JPH0351806A - Fusion splicing method for optical fiber - Google Patents

Abstract

PURPOSE:To allow the exact positioning of optical fibers by removing the resin coating of at least the parts to be crimped of the optical fibers and forming a metallic coating on these parts. CONSTITUTION:The vapor-deposited coating consisting of an Ni-Cr (nickel- chromium) alloy is formed as an underlying layer adhering well to quartz material which is the constituting material of the optical fiber 12 and a metallized coating consisting of Cu (copper) having a good adhesive property to the vapor- deposited coating is formed as a metallic coating thereon. The resin coating 20 is removed by about 13mm from the end face of the polarization maintaining optical fiber 12 by an ordinary mechanical or optical method and the part bout 5mm from the end face is coated with a cylindrical masking member 22. While the fiber and the member are kept rotating, vapor deposition is executed in a suitable vapor deposition device. The relatively positional relation of the optical fibers 12 to be fusion-spliced are exactly set in this way.

Description

[Detailed Description of the Invention] Summary Regarding a method for fusion splicing optical fibers, the present invention relates to a fusion splicing method in which the relative positional relationship of optical fibers to be fusion spliced can be accurately set, and the strength of the fusion spliced portion is less reduced. A method of fusion splicing an optical fiber by sandwiching at least a portion near the end of the optical fiber and bringing the end surfaces of the optical fiber into contact with each other in a predetermined positional relationship,
The resin coating of at least the sandwiched portion of the optical fiber is removed and a metal coating is formed on this portion.

Industrial applications The present invention relates to a method for fusion splicing optical fibers.

In the field of optical fiber communications, it is sometimes necessary to connect optical fibers to each other in order to install optical transmission lines over long distances. Various methods have been proposed for connecting optical fibers, and among them, fusion splicing, in which the ends of optical fibers are fused together at a temperature higher than the melting temperature of quartz, uses an adhesive at the joint. It is said that it is advantageous in terms of loss, stability, etc. because there are no inclusions such as. What is particularly required when fusion splicing optical fibers is that the relative positional relationship of the optical fibers to be fused be accurately set in order to prevent deterioration of loss characteristics due to axis misalignment, etc. In addition, the decrease in strength due to fusion splicing is small.

Conventional technology The principle of fusion splicing of optical fibers will be explained with reference to FIG.

Optical fiber 102 with resin coating 106 partially removed
．． The end surfaces of the bridges 104 are coaxially brought into contact with each other, and the abutting portion and its vicinity are heated and melted during the arc discharge generated between the discharge bridges 108 and 110, thereby performing fusion splicing. When performing such fusion splicing, if the relative positional relationship between the optical fibers 102 and 104 is not in a predetermined positional relationship, the splice loss after fusion splicing will increase. They are in a specified position.
It is necessary to accurately position and hold the Here, when the optical fibers to be fusion spliced are in a predetermined positional relationship, it means that normal optical fibers such as single-mode optical fibers are coaxial with no misalignment; In the case of a wavefront preserving optical fiber, in addition to the above, it refers to a state in which the principal axes (the axis where the polarization plane of the polarized light whose polarization state is preserved and the fiber abutting end face intersect) coincide with each other. Conventionally, in order to perform the above-mentioned positioning, a lamp mechanism 112 as shown in FIG. 8 has been used to clamp at least the portion near the end of the optical fiber.

Problems to be Solved by the Invention When clamping a portion near the end of an optical fiber using a clamp mechanism, if the portion of the optical fiber from which the resin coating has been removed is directly clamped, fine scratches and attached dust may occur as a result. The strength after fusion splicing may decrease due to the influence of . For this reason, conventionally, as shown in FIG. 8, the optical fiber 102 was held between the parts where the resin coating 106 was not removed. However, when optical fibers are sandwiched indirectly through resin coatings, the effects of the resin coatings deforming elastically or plastically occur when adjusting the optical fiber's axis misalignment or rotation. This makes it difficult to accurately position the optical fiber.

The present invention was created in view of these technical issues, and it is possible to accurately set the relative positional relationship of optical fibers to be fusion-spliced, and the strength of the fusion-spliced portion is minimally reduced. The purpose is to provide a method for fusion splicing optical fibers.

Means to solve problems FIG. 1 shows a diagram explaining the principle of the present invention.

The method of the present invention is a method of fusion splicing optical fibers 2.4 by sandwiching at least a portion near the end of the optical fibers 2.4 and bringing the end surfaces of the optical fibers 2.4 into contact with each other in a predetermined positional relationship. 4, the resin coating 6 of at least the sandwiched portion is removed and a metal coating 8 is formed on this portion.

Note that the two-dot chain line in the figure indicates means such as a clamp mechanism for holding the optical fiber 2.4.

Operation According to the above method, the optical fiber 2.
4, there is no possibility that the strength of the fusion spliced portion will decrease due to minute scratches on the optical fiber. In addition, the metal coating hardly undergoes elastic or plastic deformation when the optical fibers are held together for fusion splicing, making it possible to accurately adjust the position or rotation of the optical fibers. Become.

Example Embodiments of the present invention will be described below based on the drawings.

FIG. 2 is an explanatory diagram of a polarization-maintaining optical fiber that can be used to implement the present invention. This polarization-maintaining optical fiber 10 has stress applying portions 16 in the cladding 14 on both sides of the core 120, which are made of a material having a coefficient of thermal expansion different from that of the cladding 14.
．． By embedding 18 before the spinning process, two directions perpendicular to each other on the fiber cross section, namely, the main axis direction The core 12 is configured to have anisotropy in its refractive index by applying different stresses to the core 12 in other orthogonal principal axis directions y. Due to this birefringence, a propagation constant difference occurs between a polarization mode having an electric field in the X direction and a polarization mode having an electric field in the y direction, allowing propagation while maintaining a specific polarization mode.

When fusion splicing this type of polarization-maintaining optical fiber, it is necessary not only to align the cores 12 of the fibers to be spliced so that their axes do not shift, but also to align the cores 12 of the fibers to be spliced. In order to match the corresponding spindles, it is necessary to perform rotational adjustment. Therefore, in order to accurately perform this axis alignment and rotational adjustment and to prevent the fiber surface from being scratched, a metal coating is formed as shown below.

In this example, Ni-Cr is used as an underlayer that adheres well to quartz, which is the constituent material of the optical fiber.
A vapor-deposited coating made of an alloy is formed, and a metalized coating made of Cu (copper) that has good adhesion to the vapor-deposited coating is formed thereon, and these are used as a metal coating.

The method of forming the vapor deposition coating will be explained with reference to FIG.

For example, about 13 mm of the resin coating 20 is removed from the end face of the polarization preserving optical fiber 12 by a conventional mechanical or chemical method, and about 5 mm from the end face is covered with a cylindrical masking member 22, which is then rotated. Vapor deposition is carried out in a suitable vapor deposition apparatus. 5 m from the end face
The reason for not forming a vapor deposited coating on the n+ area is that if a metal coating is formed on this area, the metal coating and quartz will combine at high temperatures during fusion splicing, resulting in a decrease in strength. This is because there is a risk of Note that the Cr content of the vapor deposition material alloy is preferably 13 to 20% in consideration of adhesion and Cu wettability.

When forming a metallized coating after forming a vapor-deposited coating, as shown in FIG.
What is necessary is to immerse the polarization-maintaining optical fiber on which the vapor-deposited coating has been formed to a predetermined depth.

FIG. 5 shows the cross-sectional structure of the vapor-deposited coating and the metallized coating. A vapor-deposited coating 30 with a thickness of several hundreds is formed on a portion of the polarization-maintaining optical fiber 12 except for the vicinity of the end and on a part of the resin coating 20. A metallized coating 32 of about 1 μm is formed.

FIG. 6 is a diagram showing a state in which the metal coating formed as described above is held between the clamp mechanisms. The same figure (a
) shows a state in which the metal coating is held between a clamping mechanism 34 made up of a combination of a V-shaped groove and a flat surface, and a clamping mechanism 36 made up of a pair of V-shaped grooves shown in FIGS.
This shows the state in which the metal coating is held between the two. Even if the polarization-maintaining optical fiber is aligned or rotated after being held in this way, according to this embodiment, since the metal coating is formed with a sufficient thickness, the polarization-maintaining optical fiber 12 There is no possibility that the resin coating will be deformed and misaligned when adjustments are made, unlike in the conventional case. Conventionally, the connection loss caused by such positional deviation was 0.2 dB, but according to this embodiment, it was improved to 0.05 dB. In addition, adjustment work becomes easier because positional deviation does not occur, and the time required for fusion splicing, which previously took about 30 minutes, is reduced to 10 minutes.
Improved by about a minute.

Although the present embodiment describes a polarization-maintaining optical fiber, the present invention is also applicable to ordinary optical fibers such as single-mode optical fibers.

As described in detail, according to the present invention, it is possible to accurately set the relative positional relationship of optical fibers to be fusion spliced, and to create optical fibers with a small decrease in strength at the fusion spliced portion. This has the effect of making it possible to provide a fusion splicing method.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of the principle of the present invention; FIG. 2 is an explanatory diagram of a polarization-maintaining optical fiber that can be used to implement the present invention; FIG. 3 is an explanatory diagram of a vapor deposition method in an embodiment of the present invention; FIG. 4 is an explanatory diagram of metallization treatment in an embodiment of the present invention, FIG. 5 is a cross-sectional view of metal coating by vapor deposition and metalization treatment in an embodiment of the present invention, and FIG. 6 is a diagram illustrating metal coating in an embodiment of the present invention. FIG. 7 is a diagram illustrating the principle of fusion splicing, and FIG. 8 is a diagram illustrating a method of holding an optical fiber during fusion splicing. 2.4...Optical fiber, 6...Resin coating, 8
...metal coating.

Claims (1)

[Claims] A method of fusion splicing by sandwiching at least the portion near the end of the optical fiber (2, 4) and bringing the end faces of the optical fiber (2, 4) into contact with each other in a predetermined positional relationship. The optical fiber fusion is characterized in that the resin coating (6) of at least the sandwiched portion of the optical fiber (2, 4) is removed and a metal coating (8) is formed on this portion. How to connect.