JPS59610A - Optical fiber gyroscope - Google Patents

Abstract

PURPOSE:To improve an S/N, by providing optical fiber separately to left rotating light and right rotating light. CONSTITUTION:As left rotating light and right rotating light transfer respectively different optical fibers 2-1, 2-1, even if there is return light at incident terminals T1, T2 by Rayleigh scattering, etc., the return light does not have effects on outputting light of output terminals T3, T4. Therefore, an S/N in output signal of a differential amplifier 5 is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION fil Technical Field of the Invention The present invention relates to fiber optic gyroscopes that use optical fibers to act as angular velocity sensors.

(2) Background of the technology Gyroscopes use a single characteristic that indicates a fixed direction that is initially set regardless of the surrounding situation.
For example, it is possible to detect the angular velocity of a moving object equipped with a gyroscope and determine the direction of movement, speed, etc. Therefore, gyroscopes are essential for direction indication, attitude control, etc. of vehicles that operate over long distances, such as airplanes and ships.

In general, gyroscopes were mainly mechanical ones that utilized the moment of inertia of a rotating body, but recently, gyroscopes have become smaller and
Fiber optic gyroscopes have been proposed which have advantages such as low power consumption and low cost.

(3) Prior Art and Problems In a conventional fiber optic gyroscope, a single optical fiber is wound into a coil many times. When counterclockwise light and clockwise light are input from both ends of this optical fiber, a phase difference Δθ is generated between the left and right lights depending on the angular velocity Q of the gyroscope. This is called the Zabnak effect, and the phase difference Δθ is expressed by the following equation.

8πLR Δθn□Ω λC However, L is 7 eye length R is the radius of the curve of the fiber coil λ is the light wavelength C is the speed of light in vacuum. The input end of an optical fiber is also the output end, and as a result, an optical branch is required at the output end (input end) of the optical fiber.

However, within an optical fiber, there are minute fluctuations in the refractive index, and a scattering loss called Rayleigh scattering occurs to a greater or lesser extent. Therefore, for example, if the output light of the counterclockwise light and the input light of the clockwise light are split at the output end (input end) of an optical fiber, the output light of the counterclockwise light will always be affected by the scattering of the incident light of the clockwise light. Return light mixes in as noise. As a result, there is a problem that the S/N (signal/noise) ratio is low.

(4) Purpose of the Invention The purpose of the present invention is to provide a method for identifying the input end and the output end of the optical fiber based on the concept of separately providing a coiled optical fiber for left and right directions. As a result, the return light of the clockwise light is prevented from being mixed with the output light of the counterclockwise light at the output end of the optical fiber, thereby improving the 87N ratio and solving the above-mentioned problems with the conventional type. be.

(5) Structure of the Invention According to the present invention, a pair of optical fibers are wound many times parallel to each other in a coil shape, and a left-handed beam and a right-handed beam are simultaneously input to the input end of each optical fiber. first and second conversion means for converting the output light at the output end of each optical fiber into an electrical signal; and a difference for amplifying the difference between the electrical signals of the first and second conversion means. A fiber optic gyroscope is provided, characterized in that it comprises dynamic amplification means.

Further, according to the present invention, a pair of optical fibers are wound many times in a coil shape and parallel to each other, a light reflection device provided at one output end of the optical fiber, a laser generating means, and a light reflection device provided at one output end of the optical fiber. an optical directional coupler for making the laser beam of the laser generating means enter the input end of each party fiber as counterclockwise light and clockwise light, and receiving the returned light at the input end of each party fiber; and the light directional coupler. a first converting means for converting the returned light component of the optical fiber into an electrical signal; a second converting means for converting the output light at the other output end of the optical fiber into an electrical signal; There is provided an optical fiber gyroscope characterized by comprising differential amplification means for amplifying a difference between electrical signals of the conversion means.

(6) Examples of the invention Hereinafter, the present invention will be explained in detail with reference to the drawings.

FIG. 1 is a diagram showing a first embodiment of an optical fiber gyroscope according to the present invention. In FIG. 1, reference numeral 1 denotes a double-wound optical 7-eyeper coil, and a pair of optical fibers 2-
1.2-2 are wound many times parallel to each other. In this case, the optical fiber 2-1 is for counterclockwise light, and the optical fiber 2-2 is for clockwise light. A laser generating means such as a laser diode 2 is connected to the input end T1 of the optical fiber 2-1 and the input end T2 of the optical fiber 2-2 through an optical directional coupler (three terminals) 3 and a lens (not shown). Laser beams are simultaneously incident. Further, the output light from the output end T5 of the optical fiber 2-1 and the output end T4 of the optical fiber 2-2 is transmitted through a lens (not shown) to the air converter 4-1. For example, PIN7 otodiode,
The signal is supplied to an Avalanche photodiode (APD) and converted into an electrical signal. After that, each converter 4-1
．． The difference between the output signals 4-2 is amplified by the differential amplifier 5.

For example, the phase shift of counterclockwise light with respect to the angular velocity Ω is 2Δ
When the light is applied to the air/air converter 1 at θ, the phase shift of the clockwise light is applied to the air/air converter 4-2 at -2Δθ. That is, the output of the differential amplifier 5 has a phase shift of 4
Δθ will appear.

In FIG. 1, since the left-handed light and the right-handed light are transmitted through different optical fibers 2-1, 2-2, the input end TI is affected by Rayleigh scattering and the like.

Even if there is returned light at T2, the returned light does not affect the output light at the output end T5°T4. Therefore,
The 87N ratio in the output signal of the differential amplifier 5 is improved.

FIG. 2 is a diagram showing a second embodiment of the original fiber gyroscope according to the present invention. In FIG. 2, unlike the case in FIG. 1, the output end T4 of the optical fiber 2-2 is provided with an end 6 that reflects almost 100% of the light.
The electrical converter 4-2 receives the returned light at the input end T1 of the optical fiber 2-1 and the input end T21c of the optical fiber 2-2 via the optical directional coupler (four terminals) 3'. However, in this case, in particular, the output end T4 of the optical fiber 2-2
Since the optical fiber 2-2 is equipped with 6 light reflecting ends,
The returned light at the input end T2 of the input terminal T2 is received. The phase shift of this returned light is -2Δθ (clockwise rotation)+2Δθ (counterclockwise rotation)=0, and mainly corresponds to Rayleigh scattered light. Therefore, if the output of the optical/IL converter 4-2 is supplied to the differential amplifier 5 through an appropriate attenuator (not shown), the output of the differential amplifier 5 will be affected by Rayleigh scattered light, etc. can be reduced. Note that in this case, the phase shift in the output of the differential amplifier 5 is 2Δθ.

FIG. 3 is a diagram showing a third embodiment of the optical fiber gyroscope according to the present invention. In FIG. 3, the translucent light-reflecting end 7 is connected to the optical fiber 2-1 relative to the element of FIG.
It is attached to the output terminal T3 of. Therefore, in this case,
The optical/electrical converter 4-2 is connected to the input end T1 of the optical fiber 2-1.
This means that a large amount of return light will be received. but,
The output of the differential amplifier 5 is almost the same as in FIG.

(7) As described in detail, according to the present invention, separate optical fibers are provided for the left and right lights, so that, for example, the return light of the clockwise light does not mix into the output of the counterclockwise light. , therefore, S
/N ratio can be improved.

[Brief explanation of drawings]

FIG. 1, FIG. 2, and FIG. 3 are diagrams showing first, second, and third embodiments of the optical fiber gyroscope according to the present invention, respectively. 1: Optical fiber coil, 2-1 = Optical fiber for counterclockwise light, 2-2: Optical fiber for right-handed light reception, 3.57a optical directional coupler, 4-1.4-2: Optical/electrical converter , 5: Differential amplifier, 6: Light reflection end, 7: Translucent light reflection end. Patent applicant: Fujitsu Limited Patent application agent: Akira Aoki, patent attorney: Kazuyuki Nishidate, patent attorney: Yukio Uchida, patent attorney: Akira Yamaguchi

Claims (1)

[Claims] 1. A pair of optical fibers wound parallel to each other in a coil shape, a laser generating means for simultaneously inputting counterclockwise light and clockwise light into the input end of each optical fiber, and each of the above-mentioned optical fibers. 7. The first converts the output light at the output end of the eyeper into an electrical signal. a second converting means; An optical fiber gyroscope comprising: differential amplification means for amplifying the difference between the electrical signals of the second conversion means. λ A pair of optical fibers wound in a coil shape in parallel to each other, a light reflecting end provided at one output end of the optical fiber, a laser generating means, and a laser beam of the laser generating means An optical directional coupler for inputting counterclockwise light and clockwise light into the input end of an optical fiber and receiving returned light at the input end of each fiber, and converting the returned light component of the optical directional coupler into an electrical signal. a first converting means for converting the output light at the other output end of the optical fiber into an electrical signal; Second
A fiber optic gyroscope is provided with differential amplification means for amplifying the difference between the two layers of the conversion means. 5. The optical fiber gyroscope according to claim 2, wherein a translucent light reflecting end is added to the other output end of the optical fiber.