JPS61208010A - Optical branch device - Google Patents

Abstract

PURPOSE:To eliminate a trouble at a branch point so as to reduce a loss and to attain a mechanically strong and easy manufacture by welding directly a trunk optical fiber and plural branch optical fibers at the branch joint so as to form a core welded part. CONSTITUTION:The end parts of the branch optical fibers 2 and 3 are secured with a resin 15 and ground so as to expose smoothly the side surfaces of cores 5 and 6, after which the resin 15 is melted to take out the fibers 2 and 3. The ground surfaces are collated, heated, fused and formed in one body. Then core welded part 14' where the cores 5 and 6 are directly welded and then a clad fused welded 8' where clads 11 and 12 are clad welded each other are formed in a tumble-like shape. Still heating continues. The welded part 8' is made circular in the cross section and then the welded part 14' is also made circuit in the cross section, both of which are made into a branch joint part 4'. Next its end face is collated with that of the trunk optical fiber 1 and heated, whereby the welded part 14' and a core 9 are directly welded. Then a core welded part 14 is mutually welded with the welded part 8' and the clad 10 to form a clad welded part 8, thereby completing a branch joint part 4.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to an optical branching device in which a trunk optical fiber is connected to a plurality of branch optical fibers at a branching/coupling section.

[Summary of the Invention] The present invention provides an optical splitter configured by connecting a plurality of branch optical fibers to a trunk optical fiber at a branching/coupling section, which includes: a branching/coupling section between the trunk optical fiber and each of the branch optical fibers; This is composed of a core fusion part in which each core is directly fused and a clad fusion part in which each clad is fused to each other, thereby reducing loss at the branch joint part.

[Conventional technology] An optical splitter made only of optical fibers is a half mirror.
Compared to optical branching devices using optical fibers, it has features such as no wavelength dependence, bidirectional communication, easy adjustment, and low cost because it is made only of optical fiber.

As an optical splitter made only of conventional optical fibers,
The fused type shown in Figure 6 A, B, and C, and the one shown in Figure 7 A, B
, and the joint type shown in C.

The conventional fusion-type optical branching device shown in FIGS. 6A, B, and C has a structure in which branch optical fibers 2 and 3 are coupled to a main optical fiber 1 in a Y shape at a branching coupling section 4. . In particular, on one side in the longitudinal direction of the branching coupling section 4, the branch optical fiber 2
, 3, the end of the core 5 of the branch optical fiber 2 and the end of the core 6 of the branch optical fiber 3 each have a semicircular cross-sectional area with a cross-sectional area of about 172 times the original cross-sectional area. The mutual planar side portions of these cores 5.6 are fused face to face via a cladding layer 7 formed by mutually fusion bonding a part of the cladding of each branch optical fiber 2.3. , its outer periphery is covered with a common cladding 8 formed by fusing other parts of the cladding ends of the branch optical fibers 2.3 to each other. Such a structure is achieved by heating the side surfaces of the end portions of each branch optical fiber 2.3 in pressure contact with each other and stretching them by applying tension in the longitudinal direction, whereby the contact portions are deformed and fused together. It is formed by On the other side in the longitudinal direction of the branching coupling section 4, a portion formed by coupling the trunk optical fiber 1 and each branch optical fiber 2.3 is connected to the end face of the core 9 of the trunk optical fiber 1 and each branch optical fiber 2. The end faces of the cores 5 and 6 of .3 are butted and fused, and the end face of the cladding 10 of the trunk optical fiber 1 and the cross section of the common cladding 8 of each branch optical fiber 2 and 3 are butted and fused. It has become.

In the conventional junction-type optical splitter shown in FIGS. 7A, B, and C, each branch optical fiber 2. 3 is formed by polishing the side surface of the end of each branch optical fiber 2, 3 to expose the core 5.6 from within each cladding 11.12, and then polishing these cores 5, 6. It is formed by butting the surfaces together and bonding them with adhesive. Further, on the other side in the longitudinal direction of the branching/coupling section 4, the trunk optical fiber 1 and each branch optical fiber 2.
3 is the end face of the core 9 of the trunk optical fiber 1 and the cores 5 and 6 of each branch optical fiber 2 and 3.
It is formed by abutting the end surfaces of and bonding them with adhesive.

[Problems to be solved by the invention] However, in the optical splitters shown in FIGS. 6A, B, and C,
Since the cladding layer 7 exists between the cores 5 and 6, the light in the center of the core 9, where the light intensity is highest, is not transmitted to the core 5.6, resulting in a disadvantage that the insertion loss becomes large.

On the other hand, in the optical branching devices shown in FIGS. 7A, B, and C, the presence of the joint 13 between the core 9 and the cores 5 and 6 increases insertion loss, and the mechanical strength of the joint 13 is low. There is.

SUMMARY OF THE INVENTION An object of the present invention is to provide an optical branching device that can suppress an increase in insertion loss at a branching/coupling portion and prevent a decrease in mechanical strength.

[Means for Solving the Problems] The configuration of the present invention for achieving the above object will be explained with reference to FIGS. 1A, B, and C corresponding to the embodiment. In an optical branching device configured by connecting a plurality of branch optical fibers 2.3 to each other at a branching/coupling section 4, the branching/coupling section 4 of the trunk optical fiber 1 and each branch optical fiber 2.3 connects to each core. 9 and 5.6 are directly fused together, and the respective crunds 10 and 11.1.
2 and a clad fusion part 8 which are fused together.

[Operation of the Invention] If the cores 9, 5, 6 are directly fused at the branching/coupling section 4 to form the core fusion section 14, there will be no obstructions at the branching point, and optical signals will be will be branched with low loss. Further, since the branching joint portion 4 has a fused structure as a whole, there is no problem of reduction in mechanical strength, and manufacturing is easy.

[Embodiments] Examples of the present invention will be described in detail below with reference to FIGS. 1A, B, and C to FIG. 5. In addition, the above-mentioned Fig. 6 A, B,
C and portions corresponding to FIGS. 7A, B, and C are designated by the same reference numerals. In the optical branching device of this embodiment, the branching/coupling section 4 between the trunk optical fiber 1 and the plurality of branch optical fibers 2 and 3 is connected to the core fusion section 14 where the respective cores 9 and 5.6 are directly fused. , respective cladding 10, 11.12
and a clad fused portion 8 which are fused together.

Next, an example of how to form such a branching joint portion 4 will be explained. As shown in FIG. 2, each branch optical fiber 2, 3 is hardened with resin 15 at its end to make the grip part of the polishing jig larger, and polished in the same manner as lens processing to form the side surfaces of the cores 5, 6. expose flatly. Next, the resin 15 is melted by heat or chemicals and the polished branch optical fiber 2.3 is taken out. After polishing the branch optical fiber 2.3 in several layers in the axial direction in this way, the polished surfaces are butted against each other as shown in Figure 3, and that part is heated with a gas burner, arc discharge, etc., and melted and integrated. First, as shown in FIG. 4, there is a core fused part 14' where the cores 5 and 6 are directly fused together, and a clad fused part 8' where the claddings 11 and 12 are fused together.
is formed into a potbelly shape. Furthermore, if heating continues,
Due to the balance of surface tension, the cladding part 8' has a circular cross section. Once the tensions are balanced, the equilibrium will not be disrupted unless a force is applied in the radial direction of the fiber. Therefore, the core fused portion 14' also has a circular cross-section, resulting in a branched joint portion 4' having the cross-sectional shape shown in FIG.

The issue here is whether the cross section of the core welded part 14' also becomes circular when the clad welded part 8' becomes circular and in an equilibrium state. Core @ wearing part 14' in Figure 5
The shape of is determined by the amount of polishing of the two optical fibers 2.3 performed as shown in Figure 3, so the two optical fibers 2.3 polished with the optimum amount of polishing should be used. Insertion loss can be made very small. Next, the end face of the collar fiber 1 is brought into contact with the end face of the obtained branched coupling part 4' and heated, so that the core a1 part 14' and the core 9 are directly attached to each other, as shown in FIGS. 1A and 8. A core fused part 14, a clad fused part 8', and a clad 10 as shown are fused together to form a clad fused part 8, thereby completing the branching joint part 4.

In the above embodiment, the case where there are two branch optical fibers is shown, but the present invention is not limited to this, and can be similarly applied to a case where there are three or more branch optical fibers. In this case, the ends of the branch optical fibers are polished into a V-shape, for example, and the branch optical fibers are bundled so that the polished surfaces are butted together to form a circular shape, and the end faces of the neck fibers are bonded by heating. Formed by heat fusing.

[Effects of the Invention] As explained above, in the branching/coupling part of the optical splitter according to the present invention, the core of the collar source fiber and each core of the plurality of branch optical fibers are directly fused to form a core fused part. Therefore, there are no obstacles at the branch point, and losses can be reduced. Furthermore, because of the overall fused structure of this branched joint, there is no problem of reduction in mechanical strength, and manufacturing is also easy.

[Brief explanation of drawings]

FIG. 1A is a plan view of an embodiment of an optical splitter according to the present invention;
Figure 1B is a cross-sectional view of the branch joint in Figure 1A, Figure 1C
is a cross-sectional view of the collar fiber in Figure 1A, Figures 2 to 5 are
The figure is a cross-sectional view showing the manufacturing process of this optical splitter, Figure 6A.
, B, and C are a plan view of a conventional fusion type optical splitter, a cross-sectional view of a nine-branch coupling portion, and a cross-sectional view of a collar fiber, and FIGS. 7A and B. C is a vertical cross-sectional view of a conventional junction type optical splitter, a cross-sectional view of a nine-branch coupling portion, and a cross-sectional view of a neck fiber. 1... Collar fiber, 2, 3... Branch optical fiber, 4
...branch joint, 6,7.9...cladding, 8...
・Clad fusion part, 10.11.12... Clad,
14...Core fusion part.

Claims (1)

[Claims] In an optical splitter configured by connecting a plurality of branch optical fibers to a trunk optical fiber at a branching/coupling section, the branching/coupling section between the trunk optical fiber and each branch optical fiber is such that the respective cores are directly fused together. 1. An optical branching device comprising a core fused portion in which the clads are fused together, and a clad fused portion in which the respective claddings are fused to each other.