JPS63290913A - Manufacture of optical fiber angular velocity meter - Google Patents

Abstract

PURPOSE:To obtain high sensitivity and to reduce the drift and size of an optical fiber speed indicator by extending an optical fiber which forms a filer sensing loop and forming to a 1st directional in one body. CONSTITUTION:The 1st directional coupler 3 is formed integrally of the optical fiber 2 forming the fiber sensing loop nearby the fiber sensing loop 1. A polarizer 5 is connected to the direction coupler 3 through a splice 4and a 2nd directional coupling 7 is connected to the polarizer 5 through a splice 6. A light emitting element 10 and a light receiving element 11 are connected to this directional coupler 7 through splices 8 and 9 respectively. Consequently, the number of the splices is decreased.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method of manufacturing an optical fiber angular velocity meter, and more particularly to a method of manufacturing an all-optical fiber type angular velocity meter.

[Prior Art] Generally, there are two types of optical fiber gyrometers: a bulk type in which a polarizer and a branching coupler are constructed from bulk parts such as crystals, and an all-optical type in which these members are constructed from optical fiber type parts. The former method requires bonding glass components or bonding and fixing optical fibers to bulk components, making it vulnerable to temperature changes, whereas the latter method has high reliability against temperature changes; For this reason, all-optical fiber systems have come to be widely used in optical fiber angular velocity meters that require high sensitivity and low drift.

FIG. 11 shows the configuration of a conventional optical fiber angular velocity meter based on this all-optical fiber system. After the measurement light emitted from the light emitting element 31 passes through a directional coupler (optical fiber coupler) 32 and a polarizer 33, it is branched by a directional coupler 34 and connected to a fiber sensing loop (hereinafter referred to as FSL). 35 in opposite directions. Thereafter, these two measurement lights are combined by a directional coupler 34 and enter a light receiving element 36 via a polarizer 33 and a directional coupler 32. Note that 37 is a phase modulator using a piezo element.

Here, it is known that when the FSL 35 rotates, a phase difference occurs between the measurement lights propagated in opposite directions through the FSL 35, and the phase difference between both measurement lights incident on the light receiving element 36 is detected. By doing so, the angular velocity of the FSL 35 can be determined.

[Problems to be Solved by the Invention] Such an all-optical fiber type optical fiber angular velocity meter has problems between the conventional directional coupler 32, the light emitting element 31, the polarizer 33, the light receiving element 36, and the directional coupler. 34 and polarizer 33,
Splice between each FSL35 (permanent connection)
It was manufactured by connecting 38 to 43. That is, the measurement light passes through as many as six splices in total, and in particular, the measurement light passes through the splices 39 and 41 provided before and after the polarizer 33 twice.

Previously, this station had the following problems.

■ Reflection noise of measurement light from each splice occurs, causing drift. In particular, the influence of the splices 42 and 43 corresponding to the input and output ends of the FSL 35 is large.

■ Passing through each splice causes loss in the measurement light, reducing the minimum receiving sensitivity.

■ Fiber connection requires a lot of man-hours and is time-consuming.

■ Reinforcement and storage of each splice are required, making it difficult to downsize.

SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a manufacturing method that solves the problems of the prior art described above and allows a compact, all-optical fiber type optical fiber angular velocity meter with high sensitivity and low drift to be obtained.

[Means for Solving the Problems] In order to achieve the above object, the method for manufacturing an optical fiber gyrometer of the present invention includes connecting a polarizer to a fiber sensing loop via a first directional coupler, and In the method for manufacturing an all-optical fiber type optical fiber angular velocity meter in which a light emitting element and a light receiving element are connected to the polarizer via a second directional coupler, the optical fiber forming the fiber sensing loop is extended. This is a method of integrally molding at least the first directional coupler.

[Function 1] By integrally manufacturing at least the first directional coupler using the optical fiber forming the FSL, the number of splices existing in the gyro meter is reduced, so the gyro meter This makes it possible to improve the performance and downsize the device.

In particular, since the splices that were conventionally located at the input and output ends of FSL can be removed, anti-I31 noise is reduced.
Low drift is achieved.

Furthermore, if the polarizer and the second directional coupler are integrally molded using optical fiber for FSL, an angular velocity meter with even higher performance can be obtained.

[Example] Embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is a block diagram of an optical fiber angular velocity meter manufactured by the method of the present invention. The first directional coupler 3 is integrated with the optical fiber 2 forming the FSL1 in the vicinity of the FSL1.
is molded. A polarizer 5 is connected to the directional coupler 3 via a splice 4, and a second directional coupler 7 is connected to the polarizer 5 via a splice 6. Furthermore, splices 8 and 9 are added to this directional coupler 7.
A light-emitting element 10 and a light-receiving element 11 are connected to each other via. Note that 12 in the figure is a phase modulator composed of a piezo element.

Here, optical fiber 2 and FSL1 forming FSL1
The optical fibers used in other components are shown in Figure 2a.
Core 13. It is a polarization maintaining optical fiber consisting of a cladding 14, an elliptical jacket 15, and a support 16, each having a refractive index distribution in the X-axis direction and the Y-axis direction as shown in FIGS. It has various characteristics as shown in Table 1.

Table-1 In other words, the refractive index of the elliptical jacket 15 is supported 16
By setting it lower and giving a difference in the cut-on wavelength to the two orthogonal polarization modes, a difference is created in the bending loss of the two polarization modes, so that only one mode propagates in the polarizer 5. It is something.

Next, a method for manufacturing such an optical fiber gyrometer will be described.

First, wind the optical fiber 2 and connect it to the FSLI as shown in Figure 3.
After forming the optical fiber 2, both ends of the optical fiber 2 are extended and polished portions 17 are provided near each end. Polishing section 17
As shown in FIG. 4, a groove 19 with a predetermined curvature is provided in a quartz substrate 18, and an optical fiber (bare wire) 2 is inserted into this groove 19.
After accommodating and fixing with epoxy resin, the optical fiber 2
The cladding 14 is polished together with the quartz substrate 18 until a portion of the cladding 14 is exposed.

The directional coupler 3 is formed by bonding such polished parts 17 together as shown in FIG. At this time, one end 2 of the optical fiber 2
The relative position of each polishing part 17 was adjusted so that the power of light entering from zero and exiting from the other end 21 was minimized. As a result, the directional coupler 3 divides the light into two equal parts.
It will operate as a B coupler. Incidentally, FIGS. 6 and 7 respectively show a vertical cross-sectional structure and a cross-sectional structure of the directional coupler 3.

Next, a polarizer 5 is connected to one end 20 of the directional coupler 3 with a splice 4, and a directional coupler 7 is connected to the polarizer 5 with a splice 6. Further, the other end of the directional coupler 7 is connected to the LD module pigtail by a splice 8 and to the PD module pigtail by a splice 9, and is coupled to a light emitting element 10 and a light receiving element 11, respectively.

In this way, an optical fiber gyrometer without a splice is formed between the FSLI and the directional coupler 3.

Note that not only the first directional coupler 3 but also the polarizer 5 and the second directional coupler 7 can be manufactured integrally using the optical fiber 2 forming the FSL1. in this case,
First, as shown in FIG. 8, two polishing sections 1 similar to those shown in FIG. 3 are placed near both ends of the optical fiber 2.
7 is provided, and between these polishing parts 17 provided on one end side of the optical fiber 2, a part is provided for winding the fiber at a predetermined radius, and this is used as a polarizer 5.

Next, as shown in FIG. 9, the corresponding polishing parts 17 are bonded together to form the first. Second directional couplers 3 and 7 are formed.

At this time, the power of the light entering the optical fiber 2 from one end 22 and exiting from the other end 23 is monitored, and the power is sequentially applied to the directional couplers 3 and 7 so that the power is minimized (
The relative position of each polishing section 17 is adjusted. As a result, each directional coupler 3 and 7 divides the light into two equal parts, so-called 3 d
It will operate as a B coupler.

After that, the optical fiber 2 on the side where the polarizer 5 is not formed is cut between the directional couplers 3 and 7 (x mark in Fig. 9).
At the same time, both ends 22 and 23 of the optical fiber 2 connected to the directional coupler 7 are coupled to the light emitting element 10 and the light receiving element 11, respectively.

This forms a fiber optic gyrometer that does not include any splices, as shown in FIG.

Note that both ends 22 and 23 of the optical fiber 2 and the light emitting element 1
0 and the light receiving element 11 can also be connected using splices.

Further, a depolarizer can also be inserted between the light receiving element 10 and the directional coupler 7 without connection.

[Effects of the Invention] As explained above, according to the present invention, the following excellent effects are exhibited.

(1) Since the number of splices is reduced, loss is reduced, and the minimum reception sensitivity of rotational angular velocity is improved, and reflection noise due to splices is reduced, resulting in a reduction in drift.

(2) Improved reliability against vibration and temperature changes.

(3) Splice reinforcement and storage are no longer necessary, and the optical system can be made more compact.

(4) The number of man-hours required for connecting optical fibers is reduced, improving economic efficiency.

(5) Since it is not necessary to evaluate the characteristics of the directional coupler itself, the number of evaluation steps is reduced.

[Brief explanation of drawings]

Figure 1 is a block diagram of an optical fiber gyrometer manufactured by the method of the present invention, and Figure 2 is a cross-sectional structure of the polarization-maintaining optical fiber used in the examples and its respective refractions in the X-axis direction and Y-axis direction. 3 to 7 are process diagrams illustrating a manufacturing method according to an embodiment of the present invention; FIGS. 8 to 10 are process diagrams illustrating another embodiment; FIG. 11 is a configuration diagram of a conventional optical fiber angular velocity meter. In the figure, 1 is a fiber sensing loop, 2 is an optical fiber, 3 is a first directional coupler, 4,6°8.9 is a splice, 5 is a polarizer, 7 is a second directional coupler, 10 1 is a light emitting element, and 11 is a light receiving element. Patent Applicant Hitachi Cable Co., Ltd. Representative Patent Attorney Nobuo Kinutani Figure 4 Figure 5

Claims (2)

[Claims] (1) An all-optical fiber in which a polarizer is connected to the fiber sensing loop via a first directional coupler, and a light emitting element and a light receiving element are connected to the polarizer via a second directional coupler. In the method of manufacturing an optical fiber angular velocity meter, the optical fiber forming the fiber sensing loop is extended and at least up to the first directional coupler is integrally molded. manufacturing method. (2) The first aspect of the present invention is characterized in that the polarizer and the second directional coupler are also integrally formed by the optical fiber forming the fiber sensing loop.
Manufacturing method described in section.