JPH11344345A - Optical fiber gyro - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical fiber gyro wherein the number of components and cost are reduced. SOLUTION: In the optical fiber gyro comprising an interference light generating means 1 for generating interference light having an optical phase difference corresponding to a physical quantity, an optical phase modulator 2 for electrically adjusting the optical phase difference of the interference light, using a square wave, a light receiver 3 for photoelectrically converting the interference light, and sampling means 5 for sampling interference signals obtd. as electric signals by the photoelectric conversion, thereby measuring the physical quantity corresponding to the optical phase difference from the sampled interference signals, an amplifier 8 for amplifying the interference signal the gain of which is set so that spike signals 42 contained in the interference signal are not sampled but only true signal components have a magnitude enough to sample is provided between the light receiver 3 and sampling means 5.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a phase modulation type optical fiber gyro for measuring a physical quantity such as an angular velocity, and more particularly to an optical fiber gyro having a reduced number of parts and cost.

[0002]

2. Description of the Related Art In a phase modulation type optical fiber gyro for measuring a physical quantity such as an angular velocity, when an electric signal for driving a phase modulator uses a rectangular wave as shown in FIG. As shown in FIGS. 4B and 4C, the interference signal, which is an electric signal obtained in the above, accompanies a spike signal at the rising and falling edges of the rectangular wave. FIG. 4B shows a waveform when the optical fiber gyro is stationary, and FIG.
This is a waveform when the optical fiber gyro is rotating.
In each case, a spike signal is seen. In the figure, what is drawn flat is the true signal component 41 of the interference signal,
The vertically sharply extending portion is the spike signal 42. The spike signal 42 affects the signal processing in the course of the signal processing performed in the subsequent stage, and becomes a factor that lowers the accuracy of the output angular velocity. Therefore, it is necessary to minimize the spike signal 42 taken into the signal processing stage.

In the prior art, as shown in FIG. 5A, an amplifying stage 9 between a photodetector 3 and an A / D converter 5 is used.
And a spike filter 5 for removing spike signals.
1 is provided. The spike filter 51 is configured by an analog switch. As shown in FIG. 5C, a rectangular signal synchronized with a modulation signal (electric signal for driving the phase modulator) is given as a trigger signal of the analog switch, as shown in FIG. 5C. ON that the interference signal from the photodetector 3 is input to the A / D converter 5,
The signal is turned OFF (passed at OFF, cut off at ON), thereby passing the true signal component 41 and blocking the spike signal 42. As a result, as shown in FIG. 5D, an interference signal from which the spike signal 42 has been removed is obtained.

[0004]

In the prior art, an analog switch and an IC for generating a trigger signal are required to form a spike filter. For this reason, the number of parts increases and the cost increases.

An object of the present invention is to provide an optical fiber gyro that solves the above-mentioned problems and reduces the number of parts and cost.

[0006]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides an interference light generating means for generating interference light having an optical phase difference corresponding to a physical quantity, and an electric light phase difference of the interference light. An optical phase modulator that adjusts using a rectangular wave, a photodetector that photoelectrically converts the interference light, and a sampling unit that samples an interference signal obtained as an electric signal by the photoelectric conversion. In the optical fiber gyro for measuring the physical quantity corresponding to the optical phase difference, the interference signal is amplified between the light receiver and the sampling means, and the spike signal included in the interference signal is not sampled, and An amplifier is provided that has a gain set so that only the signal component has a size that can be sampled.

The gain of the amplifier is such that the amplitude of the amplified output is
The setting may be such that the spike signal is saturated and the true signal component is not saturated.

[0008]

An embodiment of the present invention will be described below in detail with reference to the accompanying drawings.

As shown in FIG. 1, an optical fiber gyro of the present invention includes an interference light generating means 1 for generating interference light having an optical phase difference corresponding to an angular velocity, and an optical phase difference of the interference light. Phase modulator 2 using rectangular wave for adjustment
A photoelectric converter 3 for photoelectrically converting the interference light, an amplification stage 4 for suppressing the spike signal while amplifying the interference signal obtained as an electric signal by the photoelectric conversion to a size that can be sampled, and sampling the amplified interference signal. And a signal processing unit 6 for processing the sampled interference signal to obtain an angular velocity.

The interference light generating means 1 includes a light source 11 for generating a light beam, a first fiber coupler 13 for taking the light beam into an optical fiber 12, a polarizer 14 inserted into the optical fiber 12, The second to split the beam into two
, And an optical fiber loop 16 for propagating the two branched light beams in both directions. The phase modulator 2 is provided between the optical fiber loop 16 and the second fiber coupler 15 and is connected to a phase modulator driving circuit 7 that generates a modulation signal. The photoelectric converter 3 includes a photodiode. The sampling means 5 comprises an A / D converter.

The amplification stage 4 is a main part of the present invention. As shown in FIG. 2, an amplifier 8a connected to the photoelectric converter 3 and an amplifier 8b connected to the sampling means 5 are arranged in series. Things. These amplifiers 8a, 8b
In this case, a low-cost general-purpose amplifier may be used, and it is not necessary that the accuracy be particularly high. A feature of the present invention is that the gains of these amplifiers 8a and 8b are set so that spike signals included in the interference signal are not sampled and only true signal components can be sampled. Specifically, the gain is set so that the true signal component of the amplified output is not saturated and the spike signal is saturated.

Next, the operation will be described.

The light beam from the light source 11 is taken into the optical fiber 12 from the first fiber coupler 13, propagates through the polarizer 14, reaches the second fiber coupler 15, and is branched. The two branched light beams are propagated in the optical fiber loop 16 both right and left. These light beams are modulated in optical phase in accordance with a rectangular wave modulation signal generated by the phase modulator driving circuit 7 in the phase modulator 2, and then reach the second fiber coupler 15, respectively. The light is combined by the coupler 15 to become interference light. This interference light has an optical phase difference corresponding to the angular velocity generated in the optical fiber loop 16. The interference light travels in the opposite direction through the optical fiber 12 from the second fiber coupler 15 and reaches the first fiber coupler 13 via the polarizer 14. The interference light is transmitted to the first fiber coupler 1
3, a part of which branches to the photoelectric converter 3,
Detected as an interference signal. The interference signal obtained as an electric signal is amplified by the amplification stage 4 to an appropriate level as described later. The amplified interference signal is A / D converted by the A / D converter of the sampling means 5. The signal processing unit 6
/ D converted interference signal to process optical fiber loop 1
6. The angular velocity Ω occurring in 6 is calculated, and this angular velocity Ω is output.

The manner of amplification in the amplification stage will be described with reference to FIG.

Generally, the gain of the amplifier is set so that the output signal is not saturated. For example, for a signal having a waveform as shown in FIG. 4 (c), as shown in FIG. 3 (a), the whole of the amplified output signal is not saturated and falls within the range of the output voltage amplitude value a. Set the gain.

On the other hand, in the present invention, as shown in FIG. 3B, only the spike signal 42 exceeds the output voltage amplitude value a and the true signal component 41 falls within the range of the output voltage amplitude value a. Set the gain to fit. Therefore, the true signal component 41 is amplified without being saturated, and is correctly sampled in the subsequent stage. Spike signal 42
Is saturated and disappears, so it is not sampled.

In the amplification stage 4 of FIG. 2A, when the interference signal input from the photoelectric converter includes the spike signal 42 as shown in FIG. 2B, as shown in FIG. , The spike signal 42 is saturated. For this reason, the interference signal output to the A / D converter has the spike signal 42 removed (or reduced) as shown in FIG. 2C, and the influence on the subsequent signal processing is reduced. Can be minimized. As a result, it is possible to prevent a decrease in the accuracy of the angular velocity measurement.

In the prior art, a spike filter was used, so that the number of parts increased and the cost increased. However, in the present invention, since no spike filter was used,
The number of parts and cost are reduced.

[0019]

The present invention exhibits the following excellent effects.

(1) The influence of spike signals can be minimized with a simple configuration in which the number of parts and cost are reduced as compared with the prior art.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an optical fiber gyro showing one embodiment of the present invention.

2A is a detailed configuration diagram of an amplification stage of the optical fiber gyro of the present invention, FIG. 2B is an input signal waveform diagram of the amplification stage,
(C) is an output signal waveform diagram of the amplification stage.

3A is a signal waveform diagram of a general amplifier, and FIG. 3B is a signal waveform diagram of an amplifier of the present invention.

FIG. 4A is a drive signal waveform diagram of a phase modulator,
(B), (c) is an output signal waveform diagram of the light receiver.

5A is a detailed configuration diagram of an amplification stage of an optical fiber gyro according to the related art, FIG. 5B is an input signal waveform diagram of the amplification stage,
(C) is a trigger signal logic waveform diagram of the analog switch,
(D) is an output signal waveform diagram of the amplification stage.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 interference light generating means 2 optical phase modulator 3 light receiver 4 amplifying stage 5 sampling means 6 signal processing unit 8 a, 8 b amplifier 41 true signal component 42 spike signal

Continued on the front page (72) Inventor Hisao Sonobe 7-1-1, Omika-cho, Hitachi City, Ibaraki Prefecture Within Hitachi Research Laboratory, Hitachi, Ltd.

Claims (2)

[Claims] An interference light generating means for generating interference light having an optical phase difference corresponding to a physical quantity, an optical phase modulator for electrically adjusting the optical phase difference of the interference light using a rectangular wave, An optical fiber that includes a photoelectric converter that photoelectrically converts the interference light and a sampling unit that samples an interference signal obtained as an electric signal by the photoelectric conversion, and that measures the physical quantity corresponding to an optical phase difference from the sampled interference signal. In the gyro, a gain is set between the photodetector and the sampling unit so that the interference signal is amplified, and a spike signal included in the interference signal is not sampled, and only a true signal component has a size that can be sampled. An optical fiber gyro, comprising an amplifier to be used. 2. The optical fiber according to claim 1, wherein the gain of the amplifier is set so that the amplitude of the amplified output falls within a range in which a spike signal is saturated and a true signal component is not saturated. gyro.