JPS6340810A - Optical fiber rotation sensor - Google Patents

Abstract

PURPOSE:To achieve a smaller measuring system with a simple construction, by mixing lights propagating both clockwise and counterclockwise within an optical fiber loop to detect a rotation from variation in the resonance peak of lights moving in both directions. CONSTITUTION:Light from a high coherence semiconductor laser 11 is connected to an optical fiber 13a and propagated both clockwise and counterclockwise with an optical fiber coupler 12a within a single mode optical fiber loop 17. The loop 17 composes a ring resonator to propagate light introduced in a multiplex manner within the resonator, the light thus propagated is led outside the loop 17 with an optical fiber coupler 12b and mixed with light propagated both clockwise and counterclockwise with an optical fiber coupler 12c to be converted into an electrical signal with a photodetector 14. A phase modulator 16 is provided in the loop 17 and driven by a triangular wave. This changes the phase of the light propagated in the loop 17 and a sharp resonance is observed at an output of the photodetector. A signal processor 18 processes an output of the detector 14 thereby enabling detection of rotation from the variation in the resonance peak of lights moving the both clockwise and counterclockwise.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a device for measuring rotational angular velocity using an optical fiber ring resonator.

[Conventional technology]

FIG.
LETTER3Vo1.8. No, 12. pp.6
44-646.1983) is a configuration diagram of a conventional optical fiber rotation sensor.

In FIG. 4, 1 is a laser that emits highly coherent light, 2a, 2b, 2c are beam splitters, 3a, 3
b is an ultrasonic optical modulator, 4a, 4b are photodetectors, 5a, 5
b is V CO (Voltage Control roll)
d0scillator), 5a, 5b are lenses, 7
a, 7b are phase modulators, 8 is an optical fiber coupler, 9 is a single mode optical fiber, 10 is a polarization plane controller, L
is a single mode optical fiber loop, Ca and Cb are controllers,
Ra and Rb are lock-in amplifiers.

Next, the operation will be explained. This is a ring resonance type optical fiber rotation sensor that utilizes the resonance characteristics of light propagating within the optical fiber loop L. The light from the laser 1 is split into two by a beam splitter 2a, one of which is an ultrasonic optical modulator 3a, a beam splitter 2b, and a lens 6.
The light enters the optical fiber 9 via a, and propagates counterclockwise within the optical fiber loop L via the optical fiber coupler 8. The other light similarly propagates clockwise through the optical fiber loop L.

The ultrasonic light modulator 3a is used to change the frequency of light propagating leftward through the optical fiber loop L by fl. The phase modulator 7a is made by winding an optical fiber around a cylindrical piezoelectric element several times, and uses the fact that the optical fiber expands and contracts when a voltage is applied to change the phase of the light propagating within the optical fiber loop L. It modulates.

This phase modulator 7a is driven by a signal with a frequency of (m),
The light propagated multiple times in the left direction within the optical fiber loop L is received by the photodetector 4a and converted into an electrical signal. This signal is guided to the lock-in amplifier Ra and detected in synchronization with the drive signal of the phase modulator 7a.

Thereafter, the output is fed back to the phase modulator 7a via the controller cb so that the output of the lock-in amplifier Ra is always zero. By doing this, for counterclockwise light, the resonance point is always kept constant even if the 'lL degree of the optical fiber loop L changes or the entire system rotates. On the other hand, for clockwise rotation, fluctuations in the resonance point due to temperature changes in the optical fiber loop L are removed in the same way as for counterclockwise light, but fluctuations in the resonance point occur for rotation.

The clockwise light is converted into an electrical signal by the photodetector 4b. This signal is detected by lock-in amplifier Rb, and controllers Ca and V
It feeds back to the driving frequency of the ultrasonic optical modulator 3b via CO5b.

The frequency of the clockwise light is changed by 12,
By changing f2, the phase of the light propagating in the right direction within the optical fiber loop L changes, and the resonance point changes. That is, f2 is controlled so that the lock-in amplifier Rb output becomes zero. Therefore, the rotational angular velocity can be detected from the amount of change in f2.

[Problem that the invention seeks to solve]

Since the conventional optical fiber rotation sensor is constructed using a large number of individual parts as described above, it has the drawbacks that it is impossible to miniaturize it and is extremely complicated.

The present invention has been made in view of these points, and an object of the present invention is to obtain an optical fiber rotation sensor that has a small number of parts and can be miniaturized.

[Means for solving problems]

In order to achieve such an object, the present invention includes a light source that emits highly coherent light, a first optical fiber for guiding the emitted light from the light source, and a first optical fiber for guiding the light emitted from the light source. an optical fiber loop guided in both left and right directions by a first optical fiber coupler; Second
A third optical fiber coupler for mixing the light propagating in both left and right directions in the optical fiber, and a phase modulator configured in the optical fiber loop are all provided.

In addition, a light source that emits highly coherent light, and a first optical fiber connector that divides the light emitted from this light source into two and guides it to an optical fiber and mixes the light propagating in both left and right directions taken out from the optical fiber loop. - A knobler, a second optical fiber coupler for guiding the propagating light of the optical fiber into the optical fiber loop in both left and right directions, and taking out to the outside the light that has propagated multiple times in both the left and right directions in the optical fiber loop, and the optical fiber loop. The sensor is provided with a phase modulator configured within the sensor.

[Effect]

In the present invention, a single photodetector detects the left and right rotational lights of the optical fiber ring resonator, and the rotational angular velocity is detected from the degree of separation due to the rotation of the resonance peak.

(Example) A first example of an optical fiber rotation sensor according to the present invention is described below.
As shown in the figure. In FIG. 1, 11 is a high coherence semiconductor laser, 12a, 12b, and 12C are first . Second. Third
The optical fiber couplers 13a and 13b are the first optical fiber couplers 13a and 13b. A second single mode optical fiber, 14 is a photodetector, 15 is a signal generator, 16 is a phase modulator, 17 is a single mode optical fiber loop, and 18 is a signal processor.

Next, the operation of the apparatus shown in FIG. 1 will be explained using FIGS. 1 and 2. FIG. 2 is a waveform diagram for explaining the operation of the sensor shown in FIG. 1. In FIG. 1, light from a high coherence semiconductor laser 11 is coupled to an optical fiber 13a, and propagated in both left and right directions within a single mode optical fiber loop 17 by an optical fiber coupler 12a. The single mode optical fiber loop 17 constitutes a ring resonator, and the light guided therein propagates multiple times within this resonator, and the light propagated multiple times is connected to the optical fiber loop 17 by the optical fiber coupler 12b. The light propagated in both left and right directions is mixed by the optical fiber coupler 12c and converted into an electrical signal by the photodetector 14.

The light propagated multiple times within the optical fiber loop 17 exhibits sharp resonance when all the phases are aligned.

Therefore, if the phase modulator 16 is provided in the optical fiber loop 17 and driven by a triangular wave, the optical fiber loops 1, 7
The phase of the internally propagating light changes, and a sharp resonance is observed in the photodetector output. As the phase modulator 16, for example, there is one in which an optical fiber is wound around a cylindrical piezoelectric element. In this case, when a signal voltage is applied, the optical fiber expands and contracts in accordance with the expansion and contraction of the piezoelectric element, and the phase of the light changes. In FIG. 1, since the light propagated multiple times in both left and right directions in the optical fiber loop 17 is mixed and guided to the photodetector 14, the output of the photodetector 14 has a resonance of both counterclockwise and clockwise light. appears.

Figure 2 shows this situation. When the system is stationary, the left and right beams exhibit similar resonance, so the resonance peaks are observed to overlap as shown in Figure 2 (a), but when the system rotates, the Sagnac )
As a result, a phase difference occurs between the two lights propagating clockwise and counterclockwise within the optical fiber loop 17, and the resonance state changes. Therefore, in the case of clockwise rotation, the resonance peaks separate as shown in Figure 2 (bl), and in the case of counterclockwise rotation, as shown in Figure 2 (C).The heights of the two separated peaks The difference is in the clockwise direction into the optical fiber loop 17.

This is because the intensity of light incident in both counterclockwise directions is different. The direction of rotation can be identified by the fact that the direction of resonance peak separation differs depending on the rotation direction, as shown in FIG. As the optical fiber used in this optical fiber rotation sensor, a polarization maintaining optical fiber is used.

In the above embodiment, the light emitted from both end faces of the high coherence semiconductor laser 11 is coupled to the optical fiber 13a, but as shown in FIG. The light may be separated into two by the optical fiber coupler 12d and input into the optical fiber 13C. Furthermore, in order to extract the light propagated within the optical fiber loop 17 to the outside, an optical fiber coupler 12b is used in FIG. 1, but as shown in FIG.
The second optical fiber coupler 12a for guiding light in both left and right directions may also be used for extracting light. In this way, the optical fiber coupler 12d can simultaneously mix the lights in both the left and right directions. In FIG. 3, the same or equivalent parts as in FIG. 1 are given the same reference numerals.

〔Effect of the invention〕

As explained above, the present invention mixes light propagating in both left and right directions in an optical fiber loop, and detects rotation based on the amount of change in the resonance peak of the light in both left and right directions, so the configuration is simple. This has the effect of making the system more compact.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram showing one embodiment of an optical fiber rotation sensor according to the present invention, FIG. 2 is a waveform diagram for explaining the operation of the sensor in FIG. 1, and FIG. 3 is a diagram showing another embodiment of the present invention. FIG. 4 is a block diagram showing an example of a conventional optical fiber rotation sensor. 11... High coherence semiconductor laser, 12a-12
C... Optical fiber coupler, 13a, 13b... Single mode optical fiber, 14... Photodetector, 15...
Signal generator, 16... Phase controller, 17... Single mode optical fiber loop, 18... Signal processor.

Claims (3)

[Claims] (1) A light source that emits highly coherent light, a first optical fiber that guides the emitted light from this light source, and a first optical fiber coupler that guides the propagating light of the first optical fiber in both left and right directions. a second optical fiber from which light that has propagated multiple times in both left and right directions within this optical fiber loop is taken out by a second optical fiber coupler; and a second optical fiber that propagates in both left and right directions within this second optical fiber. It is characterized by comprising a third optical fiber coupler for mixing light and a phase modulator configured in the optical fiber loop, and detecting rotation based on the amount of change in the resonance peak of light in both left and right directions. Optical fiber rotation sensor. (2) The optical fiber rotation sensor according to claim 1, wherein the light propagating in both left and right directions within the optical fiber loop has different intensities. (3) A light source that emits highly coherent light, and a first light that splits the light emitted from this light source into two and guides it to an optical fiber, and mixes the light that propagates in both left and right directions taken out from the optical fiber loop. a second optical fiber coupler for guiding the propagating light of the optical fiber into the optical fiber loop in both the left and right directions and extracting the light that has propagated multiple times in the left and right directions in the optical fiber loop to the outside; An optical fiber rotation sensor comprising a phase modulator configured in the optical fiber loop, and detecting rotation based on the amount of change in resonance peaks of light in both left and right directions.