JPH02271307A - Production of constant polarization optical fiber coupler - Google Patents

Abstract

PURPOSE:To simplify a registration stage and to automate a production process by observing the luminance distribution of the fiber images obtd. by the transmitted light of constant polarization optical fibers by using an image sensor while rotating the constant polarization optical fibers and registering stress imparting parts. CONSTITUTION:Two pieces of the constant polarization optical fibers 12A, 12B which are placed in parallel are previously so arranged that the fibers can be respectively discretely rotated by motors 30. The light from a light source 24 placed on one side of the constant polarization optical fibers 12A, 12B is observed with the image sensor, for example, TV camera 28, placed on the opposite side and the fiber images of the optical fibers 12A, 12B are processed by a computer 32. The motors 30 are rotated by the computer 32 in such a manner that the profiles of the luminance of the optical fibers 12A, 12B are both made into the same. The registering of the stress imparting parts of the two optical fibers 12A, 12B is executed automatically in such a manner.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a polarization-maintaining optical fiber coupler that splits or merges light while maintaining the polarization direction of the light. This relates to a stretching type optical cover.

[Prior Art] A fused and stretched type polarization constant optical coupler is manufactured in a first-order manner.

(1) First, as shown in Fig. 2a, the stress applying section 14 is aligned for the two polarization-controlled optical fibers 12A and H (
so that the main axis 15 is parallel).

Note that 16 is a core and 18 is a cladding.

(2) A portion 20 of them is heated and fused (FIG. 2b) and stretched to form a constant polarization optical fiber coupler 10 (ff
iZc diagram).

(3) Conventionally, in order to align the four stressed parts 14, the third
The measurement system was configured as shown in the figure.

That is, the polarization constant optical fibers 12A and 12B are
8, to eliminate refraction of light on the surface of the cladding 18, a light source 24 is placed below, and observation is made using a microscope 26 from above.

Since the stressed section 14 has a different refractive index from the cladding 18, the light emitted from the light source 24 has stress properties! It is refracted at the boundary between the f-m 14 and the cladding 18, and the stress applying part 14 is
image can be observed.

Without looking at this image, the constant polarization optical fibers 12A and 12B are rotated to perform alignment.

[Problems to be Solved by the Invention] In the conventional method, (1) a container filled with 7,000 square meters is required for observing the stress-applying portion 14, (2) it is necessary to wipe off the matching circle after positioning, etc. There are drawbacks.

[Means for Solving the Problems] In particular, the process of aligning the stress applying portions is carried out by the following operations (Fig. 1), namely: (1) Fiber images obtained by transmitted light of the constant polarization optical fibers 12A, The brightness distribution is observed using the image sensor 28, and (2) the polarization constant optical fiber is rotated based on the observation.

[Explanation] [1] Phenomena used: The present invention utilizes a third-order phenomenon.

Is there a light source 24 on one side of the polarization-controlled optical fiber 12, as in No. 451J? 1ξ, when observed from the opposite side with an image sensor (for example, a TV camera) 28, depending on the position of the stress applying part 14, the appearance of the phi/S image becomes
307193 No. 5IIQ,).

That is, (1) As shown in Fig. 5a, when observed from the direction of the main @ 15, the image of the optical fiber obtained by the TV left camera 8 is as shown in the isb diagram, and its brightness profile is fl.
It will look like the isc diagram.

A feature of this case is that a core image can be clearly seen at the center a.

The outside of the area is, in order, slightly dark (b), slightly bright (C), even darker (d), very bright (e), and dark (f).

(2) Then, when the constant polarization optical fiber 12 is rotated and observed from a direction of 45 degrees to the main axis 15 as shown in Fig. 6a, the image of the optical fiber becomes as shown in Fig. 6b; The brightness profile is as shown in FIG. 6c.

The characteristic of this case is that the center a is bright and the sides b on both sides thereof are dark.

The outside is slightly brighter (C) and darker (d).
).

(3) Roughly rotate the constant polarization optical fiber 12 to
When observed from a direction perpendicular to the principal axis 15 as shown in Fig. 7a, the image of the optical fiber becomes as shown in Fig. 7b, and its brightness profile becomes as shown in Fig. 7c.

The characteristic of this case is that the center a is dark and the sides b on both sides thereof are bright.

Note that the outside is, in order, slightly dark (C), slightly bright (d), and dark (e).

Note that although the above is a case of the PANDA type, in the case of other types of polarization constant optical fibers, although the profiles are different, each unique type is observed.

[2] Outline of stress applying unit alignment device: As shown in FIG. 1, two polarization-controlled optical fibers 12A and B placed in parallel are
By motor 3o.

Make sure each can be rotated individually.

As described above, fiber images of the constant polarization optical fibers 12A and 12H are obtained by the image sensor (TV camera) 28, and the images are processed by the computer 32.

Then, the computer 32 rotates the motor 30 so that the brightness profiles of the constant polarization optical fibers 12A and 12H are the same (for example, so that they both have the profile shown in FIG. 5c).

By doing so, the stress applying portions can be automatically aligned without requiring the matching wheel 22.

[3] Regarding fused stretching: In normal Kabra manufacturing, after aligning the stress-applying parts as described above, the fused parts are stretched while being heated with a burner to make the fused parts thinner and to improve the coupling of light. Make it happen.

If this process is also performed under the control of the computer 32, the entire process of manufacturing a constant polarization coupler can be performed automatically under computer control.

[Effect of the invention 1] By observing the brightness distribution of the fiber image obtained by the transmitted light of the constant polarization optical fiber using an image sensor, and rotating the constant polarization optical fiber based on the observation, the stress applying part can be adjusted. Since the position and alignment process is performed, the following effects are achieved.

(1) Since no matching oil is used, there is no need to put the polarization-controlled fiber in matching oil or wipe it off afterwards.

(2) A series of coupler manufacturing processes can be automated using a computer.

[Brief explanation of drawings]

FIG. 1 is a schematic explanatory diagram of an example of equipment used in carrying out the present invention. FIGS. 2a to 2C are explanatory diagrams showing a general manufacturing method of a constant polarization optical fiber coupler in the order of steps, and FIG. 3 is an explanatory diagram of a conventional method for positioning and aligning stress applying parts. FIG. 4 shows an optical fiber image y! used in the present invention. An explanatory diagram of the I detection method. Figures 5a to 57c are detailed explanatory diagrams of the present invention. FIGS. 5a, 6a, and 7a are explanatory views of observation directions. FIGS. 5b, 6b, and 7b are explanatory views of optical fiber images. The t55C diagram, the 6c diagram, and the f: JSVc diagram are explanatory diagrams of the brightness distribution profile. lO: Constant polarization optical fiber coupler 15: Main axis 12: Constant polarization optical fiber 14: Stress applying section 16: Core
18: Clad 20 part 22: Matching illumination 24: Light source 26: Microscope 28: Image sensor (TV right camera

Claims (1)

[Claims] A step of aligning the stress applying portions of two polarization constant optical fibers, and a step of fusing and stretching a portion of the two polarization constant optical fibers whose stress applying portions have been aligned. In the method of manufacturing a constant polarization optical fiber coupler, the step of aligning the stress applying portion is performed by the following operations, namely;
Manufacturing a constant polarization optical fiber coupler by observing the brightness distribution of a fiber image obtained by transmitted light of the constant polarization optical fiber using an image sensor, and rotating the constant polarization optical fiber based on the observation. Method.