupling means to obtain the right light. At least one of the left-handed light and the left-handed light is light having a sufficiently low degree of polarization, and an optical phase modulator that operates by expansion and contraction of the polarization maintaining optical fiber is provided between one end of the optical fiber loop and the branch coupling means. The right-handed light and the left-handed light are phase-modulated by being inserted, and the interfering light obtained by combining the right-handed light and the left-handed light propagating through the optical fiber loop by the branch coupling means is converted into an electric signal by a light receiver. An optical fiber gyro that is converted and whose electrical signal is synchronously detected by a synchronous detector using the modulation signal of the optical phase modulator as a reference signal to obtain a gyro output. The DC component of the optical phase difference due to the difference in optical distance between the two orthogonal optical polarization modes is an integral multiple of π radian in the total path length of the birefringent polarization maintaining optical transmission line elements connected in the same direction with respect to A fiber optic gyro characterized by being set to.
方位を一致させて可変の複屈折性光位相補償器が直列に
接続され、上記πラジアンの整数倍の設定は、上記複屈
折性光位相補償器を含めて設定させていることを特徴と
する請求項1記載の光ファイバジャイロ。2. A birefringent optical phase compensator which is variably aligned in azimuth with respect to the optical polarization axis is connected in series to the optical phase modulator, and the birefringence is set to an integer multiple of π radian. 2. The optical fiber gyro according to claim 1, wherein the optical fiber gyro is set by including an optical phase compensator.
90°位相が異なる参照信号で上記受光器の出力を同期
検波する第2同期検波器が設けられ、この第2同期検波
器の出力が上記複屈折性光位相補償器に制御信号として
負帰還されることを特徴とする請求項2記載の光ファイ
バジャイロ。3. A second synchronous detector for synchronously detecting the output of the photodetector with a reference signal whose phase is approximately 90 ° different from that of the reference signal for the synchronous detector, and the output of the second synchronous detector is the above-mentioned. 3. The optical fiber gyro according to claim 2, which is negatively fed back as a control signal to the birefringent optical phase compensator.
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP27923293A JPH07128073A (en) | 1993-11-09 | 1993-11-09 | Optical fiber gyro |
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP27923293A JPH07128073A (en) | 1993-11-09 | 1993-11-09 | Optical fiber gyro |
Publications (1)
Publication Number | Publication Date |
---|---|
JPH07128073A true JPH07128073A (en) | 1995-05-19 |
Family
ID=17608281
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
JP27923293A Withdrawn JPH07128073A (en) | 1993-11-09 | 1993-11-09 | Optical fiber gyro |
Country Status (1)
Country | Link |
---|---|
JP (1) | JPH07128073A (en) |
Cited By (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
WO2001061691A1 (en) * | 2000-02-21 | 2001-08-23 | Sony Corporation | Optical disk device |
JP2002532722A (en) * | 1998-11-12 | 2002-10-02 | ハネウエル・インコーポレーテッド | Fiber optical current sensor with rotation ineffectiveness |
-
1993
- 1993-11-09 JP JP27923293A patent/JPH07128073A/en not_active Withdrawn
Cited By (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JP2002532722A (en) * | 1998-11-12 | 2002-10-02 | ハネウエル・インコーポレーテッド | Fiber optical current sensor with rotation ineffectiveness |
WO2001061691A1 (en) * | 2000-02-21 | 2001-08-23 | Sony Corporation | Optical disk device |
US6700855B2 (en) | 2000-02-21 | 2004-03-02 | Sony Corporation | Optical disk device |
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