JPH06103187B2 - Optical interference gyro - Google Patents

Description

TECHNICAL FIELD The present invention relates to an optical interferometric angular velocity meter of a null method serrodyne modulation system.

"Prior Art" As a wide dynamic range and low drift optical interference gyro, on one end side and the other end side of the optical fiber coil,
A biasing phase modulator and a ramp phase modulator each having a pair of electrodes formed on the optical waveguide are provided, and a biasing voltage and a ramp voltage are applied to the biasing phase modulator and the ramp phase modulator, respectively. While providing a phase difference between the two lights propagating through the optical fiber coil, the phase difference between the two lights propagating through the optical fiber coil and interfering is detected from the output of the photodetector, and by the detected output, It is considered that the polarity and frequency of the lamp voltage are controlled so that the phase difference becomes a predetermined value.

FIG. 8 is an example of a conventional optical interference gyro of the zero-position serrodyne modulation system, which is a case of the linear phase ramp system.

The light 1 from the light source 11 is supplied to the optical splitter / coupler 15 through the optical coupler 13 and the polarizer 14 and split into two 5a and 5b,
The one light 5a, 5b is the one light 5a, and the one light 5a is the optical fiber coil 1
From one end 17a of 7, the other light 5b is supplied to the optical fiber coil 17 from the other end 17b of the optical fiber coil 17, respectively, one light 5a as counterclockwise light, the other light 5b as clockwise light. , Each of the two lights 7a and 7b propagating through the optical fiber coil 17 and propagating through the optical fiber coil 17, one light 7a from the other end 17b of the optical fiber coil 17, the other light 7a.
b is supplied from one end 17a of the optical fiber coil 17 to the optical branching coupler 15 and interferes with each other, and the interference light 9 thus obtained is supplied to the photodetector 19 through the polarizer 14 and the optical coupler 13. The point of conversion into an electric signal is the same as that of a general optical interference gyro.

A phase modulator 90 in which a pair of electrodes 93, 94 and 97, 98 are formed for the optical waveguides 92 and 96 formed in parallel to form two phase modulators 91 and 95, respectively.
Is provided and the optical waveguide 92 is connected between the optical branching coupler 15 and one end 17a of the optical fiber coil 17, and the optical waveguide 96 is connected to the optical branching coupler 15 and the optical fiber coil 17.
Is connected to the other end 17b of the electrodes 93, 94 of the phase modulation unit 91.
Between the biasing voltage generating circuit 51 and the biasing voltage
Bi is applied to the optical fiber coil in the phase modulator 91.
Light 5a supplied from one end 17a of 17 to the optical fiber coil 17
Also, the phase of the light 7b propagating through the optical fiber coil 17 from the other end 17b of the optical fiber coil 17 and supplied from the one end 17a of the optical fiber coil 17 to the optical branching / coupling device 15 is deviated, and the phase modulator 95 The ramp voltage Ra is applied from the ramp voltage generation circuit 61 between the electrodes 97 and 98 of the
5b supplied from the other end 17b of the optical fiber coil 17 to the optical fiber coil 17 and propagated through the optical fiber coil 17 from one end 17a of the optical fiber coil 17 and from the other end 17b of the optical fiber coil 17 to the optical branch coupler Light supplied to 15 7
The phase of a is deviated, the output voltage Va of the photodetector 19 is supplied to the synchronous detection circuit 71, is synchronously detected by the biasing voltage Bi from the biasing voltage generation circuit 51, and interferes in the optical branch coupler 15. Phase difference Δφ between lights 7a and 7b
Is detected, the output voltage Vc of the synchronous detection circuit 71 is supplied to the PID film (proportional integral derivative filter) 72, the output voltage Ve of the PID filter 72 is supplied to the ramp voltage generation circuit 61, and the above phase difference Δφ is In order to obtain a predetermined value, that is, from the phase difference Δφ to the phase modulator 91, the biasing voltage Bi
Of the Sagnac phase difference Δφs generated when the input angular velocity Ω is applied to the optical fiber coil 17 and the phase difference Δφr generated when the lamp voltage Ra is applied to the phase modulator 95, excluding the phase difference caused by the application of
The lamp voltage such that the phase difference Δφsr of the sum of zero is zero or an integral multiple of 2π radians, generally zero.
The polarity and frequency of Ra are controlled.

The biasing voltage Bi is a sine wave voltage as shown in FIG. 2 in which the time τ required for light to propagate through the optical fiber coil 17 is a half cycle, and the phase modulation in the phase modulator 91 by this is the optical fiber coil. A phase difference of π / 2 radian is given between the two lights 7a and 7b propagating in 17 and interfering with each other to set the operating point of the optical interference gyro.

The ramp voltage Ra is a positive or negative sawtooth wave voltage as shown by the solid line or broken line in FIG.
The phase modulation at is given by a phase difference Δφr that is a maximum integral multiple of 2π radians, which is generally 2π radians, between the two lights 7a and 7b propagating through the optical fiber coil 17 and interfering with each other as described above. This is to cancel the Sagnac phase difference Δφs.

That is, the two lights 7
The phase difference Δφ between a and 7b excluding the phase difference Δφ generated by applying the biasing voltage Bi to the phase modulator 91 is represented by Δφsr = Δφs + Δφr (1) as described above. As is well known, the Sagnac phase difference Δφs It is represented by. However, R is the radius of the optical fiber coil 17,
L is the optical fiber length in the optical fiber coil 17, λ is the wavelength of light propagating through the optical fiber coil 17, and C is the speed of light in vacuum.

Then, in the phase modulator 95, the optical fiber coil 17
5b supplied to the optical fiber coil 17 from the other end 17b of the
Is subjected to a phase shift according to the value of the lamp voltage Ra at that time, and after a further time of τ, one end of the optical fiber coil 17
Light 7a propagated from the optical fiber coil 17a to the optical branching coupler 15 from the other end 17b of the optical fiber coil 17a
Is subject to a phase shift according to the value of the ramp voltage Ra at that time, but when the input angular velocity Ω is added in the clockwise direction and the Sagnac phase difference Δφs becomes negative, the output voltage Ve of the PID filter 72 The above-mentioned phase difference Δφr generated by applying the ramp voltage Ra to the phase modulation unit 95 by making the voltage Ra into a positive sawtooth wave voltage becomes positive as shown on the left side of FIG. 9, and the input angular velocity Ω When the Sagnac phase difference Δφs becomes positive due to the addition of the counterclockwise direction, the ramp voltage Ra is made into a negative sawtooth wave voltage by the output voltage Ve of the PID filter 72, and the above-mentioned phase difference Δφr of FIG. It becomes negative as shown on the right.

Therefore, assuming that the cycle of the lamp voltage Ra is T and the frequency is f, as is clear from FIG. And the refractive index of the light in the optical fiber coil 17 is n, Because of the relationship Becomes Therefore, the phase difference Δφsr expressed by equation (1)
By controlling the polarity of the lamp voltage Ra and the frequency f such that Δ becomes zero, that is, Δφr = −Δφs (6), Next to It is represented by. However, when the input angular velocity Ω is applied in the clockwise direction which is the negative direction and the lamp voltage Ra becomes a positive sawtooth wave voltage, k becomes +1 and the input angular velocity Ω is applied in the counterclockwise direction which is the positive direction. When the lamp voltage Ra becomes a negative sawtooth wave voltage, k becomes -1.

Therefore, the direction and magnitude of the input angular velocity Ω can be measured from the polarity of the lamp voltage Ra and the frequency f.

In the case of the digital phase ramp method, although the system diagram is omitted, a rectangular wave voltage as shown in FIG. 4 having a half cycle of the time τ described above is obtained as the biasing voltage Bi by the reference clock. Is applied between the electrodes 93 and 94 of the phase modulation unit 91 described above, and a digital signal is obtained from the control generation circuit controlled by the reference clock, and the digital signal is converted into an analog voltage as the ramp voltage Ra described above. A positive or negative step wave voltage as shown by the solid line or broken line in FIG. 4 in which the voltage value changes stepwise every time τ is obtained, and this ramp voltage Ra is the electrode 97 of the phase modulator 95 described above. Is applied between 98, and the output voltage Va of the photodetector 19 described above is synchronously detected or sampled and held by the reference clock, and the obtained voltage is digital. Is converted to JP, the digital signal is supplied to a control generator of the above,
The generation of the digital signal from the control generation circuit is controlled so that the phase difference Δφ between the two lights 7a and 7b propagating through the optical fiber coil 17 and interfering with each other becomes a predetermined value.

[Problems to be Solved by the Invention] By the way, in the above-described zero-position serrodyne modulation optical interference angular velocity meter, for example, in the case of the linear phase ramp system shown in FIG. 8, the ramp voltage Ra has a positive sawtooth shape. When the fall time of the lamp voltage Ra when the wave voltage is a wave and the rise time of the ramp voltage Ra when the lamp voltage Ra is a negative sawtooth wave voltage are not zero, strictly speaking, as is clear from FIG. The above equation (3) is not satisfied, and the relationship between the input angular velocity Ω and the frequency f of the lamp voltage Ra deviates from the relations of the equations (7) to (8), and the scale factor error is generated in the output of the optical interference angular velocity meter. To produce
The rise time and fall time of the ramp voltage Ra, which is a sawtooth wave voltage or staircase voltage, has a great influence on the performance of the optical interference gyro. Performance deteriorates.

However, in the above-mentioned conventional zero-position serrodyne modulation type optical interference angular velocity meter shown in FIG. 8 in the case of the linear phase ramp system, the lamp voltage Ra is applied to the phase modulation unit 95 on one side of the optical fiber coil 17. So the lamp voltage
Ra having a large peak value (peak-to-peak value) is required, and the rise time and the fall time of the ramp voltage Ra, which is a sawtooth wave voltage or a staircase wave voltage, are increased accordingly, and the optical interference angular velocity is increased. There is an inconvenience that the performance of the meter deteriorates.

That is, a phase modulator such as the phase modulator 90 described above generally forms an optical waveguide by diffusion of titanium in an electro-optic crystal made of lithium niobate or the like, and forms a pair of electrodes with respect to the optical waveguide. The phase shift amount φ of light in such a phase modulator is proportional to the length l of the pair of electrodes and the value Vp of the voltage applied to the pair of electrodes, and the unit length / unit voltage If the amount of phase shift per hit is K, then φ = K · l · Vp (9) Then, in the above-described conventional optical interference gyro, the lamp voltage Ra is applied between the electrodes 97 and 98 of the phase modulation unit 95 on one side of the optical fiber coil 17 to propagate and interfere in the optical fiber coil 17. Two lights 7a, 7b
Since a maximum phase difference Δφr of 2π radians is given between the two, if the lengths of the electrodes 97 and 98 of the phase modulator 95 are lo, then the peak value Vr of the lamp voltage Ra is given by = 2π [rad], l = lo, Vp = Vr …… (10) is substituted into 2π [rad] = K ・ lo ・ Vr …… (11), Vr = 2π [rad] / K ・ lo …… If the value represented by (12) is required, and for example, K = 50rad / Vm (13) lo = 10mm = 10 × 10 ^-3 m (14), the peak value Vr is Vr. = 4π [V] ≈ 12.6 [V] (15), which is a large value, and the rise time and fall time of the ramp voltage Ra, which is a sawtooth wave voltage or a staircase wave voltage, becomes long, and the optical interference angular velocity meter Performance deteriorates.

By the way, regarding the peak value Vb of the biasing voltage Bi,
Since the biasing voltage Bi is applied between the electrodes 93 and 94 of the phase modulator 91, a phase difference of π / 2 radians is given between the two lights 7a and 7b that propagate and interfere in the optical fiber coil 17. If the lengths of the electrodes 93 and 94 of the phase modulation section 91 are made equal to the lengths lo of the electrodes 97 and 98 of the phase modulation section 95, the peak value Vr of the ramp voltage Ra becomes 1/4.

However, as is apparent from equations (11) to (12), if the length lo of the electrodes 97 and 98 is increased, the lamp voltage Ra
It is possible to reduce the peak value Vr of the lamp voltage, and to shorten the rising time and the falling time of the ramp voltage Ra that is the sawtooth wave voltage or the step wave voltage. However, when the length lo of the electrodes 97 and 98 is increased in this way, the size of the phase modulator 90 increases, and when the phase modulator 90 is arranged inside the optical fiber coil 17, the optical fiber coil
There is a disadvantage that the optical interference angular velocity meter becomes large in size such that the loop diameter of 17 must be increased.

Therefore, the present invention, in the optical interference gyro of the null method serrodyne modulation method, without increasing the size of the phase modulator, therefore, without increasing the size of the optical interference gyro, the peak value of the lamp voltage It is possible to reduce the rise time and fall time of the ramp voltage, which is a sawtooth wave voltage or a staircase wave voltage,
This is to improve the performance of the optical interference gyro.

“Means for Solving the Problems” In the present invention, as a phase modulator, two optical waveguides, which are defined as one end side optical waveguide and the other end side optical waveguide, are formed in parallel, and one end side optical waveguide is formed. A pair of electrodes are formed to form one end side biasing phase modulator and one end side lamp phase modulator, and the other end side optical waveguide is formed with a pair of electrodes to form the other end side lamp phase modulator. Provided is configured, the one end side optical waveguide is connected between one end of the optical fiber coil and the optical branching coupler, and the other end side optical waveguide is connected to the other end of the optical fiber coil and the optical branching coupler. The bias voltage is applied to the biasing phase modulator on one side and the ramp voltage is applied to the ramp phase modulator on one side and the ramp phase modulator on the other side at the same time. The light passing through the one-end side lamp phase modulating unit and the light passing through the other end-side lamp phase modulating unit are applied so as to undergo phase shifts in opposite directions.

[Operation] In the optical interference angular velocity meter of the present invention configured as described above, the light branched at the optical branching coupler and supplied to the optical fiber coil from one end and the other end of the optical fiber coil respectively has one end. Side ramp phase modulation unit and the other end side ramp phase modulation unit undergoes phase shifts in mutually opposite directions, and further propagates through the optical fiber coil from one end and the other end of the optical fiber coil to the other end and one end of the optical fiber coil. The lights supplied from the optical branching / coupling device to the optical branch coupler undergo phase shifts in opposite directions at the other end side lamp phase modulation unit and the one end side lamp phase modulation unit, respectively, and the one end side lamp phase modulation unit and the other end side lamp The phase modulation unit provides a phase difference Δφ of up to 2π radians, which is given between two lights that propagate and interfere in the optical fiber coil by the phase modulation by the lamp voltage. share r.

Therefore, the unit length of each phase modulator
Let K be the phase shift amount per unit voltage, the length of the ramp phase modulator on one end side is la-α, the length of the biasing phase modulator on one end side is lo- (la-α), and the ramp phase modulator on the other end side is Is the sum of the lengths of the ramp phase modulator on one side and the biasing phase modulator on one side, and the length of the ramp phase modulator on one side and the ramp phase modulator on the other side is l ₊ If the sum of the two is 2la, the peak value Vr of the lamp voltage is 2π [rad] = K obtained by substituting φ = 2π [rad], l = 2la, Vp = Vr (16) into the above equation (9).・ 2la ・ Vr …… (17) That is, from π [rad] = K ・ la ・ Vr …… (18), it is expressed as Vr ＝ π [rad] / K ・ la …… (19) and this (19) Dividing the equation by the above equation (12) gives Therefore, by setting la> lo / 2 (21), the ratio G expressed by equation (20) becomes smaller than 1, and even if the size of the phase modulator is not increased,
Therefore, without increasing the size of the optical interference gyro,
The peak value Vr of the lamp voltage can be reduced, the rise time and fall time of the lamp voltage that is a sawtooth wave voltage or a staircase wave voltage can be shortened, and the performance of the optical interference angular velocity meter can be improved. .

[Embodiment] FIG. 1 is an example of the optical interference angular velocity meter of the present invention, which is a case of a linear phase ramp system in which the lamp voltage is a sawtooth wave voltage.

The light source 11, the optical coupler 13, the polarizer 14, the optical branching coupler 15, the optical fiber coil 17, the photodetector 19, the biasing voltage generation circuit 51 constituting the biasing voltage generation application section 50, the lamp voltage generation application section 60. It is the same as the conventional optical interference angular velocity meter shown in FIG. 8 that a system including a constituent lamp voltage generating circuit 61 and a phase difference detection control unit 70 having a synchronous detection circuit 71 and a PID filter 72 is provided. .

Then, in this example of the present invention, the phase modulator 20
As one end side optical waveguide 21 and the other end side optical waveguide 25 are formed in parallel, a pair of electrodes 32, 33 and 42, 43 are formed for the one end side optical waveguide 21, respectively, and one end side biasing phase Modulator 31 and ramp phase modulator on one end side
41, and a pair of electrodes 36, 37 and 46, 47 are formed for the other end side optical waveguide 25, respectively, and the other end side biasing phase modulator 35 and the other end side lamp phase modulator 45 are formed.
Is provided, and one end side optical waveguide 21
Is connected between one end 17a of the optical fiber coil 17 and the optical branching coupler 15, and the other end side optical waveguide 25 is connected between the other end 17b of the optical fiber coil 17 and the optical branching coupler 15. , The biasing voltage Bi obtained from the biasing voltage generating circuit 51, which is a sinusoidal voltage as shown in FIG. 2 in which the time τ required for light to propagate through the optical fiber coil 17 is a half cycle, is one side biasing phase modulation. In the portion 31 and the other end side biasing phase modulator 35, the light passing through the one end side biasing phase modulator 31 and the light passing through the other end side biasing phase modulator 35 undergo phase shifts in mutually opposite directions at the same time point. The ramp voltage Ra which is a positive or negative sawtooth wave voltage as shown by the solid line or the broken line in FIG. And the other end ramp phase modulator 45 so that the light passing through the one end ramp phase modulator 41 and the light passing through the other end ramp phase modulator 45 undergo phase shifts in opposite directions at the same time. Is applied.

However, in this example, when α is set to zero,
That is, in this example, as shown in FIG.
The lengths of the one-end-side ramp phase modulation unit 41 and the other-end-side ramp phase modulation unit 45, that is, the lengths of the electrodes 42, 43 and 46, 47, are set to la, respectively, and the one-end side biasing phase modulation unit is set.
31 and the length of the other end side biasing phase modulator 35, that is, the lengths of the electrodes 32, 33 and 36, 37 are respectively lo-la.
To be Of course, the sum of the lengths of the one-end side ramp phase modulation section 41 and the other end side ramp phase modulation section 45 is 2la,
The sum of the lengths of the one-side biasing phase modulator 31 and the other-side biasing phase modulator 35 is 2 (lo-la).

Therefore, in this example, the one-end side ramp phase modulation section 41 and the other-end side ramp phase modulation section by the lamp voltage Ra
Regarding the phase modulation in 45, the light 5a and the optical fiber coil which are branched in the optical branching coupler 15 and are supplied to the optical fiber coil 17 from one end 17a of the optical fiber coil 17
Light 5b supplied from the other end 17b of 17 to the optical fiber coil 17
However, in each of the one-end side lamp phase modulation section 41 and the other-end side ramp phase modulation section 45, they receive equal phase shifts in mutually opposite directions according to the value of the ramp voltage Ra at that time, and further τ of Light 7a that propagates through the optical fiber coil 17 from one end 17a of the optical fiber coil 17 and is supplied from the other end 17b of the optical fiber coil 17 to the optical branching / coupling unit 15 over time.
And the light 7b propagating through the optical fiber coil 17 from the other end 17b of the optical fiber coil 17 and supplied from the one end 17a of the optical fiber coil 17 to the optical branching / coupling device 15, the other end side lamp phase modulator 45 and one end, respectively. In the side ramp phase modulator 41, equal amounts of each other depending on the value of the ramp voltage Ra at that time,
And, receiving the phase shift in the opposite direction to each other, the lamp phase modulation unit 41 on the one end side and the lamp phase modulation unit 45 on the other end side
A maximum of 2π given between two lights 7a and 7b that propagate and interfere in the optical fiber coil 17 by phase modulation by Ra
The phase difference Δφr that becomes radians is equally shared.

Further, regarding the phase modulation in the one-side side biasing phase modulation section 31 and the other-side side biasing phase modulation section 35 by the biasing voltage Bi, the one side 17a of the optical fiber coil 17 is branched by the optical branching / coupling device 15 to the optical fiber coil 17. The supplied light 5a and the light 5b supplied from the other end 17b of the optical fiber coil 7 to the optical fiber coil 17 are respectively supplied to the one end side biasing phase modulator 31 and the other end side biasing phase modulator 35 by the biasing voltage at that time. Equal amounts of each other according to the value of Bi, and undergo phase shifts in opposite directions to each other, and after a time of τ, propagates through the optical fiber coil 17 from one end 17a of the optical fiber coil 17 to the optical fiber coil 17 The light 7a supplied to the optical branching / coupling device 15 from the other end 17b and the optical fiber coil 17 from the other end 17b of the optical fiber coil 17 are propagated through the optical fiber coil 17. The light 7b supplied to the optical branching / coupling device 15 from the one end 17a of the coil 17 is, in the other end side biasing phase modulator 35 and the one end side biasing phase modulator 31, respectively, according to the value of the biasing voltage Bi at that time, etc. Amount of phase shift in the opposite direction to each other, the one-side biasing phase modulation section 31 and the other-side biasing phase modulation section 35 change the biasing voltage Bi
The phase difference of π / 2 radian given between the two lights 7a and 7b propagating through the optical fiber coil 17 and interfering with each other is equally shared.

Therefore, each phase modulator 31, 3 of the phase modulator 20
Assuming that the phase shift amount per unit length and unit voltage at 5,41,45 is K, as described above, the peak value of the lamp voltage Ra
Vr is expressed by the equation (19), and by satisfying the condition of the equation (21), the ratio G expressed by the equation (20) becomes smaller than 1, and even if the size of the phase modulator 20 is not increased, Therefore, the peak value Vr of the lamp voltage Ra can be reduced without increasing the size of the optical interference gyro and the lamp voltage Ra
It is possible to shorten the fall time of the lamp voltage Ra when the voltage is a positive sawtooth wave voltage and the rise time of the lamp voltage Ra when the lamp voltage Ra is a negative sawtooth wave voltage. The performance of can be improved. The peak value Vb of the biasing voltage Bi is π / 2 [rad, which is obtained by substituting φ = π / 2 [rad], l = 2 (lo-la), Vp = Vb (22) into the equation (9). ] = K ・ 2 (lo-la) ・ Vb …… (23) It is represented by.

As a specific example, K and lo are values represented by the above equations (13) and (14), la = 8 mm = 8 × 10 ⁻³ m (25) lo−la = 2 mm = 2 × 10 ^{− 3} m …… (26) Therefore, at this time, the peak value Vr of the lamp voltage Ra becomes Vr = 2.5π [V] ≈7.9 [V] (27) from the equation (19), and the ratio G represented by the equation (20) becomes As is clear from the fact that it becomes 0.625, the length of the electrodes 93, 94 and 97, 98 shown in FIG. 8 is represented by the formula (14), and K is represented by the formula (13). The peak value Vb of the biasing voltage Bi becomes about 63% of that of the interference gyro, and from the equation (24), Vb = 2.5π [V] ≈7.9 [V] ...... (28) It becomes equal to the peak value Vr of the voltage Ra.

As the biasing voltage Bi, a rectangular wave voltage may be used instead of the sine wave voltage. Also, PID filter 7
Instead of 2, an electric filter having a similar function may be used.

FIG. 3 is another example of the optical interference angular velocity meter of the present invention, which is a case of a digital phase ramp system in which the lamp voltage is a step wave voltage.

In the case of the digital phase ramp method, the time τ is half as the biasing voltage Bi from the biasing voltage generating circuit 51 by the reference clock Co as shown in FIG. A rectangular wave voltage as shown in FIG. 4 having a cycle is obtained, and this biasing voltage Bi is applied to one end side biasing phase modulator 31.
And a biasing phase modulator 35 on the other end side in the same manner as in the example shown in FIG.
A digital signal Dr is obtained from the control generation circuit 82 controlled by Co, and the digital signal Dr is supplied to the D / A converter 6
The voltage value is converted into an analog voltage by 5 and the voltage value changes stepwise with time τ as the ramp voltage Ra from the D / A converter 65, and a positive or negative step wave voltage as shown by the solid line or broken line in FIG. 4 is obtained. This lamp voltage Ra is supplied to the ramp phase modulation unit 41 on the one end side and the ramp phase modulation unit 45 on the other end side as the first voltage.
The photodetector is applied in the same manner as in the example shown in the figure.
The output voltage Va of 19 is supplied to the sampling and holding circuit 74 which also functions as a synchronous detection circuit, sampled and held by the reference clock Co, and the obtained voltage Vs is converted into a digital signal Dc by the A / D converter 75 and the digital signal Dc is converted. The signal Dc is supplied to the control generation circuit 82, and the digital signal Dr from the control generation circuit 82 is set so that the phase difference Δφ between the two lights 7a and 7b propagating through the optical fiber coil 17 and interfering with each other becomes a predetermined value. Is controlled.

Therefore, also in this example, by the same operation as that of the example shown in FIG. 1, the lamp voltage Ra can be increased without increasing the size of the phase modulator 20 and without increasing the size of the optical interference angular velocity meter. The peak value Vr can be reduced, the rise time and fall time of the ramp voltage Ra that is the staircase voltage can be shortened, and the performance of the optical interference angular velocity meter can be improved.

When a rectangular wave voltage is used as the biasing voltage Bi, the rise time and fall time of the biasing voltage Bi affect the performance of the optical interference gyro, and the rise time and fall time of the biasing voltage Bi are long. And the performance of the optical interference gyro deteriorates,
If the sum of the lengths of the one-side biasing phase modulator 31 and the other-side biasing phase modulator 35 is increased to the extent of the above-described specific example, the peak value Vb of the biasing voltage Bi is also (2
It can be made as small as shown by the equation (8), and the rise time and fall time of the biasing voltage Bi, which is a rectangular wave voltage, can be shortened to the extent that the performance of the optical interference gyro is not impaired.

As in the example shown in FIG. 6, the above-mentioned α is not set to zero, the lengths of the one-side biasing phase modulator 31 and the other-side biasing phase modulator 35 are changed from each other, and the one-side ramp phase modulation is performed. 41 and ramp phase modulator of the other end
The lengths of 45 may be changed from each other, and in this case also, the length of the ramp phase modulator 41 on the one end side and the ramp phase modulator on the other end side 41
The sum of the lengths of 45 becomes 2la, and the sum of the lengths of the biasing phase modulator 31 on the one end side and the biasing phase modulator 35 on the other end becomes 2 (lo-la). High price
Vr is expressed by equation (19), and the peak value Vb of biasing voltage Bi
Is expressed by equation (24).

Furthermore, as shown in FIG. 7, even if the length of the other end side biasing phase modulator 35 is set to zero, that is, the other end side optical waveguide 25 is not provided with the biasing phase modulator. Good.

When the optical branching / coupling device 15 is formed of an optical waveguide as in the example shown in FIGS. 1 and 3, the optical branching / coupling device 15 can be formed integrally with the phase modulator 20.
An optical fiber coupler may be used as the optical branching / coupling device 15.

[Advantages of the Invention] As described above, according to the present invention, it is possible to reduce the peak value of the lamp voltage without increasing the size of the phase modulator, and thus without increasing the size of the optical interference angular velocity meter. The rise time and fall time of the ramp voltage, which is a sawtooth wave voltage or a staircase wave voltage, can be shortened, and the performance of the optical interference angular velocity meter can be improved.

[Brief description of drawings]

FIG. 1 is a system diagram showing an example of the optical interference angular velocity meter of the present invention, FIG. 2 is a waveform diagram showing an example of the biasing voltage and lamp voltage, and FIG. 3 is a diagram of the optical interference angular velocity meter of the present invention. FIG. 4 is a system diagram showing another example, FIG. 4 is a waveform diagram showing an example of the reference clock, biasing voltage, and ramp voltage, and FIGS. 5, 6, and 7 are optical interference angular velocity of the present invention, respectively. The figure which shows the example of the phase modulator in the meter,
FIG. 8 is a system diagram showing an example of a conventional optical interference angular velocity meter,
FIG. 9 is a diagram showing a mode of phase modulation by the ramp voltage.

Claims (1)

[Claims] 1. A light source, an optical fiber coil, and light from the light source is branched into two and supplied to the optical fiber coil from one end and the other end of the optical fiber coil, and propagates through the optical fiber coil. An optical branching / coupling device for interfering the two light beams, a photodetector for detecting the interference light obtained from this optical branching / coupling device, and an optical branching coupler connected between one end of the optical fiber coil and the optical branching / coupling device. One end side biasing phase modulator formed by forming a pair of electrodes for the one end side optical waveguide, one end side ramp phase modulator for forming a pair of electrodes for the one end side optical waveguide, and the above A phase modulator having a ramp phase modulator on the other end, which is formed by forming a pair of electrodes with respect to an optical waveguide on the other end connected between the other end of the optical fiber coil and the optical branch coupler. , A biasing voltage generating / applying unit that generates a biasing voltage and applies the biasing voltage to the one-side side biasing phase modulating unit, and a ramp voltage, and generates the ramp voltage by using the one-side lamp phase modulating unit and the other-end side. A ramp voltage is applied to the ramp phase modulator so that the light passing through the ramp phase modulator on the one end side and the light passing through the ramp phase modulator on the other end side undergo phase shifts in opposite directions at the same time point. Detecting the phase difference between the two lights that interfere in the optical branching coupler from the output of the applying unit and the photodetector, and generating the lamp voltage so that the phase difference becomes a predetermined value by the detected output. An optical interference gyro including a phase difference detection control unit that controls an application unit.