WO1999056080A1

WO1999056080A1 - Fiber-optic gyroscope

Info

Publication number: WO1999056080A1
Application number: PCT/JP1999/002163
Authority: WO
Inventors: Yoshiyuki Okada; Yoshiaki Imamura; Mikio Morohoshi; Kanshi Yamamoto
Original assignee: Tokimec Inc.
Priority date: 1998-04-27
Filing date: 1999-04-23
Publication date: 1999-11-04

Abstract

A digital fiber-optic gyroscope that eliminates effects of modulation gain errors and changes in intensity of interference light. A digital signal processor (100) generates a composite signal containing various phase-modulated signals by combining a bias modulating signal and a serrodyne signal for canceling a Sagnac phase difference. The bias modulating signal carries out phase modulation in such a manner that the phase difference of interference light repeats a predetermined sequence of six values, i.e., either ±(η-υ), ±(η+υ+δ) and ±(η+υ-δ), or ±(η+υ), ±(η-υ-δ) and ±(η-υ+δ), with a duration of each step of τ/2, where τ is the propagation time of light in an optical fiber loop (6). The composite signal is supplied to a phase modulator (5) through a D/A converter (10).

Description

Description Optical fiber Gyro Technical field

TECHNICAL FIELD The present invention relates to an optical fiber gyro applied to, for example, an aircraft, a ship, an automobile, and the like, which detects a rotational angular velocity or a rotational angle, and in particular, cancels a sannyak phase shift by a stepped serodyne signal. The present invention relates to a digital optical fiber gyro configured in a closed loop. Background art

At the optical fiber jar opening, the light intensity change of the interference light obtained by recombining the two lights propagating in the optical fiber loop in the opposite directions is represented by d) S, the phase difference between the two lights. Then cos ((|) s). Therefore, as shown in FIG. 23, when the Sagnac phase difference is near 0, the light intensity changes only slightly with respect to the change in the phase difference.

An optical fiber gyro that solves this problem is disclosed in US Pat. No. 5,056,919.

In this technique, a phase modulator that modulates the phase of two lights propagating through an optical fiber loop is provided, and the phase modulator has a phase shift of + π / 2 and -π / 2 as shown in Fig. 23. By adding a phase modulation signal of a rectangular wave generated in a period (T: propagation time of light in an optical fiber loop), the light intensity change due to the saniac phase difference of the interference light is calculated by (PQ / 2 ) 'C 0 S ((/) S ± π / 2) (where Ρ is the peak value of the light intensity of the interference light) I'm trying.

In addition, in conventional digital fiber optic gyros, the serodin signal, which is a staircase signal whose duration is normally a staircase signal, is phase-modulated in order to expand the dynamic range of the saniac phase difference detection. Then, the phase modulator performs phase modulation so as to generate a phase difference having the same amount and a different sign as that of the Sanyak phase difference corresponding to the input angular velocity to the optical fiber gyro. As a result, a closed loop is configured to cancel the Sagnac phase difference between two lights propagating in the optical fiber loop. However, since the output of the serodyne signal cannot be increased indefinitely, it is normally reset when the phase shift due to the serodyne signal reaches ± 2π.

By the way, if the serodin signal is not accurately reset, that is, if the modulation gain contains an error, the scale factor error in the relationship between the input rate and output rate of the optical fiber gyro will be reduced. Occurs.

Digital optical fiber jar openings that solve this problem include those described in U.S. Pat. No. 5,141,316 and U.S. Pat. No. 4,948,252.

The former is a phase modulation signal input to the phase modulator.

δ Φ! = Φ 0

δ 2 ⁼ a 0

<5 ₃ =-0

δ ₄ =-ao

(Where φ is a constant phase shift, a is cos φ. = Cos (a φ. :) is a positive constant that satisfies) Is used as a signal that has four steps as one cycle. Here, the cycle of each step of the phase modulation signal is, for example, / 2 (2 in total). A is 2. In this case, the modulation phase difference is as shown in Fig. 24.

On the other hand, the latter uses a signal obtained by calculating a gain signal obtained from a phase difference electric signal and a total phase modulation signal as a phase modulation signal to be input to the phase modulator. This total phase modulation signal is obtained by summing the following signals.

• A cellodyne signal created using the first frequency.

• A velocity bias signal consisting of a periodic square wave with a first frequency. • A gain-bias signal consisting of a series of step voltages that transition at the end of a series of equally spaced periods equal to half the period of the serodin signal.

Here, for example, a continuous equal interval time is / j (j is an integer). If j is 2, the velocity bias signal will be at half the frequency. Also, the velocity bias signal is a square wave that transitions between π / 2 and -π / 2, and the gain bias signal has a series of induced phase shifts of 2π, 0, -2π, 0. . In this case, the modulation phase difference is, for example,

0 to t / 2 period: + π / 212π = † 5π II

T 1 to t period: \ π / 2 + 0 = + π II

T ~ 3 t / 2 period: 1% 11-1% = — 5 π II

3 te / 2 to 2 te period:-π / 2 + 0 =-π II

And therefore, as shown in Figure 25.

In both cases, by applying a signal to the phase modulator to shift the phase at a predetermined cycle, the point of the light intensity at which the sannyak phase difference becomes 0 can be shifted periodically. For this reason, the value near zero Light intensity sensitivity can be improved.

Also, as shown in FIGS. 24 and 25, the phase modulator places a value of i TT (± 4/3 ττ when a = 2 in FIG. 24 and ± 2 π in FIG. 25) at a given period. By applying a signal to cause a phase shift to the phase modulator, a modulation gain error generated at the time of the phase shift can be detected.

Therefore, by controlling the modulation so that the modulation gain error becomes zero and controlling the modulation gains of the phase modulation signal and the serodin signal to optimal values, the gyro output generated by the serodin signal can be controlled. The scale factor error can be reduced. Disclosure of the invention

By the way, when the characteristics of the light source and other optical components for generating two lights propagating in the opposite directions in the optical fiber loop change, the light intensity value of the detected interference light changes, and a stable cellodies Control and modulation control. In particular, in serodin control, the change in the light intensity value of the above-mentioned sensation light causes the Sanyak phase difference (Ρ. / 2) 'cos (φ s ± 7t / 2) (where P is the interference). The detection gain of the peak light intensity of the light, π / 2 is the phase modulation amplitude value, changes, and the loop gain of serodin control changes. This fluctuation of the loop gain causes fluctuation of the frequency characteristic in the closed loop operation of the serodin control, and hinders the stable operation of the serodin control and the rotational angular velocity output of the gyro. For this reason, it is preferable to control the loop gain of the serodyne control system to always have a predetermined value regardless of a change in the light intensity value of the interference light due to a change in the characteristics of the light source and other optical components.

However, the above-mentioned U.S. Pat. No consideration is given to this point in the digital optical fiber gyro described in Japanese Patent No. 4948482.

Also, in high-precision optical fiber gyros, reduction of the random walk value is desired. Here, the random walk value is a value indicating an S / N ratio of a light intensity signal of the interference light, and is defined by an execution value of a random noise component included in the signal.

In the literature “Intergrated Optics: A Practical Solution For Fiber-Optical Gyroscope” and the US Patent No. It has been reported that the amplitude of the phase modulation signal for minimizing the Mwalk value is in the range from π / 2 force to less than π.

However, this random walk value is a function in which the light intensity value of the interference light is a parameter, and if this light intensity value changes, the phase modulation amplitude for minimizing the random walk value also changes. In the digital type optical fiber gyro described in the above-mentioned conventional technology and the U.S. Pat.No. 5,530,455, the two types of light propagating in the optical fiber loop in opposite directions are generated. No consideration is given to a change in the light intensity value of the interference light due to a change in the output characteristics of the light source used or other influences, and the phase modulation signal is generated so as to have a predetermined phase modulation amplitude. Therefore, if the light intensity value of the interference light changes, the random walk value cannot be sufficiently reduced.

Further, in the digital optical fiber gyro described in the above-mentioned U.S. Pat.No. 5,141,316 and U.S. Pat.No. 4,948,252, as shown in FIG. 24 and FIG. During the phase shift, the output wave passes through the peak point (brightest point) or bottom point (bottom point) of the light beam. A spike-like noise (light spike) occurs in the shape. If the detection light includes an error due to optical spikes, an error occurs in the modulation control, and the modulation gain of the phase modulation signal and the serodin signal cannot be optimized.As a result, the optical gyro A scale factor error at the output may occur.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a high-precision digital optical fiber gyro capable of performing stable operation.

Specifically, an object is to enable stable modulation control and cellodyne control by enabling detection of a modulation gain error and a change in light intensity of interference light.

It is another object of the present invention to reduce the influence of the random walk regardless of the change in the light intensity of the interference light.

It is another object of the present invention to enable accurate modulation control by removing the influence of optical spikes generated during phase shift by a phase modulation signal.

In order to achieve the above object, the present invention provides a rotation angular velocity or rotation angle according to a saniac phase difference of interference light obtained by recombining two lights propagating in an optical fiber loop in directions opposite to each other. Optical fiber mouth that detects

A light receiving unit that detects the light intensity of the interference light and converts the light intensity into an electric signal; and, based on a signal corresponding to the light intensity of the interference light detected by the light receiving unit, determines a sanyak phase difference of the interference light. A signal phase calculating means for calculating a signal;

The saniae of the interference light generated by the saniae phase difference calculating means A cellodine signal generating means for generating a cellodine signal composed of a step-like wave for canceling the Saniyak phase difference of the interference light, according to a signal corresponding to the phase difference of the interference light;

The phase difference of the light is ± (α−0), soil (α + 0 + and ± (α + 0− (5)), or soil (α + 0), ± (α− and + δ) by synthesizing a bias modulation signal for performing phase modulation so as to repeat the six values in a predetermined time interval and in a predetermined order, and a serodin signal generated by the serodin signal generation means. Synthetic signal generating means for generating a composite signal of various phase modulations;

A phase modulator that phase-modulates each of the two lights according to the composite signal of various phase modulations generated by the composite signal generation unit;

Modulation gain calculation for calculating a signal corresponding to a modulation gain error generated at the time of phase shift by the bias modulation signal based on a signal corresponding to the light intensity of the interference light detected by the light receiving unit. Means,

Modulation gain control means for controlling the gain of the composite signal of the various phase modulations according to a signal corresponding to the modulation gain error generated by the modulation gain calculation means.

Here, the synthesized signal generating means includes:

First constant output signal generation means for generating a first constant output signal having an output value necessary to perform the phase shift of Θ,

second constant output signal generating means for generating a second constant output signal having an output value necessary for performing the phase shift of δ,

Third constant output signal generating means for generating a third constant output signal having an output value necessary for performing a phase shift of the

The first constant output signal generation unit, the second constant output signal generation unit And a bias modulation signal generating means for generating the bias modulation signal using each of the constant output signals generated by the third constant output signal generating means;

First adding means for adding the bias modulated signal generated by the bias modulated signal generating means and the serodin signal generated by the serodyne signal generating means to generate a composite signal of the various phase modulations And may have the following.

In this case, the bias modulation signal generating means modulates, for example, the first constant output signal generated by the first constant output signal generating means, so that the frequency l / τ (where τ is the optical signal First modulating means for generating a first phase modulation signal consisting of a rectangular wave having a propagation time of light in a fiber loop);

The second constant output signal generated by the second constant output signal generating means is modulated to form a second phase modulation signal in which a pulse having a pulse width of / 2 alternately appears at each time interval 2 in a positive and negative manner. A second modulating means for generating;

The first phase modulation signal generated by the first modulation means, the second phase modulation signal generated by the second modulation means, and the third phase modulation signal generated by the third constant output signal generation means. Second adding means for generating a signal by adding the constant output signal of

By modulating the signal generated by the second adding means at a frequency of 1 / _2τ , the phase difference of the interference light is represented by _α + θ + δ, _Ύ -Θ,-了 __- δ,- r + θ, γ i Θ-δ, Ύ-Θ ゝ-Ύ-Θ δ, -a + 0, a series of steps in the order,--θ, τ \ θ δ,-Ύ θ, -j- θ-δ, γ _ θ, γ i θ-δ, _-Τ θ,-τ-0 + <3, a series of steps, a-0 _ δ, a + 0, _-Ύ δ δ, Ύ _ 、, Ύ-Θ 5, + + 0, ァ + 0-(5,-Ύ-で Or a series of steps in the following order: a + 0, T-Θ-δ ヽ-Ύ-θ,-Ύ + δ, a + θ, Ύ-θ δ,-end-、,- And a third modulating means for generating a bias modulation signal for performing phase modulation so as to repeat step (period 4 and duration of each step / 2).

FIG. 1 shows an example of the modulation phase difference according to the present invention. Here, as a composite signal of various phase modulations, the phase difference of the interference light is _Ύ -Θ,-了_{-Θ_δ} , _{-Ύ ,,} r ^ Θ-6, Ύ-Θ,---Θδ. , -End + Θ Combine the serodin signal with the bias modulation signal that performs phase modulation so as to repeat a series of steps (period 4 and the duration of each step / 2) in order. 3 shows a modulation phase difference when using a composite signal of various phase modulations obtained by (1) and (2). In the example shown in FIG. 1, 0 <θ≤π / 2, r = t, and 0 <δ≤10 degrees, and the input angular velocity is set to 0 for simplicity.

As shown in FIG. 1, according to the present invention, when the phase shift is a + 0 + δ (or f is −Ύ−Θ−δ, the light intensity of the interference light detected and the a−Θ ( Or −α + Θ), the intensity difference from the light intensity of the interference light detected when ァ θ-6 (or -α-0 + <5). And Ύ -Θ (or-) based on the intensity difference from the light intensity of the interference light detected at or-or (or -0-<5). Indirectly propagates the optical fibers in opposite directions based on the difference between the light intensity of the interference light detected at the time of and + 0-δ (or-α-θ + δ). It is possible to detect a change in the light intensity value of the interference light due to a change in the characteristics of a light source or other optical components for generating the two lights. Therefore, it is possible to control the output signal gain from the optical fiber gyro interferometer to be constant according to the detected change in the light intensity value. Specifically, when the output signal from the interferometer decreases, the signal can be controlled so that the output signal gain becomes constant by electrically increasing the signal. As a result, the loop gain of the serodin control system is always constant, and stable serodin control and, consequently, stable output of the gyro rotation angular velocity or rotation angle can be obtained.

Further, according to the present invention, the light intensity of the interference light detected when the phase shift is α + 0 + (5 (or −α−Θ−δ)? ), And the difference between the light intensity of the interference light detected at the time of + 0-(5 (or---0 + <5)) and the intensity of the interference light. Based on the difference between the light intensity of the interference light detected when -0 (or -a + Θ) or the interference light detected when a +0 + <5 (or-?) The difference between the light intensity of the light beam and the light intensity of the interference light detected when a-0 (or-), and the light intensity is detected when a + 0 + <5 (or -a-0-<5) Based on the difference between the light intensity of the interference light and the light intensity of the interference light detected at α + θ-δ (or-α-), the modulation that occurs during phase shift by the combined signal of various phase modulations Gain error can be detected Therefore, it is possible to control the modulation gain of the composite signal of various phase modulations so that the detected modulation gain error becomes zero, thereby performing accurate modulation control and cellodyne control. Thus, the scale factor error in the gyro output can be reduced.

In the present invention, the composite signal generating means has the above-described configuration. In this case, the modulation gain control means adjusts an output value of the first addition means in accordance with a signal corresponding to a modulation gain error generated by the modulation gain calculation means, so that the various The gain of the composite signal of the phase modulation may be controlled. Alternatively, according to a signal corresponding to a modulation gain error generated by the modulation gain calculation means, the first constant output signal generation means, the second constant output signal generation means, and the third constant output signal By adjusting the output value of each constant output signal generated by the signal generation means and the output value of the serodin signal generated by the serodin signal generation means, the gain of the composite signal of the various phase modulations is adjusted. It may be controlled.

In the former case, the output value of the first addition means, that is, the amplitude of the synthesized signal itself of various phase modulations generated by the synthesized signal generation means is adjusted. Therefore, it is required to perform arithmetic processing using a multiplier or the like within the time width of each step (τ / 2 in the example shown in FIG. 1) of the composite signal of various phase modulations.

On the other hand, in the latter case, the output value of each of the constant output signals generated by the first constant output signal generation means, the second constant output signal generation means, and the third constant output signal generation means; Since the output value of the serodin signal generated by the signal generation means is adjusted, the speed of the arithmetic processing required for the modulation gain control can be significantly reduced as compared with the former.

Further, in the present invention, when the composite signal generation means has the above-described configuration, the first constant output signal generation means may change the value according to a change in the light intensity value of the detected interference light. The output value of the first constant output signal may be changed. For example, show the correspondence between light intensity and 0 A table is provided, and by referring to the table, a first constant output signal having an output value necessary for performing a phase shift of 対応 corresponding to the light intensity value of the detected interference light is generated. You may.

As described above, the random walk value is a function in which the light intensity value of the interference light is a parameter, and if this light intensity value changes, the phase modulation amplitude for minimizing the random walk value also changes. I do. Therefore, by performing the above, it is possible to reduce the influence of the random walk regardless of the change in the light intensity value of the interference light.

Further, in the present invention, a switch means connected to an output side of the light receiving means, and a holding means connected to an output side of the switching means are further provided, wherein the switch means The output of the signal detected by the light receiving unit is cut off for a predetermined period in synchronization with the rise and fall of the composite signal of various phase modulations generated by the composite signal generation unit, and the switch is switched by the hold unit. The value of the signal sent from the light receiving means via the means may be maintained for a predetermined time.

When phase modulating each of two lights propagating in the optical fiber loop in opposite directions, a spike noise called an optical spike is generated in the interference light obtained by recombining the two lights.

In the example shown in Figure 1, when the phase shift changes from + a-0 force to -a _-0- δ, changes from to δ, + _r -ø force, changes to _r-a- δ, and When -a + Θ changes to + a + 0 + 5, the light intensity of the interference light instantaneously reaches its peak value P as shown in the detection light intensity vs. time characteristic in Fig. 1. There is a light spike reaching. If this optical spike is included in the detection signal, an error will occur in the modulation control and various phase changes will occur. The modulation gain of the composite signal cannot be optimized, and as a result, a scale factor error may occur in the gyro output.

On the other hand, in the present invention, by providing the switch means and the hold means further, it is possible to remove an error due to an optical spike contained in a signal output from the light receiving means. Can be. Further, during a period in which the switch means blocks the signal sent from the light receiving means (that is, a period in which the error is removed), the signal immediately before the cutoff held in the holding means is held. Output, it is possible to reduce the influence of discontinuous operation due to the interruption of the switch means and to prevent external electromagnetic noise or the like from being mixed in, thereby providing a stable detection signal. Therefore, the operations of the modulation control and the serodin control can be further stabilized.

Note that the switch means does not necessarily output the output of the signal sent from the light receiving means in synchronization with all rises and falls of the composite signals of various phase modulations generated by the composite signal generation means. There is no need to shut off for a specified period. The output of the electrical signal may be cut off for a predetermined period in synchronization with only one of the rising and falling of the combined signal that performs a phase shift accompanied by an optical spike.

Further, in the present invention, when the accumulation result of the modulation phase difference due to the serrodyne signal reaches a first threshold value, the serrodyne signal generating means is reset so as to generate a phase shift of -2π, and When the accumulation result of the modulation phase difference due to the cellodyne signal reaches a second threshold which is 27 ° lower than the first threshold, the cellodyne signal generation is performed so as to generate a phase shift of + 2π. Reset the means. May be provided.

In this case, for example, by setting the first threshold value to + π and the second threshold value to -π, it is possible to use a serodyne signal as in the digital optical fiber gyro described in the background art above. The peak peak value of the cellodyne signal can be made smaller than when resetting to 0 when the phase shift reaches ± 2π. As a result, power consumption can be reduced. Further, for example, by setting the first threshold value to + 2π and the second threshold value to 0, a single power supply can be used as a power supply for generating a serodin signal. BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a diagram for explaining the relationship between the light intensity of the interference light and the modulation phase difference in the first embodiment of the present invention.

FIG. 2 is a schematic configuration diagram of a digital optical fiber jar opening to which the first embodiment of the present invention is applied.

FIG. 3 is a schematic configuration diagram of the spike remover 24 shown in FIG. FIG. 4 is a schematic configuration diagram of the digital signal processor 100 shown in FIG.

FIG. 5 is a schematic configuration diagram of the signal processing unit 110 shown in FIG.

FIG. 6 is a diagram for explaining a modulation phase difference when an angular velocity is input to the optical fiber loop 6 and a Sannyak phase difference Φs occurs in the phase modulation operation shown in FIG.

FIG. 7 is a diagram for explaining a modulation phase difference when an error is included in the modulation gain G of the phase modulation by the phase modulator 5 in the phase modulation operation shown in FIG. FIG. 8 is a diagram illustrating a relationship between a deviation signal (a signal corresponding to a modulation gain error) of a modulation control system and a modulation gain G.

FIG. 9 is a schematic configuration diagram of the serodyne control unit 140 shown in FIG. FIG. 10 is a diagram showing an operation flow of the comparator 150 when the first threshold is set to + 2π and the second threshold is set to −2π in FIG.

FIG. 11 is a diagram showing an operation flow of the comparator 150 when the first threshold is set to + 2π and the second threshold is set to 0 in FIG.

FIG. 12 is a diagram showing an operation flow of the comparator 150 when the first threshold is set to + π and the second threshold is set to −π in FIG.

FIG. 13 is a diagram showing a waveform of a serrodyne signal generated by the third computing unit 146 shown in FIG.

FIG. 14 is a schematic configuration diagram of the modulation control section 170 shown in FIG. FIG. 15 is a diagram showing a waveform of an output signal in each section of the modulation control section 170 shown in FIG.

FIG. 16 is a schematic configuration diagram of the light intensity calculation unit 210 shown in FIG. Figure 17 shows the relative intensity noise RIN of light source 1 at -115 [dB / Hz] and the peak value P of the light intensity of the interference light. FIG. 9 is a diagram showing random walk value phase modulation amplitude value characteristics when the value is set to 2 to 50 aW.

FIG. 18 is a schematic configuration diagram of the gyro output operation unit 240 shown in FIG.

FIG. 19 is a schematic configuration diagram of a digital signal processor 100a used in an optical fiber jar opening to which the second embodiment of the present invention is applied. FIG. 20 is a schematic configuration diagram of the serodyne control unit 140a shown in FIG. 2 1, _t Figure 2 2 is a schematic configuration diagram of a modulation control unit 1 7 0 a shown in FIG. 1 9 is a schematic diagram of a gyro output computing part 2 4 0 a shown in FIG 9.

FIG. 23 is a diagram for explaining a modulation phase difference by a conventional gyro.

FIG. 24 is a diagram for explaining a modulation phase difference by a conventional gyro.

FIG. 25 is a diagram for explaining a modulation phase difference by a conventional gyro. BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, each embodiment of the present invention will be described.

First, a first embodiment of the present invention will be described.

FIG. 2 is a schematic configuration diagram of a digital optical fiber gyro to which the first embodiment of the present invention is applied.

Here, reference numeral 500 denotes a light meter. The optical interferometer 500 is composed of a light source 1, a power bra 2, a polarizer 3, a power bra 4, a phase modulator 5, and an optical fiber loop 6 formed by winding an optical fiber a plurality of times. I have.

As the light source 1, a single palmescent diode (SLD) with a long coherence length or an erbium-doped optical fiber light source (EDFS) with a higher output intensity than the SLD is used.

In general, the polarizer 3, the power blur 4, and the phase modulator 5 are integrated on one substrate as an optical integrated circuit (IOC). Also, in Figure 2, one end of the optical fiber loop 6 Although the phase modulator 5 is provided, it may be provided at both ends to perform phase modulation on the optical fiber 6 in directions opposite to each other. The light emitted from the light source 1 passes through the power blur 2 and the polarizer 3 and enters the camera 4 where it is split into two lights. One of these two lights propagates clockwise in the optical fiber loop 6, is phase-modulated by the phase modulator 5, and returns to the power blur 4. The other propagates counterclockwise through the optical fiber loop 6, is phase-modulated by the phase modulator 5, and returns to the power blur 4. Then, both are combined by the force bra 4. Thereby, interference light is formed.

Here, it is assumed that a rotation angular velocity Ω is applied to the optical fiber loop 6. At this time, an optical path length difference occurs between two lights propagating in the optical fiber loop 6 in opposite directions, and as a result, a phase difference occurs. This phase difference is referred to as a Sannyak phase difference ss, as described in the background art above. This Saniyak phase difference Φ s is expressed by the following equation.

Φ s = (2 π DL / λ c) Ω (1) where D is the diameter of the optical fiber loop 6, L is the length of the optical fiber, λ is the wavelength of light emitted from the light source 1, and c is the speed of light It is.

In addition, the light intensity 干渉 of the interference light and the Sagnac phase difference Φ s have the following relationship.

Ρ = (Ρ 0/2) (Hcos φ s) (2) where Ρ. Is the peak value of the light intensity of the interference light.

The interference light formed by the force blur 4 is received by the light receiver 7 and converted into a current signal corresponding to the light intensity of the interference light. This current signal is converted into a voltage signal by a current / voltage (I / V) converter 8 and then amplified by a wideband amplifier 9. The voltage signal amplified by the amplifier 9 is removed by a DC remover 20 composed of a high-pass filter and a DC offset adder, and then amplified by a wide-band amplifier 22. . Then, the spike remover 24 removes the component due to the optical spike contained in the signal. The spike remover 24 includes a switch and a low-pass filter (LPF). The details will be described later.

The voltage signal from which the optical spike component has been removed by the spike remover 24 is input to the A / D converter 26 for serodyne control and modulation control, where the sampling from the reference signal generator 300 is performed. According to the signal D, it is sampled and converted to a digital signal.

Note that the sampling period of the sampling signal differs depending on the time constant of the LPF constituting the spike remover 24, but at least the duration of each step of the composite signal of various phase modulations described later (in this embodiment, / 2) must be shorter. Here, τ is the propagation time of light in the optical fiber loop 6, which is the optical fiber length of the optical fiber loop 6, the refractive index η ₀ of the optical fiber constituting the optical fiber loop 6, and the light speed c. Is expressed by the following equation.

= Η 0 L / c (3) The digital signal processor 100 0, based on the output from the A / D converter 26, uses the gyro output (rotation Angular velocity or rotation angle) is calculated.

Also, the digital signal processor 100 determines that the phase difference of the interference light is (α + θδ) → (τ−Θ) → (−Ύ−θ−δ) → {-Ύ ^ Θ) → {Ύ θ-δ) → (Ύ-θ) → (-7-θ δ) → (-Θ ^ Θ) (Repeat a series of steps in D order (period 4 and the duration of each step / 2) Do phase modulation And a stepped cellodyne signal with the same duration as the calculated Sanyak phase difference φ s and the duration of each step τ or τ / 2 to produce a phase difference of the opposite sign. Generates composite signals of various phase modulations.

However, in the above bias modulation signal, a = kπ (where k is an integer of 1 or more),

k is an odd number: 0 <0 ≤ π / 2

k is an even number: 7T / 2≤0 <7Γ

And Also, it is assumed that 0 <δ <0.

In the digital signal processor 100, the amplitude 0 of the phase shift of the bias modulation signal is determined in accordance with the light intensity value of the interference light so that the random walk value is minimized. . As described in the above disclosure of the invention, the phase modulation amplitude for minimizing the random walk value is said to be in the range of π / 2 to less than 7 °. Then, the random walk value is a function that makes the light intensity value of the light beam a parameter over time, and if this light intensity value changes, the phase modulation amplitude for minimizing the random walk value also changes. . Therefore, in the present embodiment, a table showing the relationship between the light intensity value of the interference light and the phase modulation amplitude for minimizing the random walk value is prepared, and referring to the table, the detection of the interferometer 500 is performed. The amplitude Θ corresponding to the light intensity value of the interference light obtained from the result is determined.

Further, in the digital signal processor 100, when the accumulation result of the modulation phase difference due to the serodin signal reaches a first threshold value (for example, + Τ), the phase difference of the interference light is changed. -Modulation phase by serodin signal, reset to 2π phase shift When the accumulated difference reaches a second threshold value 2π lower than the first threshold value, the phase difference of the interference light is reset to a phase shift of + 2π. This prevents the output of the serodin signal from increasing indefinitely.

Now, the composite signal of various phase modulations generated in the digital signal processor 100 is converted into an analog signal in the D / A converter 10 and then transmitted to the phase modulator 5 through the driver 11. Is entered.

In response to this, the phase modulator 5 performs phase modulation on the two lights propagating in the optical fiber loop 6 in opposite directions, respectively, according to the composite signal of various phase modulations.

By the phase modulation according to the present embodiment, the modulation phase difference generated between two lights propagating in the optical fiber loop 6 in opposite directions to each other and the light intensity of the interference light obtained by recombining the two lights. Explain the relationship.

FIG. 1 shows a modulation phase difference by the optical fiber gyro of the present embodiment. In the example shown in Fig. 1, Ο <0 ≤ π / 2, α = π, and Ό <6 ≤ 10 degrees. However, the present invention is not limited to this, and it is only necessary that a = kπ (k is an integer of 1 or more) and 0 <δ <θ.

According to the present embodiment, as shown in FIG. 1, the phase shift is equal to the optical intensity of the interference light detected when a + Θ + δ (or-

(Or -α + Θ), the difference between the light intensity of the interference light detected when (α + Θ), and the light intensity of the interference light detected when α + 0-δ (or-α-0 + <5) And the light intensity of the interference light detected based on the difference between the light intensity of the interference light detected at the time of α + S (or −) or the light intensity of the interference light detected at the time of α + 0 + <5 (or − α − Strength and α + 0-δ (or-α- The light intensity value of the interference light due to the characteristic change of the light source 1 and other optical components that make up the optical interferometer 500 is indirectly based on the difference in intensity from the light intensity of the interference light detected Can be detected.

Therefore, the change in the light intensity value of the interference light is detected as described above, and the serodin control system (including the digital signal processor 100, the optical interferometer 500, the light receiver 7, etc.) By controlling the AGC (Automatic Gain Control 1) so that the loop gain of the loop is always constant, stable cellodyne control and, consequently, a stable output of the rotational angular velocity or rotational angle of the jay mouth can be obtained.

Further, according to the present embodiment, as shown in FIG. 1, the light intensity of the interference light detected when the phase shift is 7 + Θ + δ (or −α−0−δ) and Ύ−Θ (Or -a + 0), the difference between the light intensity of the interference light detected at the time of (a + 0), and the light intensity of the interference light detected at a + δ (or- Based on the intensity difference from the light intensity of the interference light detected at (+0), a modulation gain error generated at the time of phase shift by the bias phase modulation signal can be detected.

Therefore, accurate modulation control and cellodyne control can be performed by detecting the modulation gain error as described above and adjusting the gain of the composite signal of various phase modulations to make this zero. Thus, it is possible to reduce the scale factor error in the jay mouth output.

Further, in the present embodiment, as described above, in the digital signal processor 100, a table showing the relationship between the light intensity value of the interference light and the phase modulation amplitude for minimizing the random walk value. And refer to the table to determine the interference light obtained from the detection result of the interferometer 500. The above-described bias modulation signal is generated so that the amplitude becomes 0 corresponding to the light intensity value.

By doing so, it is possible to suppress the influence of the random walk regardless of the change in the light intensity of the interference light.

Further, in the present embodiment, the spike remover 24 is provided to remove an erroneous difference due to an optical spike included in the detection signal of the interference light output from the light receiver 7.

As a result, more accurate modulation control can be performed, and the scale factor error of the jay mouth can be reduced. In addition, while the error due to the optical spike is being removed, the signal held immediately before is output, so that the influence of the discontinuous operation due to the interruption of the switch means can be reduced and the external Therefore, it is possible to prevent mixing of electromagnetic noise and the like, so that stable signal detection can be performed, so that the operations of the modulation control and the cellodyne control can be further stabilized.

Next, the spike remover 24 and the digital signal processor 100, which are main components of the present embodiment, will be described in detail.

First, the spike remover 24 will be described.

FIG. 3 is a schematic configuration diagram of the spike remover 24.

As shown in FIG. 3, the spike remover 24 includes a switch 40, a low-pass filter (LPF) / hold circuit 42 including a resistor and a capacitor, and an amplifier 46.

The switch 40 cuts off the output of the voltage signal sent from the amplifier 22 for a predetermined period according to the signal E generated by the reference signal generator 300. Here, the signal E has a frequency of 1 / This is a reference signal synchronized with the composite signal of various phase modulations generated by the signal processor 100. The cutoff period is set in consideration of the time of occurrence of the optical spike of the interference light. By the switch 40, it is possible to remove an error component due to an optical spike of the interference light included in the voltage signal sent from the amplifier 22.

When the switch 40 is on, the LPF / hold circuit 42 removes white noise components and other high-frequency electromagnetic noise contained in the voltage signal sent via the switch 40. I do. When the switch 40 is off (cut off), the voltage signal immediately before the cutoff is held by the electric charge stored in the capacitor constituting the LPF / hold circuit 42. This voltage signal is output to the A / D converter 26 via the amplifier 46.

As described above, the LPF / hold circuit 42 can reduce the influence of discontinuous operation due to the ON / OFF of the switch 40, and can prevent external noise such as electromagnetic noise from being mixed. Can be. As a result, stable signal detection can be performed, so that the operations of modulation control and port din control can be further stabilized.

In addition, by setting the time constant of the LPF so as to remove various noise components included in the voltage signal, and performing band limitation, the A / D converter 26 achieves the best gyro output with the minimum number of samplings. Can be obtained. In other words, since it is not necessary to perform extreme oversampling, the processing speed of the A / D converter 26 and the digital signal processor 100 can be reduced compared to conventional optical fiber gyros. This makes it possible to configure the optical fiber jar opening with less expensive parts.

In addition, in the present embodiment, the voltage signal is sufficiently converted by the amplifier 22. After amplification, the optical spike is removed by the spike remover 24. In this configuration, since the voltage signal is sufficiently amplified, the effect of noise generated by turning on / off the switch 40 can be effectively reduced, and more stable signal detection can be performed. This is a favorable configuration.

Although the amplifier 46 has a buffer configuration, the output of the LPF / hold circuit 42 may be directly input to the / 0 converter 26 without using the amplifier 46.

The spike remover 24 has been described above.

Next, the digital signal processor 00 will be described.

FIG. 4 is a schematic configuration diagram of the digital signal processor 100.

As shown in FIG. 4, the digital signal processor 100 includes a signal processing unit 110, a serrodyne control unit 140, a modulation control unit 170, and a light intensity calculation unit 210. And a gyro output operation unit 240. Each of these configurations may be realized by an integrated logic IC such as an application specific integrated circuit (ASIC) or a field programmable gate array (FPGA), or It may be realized by software using a computer such as a DSP (Digital Signal Processor). Further, the specific processing in each configuration is not limited to those described below, and may be any processing as long as the same function can be realized.

The signal processing unit 110 adjusts the gain of the signal output from the A / D converter 26 and demodulates it.

The multiplier 1 3 4 is composed of the output signal of the A / D converter 26 and the light intensity calculator 2 1 0 Multiplication with AGC (Automatic Gain Control) signal from Thereby, the gain of the output signal of the A / D converter 26 is adjusted so as to be always constant. By doing so, it is possible to stabilize the operations of the serodyne control unit 140, the modulation control unit 170, and the light intensity calculation unit 210, and, consequently, the rotation angular velocity or rotation angle of the gyro. It can output stably.

Note that an analog multiplier may be used in place of the multiplier 134. In this case, the analog multiplier is placed before the A / D converter 26. The AGC signal from the light intensity calculator 210 is converted to an analog signal by the D / A converter, and then input to the analog multiplier, where it is input to the A / D converter 26. It is adjusted so that the gain of the voltage signal is always constant.

The first demodulator 1 1 2 uses the reference signal B (frequency signal 1 /, for example, a pulse signal having two values of ± 1) generated by the reference signal generator 3 0 0 to generate a multiplier 13 4. Demodulate the output signal of 4. This demodulator is composed of, for example, a multiplier.

When the sampling interval at the A / D converter 26 is shorter than / 2, that is, when the sampling point is at two or more places during the / 2 period, the A / D converter 26 and A filter for performing an averaging process is provided between the first demodulator 112 and the first demodulator 112 so that the input signal to the first demodulator 112 is output at an interval of τ / 2.

The second demodulator 1 14 generates the first demodulator by the reference signal Α (pulse signal having a frequency of 1/2 and having a binary value of ± 1, for example) generated by the reference signal generator 300. Demodulate the output signal of 1 1 2. This demodulator is composed of, for example, a multiplier. The first computing unit 1 16 averages and outputs the output of the second demodulator 114 at every time 2 or 4 by taking the sum of the outputs shifted by time. This output is a deviation signal of a closed-loop serodyne control system including the serodyne controller 140.

Here, it is assumed that, in the phase modulation operation as shown in FIG. 1, an angular velocity is input to the optical fiber loop 6 and a Sannyak phase difference Φs is generated. In this case, the modulation phase difference is as shown in FIG.

As shown in Fig. 6, the output (detection signal) of the / 0 converter 26 is demodulated at the frequency 1 / by the first demodulator 112, and the demodulation result is obtained by the second demodulator 114. When demodulation is performed at the frequency 1/2, the sign of the demodulated detection signal changes from (+) to (-) to (-) to (+) at every て in the two periods. Therefore, by taking the sum of the deviated outputs, it is possible to extract a signal (deviation signal of the serodyne control system) corresponding to the saniac phase difference Φ s required for generating the serodyne signal. .

As shown in FIG. 1, the second computing unit 122 sets the phase shift of the output signal of the multiplier 1334 to a + 0 + δ (or −a−) in the first 2r period. 0-δ) and the signal corresponding to the light intensity of the interference light detected at a-0 (or-α + 0). X is detected, and the average _{Xave of the} detection results is obtained. In the next two periods, the phase shift force, the signal corresponding to the light intensity of the interference light detected when r + Θ-(5 (a certain value is-a-6 »+ δ), and the a-0 ( Alternatively, the difference 信号 from the signal corresponding to the light intensity of the interference light detected at −Ύθ) is detected, and the average Z _{ave of the} detection result is obtained. The output of 2 2 alternates every two periods, such as X _ave , Z _ave , X „,,, Z ,,. The third computing unit 124 generates a signal satisfying the following expression based on the output signals X _ave and Z _ave of the second computing unit 122.

Signal = X _ave + K θ _{BZ avo} (4) where K 0 B = -s in (Θ i δ / 2) · sin (r + δ / 2) / (sin (0-δ / 2) • s in (r-(5/2))

Note that in the example shown in FIG. 1, a = π.

This signal is a deviation signal of a modulation control system which is a closed loop including the modulation control section 170. This deviation signal is output to modulation control section 170.

Here, in the phase modulation operation as shown in FIG. 1, it is assumed that the modulation gain G of the phase modulation by the phase modulator 5 includes an error. In this case, the modulation phase difference is as shown in FIG.

In the present embodiment, in a modulation control unit 170 described later, the gain of the composite signal of various phase modulations output to the phase modulator 5 is set so that the deviation signal specified by the above equation (4) is always 0. Is adjusted. Equation (4) above shows that the deviation signal becomes 0 when there is no modulation gain error, so that various phase modulations should be performed so that the modulation gain error is canceled, that is, G = 1 always. The gain of the composite signal can be adjusted.

FIG. 8 shows the relationship between the above equation (4) and the modulation gain G, and the relationship between the differences X and Z and the modulation gain G. As can be seen from this figure, when the above equation (4) is 0, the modulation gain G becomes 1.

Note that this deviation signal is generated by a modulation controller 170 described later when the gain of the phase modulator 5 or the D / A converter 10 changes due to temperature change or aging. This is for adjusting the gain of the phase modulation composite signal. Therefore, the control loop of the modulation control system operates at high speed. There is no need to be. Further, the arithmetic processing in the third arithmetic unit 124 may be performed in the msec order.

The fourth computing unit 1336 generates a signal satisfying the following expression based on the output signals X _ave and Z _ave of the second computing unit 122.

Signal = X _ave -Z _ave (5) The signal calculated by the above equation (5) is the peak value P of the light intensity of the interference light. Becomes a signal proportional to. This signal is sent to the light intensity calculator ₂₁₀ as a signal _Yave .

Returning to FIG. 4, the explanation will be continued.

The serodyne control unit 140 generates a mouth din signal in accordance with the signal corresponding to the saniac phase difference Φ s output from the first computing unit 116 of the signal processing unit 110.

FIG. 9 is a schematic configuration diagram of the serrodyne controller 140 shown in FIG. The first computing unit 142 integrates the signal corresponding to the saniac phase difference Φs sent from the signal processing unit 110 at two or four time intervals. The result is a signal proportional to the input angular velocity to the optical fiber loop 6.

The second computing unit 144 functions as an amplifier or a single pass filter. The gain or filter constants are set according to the design of the serodyne control loop.

The third computing unit 146 integrates the output signal of the first computing unit 142 sent through the second computing unit 144 at a time interval of 1/2. As described above, the output signal of the first computing unit 142 is a signal proportional to the input angular velocity to the optical fiber 6. If the input angular velocity is constant, the output signal of the first computing unit 142 also becomes constant. In this case, the third The output result of the arithmetic unit 146 is a staircase signal having a constant height with a duration of each staircase of / 2. This staircase signal is output to the modulation control section 170 as a serrodyne signal.

The comparator 150 outputs the first threshold value or the second threshold value which is lower by 2 t than the first threshold value, when the accumulation result of the modulation phase difference by the serodin signal output from the third computing unit 146 is obtained. It is determined whether the threshold has been reached. Then, when the first threshold value is reached, the third computing unit 146 is reset so that the phase difference of the light is a phase shift of −2π. When the second threshold value is reached, the third computing unit 146 is reset so that the phase difference of the light beam becomes a phase shift of + 2π.

Here, the operation of the comparator 150 will be described in more detail with reference to FIGS. 10 to 12. FIG. 10 shows an operation flow of the comparator 150 when the first threshold is set to + 2π and the second threshold is set to −2π. First, the comparator 1500 determines whether or not the accumulation result of the modulation phase difference due to the serodyne signal generated by the third computing unit 144 has reached 2π (step 1001). .

When the value reaches 2π, it is determined that a phase shift (negative reset) of -2π is performed (step 1002). Thereafter, a command is issued to the third computing unit 144 so that the phase difference of the interference light becomes a phase shift of -2π (step 1003). In response to this, the third computing unit 146 adjusts the output of the serodyne signal so that the phase difference of the interference light becomes a phase shift of -2π.

On the other hand, if it has not reached 27Τ, it is determined whether or not the accumulation result of the modulation phase difference by the serodin signal has reached −2π (step 1004) _;

If -2π is reached, + 2π phase shift (positive reset) is performed. (Step 1 0 5). Thereafter, a command is issued to the third computing unit 146 so that the phase difference of the interference light becomes a phase shift of + 27T (step 106). In response to this, the third computing unit 146 adjusts the output of the cellodyne signal so that the phase difference of the interference light becomes a phase shift of + 2π.

On the other hand, if the temperature has not reached -27C, it is determined that reset is not necessary (step 107). In this case, no phase shift command is output to the third computing unit 144.

FIG. 11 shows an operation flow of the comparator 150 when the first threshold is set to + 2π and the second threshold is set to 0. The difference between this flow and the flow shown in Fig. 10 is that step 1004a is provided instead of step 104, where the accumulation result of the modulation phase difference due to the serrodyne signal is obtained. Judge whether or not is less than 0. If the value is smaller than 0, the process proceeds to step 1 05, and if not, the process proceeds to step 1 0 7.

FIG. 12 shows an operation flow of the comparator 150 when the first threshold is set to + 7t and the second threshold is set to −7t. This flow differs from the flow shown in FIG. 10 in that steps 1001 a and 1004 b are provided instead of steps 1001 and 104.

In step 1001a, it is determined whether or not the accumulation result of the modulation phase difference by the serodin signal has reached + π. If the value has reached + π, the process proceeds to step 1002; otherwise, the process proceeds to step 104b.

In step 104b, the accumulation of the modulation phase difference by the serodin signal Determine whether the product result has reached -τ. -If it has reached π, go to step 1005; otherwise, go to step 1007.

Figure 13 shows the waveform of the serrodyne signal generated by the third computing unit 146. Here, FIG. 13 (a) shows the waveform of the serrodyne signal generated by the third computing unit 146 according to the flow shown in FIG. 10, and FIG. 13 (b) shows the waveform of FIG. The waveform of the serodin signal generated by the third computing unit 146 according to the flow shown in FIG. Further, FIG. 13 (c) shows the waveform of the serrodyne signal generated by the third computing unit 146 according to the flow shown in FIG.

As can be seen from these waveforms, according to the flow of FIG. 11, a serodin signal can be generated with a single polarity regardless of the polarity of the input angular velocity to the optical fiber loop 6. This makes it possible to configure a D / A converter and driver for generating serodin signals with a single power supply.

Normally, the digital signal processor 100 and the reference signal generator 300 operate on a single power supply such as +5 V, so if the D / A converter 10 can operate on a single power supply, This makes it possible to reduce the size and cost of the equipment.

In the step of FIG. 11, in step 1001, it is determined whether or not the accumulation result of the modulation phase difference due to the serodin signal has become larger than 0. The same effect can be obtained by judging whether or not the accumulation result of the modulation phase difference due to the signal has become −2π or less.

According to the flow of FIG. 12, the peak-to-peak value of the serodyne signal is reduced by half compared to the flow shown in FIG. This allows The power consumption at the terminating resistor of the phase modulator 5 can be reduced to 1/4.

The fourth computing unit 152 includes a reference signal (a signal corresponding to the modulation gain error specified by the above equation (4)) for the modulation gain control generated by the modulation control unit 170 described later. Is set to 0, that is, based on the reference signal whose output value is corrected so that the modulation gain G becomes 1), the first and second threshold values used in the comparator 150 are specified. And outputs a value for specifying the amount of phase shift due to the reset in the third calculator 146. For example, if the reference signal has an output value necessary to perform a phase shift of 2π, a value for specifying the first and second thresholds from the output value of this reference signal and a phase shift due to reset are used. Calculate and output the value to specify the quantity.

In addition, the fourth computing unit 152 outputs, to the gyro output computing unit 240, a scale factor correction value required for gyro output computation required for controlling the modulation gain by the reference signal.

Returning to FIG. 4, the explanation will be continued.

The modulation control section 170 performs the first constant output signal having a value necessary to perform the phase shift of 0 by modulating the first constant output signal. A pulse with a pulse width of / 2 obtained by modulating a phase modulation signal and a second constant output signal having a value required to perform a phase shift of δ alternates between positive and negative at every time interval of 2. The second phase-modulated signal appearing in the signal and the third constant output signal having a value necessary for performing the phase shift of the signal are synthesized, and this is modulated at half the frequency to obtain the interference light. Phase difference force, (γ (θ ^ δ)) → (τ-θ) → (-Ύ-θ-δ) → (-γίθ) → (Ύ ^ Θ-δ) → (α-(-α- θ + <5) → (- In step 4, a bias modulation signal for performing phase modulation so as to repeat the duration of each step / 2) is generated.

Then, the bias modulation signal generated as described above and the serodin signal generated by the serrodyne control unit 140 are combined to generate a combined signal of various phase modulations.

FIG. 14 is a schematic configuration diagram of the modulation control section 170 shown in FIG. The reference value storage unit 196 stores a reference value (for example, 2π phase shift) for generating an output value required for performing phase shifts of ァ, α, and <5. Output value necessary for this) is stored, and this value is output as a reference signal.

The first computing unit 172 integrates the deviation signal of the modulation control system (the signal corresponding to the modulation gain error specified by the above equation (4)) sent from the signal processing unit 110. Integrator.

The second computing unit 174 is an amplifier or a low-pass filter. Design the gain or fill constant according to the design of the modulation loop control system.

The third computing unit 190 adjusts the reference signal outputted from the reference value storage unit 196 according to the deviation signal of the modulation control system outputted from the second computing unit 174. For example, if the deviation signal of the modulation control system has a positive value, the output value of the reference signal (for example, the value required to perform a 2π phase shift) is adjusted to be small, and modulation control is performed. If the deviation signal of the system has a negative value, adjust so that the output value of the reference signal increases.

By doing so, the deviation signal of the modulation control system becomes zero by the operation of the modulation control system (servo loop), that is, the modulation gain Generate a reference signal whose output value is corrected so that G becomes 1. As the third computing unit 190, for example, an adder is used.

Based on the reference signal whose output value has been corrected by the third computing unit 190, the amplitude 0 generator 202 has the phase of the phase modulation amplitude value 0 sent from the light intensity computing unit 210. Generates a constant output signal with the value needed to perform the shift. For example, if the reference signal has an output value necessary to perform a phase shift of 2π, it is necessary to perform the phase shift of Θ determined by the light intensity calculator 210 from the output value of this reference signal. Calculate and output necessary values.

The amplitude δ generator 180 is a constant output signal having a value necessary for performing a phase shift of <5 based on the reference signal whose output value has been corrected by the third computing unit 190. Generate For example, if the reference signal has an output value required to perform a 2π phase shift, the value required to perform a δ phase shift is calculated from the output value of the reference signal and output.

The amplitude generator 208 generates a constant output signal having a value necessary for performing a phase shift of the key based on the reference signal whose output value has been corrected by the third arithmetic unit 190. Generate. For example, if the reference signal has an output value necessary for performing a 2π phase shift, a value necessary for performing a phase shift of the key is calculated from the output value of the reference signal and output.

The phase modulation generator 204 generates an amplitude 0 generator 204 according to the reference signal generated by the reference signal generator 300 (pulse signal having a binary value of 1 / frequency, for example, ± 1). The constant output signal generated in step 2 is modulated, thereby generating a first phase modulation signal having a rectangular wave having a frequency of 1 /. This phase modulation generator 204 is constituted by, for example, a multiplier.

<3 Modulation generator 18 2 is the same as that generated by reference signal generator 300 Based on the reference signal B, a pulse signal that repeats a series of steps, 1 → 0—0 → 0, with a duration of each step of / 2, is generated by the reference signal generator 300. Modulated with the reference signal C (frequency 1/4 τ, for example, a binary pulse signal of ± 1). As a result, a pulse signal that repeats a series of steps 1 → 0 → 0 → 0 → −1 → 0 → 0 → 0 with a duration of / 2 for each step is generated.

Next, (5 the modulation generator 182 modulates the constant output signal generated by the amplitude δ generator 180 according to the generated pulse signal, and thereby, the pulse width / A second phase modulation signal is generated in which two pulses alternate in the positive and negative directions at every two time intervals.

The adder 206 includes a first phase modulation signal generated by the phase modulation generator 204, a second phase modulation signal generated by the δ modulation generator 18 2, and an amplitude generator 2 0 Adds the constant output signal generated in step 8 in synchronization.

Modulation generator 200 uses the reference signal で (pulse signal that takes two values of ± 1 at the operating point switching frequency 1/2 of the phase modulation) generated by reference signal generator 300. Then, the output signal of the adder 206 is modulated. As a result, the phase difference of the interference light becomes (α + (− α <5)

→ (-a + 6) → (a + 0-(5) → (a--(-τ-θ + δ) → (-a + 0)) a series of steps (period 4 The adder 176 generates a bias modulation signal for performing phase modulation so as to repeatedly take the duration of / 2) of the bias modulation signal generated by the modulation generator 200. By adding the serodin signal generated by the serodin control unit 140 to generate a composite signal of various phase modulations.

FIG. 15 shows the output signal waveforms at each section of the modulation control section 170. Fig. 15 (a) shows the waveform of the output signal (first phase modulation signal) of the phase modulation generator 204, and Fig. 15 (b) shows the waveform of the output signal of the 5 modulation generator 182 (second signal). Figure 15 (c) shows the output signal waveform of the adder 206, and Figure 15 (d) shows the output signal of the modulation generator 200 (bias modulation signal). Shows the waveform.

The first phase-modulated signal shown in FIG. 15 (a) has a symmetric waveform with respect to time τ, and the difference between signals shifted by τ is zero. Since the phase difference between two lights propagating in the optical fiber loop 6 in opposite directions occurs between the two lights that are shifted in time, the first phase modulation signal shown in Fig. 15 (a) No phase difference can be generated in light. That is, no phase modulation is applied.

The bias modulation signal shown in Fig. 15 (d) is composed of the first phase modulation signal shown in Fig. 15 (a), the second phase modulation signal shown in Fig. 15 (b), and the amplitude generator 208. This signal is a signal obtained by synchronizing and adding the constant output signal generated in (1) (the signal shown in Fig. 15 (c)) at half the frequency. By modulating at a frequency of 1/2, the polarity of the bias-modulated signal alternates every time and generates a phase difference of interference light generated between the signals shifted by τ time. In this cycle 4, the phase difference of the interference light is changed by (a + 0 + δ) → (a-θ) → (-Ύ-θ-δ) → ( -τ ^ θ) → (τ ^ θ-δ) → (Ύ-θ) → (-Ύ ~ θ ^ δ) → (-α + Θ) The phase modulation can be performed so that the duration / 2) is repeated.

Note that the phase difference between two lights propagating in the optical fiber loop 6 in opposite directions occurs between the two lights that are shifted in time. By setting the phase modulator 5 to perform the phase shift of S / 2 as the phase modulation signal of the phase shifter, the phase shift of the amplitude 0 is generated in the phase difference of the interference light. be able to.

Further, as the second phase modulation signal, (+ δ) —0 → 0 → 0 → (−δ) → 0—0 → 0 with respect to the phase modulator 5 with the duration r / 2 of each step. By using a phase modulator that repeats a series of phase shifts of the following equation, the phase difference of the interference light is (+ δ) → 0 → A series of phase shifts of (−δ) → 0 → (− <5) → 0 → (+ δ) → 0 can be repeatedly generated.

Further, by setting the phase modulator 5 to perform the phase shift of a / 2 as a constant output signal necessary for performing the phase shift of the above a, The phase shift of the amplitude can be generated in the phase difference of the light.

Return to Fig. 4 to continue the explanation.

The light intensity calculator 210 is a peak value 光 of the light intensity of the interference light obtained by the fourth calculator 136 of the signal processor 110. Of the interference light based on the signal Y _avt , which is proportional to, and the constant output signals output from the modulation control unit ₁₇₀ and having the values required to perform the phase shifts of 0, δ, and α. Peak light intensity Ρ. Ask for. Then, the peak value Ρ obtained by referring to a table prepared in advance showing the correspondence between the peak value of the light intensity of the interference light and the optimal phase modulation amplitude that minimizes the random walk value. Determine the amplitude value 0 of phase modulation according to.

The light intensity calculator 210 calculates the obtained peak value Ρ. Based on this, an AGC signal is generated to keep the loop gain of the cellodyne control system constant. This AGC signal is output to the multiplier 13 4 of the signal processing unit 110 described above. It is.

In addition, the light intensity calculator 210 calculates the peak value of the light intensity of the interference light and the scale factor correction coefficient for correcting the input / output scale factor error of the optical fiber gyro prepared in advance. Peak value P obtained by referring to the table showing the correspondence between Determine the scale factor correction coefficient according to.

FIG. 16 is a schematic configuration diagram of the light intensity calculation unit 210 shown in FIG. The first computing unit 2 1 2 is the peak value P of the light intensity of the interference light obtained by the fourth computing unit 1 36 of the signal processing unit 110. Based on the signal Y _aした proportional to „and the constant output signals output from the modulation control unit 170 and having the values required to perform the phase shifts of θ, δ, and ァ. Calculates the peak value of the light intensity.

This calculation process is performed by the following equation.

Ρ 0 = Y _ave / (-sin δ · sin (α + 0)) (6) However, γ = π

This arithmetic processing does not need to be performed at high speed. Processing may be performed at intervals of about msec. Therefore, the signal Y _ave obtained by the fourth computing unit 1336 of the signal processing unit ₁₁₀ is averaged, and the peak value of the light intensity of the interference light is calculated by the above equation (6) using the averaged value. Value P. You may ask for

Although not shown, the second computing unit 2 14 stores a table indicating the correspondence between the peak value of the light intensity of the interference light and the optimal phase modulation amplitude that minimizes the random walk value. Then, the peak value P of the light intensity of the light beam calculated by the first computing unit 2 12. The optimum phase modulation amplitude according to the above is searched from the table, and this is set as the phase modulation amplitude value 0, and Outputs to the amplitude 0 generator 202 of the controller 170.

The resister 216 stores, as an initial value, the peak value of the light intensity of the interference light first calculated by the first computing unit 212 when the interferometer 500 is assembled.

The third computing unit 218 is a peak value P of the light intensity of the interference light obtained by the first computing unit 221. And the initial value stored in Regis 2 16 are calculated.

The fourth computing unit 220 integrates the result of the third computing unit 218. The result of the integration is output as an AGC signal to the multiplier 1334 of the signal processing unit 110.

Although not shown, the fifth computing unit 222 has a correspondence relationship between the peak value of the light intensity of the interference light and the scale factor correction coefficient for correcting the input / output scale factor error of the optical fiber gyro. Is stored. Then, the peak value P of the light intensity of the interference light calculated by the first computing unit 2 12. The scale factor correction coefficient corresponding to the above is retrieved from the table and output to the gyro output operation unit 240.

Here, the relationship between the peak value of the light intensity of the interference light and the optimal phase modulation amplitude that minimizes the random walk value will be described. The relationship between the peak value of the light intensity of the interference light and the scale factor correction coefficient for correcting the input / output scale factor error of the optical fiber gyro will be described later.

A signal corresponding to the light intensity of the interference light detected by the optical fiber gyro is superimposed with several types of random noise as described below.

I. Relative intensity noise of light source 1 First, the relative intensity noise (RIN) of the light source 1 is superimposed on the output light of the interferometer 500. RIN is defined as follows:

RIN [dB / Hz] ≡ 10 · log (δ P / Pa / Β) (7) Ν ' _RI [l / (Hz ^1/2 )] ≡ δ P / Pa / B ^1/2 (8) [delta] [rho ² is the mean square value of the fluctuations of the light intensity, Pa is the average light intensity, B is defined equivalent bandwidth only in real space.

The average intensity when an arbitrary phase modulation amplitude Ψ [rad] is applied is expressed by the following equation.

P _a = (P. / 2) · (1 + cos Ψ) (9) Thus, the amount of random noise included in the output light of the interferometer 500 is

N ' _RI · P _a [Wrms / (Hz ¹⁷² )]

= N ' _RIK · (P o It) · (1 + cos Ψ) (10)

Π. Shot noise at Receiver 7

Next, the output light of the interferometer 500 with the RIN superimposed thereon is converted into a current signal by the photodetector 7, and at this time, the shot noise correlated with the output value of the converted signal is superimposed. You. This shot noise is defined as follows.

N _'S [Arms / (Hz ^1/2 )] 3 (2 · e · i) ^1/2

= (e · P. · S · (1 + cos Ψ)) ^{1 72} (11) where e is the charge of the electron (= 1.6X 10- ^{| 9} [c]) and i is the light Is the average current value [A] generated by the operation, and S is the sensitivity [A / W] of the photodetector 7. N ′ N is the effective value of noise defined only in the real number domain. m. Noise at the current / voltage converter 8

Next, the current signal on which the shot noise is superimposed is

At 8 it is converted to a voltage signal. At this time, the total noise of the used resistors and other current and voltage noises are superimposed. Thermal noise and current / voltage noise are expressed by the following equations.

N '"[Vrms Pas ^{Hz 1/2)] ≡ (} 4 · k · R · T) 1/2 (12) N' VN [Vrms / (Hz 1, 2)] ≡ (V ,. 2 + (· R) ² ) ¹ , ² (13) where k is the Boltzmann constant (= 1.38X10 [] / "K]), R is the resistance [Ω] of the current-Z voltage converter 8, and T Represents the absolute temperature [° K], and N 'is the effective value of noise defined only in the real number domain. Is the voltage noise of the operational amplifier, and is the current noise. N _'v, is the effective value of the noise that is defined only in the real domain.

I explained above! The voltage signal on which the random noise of Π is superimposed is sampled by the A / D converter 26, and then subjected to serodin control, rotation angular velocity (rotation angle) calculation, and the like in the digital signal processor 100. Is done. From the above equations (10) to (13), the amount of random noise in the voltage signal is

V _nojse [Vrins / (Hz ^{1 72} )]

_{= ((N 'RIN - (} P o / 2) · S - R (Hcos Ψ)) 2 + R 2 · e

• P. · S · (1 + cos Ψ) + Ν ' _TN ² + N' VN ² ) ^1/2 (14) From this equation, a theoretical equation for the random walk value for any phase modulation amplitude Ψ can be derived.

It is assumed that the angular velocity Ω [rad / s] is input to the optical fiber loop 6, and that a saniac phase difference φ s [rad] is generated. As described above, in the present embodiment, the light intensity of the interference light according to the phase difference Φ s is Detection is performed by phase-modulating two lights propagating in the fiber loop 6 in opposite directions with amplitude 光 [rad].

Now, if the above-mentioned random noise is not taken into account, the light intensity P (+ Ψ) and Ρ (-の) of the interference light phase-modulated with the amplitude サ at which the Sagnac phase difference Φ s is expressed.

Ρ (+ Ψ) = (Ρ ./2) · (l + cos ((i) s + Ψ)) (15) Ρ (—)) = (Ρ ./2) · (l + cos ((i) s—Ψ)) (16) Therefore, demodulated signal V by synchronous detection. _ul is

ν _ου1 = (Ρ (+ Ψ) -Ρ (-Ψ))

= (Ρ 0/2) · (cos (φ s + Ψ) -cos (s-Ψ)) · S - R - 1/2 = one _{(P 0/2) · S} · R · sin (s) · s in () (17) Here, by substituting the above equation (1) into this equation (17),

V. _u- (P _0/2 ) 'S · R

-sin {2 π · D · L · Ω / (λ · c)} · 8 ίη (Ψ) (18)

Ω = (λc / (2πDD)

• s in- '[V _0Ul / {(-P ./2) · S · R · sin (Y)}] (19).

Since the gyro random walk value RWK is generally defined by the equivalent bandwidth ± 2B defined in the complex domain, multiply by 1 / (2 ^1/2 ) to convert the real domain into the complex domain. When converted to the definition, the above equations (14) and (19) are expressed as follows.

RWK [rad / (s ^1/2 )]

= λ c c 2 π D L

• s in— '[V _n . _{_{isc / {(-P 0/2}} ) · S · R · δ ίη (Ψ)}] · {1 / (2 1/2)} = Λ - c / (2 π · D · L · 2 1/2)

^{• sin "1 [{N '} R1N · (P 0/2) · S · R

• (l + cos ^))} ² + R ² · e · P o ·

• (1 + cos (Ψ)) + Ν + N vx

/{(-P./2) · S · R · sin ()} (20) RWK [° / ( ^1/2 )]

= λ-c / (2 πD L L V ⁿ )

• sin-1 ¹ [{N ' _RI · (P./2) · S · R (Hcos (Ψ))} ² + R

S · (1 + cos (Ψ)) + N + N j

• P. / 2) · S · R · sin (^)}

• (3600) ^1/2 · 180 / π (21) As can be seen from the above equations (20) and (21), the random walk value is the peak value P of the light intensity of the interference light. And the phase modulation amplitude as a parameter. The peak value P of the light intensity of the interference light. If the value changes, the phase modulation amplitude that minimizes the random walk value also changes.

Figure 17 shows the random walk value versus the phase modulation amplitude value when the relative intensity noise RIN of light source 1 is -115 [dB / Hz] and the peak value P _Q of the interference light is 2 to 50 W. Is shown. Here, the horizontal axis represents the modulation depth in the cos curve of the interference light characteristics, where τ = π represents the value of _α -0, and _Ύ = _1π represents the value of Θ.

According to this figure, the peak value of the light intensity of the interference light Ρ. It can be seen that the amplitude value of the phase modulation that minimizes the random walk value also changes. For example, Ρ. At 50 W, the optimal amplitude is about 170 degrees, but at P _Q = 2 W it is 130 degrees.

Therefore, in the present embodiment, the above equation (20), The peak value P of the light intensity of the interference light obtained from the equation (21). A table indicating the correspondence between the random phase value and the optimum phase modulation amplitude that minimizes the random peak value is stored in advance, and the peak value P of the light intensity of the interference light calculated by the first computing unit 221. Is searched from the table for the optimum phase modulation amplitude corresponding to.

Returning to FIG. 4, the explanation will be continued.

The gyro output operation unit 240 sends the signal to the optical fiber loop 6 according to the signal corresponding to the saniac phase difference φ s sent from the first calculator 142 of the serodyne control unit 140. Calculate the input rotation angular velocity or rotation angle of.

The first computing unit 242 calculates the phase difference φ s of the saniac transmitted from the first computing unit 142 of the serrodyne control unit 140, that is, the input rotation angular velocity to the optical fiber pump 6. The corresponding signal is integrated over time. This result is proportional to the rotation angle of the optical fiber loop 6. When calculating the average rotational angular velocity, the integration result may be further divided by the integration time.

The register 244 stores the input / output scale factor value in the initial state of the optical fiber gyro.

The second computing unit 246 stores the scale factor value stored in the register 244, the scale factor correction coefficient sent from the fifth computing unit 222 of the light intensity computing unit 210, Signal generated by the third computing unit 190 of the modulation control unit 170 sent from the fourth computing unit 152 of the control unit 140 (the reference signal whose output value has been correctly corrected) ) By The output of the first computing unit 242 is corrected using the scale factor correction value required for the modulation gain control. Thereby, the input rotation angular velocity or rotation angle to the optical fiber loop 6 is calculated. The second computing unit 246 is constituted by, for example, a multiplier.

Here, the relationship between the peak value of the light intensity of the interference light and the scale factor correction coefficient for correcting the scale factor error of the input / output of the optical fiber jar opening will be described.

The output value of the optical fiber gyro (specifically, the rotation angular velocity or rotation angle calculated by the gyro output calculation unit 240) is the peak value P of the light intensity of the interference light. Changes in correlation with the change in This is thought to be due to the following reasons.

Gyro output with respect to the input rotational angular velocity Ω to the optical fiber loop 6 When the angle increment in the calculation unit 240 is set to 0 _angle , the angle when a phase shift of 2π occurs due to the reset of the serodin signal The increment 0 _sngle is expressed by the following equation.

Θ _anglc = n 0 · λ / D (22) This equation is equivalent to using the duration of each step of the serodin signal as

_Anganglc = c · λ · and can be expressed as / D / L (23).

By the way, the peak value of the light intensity of the interference light Ρ. Changes occur when the loss in the optical path from the light source 1 to the optical receiver 7 via the optical fiber loop 6 changes, and their loss characteristics differ depending on the wavelength of light. In the present embodiment, the light source 1 used for the optical fiber gyro has a short coherence length and a short wavelength as described above. The vector characteristics are widely distributed over tens to hundreds of nm. Therefore, the light intensity changes due to the change in loss, and the effective center-of-gravity wavelength value of the light changes. As a result, the value of the center-of-gravity wavelength λ in the above equations (2 2) and (2 3) changes, and the angle increment 0 _angle changes. This is considered to be an input / output scale factor error.

The present inventors have confirmed that the sensitivity of the scale factor was about several tens to several hundreds of ppm for a change of the light intensity value of 10%. Light intensity values easily change due to temperature, aging, and the like. This cannot be used for high-performance optical fiber gyros that require a scale factor error of several to several tens of ppm or less.

Therefore, in the present embodiment, as described above, in the fifth computing unit 222 of the light intensity computing unit 210, the peak value of the light intensity of the interference light and the scale factor correction coefficient (registration coefficient 24 (A correction coefficient of the scale factor value stored in the optical intensity calculator) is stored in advance, and the peak of the light intensity of the interference light calculated by the first calculator 212 of the light intensity calculator 210 is stored. The scale factor correction coefficient corresponding to the value is retrieved from the table. Then, in the second computing unit 246 of the gyro output computing unit 240, the scale factor value stored in the register is corrected using the searched correction coefficient (specifically, the register factor is used). The result obtained by multiplying the scale factor value stored in the gyro by the correction coefficient is converted to the result corresponding to the rotation angle or the average angular velocity output from the first computing unit 242 of the gyro output computing unit 240. Multiply).

This corrects for scale factor errors caused by changes in light intensity values.

Hereinabove, the first embodiment of the present invention has been described. In the present embodiment, in the modulation control section 170, the phase difference of the interference light is (τ \ θδ) → (τ−θ) → (−-− θ−δ) → (−τΘ) → {τ θ-δ) → (Ύ-0) → (-α-0 + (5) → (-α + 0)) Repeat a series of steps (period 4, duration of each step / 2) The duration of each staircase, which produces a bias modulation signal for performing phase modulation and a phase difference of the same amount and opposite sign as the phase difference Φ s of the saniac phase according to the input angular velocity to the optical fiber jar opening, Alternatively, the signal is combined with a / 2 step-like serodyne signal to generate a combined signal of various phase modulations, which is input to the phase modulator 5.

Then, in the signal processing section 110, what is the light intensity of the 1,000 m light detected when the phase shift is α + 0 + <5 (or −α−0−δ)? ■-Θ (or the intensity difference X from the light intensity of the interference light detected at-, and + 0-<5 (or the light intensity of the interference light detected at- Based on the intensity difference 光 of the light intensity of the interference light detected at −0 (or −), or the light intensity of the interference light detected at α + 0 + <5 (or −δ) The light source 1 and other light sources constituting the optical interferometer 500 are determined based on the intensity difference と from the light intensity of the interference light detected at the time of と + 0-δ (or--0 + <5). It detects the peak value 干渉 of the light intensity of the interference light due to a change in the characteristics of the optical components, etc., and detects the change in the light intensity value of the interference light from the obtained peak value Ρ. The AGC control is performed so that the output signal gain from the optical interferometer 500 becomes constant in response to this.Specifically, when the output signal from the optical interferometer 500 decreases, the electrical The output signal gain is controlled to be constant by making the signal larger.

In this way, the loop gain of the serodyne control system is always maintained. The constant serodin control can be achieved, and the rotational angular velocity or rotational angle of the jay mouth can be output stably. Also, in the present embodiment, the light intensity calculation unit 210 refers to a table showing the correspondence between the peak value of the light intensity of the interference light and the optimal phase modulation amplitude that minimizes the random walk value, as described above. The peak value P of the light intensity of the interference light obtained by The table is searched for the optimum phase modulation amplitude corresponding to the amplitude, and this is output to the amplitude 0 generator 202 of the modulation control section 170 as the phase modulation amplitude value 0.

By doing so, the peak value P of the light intensity of the interference light is obtained. Thus, it is possible to generate a composite signal of various phase modulations so that the phase modulation less affected by the random walk can be performed irrespective of the change of the phase.

Further, in the present embodiment, the light intensity of the interference light detected when the phase shift is a + 0 + <5 (or −α−0−δ) and the light intensity detected when the phase shift is a− シ (or −) The intensity difference X from the light intensity of the interference light, and the light intensity of the interference light detected when -δ (or -0 + <5) and the interference light detected when -Θ (or-) Based on the intensity difference Z from the light intensity of the phase modulation, the modulation gain error of the phase modulation by the composite signal of the various phase modulations is detected, and the various phase modulations are performed so that the detected modulation gain error becomes zero. Controls the gain of the composite signal.

By doing so, it is possible to perform accurate phase modulation by a composite signal of various phase modulations, and it is possible to reduce the scale factor error in the gyro output.

Further, in the present embodiment, in the signal processing unit 110, the output of the A / D converter 26 is demodulated at the frequency 1 / by the first demodulator 112, and the demodulation result is subjected to the second demodulation. Demodulation at the frequency 1/2 by the At 2, a detection signal is generated that changes polarity from (+) to (-)-(-) to (+) every / 2. Then, the above-mentioned detection signals are averaged by the first computing unit 1 16 at every time 2 or 4 times, and are summed up by the sum of the skewed signals. The signal (deviation signal of the cellodyne control system) corresponding to the saniyak phase difference Φ s required for the operation is extracted.

By doing so, for example, light interference due to fluctuations in light intensity due to temperature, vibration, etc., and the incorporation of low-frequency electromagnetic noise from the output of the receiver 7 to the input section of the A / D converter 26, etc. When a DC component having a certain slope is superimposed on the output signal from the total 500, the fluctuation of the DC component can be canceled. In other words, the polarity of the fluctuation of the DC component included in the sum of the above detection signals that are shifted by a certain amount of time is alternately changed. The component fluctuation can be canceled. This enables more accurate detection of the phase difference of the sanyak, and also improves the accuracy of the gyro output (rotational angular velocity or rotational angle).

Further, in the present embodiment, as described above, the phase difference of the interference light is generated by the bias modulation signal, and the light intensity value of the interference light detected at this time is used to determine the phase difference of the saniac and the modulation gain. Since the detection error and the change in the light intensity value of the interference light can be detected, the detection signals for serodin control, modulation control, and light intensity calculation can be shared. For this reason, only one A / D converter is required for cellodyne control, modulation control, and detection signal generation for light intensity calculation.

Further, according to the present embodiment, the following effects are obtained. In a conventional digital fiber optic gyro, for example, as described in U.S. Pat. No. 4,705,399, the signal reaches 27T for a serodin signal (digital step lamp). Then, the phase shift is reset so that the phase shift of -2π is performed. When the signal reaches 2π, the phase shift of -2π is performed on the synthesized signal of the serodin signal and the phase modulation signal. Reset to perform a reset.

For this reason, the reset is repeatedly performed from the time when the combined signal of the serodin signal and the phase modulation signal reaches 2π until the serodin signal reaches 27U. In particular, when the input angular velocity to the optical fiber gyro is extremely low, the reset is repeated over a long period of time. Will occur.

On the other hand, in this embodiment, the reset is performed only for the serodyne signal, so that the reset is repeatedly performed when the input angular velocity to the optical fiber gyro is extremely low. Never. Therefore, it is possible to prevent the lock-in phenomenon at a low input angular velocity.

Next, a second embodiment of the present invention will be described.

In the above-described first embodiment, the amplitude 0 generator 202, the amplitude δ generator 180, and the amplitude δ generator 180 of the modulation controller 170 are used as the modulation gain control so that the detected modulation gain error is set to zero. The output value of each constant output signal generated by the amplitude generator 208 is adjusted, and the first and second comparators 150 and the third computing unit 144 of the serodyne control unit 152 are used. The second threshold ゃ The gain of the composite signal of various phase modulations was controlled by adjusting the amount of phase shift by resetting the serodyne signal. In contrast, this implementation In the embodiment, the modulation gain control adjusts the amplitude of the generated composite signal of various phase modulations so that the detected modulation gain error becomes zero.

FIG. 19 is a schematic configuration diagram of a digital signal processor 100a used in an optical fiber jar opening to which the second embodiment of the present invention is applied. The other configuration of the optical fiber gyroscope of the present embodiment is the same as that of the first embodiment shown in FIG.

A digital signal processor 100a used in the present embodiment shown in FIG. 19 is different from the digital signal processor 100a used in the first embodiment shown in FIG. Instead of the modulation control section 170 and the gyro output operation section 240, the serodin control section 140a, the modulation control section 170a and the gyro output operation section 240a, respectively. Is used. Other configurations are the same as those of the digital signal processor 100 shown in FIG.

FIG. 20 is a schematic configuration diagram of the serodyne control unit 140a shown in FIG. In this figure, the same components as those of the serrodyne control unit 140 shown in FIG. 9 are denoted by the same reference numerals.

The difference between the serodyne control unit 140a shown in FIG. 20 and the serodyne control unit 140 shown in FIG. 9 is that a reference value storage unit 148 is provided instead of the fourth computing unit 152. That is. The reference value storage unit 148 is used to specify values for specifying the first and second threshold values used in the comparator 150 and the amount of phase shift due to reset in the third computing unit 146. The value of is stored.

As described above, in the present embodiment, the generated various phase modulations are performed as modulation gain control so that the detected modulation gain error is set to zero. The amplitude of the synthesized signal itself is adjusted. Therefore, as in the first embodiment, the values for specifying the first and second thresholds used in the comparator 150 and the reset in the third computing unit 144 are used for the modulation gain control. There is no need to adjust the gain for the serodyne signal by adjusting the value to specify the amount of phase shift due to the signal.

Thus, in the present embodiment, a value for specifying the first and second threshold values used in the comparator 150 and a value for specifying the phase shift amount due to the reset in the third computing unit 146 are used. As a value, a predetermined constant value is stored in the reference value storage unit 148.

FIG. 21 is a schematic configuration diagram of the modulation control section 170a shown in FIG. In this figure, the same components as those in the modulation control 140 shown in FIG. 14 are denoted by the same reference numerals.

The difference between the modulation control unit 170a shown in FIG. 21 and the modulation control unit 170 shown in FIG. 14 is that the first arithmetic unit 172, the second arithmetic unit 174, and the third arithmetic unit 1 In place of 90, a first computing unit 17 2 a, a second computing unit 17 4 a, and a multiplier 1 78 are provided.

The first computing unit 17 2 a integrates the deviation signal (signal corresponding to the modulation gain error specified by the above equation (4)) of the modulation control system sent from the signal processing unit 110. It is an integrator.

The second computing unit 174a is an amplifier or a mouth-to-pass filter. Design the gain or fill constant according to the design of the modulation loop control system.

The multiplier 178 controls the gain of the combined signals of various phase modulations output from the adder 176 so that the deviation signal of the modulation control system output from the second arithmetic unit 174 becomes zero. Adjust As described above, in the present embodiment, the modulation gain control is performed by adjusting the amplitude of the generated composite signal of various phase modulations so that the detected modulation gain error becomes zero. Therefore, as in the first embodiment, a constant output signal and an amplitude δ generator 18 necessary for performing a phase shift of 行う output from the generator 102 for the modulation gain control are provided. Output from 0 (the constant output signal required to perform the phase shift of 5 and the constant output signal required to perform the phase shift of the output from the amplitude generator 208) There is no need to adjust the output value. Therefore, the values stored in the reference value storage unit 196 can be directly stored in the amplitude Θ generator 102, amplitude δ generator 180, and amplitude generator 200. 8 to give.

FIG. 22 is a schematic configuration diagram of the gyro output operation unit 240a shown in FIG. In this figure, the same components as those of the gyro output operation unit 240 shown in FIG. 18 are denoted by the same reference numerals.

The point that the gyro output operation unit 240 a shown in FIG. 22 differs from the gyro output operation unit 240 shown in FIG. 18 is that the second operation unit 2 46 is replaced with the second operation unit 2 46. a. The second calculator 246a calculates the scale factor value stored in the register 244 and the scale factor correction coefficient sent from the fifth calculator 222 of the light intensity calculator 210. To correct the output of the first computing unit 242. Thereby, the input rotation angular velocity or rotation angle to the optical fiber loop 6 is calculated. The second embodiment of the present invention has been described above.

Also in the present embodiment, similarly to the first embodiment, the modulation gain can be controlled so that the detected modulation gain error becomes zero. However, in the present embodiment, as shown in FIG. A multiplier 178 is provided on the output side, and the multiplier 178 adjusts the amplitude of the composite signal of each phase modulation output from the adder 176 so that the detected modulation gain error becomes zero. By adjusting, the modulation gain is controlled. In this case, the multiplier 176 is required to perform the arithmetic processing every time width of each step of the composite signal of various phase modulations, that is, every half time. For example, if the optical fiber length L of the optical fiber loop 6 is 100π! When the distance is about 2 km, the light propagation time in the optical fiber loop 6 is about 500 nsec to 10 tsec from the above equation (3). In this case, in the present embodiment, a calculation every τ / 2, that is, a calculation every 250 nsec to 5 sec is required.

On the other hand, in the first embodiment, the amplitude S generator 202 and the amplitude δ generator 1 of the modulation controller 170 are used as the modulation gain control so that the detected modulation gain error is set to zero. In addition to adjusting the output value of each constant output signal generated by 80 and the amplitude generator 208, the comparator 150 of the cellodyne control unit 152 and the third computing unit 144 The gain of the combined signal of various phase modulations is controlled by adjusting the amount of phase shift by resetting the first and second threshold values ゃ serodin signal used.

For this reason, in the first embodiment, the calculation may be performed at a processing speed necessary to correct the modulation gain error. The modulation gain error is caused by changes in temperature, which is a disturbance source, and does not depend on the length of the optical fiber loop. For this reason, usually, if the processing speed of about several milliseconds is calculated, sufficient modulation gain control becomes possible.

Therefore, in the first embodiment, the speed of the arithmetic processing required for the modulation gain control can be made lower than in the present embodiment. In this regard, the first embodiment is more advantageous. The embodiments of the present invention have been described above.

Note that the present invention is not limited to the above embodiments, and various modifications are possible.

For example, in each of the above embodiments, when the phase shift is α + 0 + <5 (or −α−0− <5) by the second computing unit 122 of the signal processing unit 110, The difference X between the light intensity of the interference light detected at the time and the light intensity of the interference light detected at a−0 (or −α + 0), and α + 0−0 (or

-Ύ-δ δ), and the intensity difference z between the light intensity of the interference light detected at a-ø (or-r + θ) and the light intensity of the interference light detected at

The three computing units 124 generate a signal (deviation signal of the modulation control system) corresponding to the modulation gain error by the above equation (4).

However, the present invention is not limited to this. The light intensity of the interference light detected when the phase shift is ++ 0 + <5 (or ァ δ) by the second arithmetic unit 122 of the signal processing unit 110 and the --Θ (Or -a +)) Intensity difference X from the light intensity of the stellar light detected during phase shift and a + 0 + 6 (or detected when-Ύ-Θ-δ The third arithmetic unit 1 2 4 is obtained by calculating the intensity difference Υ between the light intensity of the detected interference light and the light intensity of the interference light detected when α + 0−δ (or −α−0 + <5). In,

Signal = Κ Θ CX-Υ (24) where C = 2s in 0 'sin (a + 0) bar COS (T-0)-cos (a + 6> + δ)) A corresponding signal may be generated. In this case, it is not necessary to provide the signal processing unit 110 with the fourth computing unit 1336. That is, the intensity difference で obtained by the second computing unit 122 can be output to the light intensity computing unit 210. Light intensity performance Using the intensity difference Y, the first computing unit 2 12 of the arithmetic unit 2 10 calculates the peak value P of the light intensity of the interference light according to the above equation (6). Can be requested. Further, in each of the above embodiments, the modulation control section 170, 170a modulates the first constant output signal having a value necessary for performing the phase shift of Θ. And a second constant output signal having a value necessary for performing a phase shift of δ. A second phase modulation signal in which a pulse having a pulse width of / 2 alternates between positive and negative at a time interval of 2 τ is synthesized with a third constant output signal having a value necessary for performing a phase shift of ァ. By modulating this at half the frequency, the phase difference of the interfering light is

→ (Ύ-θ) → (-Ύ-θ -6) → (-τ θ) → (τ θ-δ) → (τ-θ) → (-τ-Θ + δ) → (- Generates a bias modulation signal that performs phase modulation so that a series of steps (period 4, duration of each step / 2) is repeated, and bias modulation generated as described above. The signal and the serodin signal generated by the serodin control unit 140 are combined to generate a combined signal of various phase modulations.

However, the bias modulation signal is not limited to the above. The bias modulation signal has a phase difference of the interference light of six values of ± (α−0), soil (α + 0 + 5), and soil (α + 0−δ), or soil (α + 0). , ± (α−0−δ), and ± (τ−0 + δ) as long as the phase modulation is performed so as to be repeated at predetermined time intervals and in a predetermined order.

For example, a first phase modulation signal consisting of a square wave of frequency l / τ obtained by modulating a first constant output signal having a value necessary to perform a phase shift of Θ, The second one with the value required to perform the phase shift The second phase modulation signal obtained by modulating the constant output signal of (2) and having a pulse width of / 2 that alternates positive and negative at every time interval (2) is used to shift the phase of (a). By synthesizing with the third constant output signal having the required value and modulating this at the frequency 1/2 τ, the phase difference of the interference light becomes (了-Θ) → (τ ί θ ί δ) → (-τ + θ) → (-τ-θ-δ) → (Ύ-θ) → (Ύ + θ-δ) → (--A series of steps in the order, or (a-θ-δ ) → (γ θ) → (-τ + θ + δ) → (-τ-θ) → (γ-θ δ) → (Ύ + θ) → (-α + 0-δ) → (-? ”-ステップ) or a series of steps,

(Ύ θ) → (Ύ-θ-δ) → (-Ύ-θ) → (-Ύ θ δ) → (τ θ) → (τ-θ _{δ) →} (—a- _{0) →} (—a _δ ) May be generated to generate a bias modulation signal for performing phase modulation so as to repeat a series of steps (period 4, duration of each step / 2).

That is, in the modulation control sections 170 and 170a, a first phase modulation signal, a second phase modulation signal, and a third constant output signal are generated, and these are added by an adder 206. Then, when the modulation generator 200 modulates with the modulation signal of the frequency 1/2 and generates the bias modulation signal, the first phase modulation signal, the second phase modulation signal, and This can be achieved by adjusting the phase (synchronization) relationship between the modulated signals at half the frequency. As described above, according to the present invention, a change in the light intensity value of the interference light can be detected from the phase difference of the interference light. By controlling the output signal gain to be constant, the loop gain of the serodyne control system can always be kept constant, and this enables stable serodyne control and, consequently, the gyro rotation angular velocity or angle. It is possible to output stably. Similarly, since the modulation gain error can be detected from the phase difference of the interference light, accurate phase modulation can be performed by controlling the modulation so that the detected modulation gain error becomes zero. Thus, the scale factor error in the gyro output can be reduced.

Claims

The scope of the claims

1. An optical fiber gyro that detects the rotation angle speed or rotation angle according to the saniac phase difference of the interference light obtained by recombining two lights propagating in the optical fiber loop in opposite directions. hand,

A light receiving unit that detects the light intensity of the interference light and converts the light intensity into an electric signal; and, based on a signal corresponding to the light intensity of the interference light detected by the light receiving unit, determines a saniac phase difference of the interference light A saniac phase difference calculating means for calculating a corresponding signal;

In accordance with a signal corresponding to the Sagnac phase difference of the interference light generated by the Sagnac phase difference calculating means, a serodyne signal composed of a staircase wave for canceling the Sagnac phase difference of the interference light is obtained. A cello din signal generating means for generating;

The phase difference of the interference light is six values of ± (α−0), ± (α + 0 + 5) and soil (α + 0−δ), or soil (τ + 6 »), soil (τ− A bias modulation signal for performing phase modulation so as to repeatedly take six values of 0− <5) and soil (α−0 + <5) in a predetermined time interval and in a predetermined order; A synthesized signal generation unit that synthesizes the generated serodyne signal to generate a synthesized signal of various phase modulations;

A modulation gain for calculating a signal corresponding to a modulation gain error generated at the time of phase shift by the bias modulation signal based on a signal corresponding to the light intensity of the interference light detected by the light receiving means. Arithmetic means;

A signal corresponding to the modulation gain error generated by the modulation gain calculation means. Modulation gain control means for controlling the gain of the composite signal of the various phase modulations according to

An optical fiber gyro characterized by the above.

2. The optical fiber gyro according to claim 1, wherein

The synthesized signal generation means includes:

Third constant output signal generating means for generating a third constant output signal having an output value necessary to perform a phase shift of the

Bias modulation that generates the bias modulation signal using each of the constant output signals generated by the first constant output signal generation unit, the second constant output signal generation unit, and the third constant output signal generation unit. Signal generation means,

First adding means for adding the bias modulation signal generated by the bias modulation signal generation means and the serodin signal generated by the serodyne signal generation means to generate a composite signal of the various phase modulations; Has,

The modulation gain control means includes:

According to a signal corresponding to a modulation gain error generated by the modulation gain calculation means, the first constant output signal generation means, the second constant output signal generation means, and the third constant output signal generation By adjusting the output value of each constant output signal generated by the means and the output value of the serodin signal generated by the serodin signal generation means, Control the gain of the composite signal

An optical fiber gyro characterized by the above.

3. The optical fiber gyro according to claim 1, wherein

The synthesized signal generation means includes:

First constant output signal generating means for generating a first constant output signal having an output value necessary for performing a phase shift of 0;

The modulation gain control means includes:

By controlling the output value of the first addition means according to a signal corresponding to the modulation gain error generated by the modulation gain calculation means, the gain of the composite signal of the various phase modulations is controlled. Do

An optical fiber jay mouth characterized by the above.

4. The optical fiber gyro according to claim 2, wherein

The modulation gain calculation means includes: When the phase shift by the composite signal of the various phase modulations is a + θ + δ (or −a−, the signal detected by the light receiving unit and the phase shift are a− ァ (or −α + 0), the difference X from the signal detected by the light receiving means, and the signal detected by the light receiving means when the phase shift is a + 0- <5 (or -a-). And a phase difference ァ between the signal detected by the light receiving means when the phase shift is ァ (or-),

Signal = Χ + Κ θ Β · Ζ

Where Κ Θ B = -sin (^ + δ / 2)-s i n (r + (5/2) / (s i η (0-δ / 2)-s in (r-<5/2))

And outputting a signal that satisfies the following as a signal corresponding to the modulation gain error;

The modulation gain control means includes:

The first constant output signal generating means, the second constant output signal generating means, and the third constant output signal generating means each set so that the signal output from the modulation gain calculating means becomes zero. The output value of the generated constant output signal and the output value of the serodin signal generated by the serodin signal generation unit are adjusted.

An optical fiber gyro characterized by the above.

5. The optical fiber gyro according to claim 3, wherein

The modulation gain calculation means includes:

When the phase shift by the composite signal of the various phase modulations is a + 0 + δ (or −α−0−δ), the signal detected by the light receiving unit and the phase shift are r− e (or −α + 0), the difference X from the signal detected by the light receiving means, and the phase shift is α + θ−δ (or Is the signal detected by the light receiving means when −a−0 + (5) and the signal detected by the light receiving means when the phase shift is T−Θ (or −α + 0). Find the difference Z with the output signal,

Signal = Χ + Κ θ Β-Ζ

Where Κ 0 B = _s in (0 + δ / 2) sin (τ + <5/2) / (s in (0 _ δ / 2) s in (r-δ / 2))

The modulation gain control means includes:

The output value of the first addition means is adjusted so that the signal output from the modulation gain calculation means becomes zero.

An optical fiber gyro characterized by the above.

6. The optical fiber gyro according to claim 2, wherein

The modulation gain calculation means includes:

When the phase shift by the composite signal of the various phase modulations is “+ Θ + <5 (or −α−0−δ), the signal detected by the light receiving unit and the phase shift are a−0. (Or −α + 0) when the difference X from the signal detected by the light receiving means and when the phase shift is α + 0 + δ (or −α−θ−6) Then, the difference と between the signal detected by the light receiving means and the signal detected by the light receiving means when the phase shift is α + 0− <5 (or −α−θ + δ) is obtained,

Signal = Κ 0 C · Χ-Υ

However, a signal that satisfies C = 2s in δsinir ^ θ) / (sos (r-θ) -cos (Ύ ^ θ + δ)) is output as a signal corresponding to the modulation gain error. , The modulation gain control means includes:

An optical fiber gyro characterized by the above.

7. The optical fiber gyro according to claim 3, wherein

The modulation gain calculation means includes:

When the phase shift due to the composite signal of the various phase modulations is a + 0 + δ (or −a−0− <5), the signal detected by the light receiving unit and the phase shift are a−0 (Or −α + Θ), the difference X from the signal detected by the light receiving means, and when the phase shift is α + 0 + δ (or −Ύ−Θ−δ). The difference と between the signal detected by the light receiving means and the signal detected by the light receiving means when the phase shift is α + + − <5 (or −α−6> + δ) is obtained,

Signal = Κ 0 CX-Υ

However, a signal that satisfies C = 2s in 5 * sin (α + 6>) / (cos (7—−cos (α +) is output as a signal corresponding to the modulation gain error.

The modulation gain control means includes:

An optical fiber gyro characterized by the above.

8. The optical fiber gyro according to claim 1, wherein A gyro output calculating means for calculating a rotation angular velocity or a rotation angle according to a Sagnac phase difference of the interference light based on a signal corresponding to the light intensity of the interference light detected by the light receiving means;

Light intensity calculating means for obtaining a light intensity value of the interference light based on a signal corresponding to the light intensity of the interference light detected by the light receiving means, further comprising:

The gyro output operation means includes:

The calculation result is corrected and output according to the light intensity value of the interference light obtained by the light intensity calculation means.

An optical fiber gyro characterized by the above.

9. The optical fiber gyro according to claim 8, wherein

The gyro output operation means includes:

It has a table showing the correspondence between the light intensity value and the correction coefficient for correcting the scale factor error of the gyro output, and the light intensity of the interference light obtained by the light intensity calculating means shown in the table Corrects the calculation result according to the correction coefficient corresponding to the value and outputs it

An optical fiber gyro characterized by the above.

10. The optical fiber gyro according to claim 8, wherein

AGC signal generation means for generating an AGC (Automatic Gain Control) signal according to a difference between the light intensity value of the interference light obtained by the light intensity calculation means and a predetermined reference value,

Loop gain control means for controlling the gain of the signal detected by the light receiving means in accordance with the AGC signal generated by the AGC signal generation means.

An optical fiber gyro characterized by the above.

11. The optical fiber gyro according to claim 8, wherein the combined signal generating means is

(Second constant output signal generating means for generating a second constant output signal having an output value necessary to perform the phase shift of 5,

The first constant output signal generation means,

The output value of the first constant output signal is changed so that the value of Θ changes according to the light intensity value of the interference light obtained by the light intensity calculation means.

An optical fiber gyro characterized by the above.

12. The optical fiber gyro according to claim 11, wherein

The first constant output signal generation means,

It has a table showing the correspondence between the light intensity value and 0, and performs a phase shift of 対応 corresponding to the light intensity value of the interference light obtained by the light intensity calculation means shown in the table. Said first having the required output value Generate constant output signal of

An optical fiber gyro characterized by the above.

1 3. The optical fiber gyro according to claim 8, wherein

The light intensity calculation means includes:

When the phase shift by the composite signal of the various phase modulations is a + 0 + δ (or −α−θ−δ), the signal detected by the light receiving unit and the phase shift are a−0 ( Or -a + 0), the difference と from the signal detected by the light receiving means, and when the phase shift is a + Θ-δ (or -a-θ + δ), The difference の between the signal detected by the light receiving means and the signal detected by the light receiving means when the phase shift is a−0 (or −α + 0) is obtained, and the obtained difference X, The peak value of the interference light is determined as the light intensity value of the interference light based on Ζ.

An optical fiber gyro characterized by the above.

1 4. The optical fiber gyro according to claim 13, wherein

The light intensity calculation means includes:

The peak value of the light intensity of the light beam is indicated by Ρ. Then,

Ρ 0 = (X-Z) / (-sin δsin (end + 0))

To determine the peak value of the light intensity of the interference light

An optical fiber gyro characterized by the above.

1 5. The optical fiber gyro according to claim 8, wherein

The light intensity calculation means includes:

The phase shift by the combined signal of the various phase modulations is +0+ <5 (or the signal detected by the light receiving means when _−Ύ− θ−δ and the phase shift is +0 − At the time of δ (or −0−δ), a difference Υ from the signal detected by the light receiving means is obtained, and based on the obtained difference Υ, Find the peak value of the interference light as the light intensity value of the interference light

An optical fiber gyro characterized by the above.

16. The optical fiber gyro according to claim 15, wherein

The light intensity calculation means includes:

P is the peak value of the light intensity of the interference light. Then,

P 0 = Y / (-s i n δs i n (r + 0))

To determine the peak value of the light intensity of the interference light

An optical fiber gyro characterized by the above.

17. The optical fiber gyro according to claim 1, wherein

Switch means connected to the output side of the light receiving means,

Holding means connected to the output side of the switch means, and

The switch means includes:

Synchronizing with the rise and fall of the composite signal of various phase modulations generated by the composite signal generation unit, shuts off the output of the signal detected by the light receiving unit for a predetermined period,

The holding means,

The value of the signal sent from the light receiving means via the switching means is maintained for a predetermined time.

An optical fino gyro characterized by the above.

18. The optical fiber gyro according to claim 17, wherein

The holding means,

It is a filter consisting of a resistor and a capacitor

An optical fiber jay mouth characterized by the above.

1 9. The optical fiber gyro according to claim 1, wherein When the accumulation result of the modulation phase difference by the serodin signal reaches a first threshold value, the serodin signal generation means is reset so as to generate a phase shift of -2π, and When the accumulation result of the modulation phase difference due to the above reaches a second threshold value which is 27 ° lower than the first threshold value, the cellodyne signal generating means is reset so as to generate a phase shift of + 27 °. Additional resetting means

An optical fiber gyro characterized by the above.

20. The optical fiber gyro according to claim 19, wherein

The optical fiber gyro, wherein the first threshold is + π and the second threshold is −7 °.

21. The optical fiber gyro according to claim 19, wherein

The optical fiber gyro, wherein the first threshold is + 27t, and the second threshold is 0.

22. The optical fiber gyro according to claim 19, wherein

The modulation gain control means includes:

According to a signal corresponding to a modulation gain error generated by the modulation gain calculation means, the first constant output signal generation means, the second constant output signal generation means, and the third constant output signal generation The gain of the composite signal of the various phase modulations is controlled by adjusting the output value of each constant output signal generated by the means and the output value of the serodin signal generated by the serodin signal generation means. Things,

The adjustment of the output value of the serodin signal generated by the serodin signal generation means is performed according to a signal corresponding to the modulation gain error generated by the modulation gain calculation means, and The first and second thresholds and the amount of phase shift caused by the reset Done by adjusting,

The optical fino 'jay' mouth.

23. The optical fiber gyro according to claim 1, wherein

r = k π (where k is an integer of 1 or more)

k is an odd number: 0 <0 ≤ 7t / 2

k is even: 7T / 2≤S <π

Is

An optical fiber gyro characterized by the above.

24. The optical fiber gyro according to claim 23,

k is 1

An optical fiber gyro characterized by the above.

25. The optical fiber gyro according to claim 2, wherein

The bias modulation signal generation means includes:

The first constant output signal generated by the first constant output signal generation means is modulated to form a first constant output signal having a frequency of 1 / τ (where, however, the propagation time of light in the optical fiber loop) is a rectangular wave. First modulating means for generating a phase modulated signal;

The second constant output signal generated by the second constant output signal generating means is modulated to generate a second phase modulated signal in which a pulse having a pulse width of / 2 alternately appears at each time interval 2 τ. A second modulating means for generating;

Modulate the signal generated by the second addition means at a frequency of 1/2 τ Thus, the phase difference of the stigmatic light is given by α + θ + δ, -−θ, −7−θ−δ, −J

+ Θ, r + θ-δ, Ύ-θ,-τ-Θ i δ,-α + 6 », a series of steps in order, τ-、, τ i Θ + δ,-τ θ,- Ύ-θ _ δ, _ θ, r θ-δ, α + θ, -α-0 + (a series of steps in the order of 5, γ-Θ-δ, γ + θ,-r + θ +ステップ, -end_θ, γ-θ + δ, r + θ, -γ + θ-δ, -a-Θ, or a series of steps in the order of r + θ, γ-Θ-δ, -end -Θ ゝ-Τ i Θ +6, r + Θ r-Θ i 6, -end-θ, -a + δ A series of steps (period 4 and duration of each step / 2 ), And a third modulation means for generating a bias modulation signal for performing phase modulation so as to repeatedly perform

An optical fiber gyro characterized by the following.

26. The optical fiber gyro according to claim 3, wherein

The bias modulation signal generating means includes:

The first constant output signal generated by the first constant output signal generation means is modulated to form a first constant output signal having a rectangular wave having a frequency l / τ (where, at least, the propagation time of light in the optical fiber loop). First modulating means for generating a phase modulated signal;

The second constant output signal generated by the second constant output signal generating means is modulated to generate a second phase modulation signal in which a pulse having a pulse width τ / 2 alternately appears at each time interval 2 τ. A second modulating means for generating;

Modulate the signal generated by the second adding means at a frequency of 1/2 Here, the phase difference of the light beam is given by +6> + <5, τ_Θ, -7-θ-δ, -τIθ, α + 0-<5, 了 -θ, -Τ -Θ i δ,-end + 一連, a series of steps, Ύ-Θ, r θ δ,-end + θ,-θ-θ-δ, _ Θ, α + 0-δ,- Ύ,, -a -0 + (a series of steps in the order of 5, Ύ-Θ-δ, τ θ, -γ θ 6,-了-θ, r -θ δ, r θ, -r θ-δ , -A-0 or a series of steps, or Ύ-Θ -δ, -end -θ,-Ύ Θ

+ δ, r ^ θ, r-θ ^ δ,-Ύ-Θ,-丫 + Θ-δ Repeat a series of steps (period 4, duration of each step / 2) A third modulation means for generating a bias modulation signal for performing phase modulation as described above.

An optical fiber gyro characterized by this.

27. The optical fiber gyro according to claim 25, wherein

The sanitary phase difference calculating means includes:

First demodulating means for demodulating a signal detected by the light receiving means at 1 / th of the frequency;

Second demodulation means for demodulating the output of the first demodulation means at a frequency of 1 / 2τ,

By averaging the output of the second demodulation means for each time 2 τ or 4 τ and summing the outputs shifted by time, the output of the second demodulation means is adjusted according to the saniac phase difference of the interference light. Computing means for generating a signal,

The serodin signal is a step-like signal having a duration of t or t / 2.

An optical fiber gyro characterized by this.

28. The optical fiber gyro according to claim 26, wherein

The sanitary phase difference calculating means includes: First demodulating means for demodulating a signal detected by the light receiving means at a frequency of l / τ;

Second demodulation means for demodulating the output of the first demodulation means at a frequency of 1/2 τ,

By averaging the output of the second demodulation means every two or four times and taking the sum of the ones shifted by the time, a signal corresponding to the saniac phase difference of the interference light is obtained. Computing means for generating, and

The serodin signal is a stepped signal having a duration of τ or t / 2.

An optical fiber gyro characterized by the above.