JPS6257002B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement of an optical splitter/coupler in an optical fiber transmission system.

Generally, in a transmission system using optical fiber, for example, an optical fiber transmission system incorporating a large number of terminals,
In order to integrate or divide optical signals from an arbitrary number of terminal devices and transmit them to other terminal devices, an optical coupler that performs optical synthesis or optical distribution is essential.

Conventionally, this type of optical coupler includes, for example, a relay rod for mixing light, as shown in FIG.
That is, a relay rod 1 made of a large-diameter optical fiber of a graded refractive index type having a core portion 2 having a larger diameter than the core diameter of a bundle of input/output optical fibers, input optical fibers 5 and 6, and a plurality of output optical fibers. Optical fiber group 7
(In this case, seven output optical fibers are shown)
It consists of and the input optical fiber 5
The lights incident on the relay rod 1 from the relay rods 1 to 6 or 5 and 6 are mixed while propagating within the relay rod 1, and are evenly distributed and coupled to the output optical fiber group 7.

By the way, in the conventional optical coupler having the above-mentioned configuration, each of the input/output optical fibers 5, 6, and 7 is provided on the exposed surface of the core portion 2 of both end surfaces 3, 4 of the relay rod 1 made of a large-diameter optical fiber. Since the coupling structure is such that the end faces are directly butt-connected, the cladding connection face and Since the propagating light hitting the gap between each output optical fiber is not optically coupled effectively to the output optical fiber group 7, optical loss inevitably occurs at that location, increasing the insertion coupling loss. There were some drawbacks.

In order to solve the above-mentioned conventional drawbacks, the present invention has the following features:
The optical conductor part of the relay rod interposed between the input and output optical fibers is placed between the core of the input and output optical fibers, and the center layer whose refractive index is smaller than that of the optical fiber, and the outer layer. The relay rod has a cylindrical structure with a thickness approximately equal to the diameter, and one
The present invention provides a novel optical coupler capable of evenly and highly efficiently distributing and coupling light from more than one input optical fiber to a plurality of output optical fiber groups with low insertion loss.

Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 2 is a schematic perspective view showing an embodiment of the optical coupler according to the present invention. In the figure, reference numeral 11 denotes a relay rod, and in this embodiment, it is inserted between the outer peripheral layer 12 and the center layer 14, which have a refractive index lower than the refractive index of the light guide section 13 through which light is propagated, for example, by CVD method or the like. A dielectric material having a thickness substantially equal to the core diameter of the input/output optical fiber and having a cylindrical structure with a high refractive index light guide section 13 interposed therebetween, and having a numerical aperture higher than that of the input/output optical fiber. The body is shaped like a rod. Input optical fibers 17 and 18 are connected to one end surface 15 of the rod 11, and the core portion 17 of the optical fiber is connected to the input optical fibers 17 and 18.
a, 18a are installed in such a way as to be in contact with the optical conductor section 13, and in the same way, a plurality of output optical fiber groups 19 (in this case, six output optical fibers) are installed on the other end surface 16 of the rod 11. Optical fibers (shown as fibers) are installed at equal intervals with each core portion 19a of the optical fiber in contact with the light guide portion 13. Note that the abutting portions of the optical fibers 17 and 1 are
The core portions 17a, 18a, 19a of the relay rods 8 and 19 and the optical guide portion 13 of the relay rod 11 are fixed with a transparent matching adhesive or the like having the same refractive index.

If the optical distributor is configured in this way, each input/output optical fiber 17 with a smaller numerical aperture than the relay rod 11 is connected to the optical guide portion 13 in both end faces 15 and 16 of the relay rod 11 with a high numerical aperture. , 18, 19 are optically coupled, and each input/output optical fiber 17, 1
Compared to conventional coupling structures, the areas where the portions other than the core portions 17a, 18a, and 19a of 8 and 19 come into contact with the light guide portion 13 and the surfaces that do not contribute to optical coupling, such as the gaps between the output optical fibers, are Therefore, the light incident from the input optical fibers 17 and 18 into the light guide section 13 in the relay rod 11 is
The light is mixed while propagating within the light guide section 13, and can be evenly distributed and coupled to each of the output optical fiber groups 19 for transmission with low insertion loss. It should be noted that the diameter of the relay rod 11 of this embodiment can of course be modified in various ways depending on the number of output optical fibers disposed on the distribution side.

The relay rod 11 has only to have a low refractive index layer with a minimum thickness of the outer layer 12 and the center layer 14 capable of transmitting light to the light guide portion 13, and for this purpose, a hole is formed in the center. It goes without saying that it may be in the form of a formed form, or of course, it may be in a complete form.

As is clear from the above description, the optical coupler according to the present invention has the optical coupler of the relay rod inserted between the center side layer and the outer layer having a refractive index smaller than the refractive index of the optical waveguide.・It has a ring-shaped cross section with a thickness that is approximately equal to the core diameter of the output optical fiber, and has a structure in which a plurality of input and output optical fibers are butted and coupled to each end face light guide portion of such a relay rod. , it is possible to provide a highly reliable and practical optical coupler that can efficiently distribute and couple light from multiple input optical fibers to multiple output optical fibers with low insertion loss. Become.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram for explaining a conventional optical coupler, and FIG. 2 is a schematic perspective view showing an embodiment of the optical coupler according to the present invention. In the figure, 11 is an optical relay rod, 12 is an outer layer, 13 is a light guide, 14 is a center layer, 15, 1
6 is an end face of an optical relay rod, 17 and 18 are input optical fibers, 19 is a group of a plurality of output optical fibers, 17
a, 18a, and 19a indicate the core portions of input/output optical fibers.

Claims (1)

[Claims] 1 Forming a cylindrical light guide portion having a wall thickness approximately equal to the core diameter of the optical fibers to be attached to both end faces and to which multiple optical fibers are attached, and having a refractive index smaller than the refractive index of the light guide portion. It is made of a material that has
An optical coupling characterized in that a plurality of input/output optical fibers are attached to both end faces of the light guide portion of the relay rod, which has an outer peripheral layer on the outside and a center layer on the inside of the light guide portion. vessel.