JPH04198903A - Optical fiber coil - Google Patents

Abstract

PURPOSE:To make output drift small by a simple constitution and to accomplish very stable temperature characteristic by winding an optical fiber symmetrically in the radial direction and the center axis direction of an optical fiber coil and also arranging a polarization cancelling device for controlling the plane of polarization in the center part of a sensing coil. CONSTITUTION:The optical fiber 1 having desired length is wound on bubbins 11 and 12 for the same length from both ends to be divided into two, and the fiber type polarization cancelling device 5 is fused and spliced in the center part. Furthermore, the optical fibers which are mutually in an equal distance from the center part by taking the center part 2 as reference are wound to a bubbin 3 for a fiber coil so that they may be nearly at the same position in the radial direction of the coil and symmetrical with the center axis. Thus, a temperature difference between the optical fibers 1 wound around to the respective layers of the coil is reduced and a phase error in an optical interference output signal is made extremely small and detection sensitivity is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application This invention relates to an optical fiber coil for sensors.Conventional technology related to an optical fiber coil for sensors in which a portion used as a sensing loop is wound into a coil shape. Sensors using optical fibers are increasingly being used as sensors for applications such as high sensitivity, small size, lightness, and good environmental resistance. In optical fiber gyroscopes used to detect rotational angular velocity, the optical fiber is wound into a coil to improve sensitivity.
Even if the area surrounded by the fiber is increased, however, when the optical fiber is wound in a coil shape and in multiple layers, the temperature of each part of the optical fiber becomes different from each other.As a result, the measurement accuracy decreases. However, in order to reduce the effects of such temperature differences, various methods have been proposed for winding the optical fiber symmetrically around the sensing coil. Figures 1 and 4 show conventional optical fiber coils. In the figures, 1 is the optical fiber 2 is the central part of the optical fiber, 3 is the coil bobbin,
4 is the central axis method of the sensing coil. 3rd and 4th
As shown in the figure, starting from the middle part 2 of the entire length of the optical fiber 1, starting from the middle part 2 of the entire length of the optical fiber 1, starting from the winding point M1 layer or every 2 layers, both optical fibers can be alternately coiled. As shown in Figure 1, after winding optical fibers of desired length onto two rewinding bobbins 11 and 12 so that they are of equal length, these bobbins are used as the supply side, and By replacing the supply coil for each layer, a symmetrically wound optical fiber coil is created.In addition, the optical fiber used is
Problems to be Solved by the Invention However, in the above-mentioned wound optical fiber coil, it is possible to maintain the incident polarization direction with a polarization-maintaining fiber.
i The coil manufacturing process has become extremely complicated.The time required to manufacture the coil has increased, and the manufacturing yield has not been improved.Additionally, there is a problem with optical fibers, or the need to skip just one or two layers. Due to the fact that the optical fiber is wound, distortion occurs in the optical fiber, deteriorating the optical propagation characteristics, and there is also the problem that the optical fiber itself is easily damaged.In addition, the desired optical fiber is The fiber had to be divided into two parts without being cut into equal lengths, which required a manufacturing process to rewind the fiber.Furthermore, the optical fiber used was a polarization-maintaining fiber. Currently, the cost of fiber coils is extremely high, and the productivity of coils is extremely low.The present invention solves these conventional problems and eliminates output drift with a simple configuration. To provide an optical fiber that is extremely small and has extremely stable temperature characteristics, and at the same time to provide an optical fiber coil that is excellent in mass productivity.Means for Solving the ProblemsThe optical fiber coil of the present invention is an optical fiber coil. The optical fibers constituting the optical fiber coil are wound at approximately the same position in the radial direction of the optical fiber coil, and at the same distance from the central part in the longitudinal direction of the optical fiber coil. The coil also has symmetry with respect to the center of the coil.Fiber-type depolarization is applied to the center of the coil in order to reduce the fluctuation factors of the plane of polarization when a single mode fiber is used as the optical fiber. In addition, the bobbin around which the optical fiber is wound is made of a material with excellent thermal conductivity. With such a configuration, it is possible to reduce the temperature difference between the optical fibers wound in each layer of the coil due to changes in ambient temperature (2. Optical interference and to minimize the phase error in the power signal) By inserting an L-fiber-type depolarization device, variations in optical propagation characteristics can be extremely reduced, and calibration It is also possible to improve the sensitivity.The method for manufacturing the optical fiber coil here is to create symmetry with respect to the central axis direction of the optical fiber coil.After winding one side of the fiber, the fiber coil It is possible to create an optical fiber coil for a sensing loop by simply reversing the fiber coil without changing the rotation direction of the fiber coil. An embodiment of the present invention will be briefly explained below with reference to the drawings. Fig. 1 shows a method of manufacturing an optical fiber coil in an embodiment of the present invention. Figure 2 shows a cross-sectional view of the optical fiber coil. First, the manufactured optical fiber 1 (FIG. 1 a) of a desired length is wound onto rewinding bobbins 11 and 12 to the same length from both ends thereof.
A fiber-type depolarizer (
(Fig. 1b) Furthermore, this depolarizer connects the optical fibers connected at the center to the fiber coil bobbin 3, and connects them to the optical fibers that are equidistant from the center with reference to the center 2. force (in the radial direction of the coil, make sure that the coils are at approximately the same position, and also wrap the coil symmetrically about the center axis (first
Figure C) In other words, the optical fiber coil 3 and the rewinding bobbin 1
2 are arranged on the same plane and rotated, and at the same time, the optical fiber 1 is wound around the optical fiber coil 3 from the rewinding bobbin 11 while applying tension. Repeat the same operation to wrap the rewinding bobbin 11 around the optical fiber coil 3.
In this method of manufacturing an optical fiber coil, the optical fiber coil 3 can be
This makes it possible to wind the fiber symmetrically around the fiber coil.The manufacturing process of the fiber coil becomes very simple and can be manufactured in a short time. is as shown in Figure 2.a In this example, Kovar material, stainless steel material, etc. were used as the material for the bobbin of the optical fiber coil. Other materials may be used as long as they have good thermal conductivity. None~ MaL
It goes without saying that an ordinary single-mode fiber may be used as the optical fiber, and a polarization-maintaining fiber may be used as the coil of the sensing fiber loop.The present invention is limited to the above-mentioned embodiments. However, various modifications are possible based on the spirit of the present invention, and these are not excluded from the scope of the present invention. The optical fiber is wound symmetrically around the fiber coil in the radial direction and central axis direction, and in addition, a depolarization device ( Since the optical fiber coil is made of a photothermal conductive material, the optical fiber coil for sensing can provide stable high optical interference power even with changes in ambient temperature, and is available at an inexpensive price. Deshika I have the ability to provide stable services＼ It is possible and practically very effective.

[Brief explanation of the drawing]

Fig. 1 shows a procedure for symmetrically winding an optical fiber coil according to an embodiment of the present invention. Fig. 2 shows a cross-sectional view of an optical fiber coil manufactured by the same method. This is a cross-sectional view of the symmetrical winding of the optical fiber 2... the intermediate plate of the fiber 3...
・Fiber coil k 4...Coil center #L 5・
...Fiber type depolarization device M, 11, 12... Bobbin for rewinding. Name of agent: Patent attorney Akira Okaji and two others Figure 1 (b) Figure 2 Figure 6 Figure 4

Claims (1)

[Claims] (1) The entire length of the optical fiber is divided into sections (a) and (b).
An optical fiber coil (2) characterized in that it is equally divided into two sections, and an optical fiber type depolarizer is disposed in the center of the sections (a) and (b); the material of the bobbin around which the optical fiber is wound; (3) The optical fiber coil according to claim 1, characterized in that a single mode optical fiber is used as the optical fiber.