JPS62134610A - Splicing method for optical fiber - Google Patents

Abstract

PURPOSE:To adhere optical fibers with a high reliability by using optical fibers where metallic coatings are provided on outside peripheral parts and splicing optical fibers mutually or the optical fiber and an apparatus or an element. CONSTITUTION:In case of mutual splicing of optical fibers by soldering, a proper jig is used to put a solder 6 on butted end parts where sheaths are removed to expose metallic coatings. It is preferable that a copper V groove metallic fitting having a V groove 9 is used as the jig 6. The V groove 9 functions to fix fibers, prevent the break and cracks in the fiber junction part, and improve centering. Butted end parts of optical fibers and the jig are soldered integrally into one body to connect optical fibers.

Description

DETAILED DESCRIPTION OF THE INVENTION FIG. 1 shows an optical fiber core F used in the method of the present invention.
An example of a cross section is shown. A core 1 and a cladding 2 made of glass or plastic constitute an optical fiber. For light, the boundary between the core and cladding acts as a wall, and the refractive index of the core is designed to be larger than the refractive index of the cladding.

The basic principle of optical fibers is that light can propagate through a medium with a high refractive index by surrounding it with a medium with a low refractive index. A metal coating 5 consisting of one or more metal release layers is formed around the outer periphery of the cladding. On the outside of the metal coating, outer skin layers 4 such as a primary coating layer, a buffer layer, and a secondary coating layer are formed. The outer skin layer is made of silicone resin, nylon, or the like. In addition to coating the whole or part of the fiber with metal, only the connecting portion may be coated with metal.

The metal coating layer has good bondability with the glass layer, weldability with solder,
It is composed of several layers from the viewpoint of resistance to induction, etc., and the lower layer is mainly focused on bonding with the glass layer, and the surface layer is selected with an appropriate metal type, focusing on adhesion with solder, resistance to induction, etc. It is preferable. It is also necessary that the surface layer and the lower layer have good consistency. For example, Ni can be used as the lower layer because it has good compatibility with glass.
and the surface layer is Cu, A12,
Au etc. can be used. Therefore, as a combination example of the lower layer-Table 1d, Ni-Cu r Ni-Ag +
Examples include Ni-Au, and furthermore, Ni-Cu-
Ag, Cu-Ni-Ag*Ni-Cu
-Au, Cu-Ni-Au three-layer Sakaki construction is more effective. However, Cu, Ag,
Even a single layer of Au or the like can sufficiently withstand use.

Metal coating can be performed by vacuum deposition (including sputtering) or +1 deposition or electroless plating.

Electroless plating is preferred from the viewpoint of cost and production speed, but vacuum evaporation is better in terms of compatibility with glass. The thicker the coating layer, the better the soldering properties, but if it is too thick, peeling is likely to occur and costs are high. Taking these into account, the total thickness of the metal coating is Q, 1
The thickness is preferably 0.7 to 1.2 μm, more preferably 0.7 to 1.2 μm. For example, 1 μm (::u single layer, Cl
3 μm Ni-Q, 2 μm Au, Q, 3
A μm Ni-Q, 7 μm cu bilayer is suitable. After metal coating, it is preferable to perform anti-corrosion treatment to avoid surface oxidation.

To connect optical fibers by soldering, in the case of two fibers, use an appropriate jig 6 as shown in Figure 2 to remove the outer jacket and apply solder 7 to the exposed butt ends of the metal coating. Implemented by As the jig 6, it is preferable to use, for example, a V-groove metal fitting made of copper and having VflQ9 as shown in FIG. 2(b). ■Grooves serve the functions of fixing fibers together, preventing bending and cracking at fiber joints, and improving centering.

The connection is effected by soldering the abutting ends of the optical fibers and the jig together.

For splicing, it is necessary to cleanly remove the outer sheath from the end of the optical fiber and cut the optical fiber at right angles and smoothly. The optical fiber that has been subjected to such terminal treatment and has its metal coating exposed is placed in the groove with its ends abutting each other. The gaps between the fibers are brought into close contact to such an extent that no space can be visually confirmed. Thereafter, solder is applied to the mating ends in the usual manner using a soldering iron. As the solder, it is preferable to use resin-free solder.

FIG. 3 shows another example of connection of optical fibers. This method connects optical fibers together through a metal sleeve 8, which is made of solderable metal and has a hole with a diameter 1 to 2 μm larger than the outer diameter of the optical fiber.
Insert the optical fibers from both sides of the hole in the sleeve, and fix both fibers by soldering at both ends of the sleeve. As the material of the sleeve, gold- or silver-plated copper, yellow silk, or the like can be used.

As shown in FIG. 4, when a connection is made between a device or element such as a photoelectric converter 11 and an optical fiber, soldering is performed directly to the output port of the metal case 10. The output port of the case 10 must be made of a solderable metal or plated with a solderable metal.

The present invention can also be applied to multi-fiber batch connection of multi-fiber optical fiber cables. Connection is made in the same manner as before using metal fittings having a predetermined number of grooves.

The presence of the metallization is also effective in preventing damage and bending of the glass cladding as seen in the past.

Effects of the Invention With the simple method of soldering, it is possible to obtain a loss level equivalent to or better than that of the optical connector method and reliability comparable to that of fusion splicing. The cost is also relatively low. This method has the following advantages in terms of low cost, ease of connection, and stability of connection state.
This will greatly contribute to the spread of optical fiber. No connection techniques that require special skill are required. Also, unlike the fixing method using resin, the connection is made using metal with a small coefficient of expansion, so reliability is poor near normal temperatures.

Example 1 An optical fiber having a core diameter of 50 μm and a cladding diameter of 125 μm is coated with copper to a thickness of 1 μm by electroless plating on the surface of the GII optical fiber. The gap between the optical fibers is set to 2 μm, and the surface is coated with a copper V-groove fitting made of copper. I connected it by soldering. The splice loss in this case is 14 dB and the temperature characteristic (-20
~+600C) was ±α10 dB. The connection loss was better than the general value α5 dB in the case of connector connection.

This seems to be because the way the core comes out is much better. Further, good results were obtained when the gap between the optical fibers was in the range of 0 to 5 μm.

Example 2 GI type mold 747 with a core diameter of 50 μm and a cladding diameter of 125 μm. Electroless plating on the lower layer as a metal coating on the surface.
A 5μm nickel layer is applied to the surface by electrolytic plating.
．． Connection was made in the same manner as in Example 1 using an optical fiber coated with 2 μm of gold 1.

This match was achieved with a connection loss of 1135 dB and a temperature characteristic of ±0.08 dB, which were better results than Example 1.

Figure 1

[Brief explanation of drawings]

Figure 1 is a cross-sectional view of the optical fiber, Figure 2 (a) is an explanatory diagram showing how the optical fibers are soldered together on the V-groove fitting, and Figure 2 (b) is Figure 2 (a). Figure 3 (a) is a perspective view of the sleeve, Figure 3 (b) is an explanatory diagram showing how optical fibers are soldered together using a sleeve, and Figure 4 FIG. 2 is an explanatory diagram showing an example of connection between an optical fiber and an element. 1: Core 2: Clad 3: Metal coating 4: Outer skin 6: Jig 7: Solder 8: Sleeve 9: ■Groove 10: Metal case 11: Element j・-”f. Name of agent: Motohiro Kurauchi・1 Figure 2(.) Figure 2(b) Figure 4 Figure 3(0)? 7 Figure 3(b)

Claims (1)

[Claims] 1) A method for connecting optical fibers, which uses optical fibers whose outer peripheries are coated with metal, and connects the optical fibers or the optical fibers and devices or elements by soldering.