JPH0961174A - Optical fiber gyro - Google Patents

Abstract

PROBLEM TO BE SOLVED: To simplify the structures of a signal processing system and an arithmetic system by increasing the period of a phase difference indicated by a specific formula larger than at least the specific magnification of the time required to propagate a light in an optical fiber loop. SOLUTION: The optical fiber gyro comprises X, Y and X optical fiber gyros for detecting the angular velocities around X-axis, Y-axis and Z-axis, and current-voltage converters 7-1 to 7-3 and phase modulators 8-1 to 8-3 of the respective optical fibers gyros. The gyro further comprises a multiplexer 13, a timing signal generator 9, a phase modulation signal generator 10, an A-D converter 11, and a CPU 12. The phase difference Δβ generated by the interference light intensity signal by the phase modulation of the three optical fiber gyros X, Y and X become, Δβ=π/2 for the first time τ of the one period τ, Δβ= Δβ-π/2 for the second time τ, and Δβ=-π/2 for the residual time τ, and the period T is larger than at least six times as large as the time τrequired for propagating in the optical fiber loop.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical fiber gyro device suitable for use as, for example, an angular velocity meter for aircraft, ships, automobiles, etc., and more particularly to an interferometric digital modulation type optical fiber gyro device.

[0002]

2. Description of the Related Art An optical fiber gyro is widely used as an apparatus for measuring an angular velocity, and has an advantage that it is small and highly reliable. The optical fiber gyro is configured to measure the angular velocity by utilizing the Sagnac effect of light (also referred to as Sagnac effect). The interference type optical fiber gyro includes a phase modulation system, a serrodyne modulation system, a digital modulation system, and the like. The digital modulation system has excellent characteristics such as good bias characteristics and suitable for a digital arithmetic system.

A conventional digital modulation type optical fiber gyro will be described with reference to FIG. The digital modulation type optical fiber gyro is disclosed in Japanese Patent Application No. 4-283223 filed on Oct. 21, 1992 by the same applicant as the present applicant, and the details are the same. See application. The optical fiber gyro device includes a light emitter 1 such as a semiconductor laser and a light emitting diode, a light receiver 2 for converting detection light into current, an optical fiber loop 3 formed by winding one optical fiber a plurality of times, and a polarizer 4. It has first and second couplers 5 and 6 for combining or splitting light propagating through an optical fiber, and a phase modulator 8 provided at one end of the optical fiber loop 3.

The light output from the light emitter 1 passes through the first coupler 5 and the polarizer 4, and is branched into two propagating lights by the second coupler 6 and propagates in the optical fiber loop 3 in opposite directions. . That is, one propagates rightward in the optical fiber loop 3 and the other propagates counterclockwise.

When the angular velocity Ω is applied to the optical fiber loop 3 from the outside, the optical fiber loop 3 is caused by the Sagnac effect.
A phase difference Δθ occurs between lights propagating in the opposite directions. Such a phase difference Δθ is called a Sagnac phase difference,
It is proportional to the angular velocity Ω and is expressed by the following equation.

[0006]

Equation 1 Δθ = (2πDL / λc) Ω

Here, D is the loop diameter of the optical fiber loop 3, L is the length of the optical fiber loop 3, λ is the wavelength of the light output from the light emitter 1, c is the speed of light, and Ω is the optical fiber loop 3. It represents the angular velocity about the central axis of the loop.

The light propagating rightward and the light propagating counterclockwise in the optical fiber loop 3 are respectively phase-modulated by the phase modulator 8. The light E _C propagating clockwise in the optical fiber loop 3 and the light E _CC propagating counterclockwise are expressed as follows at both ends of the optical fiber loop 3.

[0009]

## EQU2 ## E _C = E ₀ sin (ωt−Δθ / 2 + β ₀ ) E _CC = E ₀ sin (ωt + Δθ / 2 + β _T )

Where E ₀ is the amplitude, ω is the angular frequency with respect to the frequency of the light, t is the time, Δθ / 2 is the phase difference caused by the Sagnac effect, and β ₀ and β _T are generated by the phase modulator 8. It is a phase difference. The phase difference β ₀ of the light E _C propagating in the clockwise direction is generated by propagating in the clockwise direction in the optical fiber loop 3 and then phase-modulated at the exit of the optical fiber loop 3. The phase difference β _T of E _CC is generated in the light that propagates in the counterclockwise direction through the optical fiber loop 3 after being phase-modulated at the entrance of the optical fiber loop 3.

The two propagating lights E _C and E _CC are combined by the second coupler 6 to generate interference light. Such interference light is detected by the light receiver 2 via the first coupler 5 and the polarizer 4. The intensity I of the interference light detected by the light receiver 2 is represented by the following equation.

[0012]

## EQU3 ## I = 2E ₀ ² [1 + cos (Δθ + β _T −β ₀ )] = 2E ₀ ² [1 + cos (Δθ + Δβ)] = I ₀ (1 + cosx)

However, Δβ = β _T −β ₀ , x = Δθ + Δβ
It is. I ₀ = 2E ₀ ² . Δθ is the Sagnac phase difference generated by the external force angular velocity Ω, and Δβ is the phase modulator 8
Is the phase difference generated by.

According to the digital modulation method, the phase difference Δβ generated in the intensity I of the interference light by the phase modulator 8 is
It is a rectangular wave that alternates between Δβ ₁ = + π / 2 and Δβ ₂ = −π / 2 for each time τ. Therefore, the interference light intensity signal I
Is expressed as follows by substituting Δβ = ± π / 2 into the expression of Equation 3.

[0015]

I ₁ = I ₀ {1 + cos (Δθ + Δβ ₁ )} = I ₀ {1 + cos (Δθ + π / 2)} = I ₀ (1-sin Δθ) I ₂ = I ₀ {1 + cos (Δθ + Δβ ₂ )} = I ₀ {1 + cos (Δθ−π / 2)} = I ₀ (1 + sin Δθ)

From this, the difference ΔI in the intensity I of the interference light when the phase difference is Δβ ₁ = + π / 2 and Δβ ₂ = −π / 2.
= I ₂ −I ₁ is calculated.

[0017]

ΔI = I ₂ −I ₁ = I ₀ (1 + sin Δθ) −I ₀ (1-sin Δθ) = 2I ₀ sin Δθ

The constant I ₀ can be obtained in advance from the intensity I of the interference light when the Sagnac phase difference Δθ = 0 and the phase difference Δβ = 0. Thus, according to the digital modulation method, the phase modulator 8 generates the phase difference Δβ = ± π / 2 in the interference light I which changes every time τ, and the phase difference Δβ ₁ = +.
The Sagnac phase difference Δθ is calculated by measuring the difference ΔI between the light intensity I ₁ at π / 2 and the light intensity I ₂ at Δβ ₂ = −π / 2, and performing the backward calculation of the equation (5). Can be asked.

The digital modulation method will be described in detail with reference to FIGS. According to the digital modulation method, the right-handed light E _C is phase-modulated so that the phase difference β ₀ thereof becomes a periodic rectangular wave having a period 2τ and an amplitude π / 4 as shown in FIG. The light E _CC is phase-modulated so that the phase difference β _T becomes a periodic rectangular wave having a period 2τ and an amplitude π / 4 as shown in FIG. 7B. Although the phase difference beta _T of light E _CC around the left have the same rectangular wave and the waveform of the phase difference of light E _C around the right, it is delayed by time τ with respect to the phase difference of the light E _C around right .

Thus, the difference between the phase difference β _{0 of the} right-handed light E _C and the phase difference β _T of the left-handed light E _CC , that is, the phase difference Δβ =
β ₀ −β _T alternates with + π every time τ as shown in FIG. 7C.
It becomes a rectangular wave that changes to / 2 and -π / 2.

FIG. 7D shows the waveform of the phase x = Δθ + Δβ in the equation (3). When the angular velocity Ω does not work in the optical fiber gyro, Δθ = 0, so the waveform of the phase x in FIG. 7D is shown in FIG. 7C.
Coincides with the phase difference Δβ.

Next, referring to FIG. 8, the intensity of the interference light I ₁ , Δβ ₂ = −π / 2 when the phase difference Δβ is Δβ ₁ = + π / 2, using the equation (3). A method of obtaining the intensity I ₂ of the interference light in the case of is shown.

FIG. 8A is a graph of the equation (3), which is often used to express the relationship between the phase difference x and the light intensity I. In such a graph, the horizontal axis represents the phase difference x (= Δθ + Δβ), and the vertical axis represents the intensity I (x) of the interference light. 8B and 8C shown on the lower side of FIG. 8A, the horizontal axis (vertical axis direction of FIG. 8A) is time, and the vertical axis (horizontal axis direction of FIG. 8A) is phase x (= Δθ + Δ).
β). 8D and 8E shown on the right side of FIG. 8A.
Is the horizontal axis (horizontal axis direction of FIG. 8A) is time, and the vertical axis (vertical axis direction of FIG. 8A) is intensity I of the interference light.

FIG. 8B shows a waveform of the phase x (= Δθ + Δβ) when the Sagnac phase difference Δθ = 0, and corresponds to the waveform of FIG. 7C. FIG. 8D shows the intensity I of the interference light in such a case.
Represents Similarly, FIG. 8C shows the waveform of the phase x (= Δθ + Δβ) when the Sagnac phase difference Δθ ≠ 0, and corresponds to the waveform of FIG. 7D. FIG. 8E shows the intensity I of the interference light in such a case.

When the Sagnac phase difference Δθ = 0, even if the value of the phase x changes alternately between + π / 2 and −π / 2 as shown in FIG. As shown in 8D, it becomes a constant value (excluding spike-shaped protrusions). However, when the Sagnac phase difference Δθ ≠ 0,
As shown in C, the value of the phase x is alternately Δθ−π every time τ.
, And Δθ + π / 2, and at this time, the intensity I of the interference light
As shown in Figure 8E (excluding spikes)
Alternates every time τ.

In FIG. 8D, the value of the intensity I of the interference light has a spike-shaped protrusion at every time τ, and the value of the phase x shown in the waveform of FIG. 8B is -π / 2 and + π / 2. This is because the intensity I of the interference light of the sine wave in FIG. 8A increases when changing between and. Similarly, in FIG. 8E, the value of the intensity I of the interference light has a spike-shaped protrusion at each time τ, because the value of the phase x shown in the waveform of FIG. 8C is Δθ−π / 2 and Δθ + π / Intensity I of the sinusoidal interference light of FIG.
Is increased.

The high level of the rectangular wave of FIG. 8E represents the intensity I ₂ of the interference light when the phase x = Δθ−π / 2,
The low level of the rectangular wave represents the intensity I ₁ of the interference light when the phase x = Δθ + π / 2. Therefore, the difference between the high level and the low level of the rectangular wave in FIG. 8E corresponds to the deviation Δ = I ₂ −I ₁ of the intensity of the interference light.

That is, the magnitude of the difference between the high level and the low level of the rectangular wave in FIG. 8E represents the right side of the equation (5). Thus, in the digital modulation method, a rectangular wave having the intensity I of the interference light of FIG. 8E is generated from the sine wave showing the intensity I of the light of FIG. 8A, and a number is calculated from the difference between the high level and the low level of the rectangular wave. Δθ is obtained by the equation of 5.

Referring again to FIG. The optical fiber gyro of this example further includes a timing signal generator 9, a phase modulation signal generator 10, an AD converter 11, and a signal processor 12. The timing signal generator 9 generates a timing signal having a period τ and supplies it to the phase modulation signal generator 10 and the signal processor 12. The phase modulation signal generator 10 includes the phase differences β ₀ , β _T , as shown in FIGS. 7A, 7B and 7C.
Generate a phase modulator drive signal to generate Δβ.

On the other hand, the A / D converter 11 inputs the voltage signal (shown in FIGS. 8D and 8E) from the current-voltage converter 7 to generate a digital signal indicating the intensity I of the interference light,
The values I ₁ and I ₂ are supplied to the signal processing unit 12.

FIG. 9 shows a configuration example of the signal processing unit 12. The signal processing unit 12 operates on the basis of the timing signal from the timing signal generator 9, and the first and second gate circuits 20 that alternately store _two digital values I ₁ and I ₂ based on the operation of the gate circuit 20. Registers 21A and 21B
And a subtraction unit 23 for performing the subtraction of the formula 5 and a calculation unit 25 for performing the calculation of the formula 1.

[0032]

The optical fiber gyro is constructed so as to detect the angular velocity Ω around the central axis of the optical fiber loop 3. When detecting the angular velocity in the three axial directions, three optical fiber gyros are used. Are used so that the central axes of the optical fiber loops 3 are orthogonal to each other.

Therefore, each optical fiber gyro is connected to the timing signal generator 9, the phase modulation signal generator 10 and the timing signal generator 10, respectively.
The D converter 11 and the signal processing unit 12 are provided, and these are provided in an overlapping manner.

In view of the above point, the present invention aims to simplify the structure of a signal processing system and a computing system in an optical fiber gyro device including three optical fiber gyros for detecting angular velocities in three axial directions. And

[0035]

According to the present invention, an X optical fiber gyro that measures an angular velocity about an X axis, a Y optical fiber gyro that measures an angular velocity about a Y axis, and a Z light that measures an angular velocity about a Z axis. A fiber gyro, and each of the three optical fiber gyros has a light source, an optical fiber loop, and a phase for phase-modulating first and second propagating lights propagating in opposite directions in the optical fiber loop. A modulator and a photodetector for detecting the interference light of the first and second propagation lights are provided, and the angular velocity Ω is obtained from the Sagnac phase difference Δθ generated in the interference light. In the optical fiber gyro device, the phase difference Δβ generated in the intensity signal of the interference light by the phase modulation in each of the three optical fiber gyros is Δβ at the first time τ in one cycle T. = Π / 2 and Δβ = −π / 2 during the second time τ and 0 during the remaining time T−2τ, and the period T is at least 6 times the time τ required for light to propagate through the optical fiber loop. Characterized by being larger.

According to the present invention, in the optical fiber gyro device, the intensity signal I _{1 of the} interference light and the second signal of the interference light at the first time τ in the one cycle T in each of the three optical fiber gyros are provided. It is characterized in that the Sagnac phase difference Δθ is obtained from the difference ΔI of the intensity signal I ₂ of the interference light at time τ.

According to the present invention, in the optical fiber gyro device, the calculation for obtaining the Sagnac phase difference Δθ from the difference ΔI between the intensity signals I ₁ and I ₂ of the two interference lights is the rest of the one cycle T. Is performed at time T−2τ.

According to the present invention, in the optical fiber gyro device, the phase difference Δβ _X generated in the intensity signal of the interference light in the X optical fiber gyro and the intensity signal of the interference light in the Y optical fiber gyro are generated. The phase difference Δβ _Y and the phase difference Δβ _Z generated in the intensity signal of the interference light in the Z optical fiber gyro have the same waveform and are different in phase by time 2τ.

According to the present invention, in the optical fiber gyro device, an A / A system for sequentially inputting signals from the respective photodetectors of the above three optical fiber gyros through the multiplexer
Sequentially storing the output signals of the D converter and the A / D converter 3
A difference ΔI between the intensity signals I ₁ and I ₂ of the above two interference lights is obtained by inputting and subtracting the output signals of the pair of registers and the pair of registers.
It is characterized in that it has three subtraction units for calculating and three calculation units for calculating the angular velocity from the output signals of the three subtraction units.

According to the present invention, the light source, the optical fiber loop, and the phase modulator for phase-modulating the first and second propagating lights propagating in the optical fiber loop in mutually opposite directions,
An optical fiber gyro having a light receiver for detecting interference light of the first propagation light and the second propagation light, and configured to obtain an angular velocity Ω from a Sagnac phase difference Δθ generated in the interference light. , The phase difference Δβ generated in the intensity signal of the interference light by the phase modulation becomes Δβ = π / 2 in the first time τ of one cycle T, and becomes Δ in the second time τ.
β = −π / 2 and 0 during the remaining time T−2τ,
The period T is characterized by being greater than at least twice the time τ required for light to propagate through the optical fiber loop.

In each optical fiber gyro, the phase modulator 8 produces a phase difference Δβ in the intensity signal I of the interference light. The phase difference Δβ is the first time τ in one cycle T.
It changes to π / 2 and -π / 2 alternately every time, and the remaining time T-2
It is a signal that becomes 0 at τ. One cycle T is larger than twice the time τ required for light to propagate through the optical fiber loop 3.

Interference light in three optical fiber gyros
Difference Δβ generated in the strength signal _X, Δβ_Y, Δβ_Z
Have the same waveform and are in phase with each other for a time 2τ.
different. Therefore, an X optical fiber gyro and a Y optical fiber gyro
Dried from each of the gyro and the Z fiber optic gyro
The intensity of the light is transmitted by one signal processing system and arithmetic system.
Can be processed.

The phase modulator drive signal supplied to each phase modulator of the X optical fiber gyro, the Y optical fiber gyro and the Z optical fiber gyro can be generated by one phase modulation signal generator. Further, the timing signal supplied to the signal processing system and the arithmetic system can be generated by one timing signal generator.

[0044]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows the main part of an optical fiber gyro device according to the present invention. The optical fiber gyro device of the present invention includes an X optical fiber gyro for detecting an angular velocity about the X axis, a Y optical fiber gyro for detecting an angular velocity about the Y axis, and a Z for detecting an angular velocity about the Z axis.
As shown in FIG. 6, each optical fiber gyro has an optical fiber gyro, and each optical fiber gyro includes a light emitter 1 as a light source, a light receiver 2, an optical fiber loop 3, a polarizer 4, two couplers 5 and 6, and a current-voltage converter. And a container 7. FIG. 1 shows current-voltage converters 7-1, 7-2, 7-3 and phase modulators 8-1, 8-2, 8-3 of each optical fiber gyro.

The optical fiber gyro device according to this embodiment further includes a multiplexer 13, a timing signal generator 9, a phase modulation signal generator 10, an A / D converter 11 and a signal processor (C).
PU) 12.

The digital modulation method according to this embodiment will be described with reference to FIG. FIG. 2 shows the phase difference in the X optical fiber gyro. According to this example, the phase difference β ₀ of the light E _C propagating clockwise in the optical fiber loop 3 is a rectangular wave pulse having a period T of π / 2 at time τ, as shown in FIG. 2A. The time τ is the time required for light to propagate through the optical fiber loop 3. The period T is at least more than twice the time τ, preferably more than six times. The phase difference β of the light E _CC propagating counterclockwise in the optical fiber loop 3
_As shown in FIG. 2B, _T becomes a rectangular wave pulse delayed by time τ from the rectangular wave pulse of FIG. 2A.

Therefore, the phase difference Δβ = β ₀ -β _T generated in the intensity signal I _P of the interference light is 1 cycle T as shown in FIG. 2C.
At the first time τ of Δβ = π / 2, and at the next time τ of Δβ
= −π / 2, and Δβ = 0 during the remaining time T−2τ.
When an external force angular velocity is applied, a Sagnac phase difference Δθ occurs, and the phase difference x of the intensity signal I _P of the interference light is x = Δθ + Δβ, as shown in FIG. 2D.

The interference light at the first time τ of one cycle T
I for strength signal₁, The intensity signal of the interference light at the next time τ
To I₂Then, the above equation (4) is established. 1 cycle T
Of the intensity signal of the interference light in the remaining time T-2τ of_Three
Then, the intensity signal of the interference light is I_ThreeIn the formula of Equation 3
It is obtained by substituting 0. The intensity signal of such interference light
I ₁, I₂, I_ThreeIs expressed as follows.

[0049]

I ₁ = I ₀ {1 + cos (Δθ + Δβ ₁ )} = I ₀ {1 + cos (Δθ + π / 2)} = I ₀ (1-sin Δθ) I ₂ = I ₀ {1 + cos (Δθ + Δβ ₂ )} = I ₀ {1 + cos (Δθ−π / 2)} = I ₀ (1 + sin Δθ) I ₃ = I ₀ (1 + cos Δθ)

Therefore, in this example, similarly, 2 in the equation (6) is obtained.
The equation (5) is obtained from one equation. Therefore, the Sagnac phase difference Δθ can be obtained from the ΔI difference between I ₁ and I ₂ of the _two intensity signals of the interference light.

FIG. 3 is a graph of the equation (3) similar to FIG. 8, showing the relationship between the phase difference x and the light intensity I. With reference to FIG. 3, the phase difference Δβ is Δ
Intensity I ₁ of interference light when β ₁ = + π / 2, Δβ ₂ = −
A method of obtaining the intensity I ₂ of the interference light at π / 2 will be described.

In this graph, the horizontal axis represents the phase x (= Δθ
+ Δβ), and the vertical axis represents the intensity I (x) of the interference light. Figure 3A
3B and 3C shown on the lower side of FIG. 3, the horizontal axis (vertical axis direction of FIG. 3A) represents time, and the vertical axis (horizontal axis direction of FIG. 3A) represents phase x.
(= Δθ + Δβ). FIG. 3 shown on the right side of FIG. 3A
In D and FIG. 3E, the horizontal axis (horizontal axis direction in FIG. 3A) is time, and the vertical axis (vertical axis direction in FIG. 3A) is interference light intensity I.

FIG. 3B shows the waveform of the phase x (= Δθ + Δβ) when the Sagnac phase difference Δθ = 0, and corresponds to the waveform of FIG. 2C. FIG. 3D shows the intensity I of the interference light in such a case.
Represents Similarly, FIG. 3C shows the waveform of the phase x (= Δθ + Δβ) when the Sagnac phase difference Δθ ≠ 0, and corresponds to the waveform of FIG. 2D. FIG. 3E shows the intensity I of the interference light in such a case.

When the Sagnac phase difference Δθ = 0, the value of the phase x is + π / 2 during one period T as shown in FIG. 3B.
And becomes −π / 2, and then becomes 0, and the intensity I of the interference light becomes constant values I ₀ and 2I ₀ (excluding spike-like protrusions), as shown in FIG. 3D. However, when the Sagnac phase difference Δθ ≠ 0, as shown in FIG. 3C, the value of the phase x is alternately Δθ− every time period τ during one period T.
After changing to π / 2 and Δθ + π / 2, it becomes Δθ. At this time, the intensity I of the interference light changes alternately every time τ (excluding spike-like protrusions), as shown in FIG. 3E. It becomes a predetermined value I ₀ (1 + cos Δθ).

In FIG. 3D, the value of the intensity I of the interference light has a spike-like protrusion between two times τ, that the value of the phase x shown in the waveform of FIG. 3B is −π / 2. This is because the intensity I of the interference light of the sine wave in FIG. 3A increases when changing between + π / 2. Similarly, in FIG. 3E, the intensity I of the interference light is
Has a spike-like protrusion between two times τ because the value of the phase x shown in the waveform of FIG. 3C is Δθ−π / 2.
This is because the intensity I of the interference light of the sine wave in FIG. 3A increases when changing between Δθ + π / 2 and Δθ + π / 2.

The rectangular wave of FIG. 3E has a predetermined value I ₀ (1 + cos).
Δθ) is the intensity I of the interference light when the phase x = Δθ
₃ represents the high-level phase x = Δθ−π / 2
The intensity I ₂ of the interference light is expressed as follows, and the low level of the rectangular wave is the intensity I ₁ of the interference light when the phase is x = Δθ + π / 2. Therefore, the difference between the high level and the low level of the rectangular wave in FIG. 3E corresponds to the deviation Δ = I ₂ −I ₁ of the intensity of the interference light.

That is, the magnitude of the difference between the high level and the low level of the rectangular wave in FIG. 3E represents the right side of the equation (5). Thus, in the digital modulation method of this example, a rectangular wave having the intensity I of the interference light of FIG. 3E is generated from the sine wave showing the intensity I of the light of FIG. 3A, and the high level and the low level of the rectangular wave are generated. From the difference, Δθ can be obtained by the equation of Formula 5.

Although the X optical fiber gyro has been described above, the light propagating through the optical fiber loop 3 is also phase-modulated in the Y optical fiber gyro and the Z optical fiber gyro.

Phase modulation of three optical fiber gyros will be described with reference to FIG. FIG. 4A shows the waveform of the phase difference Δβ _X of the intensity signal I _X of the interference light in the X optical fiber gyro, and is the same graph as FIG. 2C. FIG. 4B shows the phase difference Δ of the intensity signal I _Y of the interference light in the Y optical fiber gyro.
4C shows the waveform of β _Y , and FIG. 4C shows the waveform of the phase difference Δβ _Z of the intensity signal I _Z of the interference light in the Z optical fiber gyro.

As shown, such three fiber optic gyros are phase modulated to produce identical phase difference waveforms. However, the phase difference waveforms Δβ _X , Δβ _Y , and Δβ _Z of the three optical fiber gyros are delayed by 2τ from each other.

In this example, the period T of the phase difference Δβ is 6τ, but the period T may be larger than 6τ as described above. Thus, the three phase difference waveforms Δβ _X , Δβ _Y , and Δβ
The phases of _Z are delayed by 2τ from each other, and the cycle T is set to 6
By making it larger than τ, as explained later,
The intensity signals of the three interference lights are converted into one signal processing system, for example, 1
It can be processed by one A / D converter.

According to this example, the first time 2τ of one cycle T is
The phase difference Δβ = ± π / 2 is generated in the intensity signal I of the interference light at, and the Sagnac phase difference Δθ is calculated at the remaining time T−2τ. The period T does not have to be constant and may be different each time. Therefore, the time T-2τ for calculating the Sagnac phase difference Δθ can be freely set.

In the above, the case where the XYZ triaxial optical fiber gyro is included has been described. However, when only the uniaxial optical fiber gyro is used, the period T may be larger than 2τ.

Referring again to FIG. The timing signal generator 9 generates a timing signal having a period T and a timing signal having a period τ, and supplies the timing signal to the multiplexer 13, the phase modulation signal generator 10 and the signal processor 12. The phase modulation signal generator 10 includes a phase modulator 8-1, Y of an X optical fiber gyro.
The modulator drive signal is supplied to the phase modulator 8-2 of the optical fiber gyro and the phase modulator 8-3 of the Z optical fiber gyro, respectively. The light propagating in the optical fiber loop 3-1 of the X optical fiber gyro is phase-modulated by the X-axis phase modulator 8-1, and the light propagating in the optical fiber loop 3-2 of the Y optical fiber gyro is Y-axis phase modulated. The light phase-modulated by the modulator 8-2 and propagating through the optical fiber loop 3-3 of the Z optical fiber gyro is phase-modulated by the phase modulator 8-3.

A phase difference Δβ _{X as} shown in FIG. 4A is generated in the intensity signal I _PX of the interference light in the X optical fiber gyro, and the intensity signal I of the interference light I I in the Y optical fiber gyro.
_The phase difference Δβ _{Y as} shown in FIG. 4B is generated in _PY, and the intensity signal I _PZ of the interference light is generated in the Z optical fiber gyro as shown in FIG. 4C.
A phase difference Δβ _{Z as} shown in is generated.

Current-voltage converter 7 of each optical fiber gyro
Input signal I of -1, 7-2, 7-3 _PX, I_PY, I_PZIs a number
The phase difference Δβ is represented by
Waveform Δβ in FIG. 4A_X, The waveform Δβ of FIG. 4B_Y, The wave in Figure 4C
Shape Δβ_ZIt is.

The current signal representing the intensity of the interference light is converted into a voltage signal by the current / voltage converters 7-1, 7-2 and 7-3. The multiplexer 13 inputs the timing signal from the timing signal generator 13 and sequentially outputs the output signals of the three current-voltage converters 7-1, 7-2, 7-3 to A /
It is supplied to the D converter 11.

The A / D converter 11 inputs the output signal V _PX of the X-axis current-voltage converter 7-1 at the first time 2τ of one cycle T, and Y at the next time 2τ of one cycle T, for example. The output signal V _PY of the axis current-voltage converter 7-2 is input, and the output signal V _PZ of the Z-axis current voltage converter 7-3 is input at the next time 2τ of one cycle T.

The A / D converter 11 is shown in FIGS. 3D and 3E.
Generates a digital signal indicating the magnitude of a rectangular wave signal
I do. That is, the intensity signal of the interference light expressed by the equation (6)
Issue I ₁, I₂The digital values of are sequentially generated. Such
The output signal of the A / D converter 11 is supplied to the signal processing unit 12.
It is.

The configuration and operation of the signal processing unit 12 will be described with reference to FIG. The signal processing unit 12 of this example is the gate circuit 1
2-1 and three pairs of registers 12-2A to 12-2F, three subtraction units 12-3A, 12-3B, 12-3C and three calculation units 12-4A, 12-4B, 12-4C. .

The gate circuit 12-1 sequentially outputs the output signal of the A / D converter 11 according to the timing signal supplied from the timing signal generator 9 into six registers 12-2A-1.
Supply to 2-2F.

For example, at the first time τ of one cycle T, the digital value I _X1 of the intensity of the interference light in the X optical fiber gyro is registered in the first register 12-2A, and one cycle T
At time τ next to, the digital value I _X2 of the intensity of the interference light in the X optical fiber gyro is stored in the second register 12-2B.
Registered in. Similarly, at the third time τ of one cycle T, Y
The digital value I _Y1 of the intensity of the interference light in the optical fiber gyro is registered in the third register 12-2C, and the digital value I _Y2 of the intensity of the interference light in the Y optical fiber gyro is registered at the next time τ of one cycle T. Is the fourth register 12-2
Registered in D. Similarly, at the fifth time τ of one cycle T, the digital value I _Z1 of the intensity of the interference light in the Z optical fiber gyro is registered in the fifth register 12-2E, and at the next time τ of the one cycle T, Z. The digital value I _Z2 of the intensity of the interference light in the optical fiber gyro is the sixth register 12-
Registered on the 2nd floor.

Each of the registers 12-2A to 12-2F sequentially subtracts the recorded value for each cycle T from the subtraction units 12-3A and 12-3.
B, 12-3C. The three subtracting units 12-
3A, 12-3B, and 12-3C each have a difference Δ in the intensity of interference light in each optical fiber gyro according to the equation (5).
I _X , ΔI _Y , and ΔI _Z are calculated. This is expressed as:

[0074]

Equation 7] _{ΔI X = I X2 -I X1 =} I X0 (1 + sinΔθ X) -I X0 (1-sinΔθ X) = 2I X0 sinΔθ X ΔI Y = I Y2 -I Y1 = I Y0 (1 + sinΔθ Y) -I _Y0 (1-sin Δθ _Y ) = 2I _Y0 sin Δθ _Y ΔI _Z = I _Z2 −I _Z1 = I _Z0 (1 + sin Δθ _Z ) −I _Z0 (1-sin Δθ _Z ) = 2I _Z0 sin Δθ _Z

Each computing unit 12-4A, 12-4B, 12-
4C inputs the difference signals ΔI _X , ΔI _Y , and ΔI _Z of the intensity of the interference light in each optical fiber gyro supplied from each subtraction unit 12-3A, 12-3B, 12-3C. Then, the Sagnac phase differences Δθ _X , Δθ _Y , and Δθ _Z are obtained, and the triaxial angular velocities Ω _X , Ω _Y , and Ω _Z are obtained by the equation (1).

Referring again to FIG. 4, each subtracting section 12-3A,
Subtraction in 12-3B and 12-3C and each calculation unit 12
Calculation timings in -4A, 12-4B, and 12-4C will be described. The first and second registers 12-2A,
12-2B takes in the intensity signals I _X1 and I _X2 of the interference light in the X optical fiber gyro at the first time 2τ of one cycle T, respectively, and takes the first at the remaining time T-2τ of one cycle T.
Subtraction unit 12-3A and the first calculation unit 12
-4A is calculated.

For example, the first and second registers 12-2
When the new signals I _X1 and I _X2 are supplied, the A and 12-2B supply the held signals I _X1 and I _X2 to the first and second subtraction units 12-3A, respectively, and one cycle T The new signals I _X1 and I _X2 are supplied until the next signals I _X1 and I _X2 are supplied.
Hold. Meanwhile, the first subtraction unit 12-3A and the first calculation unit 12-4A perform respective calculations from the supplied signals I _X1 and I _X2 . Repeat this. Third to sixth registers 12-2C to 12-2F and second and third subtraction units 12-3B and 12- connected to them.
The same applies to the operations of 3C and the arithmetic units 12-4B and 12-4C.

Although the embodiments of the present invention have been described above, it will be apparent to those skilled in the art that various other examples can be made without departing from the scope of the present invention.

[0079]

According to the present invention, in the optical fiber gyro device for detecting the angular velocities around the three axes of XYZ, one A / D converter and one signal processing unit are used.
There is an advantage that the angular velocity around the axis can be calculated.

According to the present invention, in the optical fiber gyro device including three optical fiber gyros for detecting the angular velocities around the three axes of XYZ, the timing signal for generating the signal to be supplied to each phase modulator is set to 1. Since it is generated by one timing signal generator, there is an advantage that the device can be downsized and the cost can be saved.

According to the present invention, the period T of the phase difference Δβ does not have to be constant, and may be a different value each time or a sufficiently large value. Therefore, an inexpensive timing signal generator can be used. Further, since it is possible to take a sufficiently long time to calculate the angular velocity Ω, there is an advantage that an inexpensive CPU can be used as a calculation device.

[Brief description of drawings]

FIG. 1 is a diagram showing a main part of an optical fiber gyro device according to the present invention.

FIG. 2 is a diagram showing a waveform of a phase difference of interference light in the optical fiber gyro device according to the present invention.

FIG. 3 is a diagram showing the relationship between the intensity of interference light and the phase difference.

FIG. 4 is a diagram showing waveforms of phase differences generated by a phase modulator in three optical fiber gyros.

FIG. 5 is a diagram showing an example of a signal processing unit of an optical fiber gyro device according to the present invention.

FIG. 6 is a diagram showing an example of a main part of a conventional optical fiber gyro.

FIG. 7 is a diagram showing a waveform of a phase difference of a conventional optical fiber gyro.

FIG. 8 is a diagram showing the relationship between the intensity of interference light and the phase difference of a conventional optical fiber gyro.

FIG. 9 is a diagram showing a configuration example of a conventional optical fiber gyro.

[Explanation of symbols]

 1 light source 2 light receiver 3 optical fiber loop 4 polarizer 5, 6 coupler 7 current-voltage converter 8 phase modulator 9 timing signal generator 10 phase modulation signal generator 11 A / D converter 12 signal processor (CPU)

Claims (6)

[Claims] 1. An X optical fiber gyro for measuring an angular velocity about an X axis, a Y optical fiber gyro for measuring an angular velocity about a Y axis, and a Z optical fiber gyro for measuring an angular velocity about a Z axis, wherein Each of the two optical fiber gyros includes a light source, an optical fiber loop, a phase modulator that phase-modulates first and second propagating lights propagating in the optical fiber loop in mutually opposite directions, and the first propagation. Light and second
And a light receiver for detecting interference light of the propagating light, and an optical fiber gyro device configured to obtain an angular velocity Ω from a Sagnac phase difference Δθ generated in the interference light. In each case, the phase difference Δβ generated in the intensity signal of the interference light by the phase modulation is Δβ = π / 2 in the first time τ of one cycle T, and Δβ = −π / 2 in the second time τ. And 0 for the remaining time T−2τ, and the period T is at least 6 times longer than the time τ required for light to propagate through the optical fiber loop. 2. A fiber optic gyroscope according to claim 1, wherein the three above and intensity signal I ₁ of the interference light in the first time τ of the one period T in each of the optical fiber gyro second 2. The optical fiber gyro device, wherein the Sagnac phase difference Δθ is obtained from the difference ΔI of the intensity signal I ₂ of the interference light at the time τ of ₂ . 3. The optical fiber gyro device according to claim 1 or 2, wherein the calculation for obtaining the Sagnac phase difference Δθ from the difference ΔI between the intensity signals I ₁ and I ₂ of the two interference lights is performed in the one cycle T. An optical fiber gyro device characterized by performing the remaining time T-2τ. 4. The optical fiber jig according to claim 1, 2 or 3.
In the gyro device, the X optical fiber gyro
Phase difference Δβ generated in the intensity signal of the interference light_XAnd Y above
Intensity of interference light generated in optical fiber gyro
Phase difference Δβ_YAnd in the above Z optical fiber gyro
Phase difference Δβ generated in the intensity signal of the interference light _ZAnd each other
It has the same waveform and is different in phase for time 2τ.
Fiber optic gyro device as a characteristic. 5. The optical fiber gyro device according to claim 1, 2, 3 or 4, and an A / D converter for sequentially inputting signals from respective photo detectors of said three optical fiber gyros via a multiplexer. The difference ΔI between the intensity signals I ₁ and I ₂ of the two interference lights is input by inputting and subtracting the output signals of the three pairs of registers and the three pairs of registers that sequentially store the output signals of the A / D converter. Seeking 3
An optical fiber gyro device having one subtraction unit and three calculation units for calculating an angular velocity from output signals of the three subtraction units. 6. A light source, an optical fiber loop, and first and second propagating in the optical fiber loop in mutually opposite directions.
From the Sagnac phase difference Δθ generated in the interference light, and a phase modulator that phase-modulates the propagation light of 1) and a light receiver that detects the interference light of the first propagation light and the second propagation light. In the optical fiber gyro configured to calculate Ω, the phase difference Δβ generated in the intensity signal of the interference light by the phase modulation is Δβ = at the first time τ in one cycle T.
It becomes π / 2 and Δβ = −π / 2 during the second time τ and 0 during the remaining time T−2τ, and the period T is at least twice the time τ required for light to propagate through the optical fiber loop. An optical fiber gyro characterized by being large.