JPS6343111A - Optical fiber branching device - Google Patents

Abstract

(57) [Abstract] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention is characterized in that two or more transmission optical fibers are arranged in parallel,
The following is a description of an optical fiber branching device that is attached to the end of a bundle of fibers.

(Prior Art) Multi-core optical cables called bunch fibers are known in the fields of optical communications and optical information processing. Bunch fibers are two or more optical fibers bundled in parallel to form a single fiber. It is an optical cable, and a perspective view thereof is shown in FIG.

In FIG. 7, each transmission optical fiber 1 has an independent core 1 and cladding 2, which are arranged in parallel. The claddings of each optical fiber 1 are in contact with each other and fixed by fusion. The optical fiber 1 can be arranged one-dimensionally as shown in a perspective view in FIG. 7 and in a sectional view in FIG.
) are two-dimensionally arranged as shown in the cross-sectional view. Further, each optical fiber may be a single mode fiber or a multimode fiber.

By the way, a conventional standard single core, single clad optical fiber has a diameter of about 125 μ7n, and when coated, the diameter is about 250 to 900 μm.

On the other hand, in a bunch fiber, the outer diameter of the cladding of each individual fiber is about 70 to 90 μm, and the diameter when a common coating is applied to it is about 500 to 900 μm in the examples shown in Figures 7 and 8. is. Therefore, the substantial outer diameter does not necessarily differ between a single core, single clad optical fiber and a bunch fiber. For this reason, bunch fibers are suitable for realizing ultra-multi-core optical cables in which the outer diameter of the cable is restricted.

(Problems to be Solved by the Invention) However, bunch fibers have the following problems compared to single-core, single-clad fibers.

The first problem is that highly accurate alignment technology is required to interconnect two bunch fibers.

This is because each fiber that makes up a bunch fiber has an extremely small diameter, and because a bunch fiber is made up of multiple fibers arranged in an easterly manner, it is difficult to align all the fibers accurately using one relatively thick fiber. This is because it is not as easy as interconnecting two.

The second problem is that it is not easy to separate the fibers into individual fibers at the end of the bunch fiber and connect them to a light source or receiver. Possible branching methods at the terminal include a method in which the individual optical fibers constituting the bunch fiber are branched at the terminal, and a method in which a branching device in which one end is branched and the other end is fusion-spliced is attached to the terminal of the bunch fiber. However, as mentioned above, individual optical fibers have extremely small diameters, and fusion must be performed at a high temperature of 1000'C or higher, so it is difficult to process only extremely short end portions of a few millimeters to avoid fusion. It's not easy. Roughly speaking, it is not easy to peel off only the terminals after the whole is fused once, because the cladding is hard.

In view of the above-mentioned second problem, an object of the present invention is to provide an optical fiber branching device that can easily branch a bunch fiber at its terminal.

(Means for Solving the Problems) The optical fiber branching device of the present invention has at least two transmission optical fibers arranged in parallel between a core and a cladding having an outer diameter of D (D is positive). The claddings are brought into contact with each other, and the transmission optical fibers are fused to each other at this contact portion to form an integrated bunch fiber.

That is, in the first aspect of the present invention, the core of the transmission optical fiber has a core of 1IIIi and a cladding with an outer diameter of D-2t (t is positive), and the arrangement state of the cores on one end surface is At the terminal of the bunch fiber (at least two branching optical fibers arranged in parallel to each other so as to match the arrangement of the cores of the transmission optical fibers) A coating layer with a thickness of (IIIi) fixedly formed on the outside of each cladding of the fiber.
Furthermore, this coating layer is characterized in that the coating layers are mutually fused near one end face of the branching optical fiber.

A second version of the present invention has a core equivalent to the core of a transmission optical fiber and a cladding having an outer diameter of D-2t (t is positive), and the arrangement state of the cores on one end face is like that of a bunch fiber. at least two wires arranged in parallel with each other to match the arrangement of the cores of the transmission optical fiber at the terminal of the
A core branching optical fiber, a coating layer having a thickness of t fixedly formed on the outside of each of the claddings of the at least two branching optical fibers, and a coating layer near one end face of the branching optical fiber. It is characterized by leaking a fixing member that brings the layers into contact with each other and fixes them.

[Function] According to the first aspect of the present invention, since the branching optical fiber is surrounded by a coating layer, this coating layer works to facilitate mutual suspension by fusion at one end, and this coating Since the outer diameter of the layer matches the outer diameter of the transmission optical fiber, it moves to facilitate alignment with the bunch fiber.

According to the second aspect of the present invention, since the branching optical fiber is surrounded by the coating layer, the branching optical fiber is mutually rested at one end by the fixing member,
Furthermore, since the outer diameter of the coating layer is made to match the outer diameter of the transmission optical fiber, alignment with the bunch fiber is facilitated.

〔Example〕

Hereinafter, some embodiments of the present invention will be described with reference to FIGS. 1 to 6 of the accompanying drawings.

FIG. 1 is a perspective view of a first embodiment of the invention.

As shown in the figure, a branching optical fiber consisting of a core 11 and a cladding 12 is surrounded by a coating layer 13 made of a material that is easily fused. When the outer diameter of the cladding of the transmission optical fiber constituting the bunch fibers to be optically coupled is D, the outer diameter of the cladding 12 of the branching optical fiber is D-2.
t, and the thickness of the covering layer 13 is set to t. Such branching optical fibers are arranged in parallel and in contact with each other in the range indicated by A in the figure, and the coating layers 13 are fusion-spliced.

According to the branching device having such a structure, the outer diameter of the branching optical fiber is (outer diameter of cladding 12) + (thickness of coating layer 13) x2 -
(D-2t) +2t=D, so it matches the outer diameter of the transmission optical fiber constituting the bunch fiber, and therefore alignment with the bunch fiber of the structure shown in Fig. 7 can be easily performed. S'ru. In addition, since the material 1 of the coating layer 13 is selected from a material that is easy to fuse (for example, a metal material with a low melting point), one end of the branching optical fiber is connected to the AT? It is easy to integrate the two ends and keep the other end separated. In particular, since the length of the branching optical fiber is approximately several millimeters, this method has a significant advantage over the case where the cladding is heated to a high temperature and fused directly.

FIG. 2 is a sectional view of a modification of the first embodiment. This differs from the one in FIG. 1 in that the branching optical fibers are arranged two-dimensionally rather than one-dimensionally. Also in this modification, the outer diameter of the cladding 12 is set to D
= 2t and the thickness of the coating layer 3 is t, the overall outer diameter is (D - 2t) + 2t = [), so alignment with the bunch fiber with the cross-sectional structure shown in Figure 8(b) can be easily carried out.

It goes without saying that the arrangement of the branching optical fibers is not limited to that shown in Figures 1 and 2, and that various arrangements can be made. Also, regarding the integration of the branching optical fibers, only one end may be used. The method is not limited to the one in which the whole is fused together and then the other parts are separated.

In this case, the material of the covering layer may be changed to one that is easy to separate.

Next, points to be noted when putting the first embodiment and its modifications into practical use will be described.

First of all, it is necessary to match the outer diameter of the core 1 of the transmission optical fiber constituting the bunch fiber with the outer diameter XJ method of the core 11 of the branching optical fiber. This allows optical energy to be transmitted without leaking when interconnected, reducing loss of connection, and preventing leakage light from entering the core of an adjacent optical fiber and causing interference. This is particularly important to ensure that

Second, in optical coupling with a bunch fiber, it is necessary to accurately align the core 1 of the transmission optical fiber and the core 11 of the branching optical fiber.

This is because if alignment is not accurate, connection loss will occur accordingly. For this purpose, it is desirable to use a material that is stable under the usage environment as the coating layer 13, and the thickness of the coating layer 13 needs to be precisely controlled υ11. Metal can be used as such a covering material, and can be realized by plating with aluminum or low melting point solder. (FI L, needless to say, it is not limited to this.

Thirdly, it is desirable that the optical coupling between the transmission optical fiber and the branching optical fiber be capable of reducing coupling loss.

Such methods include aligning the end faces of the two along a separately prepared guide and fixing them with adhesive, or housing each in a sleeve and fixing it, and then fitting the sleeves into each other. Some are in the form of optical connectors.

FIG. 3 is a perspective view of a second embodiment of the invention.

This differs from the one in FIG. 1 in that one end of the branching optical fiber is fixed in contact with the phase 11 by a fixing member 15. This construction is realized by arranging branching lights (7) and fibers (with coating layer 14) one-dimensionally in contact with each other and hardening one end with adhesive to form fixing member 15. can.

The arrangement of the branching optical fibers is not limited to that shown in Fig. 3;
It is also possible to arrange the sea urchins two-dimensionally as shown in the figure, or in other arrangements.

The embodiments shown in FIGS. 3 and 4 can also achieve the same functions and effects as the first embodiment, but they are also more effective due to fusion than the first embodiment. It has the advantage of preventing fluctuations in the outer diameter.

Further, when putting this second embodiment into practical use, it is necessary to pay attention to the following first to third points, as in the first embodiment. Firstly, it is necessary to match the core diameter of the transmission optical fiber and the branching optical fiber that make up the bunch fiber, and secondly, when aligning with the bunch fiber, the cores must be aligned accurately. Thirdly, the optical coupling with the bunch fiber can be done by devising ways to reduce the coupling loss. At this time, it is particularly important to take into account changes in the thickness of the coating layer due to temperature changes and deformation when subjected to pressure, and it is desirable to make the coating as hard and thin as possible.

In order to confirm the usefulness of the second embodiment, the present inventor
The following experiment was conducted. First, as shown in the cross-sectional view in FIG. 5(a), two multimode fibers having an outer diameter of 90 μm were used as bunch fibers, and these were fusion-spliced. Next, as shown in the cross-sectional view in FIG. 5(b), two multimode fibers for branching were used as an optical fiber branching device. Here, the cladding diameter of the branching optical fiber is 80
μTn and coated with polyimide resin (Young's modulus 300 to 9/rrvn2) with a thickness of 5 μm, while (7) Gi
' section was fixed with epoxy resin for 20 m. The dimensions of such a fixing member are 400μ7n in width and 300μ in thickness.
It is μm.

Then, after mirror-finishing the end faces of both to a plane perpendicular to the optical axis, they were butted against a bunch fiber. As a result, the connection loss of both cores was 0.2 dB and 0.3 dB, respectively.
dB, demonstrating sufficiently low loss for practical use.

FIG. 7 is a perspective view for explaining how the embodiment shown in FIG. 1 is used. As shown in the figure, one end of the bunch fiber 10 and one end of the optical fiber branching device 20 are arranged and brought into contact with each other at the arrow j in the figure. Then, an optical sensor 969 light emitting element (for example, a semiconductor laser) is optically coupled to the thin end of each branching optical fiber. In this way, it is possible to easily transmit various types of optical information using a narrow bunch fiber.

(Effects of the Invention) As described above, according to the present invention, since the branching optical fiber is surrounded by a coating layer of a predetermined thickness, fiber branching can be easily realized by fusion or bonding, and bunching This has the effect of allowing easy and accurate alignment with the fiber.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of the first embodiment of the present invention, FIG. 2 is a cross-sectional view of a main part of a modification thereof, FIG. 3 is a perspective view of the second embodiment,
The figure is a cross-sectional view of a main part of a modified example, FIG. FIG. 8 is a perspective view of an example, and FIG. 8 is a sectional view of a bunch fiber. 1... core of bunch fiber (transmission optical fiber),
2... Cladding of bunch fiber (transmission optical fiber), 11... Core of branching optical fiber, 12... Cladding of branching optical fiber, 13.14... Covering layer,
15...Fixing member. Patent Applicant Sumitomo Electric Industries Co., Ltd. Applicant Agent Yoshiki Hase 1st Embodiment O Oblique? I! Figure 1 Area 2 Figure 2 Embodiment ■ Cross-sectional view of a modified example Figure 4 2nd embodiment ■ Perspective view Figure 3 (b) Figure 5

Claims (1)

[Claims] 1. At least two transmission optical fibers having a core and a cladding having an outer diameter of D (D is positive) are arranged in parallel, and the claddings are brought into contact with each other, and the contact portion In an optical fiber branching device that is attached to the terminal of a bunch fiber in which the transmission optical fibers are fused together and integrated, the core and outer diameter equivalent to the core of the transmission optical fiber are D-.
2t (t is positive), and are arranged in parallel to each other so that the arrangement of the cores on one end surface matches the arrangement of the cores of the transmission optical fiber at the terminal of the bunch fiber. It includes a two-core branching optical fiber and a coating layer having a thickness t fixedly formed on the outside of the cladding of each of the at least two branching optical fibers, and the coating layer has a thickness of t. An optical fiber branching device characterized in that fibers are mutually fused near one end face. 2. The optical fiber branching device according to claim 1, wherein the coating layer is a metal layer. 3. At least two transmission optical fibers having a core and a cladding with an outer diameter of D (D is positive) are arranged in parallel, and the claddings are brought into contact with each other, and at this contact portion, the transmission optical fiber In an optical fiber branching device that is attached to the terminal of a bunch fiber that is integrated by fusing them together, the core and outer diameter equivalent to the core of the transmission optical fiber are D-
2t (t is positive), and are arranged in parallel to each other so that the arrangement of the cores on one end surface matches the arrangement of the cores of the transmission optical fiber at the terminal of the bunch fiber. a two-core branching optical fiber; a thick coating layer fixedly formed on the outside of each cladding of the at least two branching optical fibers; and near one end surface of the branching optical fiber. An optical fiber branching device comprising: a fixing member for fixing the coating layers in contact with each other. 4. The optical fiber branching device according to claim 3, wherein the coating layer is a hard resin layer. 5. The optical fiber branching device according to claim 3, wherein the fixing member is made of adhesive material.