JPS6146803B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for forming optical connections between multiple terminals of an optical fiber for optical communications.

When you want to combine multiple light waves and strengthen the light intensity, or use WDM (wave length
When using 1-input, multiple-output, or multiple-input, 1-output light, it is necessary to spatially demultiplex and combine light. A combiner is used when the wavelengths are the same, and a multiplexer is used when the wavelengths are different. In particular, WDM is said to be economically advantageous when combined with FDM systems using ordinary carrier waves, and this connection configuration is required.

Generally, for this purpose, a demultiplexer or multiplexer using an optical interference filter or a diffraction grating is used.
Direct coupling is required to reduce losses due to spatial propagation.

FIG. 1 is an explanatory diagram of a conventional single mode optical fiber processing method. The cladding portion 3 of the optical fiber 1 close to the core portion (approximately 50 μm) 4 is dissolved and removed using hydrogen fluoride (HF). The outer diameter d of the shaft 2 after this melting is slightly larger than the diameter of the core portion 4.

Figure 2 shows the shaft part 2 in which the optical fiber in Figure 1 is melted.
FIG. The contact portions of the respective optical fiber shaft portions 2 are accurately fused or bonded while keeping the axes parallel to each other. This method requires a high degree of skill. In particular, if the shaft parts 2 are not close enough, a speed difference will occur when the light waves emitted from the two core parts 4 enter the core part (not shown) of one opposing optical fiber, and mode conversion is likely to occur. . Furthermore, since there is less cladding part 3 of the reflective layer in the exposed shaft part 2, there is a drawback that loss increases.

FIG. 3 is a perspective view of another conventional single mode optical fiber processing method.

Figure A shows before connection, and figure B shows after connection.

In Figure A, two optical fibers 5 are placed with their axes facing each other, arc-discharge melted (spliced), and their tips mutually bonded, and then pulled apart while still in a high-temperature state. 6 is given. As shown in Figure B, these two optical fibers 5'
The tapered portions 6 of are fused and bonded to each other.

This method also requires handicraft skills, and it is difficult to accurately determine the precision and straightness of the tapered portion, especially the position and diameter of the core portion, and it is difficult to uniformly manufacture in large quantities.

The present invention eliminates the above-mentioned skilled craftsmanship. That is, in the optical fiber coupling part of optical multiplex communication, an optical fiber is inserted into a hollow tube and glued.
Leaving the core part of the optical fiber, both the optical fiber and the hollow tube are processed obliquely at a predetermined angle in the axial direction, and the end surfaces of the optical fiber and the hollow tube are both made at a predetermined angle with respect to the axial direction. The objective is to establish a mass production method with good reproducibility using an optical fiber multi-terminal molding method, which is characterized by adhesively bonding a plurality of diagonally processed fibers.

Examples according to the present invention will be described in detail below. Note that the same reference numerals in the figures from FIG. 4 to FIG. 9 indicate the same parts.

FIG. 4 is a cross-sectional view of a single mode optical fiber processing method according to the present invention.

Figure A is a perspective view of the optical fiber before bonding.

Figure B is a cross-sectional view of the optical fiber after bonding.

The figure shows the shape obtained by inserting an optical fiber 10 into a ceramic hollow tube 11 and grinding it obliquely to a predetermined angle θa (shown in the figure), leaving the core portion 14 of the optical fiber 10 intact. The outer diameter of an optical fiber is generally about 125 μm, but it is currently possible to sinter and form ceramic into a hollow tube shape using a wire with almost the same outer diameter as a core metal, and it is also possible to form a hollow tube with sufficient accuracy. Therefore, this hollow tube 11 is utilized in the present invention. hollow tube 1
It is also relatively easy to insert the optical fiber 10 through 1. In the present invention, the optical fiber 10
is inserted into the hollow tube 11 and held with a jig in a state where it is adhered, and polished at a predetermined angle θa parallel to the optical axis of the optical fiber 10. Next, while keeping the same state, the end faces of the optical fiber 10 and the hollow tube 12 are aligned with the aforementioned slope 1.
Grinding is performed obliquely to a predetermined angle θb (shown in the figure) with respect to the right-angled surface of 2a. For the purpose of explanation, this state will be tentatively named optical fiber hollow tube 12.

In the figure, the surfaces 12a of two hollow optical fiber tubes 12 are symmetrically polished obliquely and joined together with an adhesive. For the sake of explanation, this state will be temporarily named a spliced optical fiber hollow tube 13.

Joint center line A of each optical fiber hollow tube 12
With respect to A, the optical axis of each optical fiber hollow tube 12 is inclined by an angle θa, and the end surface 12b of the optical fiber hollow tube 12 is inclined by the slope 12a of the optical fiber hollow tube 12.
It is inclined by an angle θb with respect to a plane perpendicular to the plane.
The reason for this is to make the output optical axes CC of the two optical fiber hollow tubes 12 parallel and coincide with the basic optical axes of the opposing optical fibers. That is, the light propagating along the optical axis DD of the optical fiber hollow tube 12 is refracted at the end face 12b and exits parallel to the joining center line AA. Therefore, the relationship between θa and θb is given as θb=θa/(n-1), where n is the refractive index of the optical fiber. In this example, θa
selected 5°.

FIG. 5 shows an end face of the spliced optical fiber hollow tube 13 viewed from the direction of arrow B in FIG. optical fiber 10
The core portions 14 of are close to each other.

FIG. 6 is a sectional view of the end face of a spliced optical fiber when a plurality of input lights are input. Figure A shows the case with three input lights, and Figure B shows the case with four input lights.
In either example, the output light from the core section is multiplexed and input into the opposing optical fiber.

Figure 7 shows two inputs and one input using optical fiber hollow tubes.
FIG. 6 shows a block diagram of another embodiment of output combination. The output optical axis of the optical fiber hollow tube 12 is formed at an angle θb in a direction slightly open from the joint center line AA. The two light waves enter the lens 13, become parallel light beams, propagate through space, and are again focused by the lens 15.
It enters the optical fiber 16.

FIG. 8 is a block diagram of an embodiment of a duplexer using a hollow optical fiber tube. The optical fiber hollow tube 21 is used as a single mode input light, and the optical fiber hollow tube 2
Let 1' be the multimode output light. In this embodiment, the end surface 23a of the coupling optical fiber hollow tube 23 constitutes a plane perpendicular to the joint center line AA.

The optical interference filter 22 is also provided perpendicularly to the joining centerline AA line. A condensing lens 23 is provided on the optical axis extension fiber of the optical fiber hollow tube 21 on the left side of the optical interference filter 22 in the figure, and the optical fiber 2 is provided in close proximity to the condensing lens 23 .
4 is further arranged on the optical axis extension of the optical fiber hollow tube 21.

Two light waves with wavelengths λ1 and λ2 from the optical fiber hollow tube 21 are separated by an optical interference filter 22 into reflected light (temporarily assumed to be λ1) and transmitted light (temporarily assumed to be λ2).
It is split into two waves. The reflected light λ1 becomes multimode and is propagated through the optical fiber hollow tube 21'. On the other hand, the transmitted light λ2 is condensed by the condenser lens 23, inputted from the end face of the optical fiber 24, and propagated.

FIG. 9 is a block diagram of another embodiment of a duplexer using a hollow optical fiber tube. Optical fiber hollow tube 3
The arrangement of 1, 31' and 34 is the same as in FIG. 7, but the angle .theta.c is equal to the angle .theta.a. However, both optical fibers are in close contact with the interference filter 32 and there is no spatial propagation.

In this embodiment, ceramic is used for the hollow tube, but it is assumed that metal, glass, etc. can also be used with the development of hole processing technology.

As described above, according to the present invention, a structure for multiplexing input light from a plurality of optical fibers into a single optical fiber and propagating the same does not require skilled skills and can be reliably manufactured mechanically. Mass production is easy.
Furthermore, the image quality is stable and highly reliable.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram of a conventional single mode optical fiber processing method, Fig. 2 is a side view showing a state in which two optical fibers of Fig. 1 are joined at the core, and Fig. 3 is an explanatory diagram of a conventional single mode optical fiber processing method. A perspective view of the single mode optical fiber processing method, Figure A shows the state before connection, and Figure B shows the state after connection. FIG. 4 is a sectional view of the single mode optical fiber processing method according to the present invention, FIG. 4 is a perspective view of the optical fiber before bonding, and FIG. 4 is a sectional view of the optical fiber after bonding. FIG. 5 shows the end face of the spliced optical fiber hollow tube 13 viewed from the direction of arrow B in FIG.
The figure is a cross-sectional view of the end face of an optical fiber when a plurality of input lights are used, Figure A is for three input lights, and Figure B is for four input lights. Fig. 7 is a block diagram of another embodiment of a 2-input, 1-output coupling using a hollow optical fiber tube, and Fig. 8 is a block diagram of an embodiment of a duplexer using a hollow optical fiber tube. FIG. 9 is a block diagram of another embodiment of a duplexer using a hollow optical fiber tube. In the figure, 10 is an optical fiber and 11 is a hollow tube.

Claims (1)

[Claims] 1. In an optical fiber coupling part for optical multiplex communication, an optical fiber is inserted into a hollow tube and glued, and the optical fiber and hollow tube are both processed diagonally at a predetermined angle in the axial direction, leaving the core part of the optical fiber. Furthermore, a method for forming multiple terminals of an optical fiber is formed by adhesively bonding a plurality of optical fibers and hollow tubes whose end surfaces are both processed obliquely at a predetermined angle with respect to the axial direction.