JPS61226609A - Optical fiber gyro - Google Patents

Abstract

PURPOSE:To remove the noise which occurs due to the local distortion of the optical fiber by a local temperature change, etc., applied to the optical fiber, and to obtain the optical fiber gyro with a high measuring accuracy by winding one optical fiber so that the part of the equal distance can be close from the center. CONSTITUTION:A central part 12c of the optical fiber is fixed to one edge part 11a of a bobbin 11, one edge 12a is clogged and wound from one edge 11a of the bobbin 11 to other edge part 11b, and next, other edge 12b of the optical fiber is clogged and wound from one edge part 11a to other edge part 11b in the reverse direction on it. Here, for the winding direction of the optical fiber, when respective edges 12a and 12b are wound, they are wound in the opposite direction, and the optical fiber as a whole is finally wound so that it can be the same direction. Next, one edge 12a of the optical fiber is clogged and wound from other edge part 11b of the bobbin 11 to one edge part 11a as the third layer. Further, other edge 12b of the optical fiber is also clogged and wound from other edge part 11b of the bobbin 11 to one edge 11a as the fourth layer.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field of the Invention) The present invention relates to an optical fiber gyro that detects angular velocity using an optical fiber loop.

(Background of the Invention) An optical fiber gyro using a conventional optical fiber loop detects the rotational angular velocity of the optical fiber loop by detecting the phase difference due to the Saniac effect of the optical fiber loop, and its output is 5=cos Δφ. However, this output has the disadvantage of low sensitivity to minute rotational angular velocities (Ω). A phase modulation method is often used as a method to solve this drawback.As a phase modulation method, a method of expanding and contracting the length of an optical fiber using a piezo element (such as PZT) is often used.

Here, the phase modulation signal is f(t) = a sinω,
t, and the time from the modulation point to both output ends of the optical fiber is T,,T, the interference output signal S is 5=cos
(Δφ+r 1I(t Tt) f # (t
−Tz)]ζΔφJ+(77) Xcosω−a (
t −+ (Tt + h) ) + (harmonic component of ω) Itanshirt = 2a 5ini (Tt Tt) (
al+a, so by lock-in detection of this at the frequency of ω, it becomes S″qJt(η)Δφ, and a signal proportional to the angular velocity Ω to be measured can be detected with high sensitivity. will be explained in more detail below with reference to the drawings. Fig. 3 is a diagram showing the principle of a conventional optical fiber gyro, in which 1 is an optical fiber loop, 2 is a light source section, and 3 is a diagram showing the principle of a conventional optical fiber gyro.
A half mirror 14 is a light detector, and 5 is a modulation section formed by tightly winding an optical fiber around a piezo element. Light source part 2
The light is divided into light reflected by the half mirror 3 and light transmitted, and these lights travel clockwise and counterclockwise through the optical loop, respectively.

The light traveling through the optical fiber loops is reflected and transmitted by the half mirror 3 and enters the optical detector 4. The light traveling clockwise through the optical fiber loop and the light traveling counterclockwise interfere with each other on the light receiving surface of the optical detector 4. At this time, when the optical fiber loop rotates, a Saniac effect occurs depending on the angular velocity Ω. The phase shift amount Δφ of the light wave due to the Sanitec effect is expressed by the following equation.

Δφ=8πANΩ/λ where A is the area surrounded by the optical fiber loop, N is the number of turns of the optical fiber, λ is the wavelength of light in vacuum, and C is the speed of light in vacuum.

The modulator 5 expands and contracts the optical fiber tightly wound around the piezo element by driving the piezo element at a constant frequency. Due to this expansion and contraction of the optical fiber, the phase of the light traveling counterclockwise and the light traveling clockwise in the optical fiber loop is modulated, and as a result, the fundamental wave component of the interference light on the light receiving surface of the optical detector 4 is given by the following equation. .゛S, = ΩJ+(η) cos ω11 (t-4(
T+ +Tz) )・−・−・−−−−１・−・・−
・−・−・−・−−−−−−−−・・・−(1) Here, K is a constant, J, and (η) are the above-mentioned 1st order 1st type Be5sel
It is a function.

(1) In equation η=2asin÷(↑+−Tt)ω.

-2asin (gf, T) It is.

Here, f is the modulation frequency of phase modulation, a is the amplitude of modulation,
T is the optical propagation time in the optical fiber loop.

It is understood that by synchronously detecting the output of the optical detector 4, an output proportional to Δφ, that is, the angular velocity Ω, is obtained, and that detection is possible even when the angular velocity is particularly small.

However, since J+(0)=O, it is necessary to shift the modulation point from the center of the optical fiber so that T,≠T8.

Therefore, although it is possible to detect minute angular velocities with this method,
If the same noise source occurs at the same time in parts other than the modulation point that are equidistant from the center of the optical fiber, the noise is canceled, but otherwise the noise appears as it is in the output signal.

Incidentally, noise is generated due to local elongation, stress, etc. due to local temperature changes applied to the optical fiber. In other words, noise generally occurs at the point T, ≠ TzO, and in that case, the noise is included in the output signal.In other words, this configuration prevents local expansion and contraction due to temperature changes in the optical fiber loop itself. Since compensation is impossible, there is a problem in that highly accurate measurements cannot be made after all.

(Objective of the Invention) The present invention solves the above-mentioned drawbacks and uses a simple configuration to prevent measurement errors caused by local expansion and contraction of the optical fiber loop due to temperature changes locally applied to the optical fiber loop, stress applied locally, etc. The purpose of this study is to obtain an optical fiber gyro that is capable of correction and has high measurement accuracy.

(Summary of the Invention) The present invention provides an optical fiber gyro that uses the phase modulation method even if the same noise generation source is applied to two points at the same distance from the flea point (center) of the entire length of the optical fiber. Focusing on the property that noise is canceled and does not appear in the output, the technical point is that the optical fiber is wound in one direction as a whole so that the optical fiber parts that are equidistant from the center of one optical fiber are close to each other. There is.

(Embodiment) FIG. 1 shows an embodiment of the present invention, in which (a) to (d) show the order in which an optical fiber loop is wound around a bobbin.

In FIG. 1, 11 is a bobbin, and 12 is an optical fiber.

One end of the optical fiber is 12a, the other end is 12b, and the center part is 12a.
2C, one end of the bobbin is 11a, and the other end is 11b.The optical fiber loop is wound in the following order.

FIG. 1(a) - - - - - - Fixing the central part 12C of the optical fiber to one end 11a of the bobbin 11,
One end 12a of the optical fiber is packed and wound from one end 11a of the bobbin 11 to the other end 11b, and then the other end of the optical fiber is wound. 12b is packed and wound thereon from one end 11a to the other end 11b of the bobbin 11 in the opposite direction to the winding direction.

Here, the winding direction of the optical fiber is as described above, when each end 12a, 12b of the optical fiber is wound, it is wound in the opposite direction, but the optical fiber as a whole is wound in the same direction after all. .

FIG. 1(d) --- Next, one end 12a of the optical fiber is wound as the third layer from the other end 11b of the bobbin 11 to the one end 11a, and then the other end 12b of the optical fiber is wound. Similarly, as the 411th stitch, the bobbin 11 is wound from the other end 11b to the one end 11a. ' Note that if the optical fiber is filled with silicone resin or the like after being wound, noise generated due to distortion of the optical fiber due to external temperature changes or forces can be reduced.

Furthermore, if the optical fibers are coated with metal and the optical fibers are brought into contact with each other with solder or the like after being wound around the bobbin 11, the distortion of the optical fibers due to locally applied temperature changes will be reduced and the generation of noise will be reduced. can be reduced.

FIG. 2 shows another embodiment of the invention.

In this embodiment, the central portion 12C of the optical fiber is connected to the bobbin 1.
1, and one end 12a of the optical fiber is wound from the one end 11a of the bobbin 11 to the other end 11b with a gap provided without crowding.

Next, the other end 12b of the optical fiber is wound thereon in the opposite direction to the winding direction from one end 11a of the bobbin 11 to the other end 11b in the gap where the one end 12a of the optical fiber is wound.

Here, the winding direction of the optical fiber is as described above, when each end 12a, 12b of the optical fiber is wound, it is wound in the opposite direction, but the optical fiber as a whole is wound in the same direction after all. The matter is as described above.

(Effects of the Invention) According to the present invention, a simple structure in which a single optical fiber is wound so that the parts equidistant from the center are close to each other allows light to be absorbed by local temperature changes applied to the optical fiber. Noise caused by local distortion of the fiber can be removed, and an optical fiber gyro with high measurement accuracy can be obtained.

[Brief explanation of the drawing]

1 and 2 are diagrams showing an embodiment of the present invention, and FIG. 3 is a diagram showing a conventional optical fiber gyro. (Explanation of symbols of main parts) 1. --- Optical fiber loop 2. ---
1---・---・Light source section 3------・Half mirror 4・------
-----One light detector 11------------
Bobbin 12 --- Optical fiber

Claims (1)

[Claims] By winding one end of a single optical fiber in a fixed direction with the center as a starting point and winding the other end in the opposite direction, optical fiber sections that are equidistant from the starting point are brought into close proximity. An optical fiber gyro characterized in that the optical fiber is wound in the same winding direction as a whole when the optical fiber is in the same state.