JP2001141464A - Signal processing method and apparatus in phase modulation type optical fiber gyro - Google Patents

Abstract

(57) Abstract: The present invention provides a signal processing method and apparatus in a phase modulation type optical fiber gyro in which a detection clock is corrected by an optical system output including phase delay information to reduce a detection error. Aim. SOLUTION: The signal processing method in the phase modulation type optical fiber gyro according to the present invention modulates light based on an angular velocity transmitted from an oscillation circuit (15) and interferes with a phase difference of the light to output an optical system output ( (S) to generate the optical system output (S)
The detected optical system output (S1) obtained by amplifying the signal by the electric input amplifier (11) is input to the lock-in amplifier (17) and based on the phase delay information included in the detected optical system output (S1). Gyro output (18a) with reduced detection error by correcting the angular velocity transmitted from the oscillation circuit (15) and performing synchronous detection
Get.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rate sensor mounted on a vehicle, a ship, a robot, or the like, for measuring an angular velocity generated, and a phase modulation type optical fiber for measuring an angular velocity by utilizing a Sagnac effect of light. It is about gyro.

[0002]

2. Description of the Related Art A phase modulation type optical fiber gyro shown in FIG. 3 is an example of this type of apparatus conventionally used. That is, what is indicated by reference numeral 1 in FIG. 3 is an optical system having a ring-shaped sensing coil 2 formed of an optical fiber, and the sensing coil 2 includes a first coupler 3, a polarizer 4, and a second coupler 5.
Are connected to a light source module 6 and a detector module 7 via an optical fiber 8. The sensing coil 2
A phase modulator 9 composed of a well-known piezo element (PZT) is provided between the first coupler 3 and the optical fiber 8 in a state of being in contact with the optical fiber 8 and in the vicinity of the sensing coil. In such an optical system 1, laser light entering the fiber 8 from the light source module 6 is transmitted to the second coupler 5,
After being modulated by the phase modulator 9 via the polarizer 4 and the first coupler 3, the light enters the sensing coil 2. The laser light incident on the sensing coil 2 passes through the first coupler 3, the polarizer 4, and the second coupler 5 again, is photoelectrically converted by the detector module 7, and the optical system output S is extracted.

[0003] An electric system 10 is connected to the optical system 1, and an input amplifier 11 of the electric system 10 receives the optical system output S and outputs it as an output S1 to be detected. . The detected optical system output S1 includes a phase difference Δθ due to the well-known Sagnac effect. A light source drive circuit 12, a modulation control circuit 14, and a lock-in amplifier 17 are connected to the output side of the input amplifier 11. The light source drive circuit 12 is connected to the light source module 6 via a laser driver 13, and the modulation control circuit 14 is connected to an oscillation circuit 15 that supplies a detection clock 15 a to a lock-in amplifier 17 and the phase modulator 9. The lock-in amplifier 17 is connected to an output amplifier 18. The conventional phase modulation type optical fiber gyro apparatus has a configuration as described above, and synchronously detects the output S1 of the optical system to be detected by the lock-in amplifier 17 and interferes with the phase difference of the light generated due to the angular velocity to produce a known light Sagnac. The gyro output 18a is obtained through the output amplifier 18 by the effect. The relational expression between the output S1 of the test wave optical system and the Sagnac phase difference will be described later.

[0004]

Since the conventional phase modulation type optical fiber gyro has the above-mentioned structure,
The following issues existed. That is, the light quantity fluctuation due to the Sagnac effect generated according to the angular velocity in the sensing coil 2 as described above is synchronously detected by the lock-in amplifier 17 with the detection clock 15a having the frequency equal to the modulation frequency, and the angular velocity signal is extracted. I have. However, a piezo element (PZT) constituting the phase modulator 9
Causes a mechanical delay because the fiber is wound around the piezoelectric element to compress the fiber, and also causes a phase delay in the path to the lock-in amplifier 17. In the actual synchronous detection, there was a phase delay between the detection clock 15a and the output S1 of the detection target optical system. As described above, since the phase delay with respect to the modulation signal included in the output S1 of the detection target optical system fluctuates due to various factors (for example, a temperature change), an error occurs due to the synchronous detection.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems. In particular, in order to compensate for errors in synchronous detection, clocks of modulation frequency components used for synchronous detection have phase delay information. To provide a signal processing method and apparatus in a phase modulation type optical fiber gyro that corrects a detection clock by a phase delay and its fluctuation component by mixing the output of the optical system, and eliminates an error due to synchronous detection. It is the purpose.

[0006]

A signal processing method in a phase modulation type optical fiber gyro according to the present invention guides light from a light source to a sensing coil formed of an optical fiber, and controls a phase based on an angular velocity transmitted from an oscillation circuit. The optical system output is generated by modulating the light with the modulator and interfering the phase difference of the light, and the output of the detected optical system obtained by amplifying the output of the optical system by the input amplifier of the electric system is supplied to the lock-in amplifier. A signal processing method in an optical fiber gyro that obtains a gyro output by synchronously detecting an output of the detected optical system using an angular velocity that is input and transmitted from the oscillation circuit, wherein a phase delay included in the output of the detected optical system is provided. A method for correcting an angular velocity of a detection clock transmitted from the oscillation circuit to the lock-in amplifier based on information. More specifically, the angular velocity of the detection clock is corrected by a phase corrector provided between the oscillation circuit and the lock-in amplifier. Further, the phase modulation type optical fiber gyro device of the present invention guides light from a light source to a sensing coil formed of an optical fiber, modulates the light based on an angular velocity transmitted from an oscillation circuit by a phase modulator, and modulates the light. The optical system output is generated by causing the phase difference of the optical system to interfere, and the detected optical system output obtained by amplifying the optical system output by an electrical input amplifier is input to the lock-in amplifier and transmitted from the oscillation circuit. In an optical fiber gyro device that obtains a gyro output by synchronously detecting the output of the detected optical system with a lock-in amplifier using an angular velocity, the output of the detected optical system is provided between the oscillation circuit and the lock-in amplifier. And a phase corrector that corrects the angular velocity of the detection clock transmitted to the lock-in amplifier based on the phase delay information included in the lock-in amplifier.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1 FIG. 1 is a block diagram showing a configuration of a phase modulation type optical fiber gyro according to the present invention. FIG. 2 is a characteristic diagram showing output characteristics of the phase modulation type optical fiber gyro according to the present invention. Note that the same or equivalent parts as those in the related art will be described using the same reference numerals. 1 is a phase corrector constituted by, for example, a flip-flop circuit. The modulation angular velocity ω output from the oscillation circuit 15 is input to the input terminal of the flip-flop of the phase corrector 20.
_The circuit configuration is such that the detection clock 15a of _m is input and the output S1 of the optical system to be detected is input to the gate of the flip-flop via the input amplifier 11.

The output S1 of the optical system to be detected in the phase modulation type optical fiber gyro is represented by the following equation (1).

(Equation 1) Here, L: effective interference fiber length, a: coil radius,
C: speed of light, λ: wavelength of light, ω: input angular velocity. The Sagnac phase difference △ θ, which is the interference phase difference between the left and right bidirectional lights, is represented by the following equation (2), and includes the angular velocity (ω).

(Equation 2) Here, E _L and E _R are the amplitudes of the left and right light, ω _{λ is} the angular velocity of the light, ω _{m is the} modulation angular velocity, b is the amplitude of the modulation signal, and φ is the phase difference of the light of the left and right light. is there. here,
The following equation (3) is obtained by expanding the equation (1) for each order using the Bessel function.

(Equation 3) Here, J _n (m) is the coefficient of the n-th wave when the modulation index is m (first
Kind Bessel function). Therefore, from the above equation (3),
The lock-in amplifier 17 uses the modulation frequency of the angular velocity ω _m input from the oscillation circuit 15 to output the output S
By performing the synchronous detection of 1, the Sagnac phase difference Δθ can be detected. Although the relationship between the detected optical system output S1 and the Sagnac phase difference Δθ has been described here, the above equations (1) to (3) are used to calculate the optical system output S output from the detector module 7 and the Sagnac phase difference. This is a general expression that holds between Δθ.

Next, a signal processing method in the phase modulation type optical fiber gyro of the present invention will be specifically described.
As described above, in the actual phase modulation type optical fiber gyro, the detected optical system output S1
Contains phase delay information, but in the present invention, the angular velocity ω input from the oscillation circuit 15 in the phase corrector 20 is
_The detection clock 15 input to the lock-in amplifier 17 by mixing the detected optical system output S1 with the detection clock
The angular velocity of a is corrected. Thus, the detection clock 15a
By correcting based on the angular velocity to the phase lag information included in the detection optical system outputs S1, be varied from the angular velocity of the detection optical system outputs S1 is omega _m in omega _m ^* in the formula (3), since correcting the angular velocity of the detection clock 15a that is input to the lock-in amplifier 17 in omega _m ^* from omega _m in accordance with this, the phase of the detection clock is shifted with the detection optical system outputs S1 input to the lock-in amplifier 17 And the occurrence of a detection error can be suppressed.

FIG. 2 exemplarily shows the output of the optical system under test when the Sagnac phase difference Δθ is 0 ° and 30 °, and the detected wave transmitted from the optical system 1 via the detector module 7 is shown in FIG. Since the output S1 of the optical system is mainly composed of the second harmonic component of the modulation signal, the gate of the flip-flop of the phase corrector 20 is opened in synchronization with the rising or falling of the second harmonic, thereby obtaining the optical system to be detected. Even if the output S1 includes the phase delay information, the detected optical system output S is output without causing a detection error in the lock-in amplifier 17.
1 can be synchronously detected.

As described above, according to the signal processing method and apparatus in the phase modulation type optical fiber gyro of the present invention, the output of the optical system to be detected includes the mechanical delay in the phase modulator 9 and the phase delay in the circuit. Even in such a case, if the detection clock 15a is corrected based on such a phase delay, even if the angular velocity of the output of the detection optical system changes, the phase of the output of the detection optical system and the detection clock 15a does not shift. Therefore, generation of a detection error in the lock-in amplifier 17 can be suppressed.

[0012]

According to the signal processing method in the phase modulation type optical fiber gyro of the present invention, the light from the light source is guided to the sensing coil composed of the optical fiber, and the phase modulation is performed by the phase modulator based on the angular velocity transmitted from the oscillation circuit. The optical system output is generated by modulating the light and causing the phase difference of the light to interfere, and the output of the optical system to be detected obtained by amplifying the output of the optical system by the input amplifier of the electric system is input to the lock-in amplifier. A signal processing method in an optical fiber gyro that obtains a gyro output by synchronously detecting the output of the detected optical system using an angular velocity transmitted from an oscillation circuit, wherein the signal processing method is performed based on phase delay information included in the output of the detected optical system. Since the angular velocity of the detection clock transmitted from the oscillation circuit to the lock-in amplifier is corrected, phase delay information is included in the output of the optical system. The phase of the detection clock and the output of the optical system can be aligned, and even if the angular speed of the output of the optical system fluctuates due to external factors such as temperature fluctuations, the occurrence of detection errors in the lock-in amplifier is suppressed, and a highly accurate phase modulation type A signal processing method in an optical fiber gyro can be provided. More specifically, since the correction of the angular velocity of the detection clock is performed by a phase corrector provided between the oscillation circuit and the lock-in amplifier, a phase modulation type in which a detection error in the lock-in amplifier is reliably suppressed. A signal processing method in an optical fiber gyro can be provided. Further, the phase modulation type optical fiber gyro device of the present invention guides light from a light source to a sensing coil formed of an optical fiber, modulates the light based on an angular velocity transmitted from an oscillation circuit by a phase modulator, and modulates the light. The optical system output is generated by causing the phase difference of the optical system to interfere, and the detected optical system output obtained by amplifying the optical system output by an electrical input amplifier is input to the lock-in amplifier and transmitted from the oscillation circuit. In an optical fiber gyro device that obtains a gyro output by synchronously detecting the output of the detected optical system with a lock-in amplifier using an angular velocity, the output of the detected optical system is provided between the oscillation circuit and the lock-in amplifier. A phase corrector for correcting the angular velocity of the detection clock transmitted to the lock-in amplifier based on the phase delay information included in the output of the optical system. Even if phase delay information is included, the phase of the detection clock and the optical system output can be aligned, and even if the angular velocity of the optical system output fluctuates due to external factors such as temperature fluctuation, the detection error in the lock-in amplifier will not occur. It is possible to provide a suppressed and highly accurate phase modulation type optical fiber gyro device.

[Brief description of the drawings]

FIG. 1 is a block diagram schematically showing a configuration of a phase modulation type optical fiber gyro according to the present invention.

FIG. 2 is a characteristic diagram showing a relationship between a modulation signal and an optical system output (AC component) in the phase modulation type optical fiber gyro of the present invention.

FIG. 3 is a block diagram schematically showing a configuration of a conventional phase modulation type optical fiber gyro.

[Explanation of symbols]

 Reference Signs List 1 optical system 2 sensing coil 3 first coupler 4 polarizer 5 second coupler 6 light source module 7 detector module 8 optical fiber 9 phase modulator 10 electric system 11 input amplifier 12 light source drive circuit 13 laser driver 14 modulation control circuit 15 oscillation circuit 15a Detection clock 16 Driver 17 Lock-in amplifier 18 Output amplifier 18a Gyro output 20 Phase corrector S Optical system output S1 Output of detected optical system

Claims (3)

[Claims] The light from a light source (6) is guided to a sensing coil (2) composed of an optical fiber (8), and is transmitted to a phase modulator (9) based on an angular velocity transmitted from an oscillation circuit (15). The optical system output (S) is generated by modulating the light and interfering the phase difference of the light, and the output of the optical system to be detected is obtained by amplifying the optical system output (S) by the input amplifier (11) of the electric system. The gyro output (18a) is obtained by inputting (S1) to the lock-in amplifier (17) and synchronously detecting the output (S1) of the detected optical system using the angular velocity transmitted from the oscillation circuit (15). In the signal processing method in the optical fiber gyro, the detection clock (15a) transmitted from the oscillation circuit (15) to the lock-in amplifier (17) based on the phase delay information included in the detected optical system output (S1) Signal processing method for phase modulated optical fiber gyro characterized by correcting angular velocity . 2. The correction of the angular velocity of the detection clock (15a) is performed by a phase corrector (20) provided between the oscillation circuit (15) and the lock-in amplifier (17). The signal processing method in the phase modulation type optical fiber gyro according to claim 1. The light from a light source (6) is guided to a sensing coil (2) composed of an optical fiber (8), and is transmitted to a phase modulator (9) based on an angular velocity transmitted from an oscillation circuit (15). The optical system output (S) is generated by modulating the light and interfering the phase difference of the light, and the output of the optical system to be detected is obtained by amplifying the optical system output (S) by the input amplifier (11) of the electric system. (S1) lock-in amplifier
Gyro output (1) by synchronously detecting the detected optical system output (S1) with a lock-in amplifier (17) using the angular velocity input from (17) and transmitted from the oscillation circuit (15).
8a), the lock-in between the oscillation circuit (15) and the lock-in amplifier (17) based on the phase delay information contained in the output (S1) of the optical system to be detected. The detection clock (1) transmitted to the amplifier (17)
A phase modulation type optical fiber gyro device comprising a phase corrector (20) for correcting the angular velocity of 5a).