JPS6312323Y2 - - Google Patents

Description

[Detailed explanation of the idea]

[Industrial Field of Application] The present invention relates to the structure of the connecting end of an optical fiber used for optical communication and other purposes, and particularly relates to the connecting end of an optical fiber installed in a space where environmental temperature changes significantly. [Prior art] When connecting optical fibers, it is necessary that the optical axes of the strands of the opposing optical fibers be in a straight line, and the relative positions of the connecting parts should not change as much as possible even after installation. It is necessary. Conventionally, as shown in FIG. 5, the connection end surface of an optical fiber was constructed so that the end surfaces of the ferrule 1, the capillary 2, and the strands 4 of the optical fiber 3 were on the same plane, that is, flush with each other. . [Problems that the invention aims to solve] However, since the materials of conventional optical fiber connectors are, for example, metal materials for ferrules and inorganic materials such as ceramics for capillaries, it is difficult to make proper connections during installation. However, if the environmental temperature rises after installation, a mutual spacing of dimension t will occur between the end faces of the opposing optical fibers, as shown in FIG. This is because the coefficient of thermal expansion of capillaries made of metal ferrules, ceramics, etc. is considerably larger than that of quartz glass-based optical fiber wires. When such a gap occurs, the transmission loss of light increases, which adversely affects the propagation characteristics of the optical communication system. The object of the present invention is to provide an optical fiber connection structure that provides stable propagation characteristics even under changes in environmental temperature. [Means for Solving the Problems] The present invention includes a capillary that covers the strand of the optical fiber from which the end coating has been removed, and a metal cylinder in which the capillary and the coated portion of the optical fiber are housed. Two connectors are disposed with their connecting ends facing each other, and each of the two connectors includes a ferrule shaped like a ferrule and is processed so that the connecting end of the capillary is flush with the strand of the optical fiber. The device includes a connecting means commonly attached to the two ferrules so that the strands of each optical fiber are arranged on the same optical axis, and the connecting end of the capillary slightly protrudes from the connecting end of the ferrule. In the optical fiber connection structure according to the present invention, the capillary is made of heat-resistant crystallized glass. The connecting end of the capillary protrudes 50 μm to 2 mm from the connecting end of the ferrule, and the connecting means that is commonly attached to the two ferrules is
Preferably, it is a single metal cylinder into which the ferrule is inserted. [Function] If the end faces of the optical fibers are slightly protruded outward from the end faces of metallic ferrules, which have a large amount of thermal deformation, and are connected, even if the amount of thermal expansion of the ferrules becomes large, the end faces of the ferrules can be connected to each other. Since there is no contact, even if a gap occurs at the end face of the optical fiber, it can be made very small. At this time, since the capillary is made of heat-resistant crystallized glass having a coefficient of thermal expansion close to that of the optical fiber, the capillary does not protrude from the optical fiber due to temperature changes and the end face does not shift. [Example] An example of the present invention will be described with reference to the drawings. FIG. 1 is a sectional view of one of the connecting portions according to the above embodiment. In FIG. 1, the coating 5 is removed from the connection end of the optical fiber 3 (on the right side of FIG. 1), and this strand 4
A capillary 2 covers this portion, and the optical fiber 3 including the capillary 2 and the coating 5 is inserted into a metal ferrule 1. Capillary 2
The end faces of the connecting ends of the wires 4 and 4 are assembled so that they are flush with each other. The two connectors assembled in this way are arranged with their respective connection end faces facing each other, and as shown in FIG.
The outer peripheral portions of the ferrules 1 of the two connectors are inserted and connected. Here, the connection end surface of the capillary 2 and the wire 4 is
It protrudes from the connecting end surface of the ferrule 1 by a distance l. This dimension l is typically several tens of μm to 200 μm
That's about it. According to this structure, even if a dimensional deviation occurs between the ferrule 1 and the capillary 2 due to thermal expansion, the gap 2l absorbs this as shown in FIG.
The mutual contact surfaces of the capillaries 2 do not separate. In reality, however, there is an error in polishing the end face, and the end face is not perpendicular to the optical axis. If this error is emphasized, it will be as shown in Figure 4. In this case as well, the mutual spacing t of the wires 4 is constant without being affected by temperature, so the light passing loss at the connection part can be kept constant. I can do it. Generally, the ferrule 1 is made of metal such as stainless steel, which has a linear expansion coefficient of about 160×10 ^-7 /°C, as shown in item (a) in the table below, and is made of quartz glass, which is the material of the optical fiber. This is several tens of times larger than 4 to 6×10 ⁻⁷ /°C. Assuming that the length of the wire 4 inserted into the capillary 2 and the length of the part of the ferrule affected by thermal deformation are each 3 mm, the amount of elongation when the temperature rises by 100°C is as shown in table (c). As shown in the section, the diameter is 0.15μm for optical fiber strands, and the diameter for stainless steel is 0.15μm.
It is 4.8μm. Therefore, the difference is 4.8−0.15=4.65μm. This embodiment is characterized in that the capillary is made of a glass-based material with low thermal expansion. Here, heat-resistant crystallized glass is used.

[Effect of idea]

By implementing the present invention, the influence of thermal expansion on the connection portion can be extremely reduced.
That is, the generation of a gap where the capillary protrudes from the optical fiber is prevented. Therefore, it can be used to install optical fibers in environments with rapid temperature changes, such as in polar regions or outer space, and because the amount of thermal deformation at the connection point is small, the lifespan of each component at the connection point can be extended. be.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of an embodiment of the present invention. FIG. 2 is an explanatory diagram showing the connection state of the above embodiment. FIG. 3 is a sectional view of the connecting portion of the above embodiment. FIG. 4 is a cross-sectional view of the connection portion including polishing errors in the above embodiment. FIG. 5 is a sectional view of a conventional structure. FIG. 6 is a sectional view of a connecting portion of a conventional structure. 1...Ferrule, 2...Capillary, 3...
Optical fiber, 4... Optical fiber strand, 5... Optical fiber coating, 6... Adapter, l... Dimension in which the end face of the capillary protrudes from the end face of the ferrule, t... Mutual spacing between the end faces of the strand .

Claims (1)

[Claims for Utility Model Registration] (1) A capillary that covers the strand of the optical fiber from which the end coating has been removed, and a metallic cylindrical ferrule in which the capillary and the coated portion of the optical fiber are housed. and a connecting tool processed so that the connecting end of the capillary is flush with the strand of the optical fiber;
These two connectors are provided with connecting means commonly attached to the two ferrules so that the strands of each optical fiber are arranged on the same optical axis. , an optical fiber connection structure in which the connection end of the capillary slightly protrudes from the connection end of the ferrule, wherein the capillary is made of heat-resistant crystallized glass. (2) The optical fiber connection structure according to claim (1), in which the connection end of the capillary protrudes 50 μm to 2 mm from the connection end of the ferrule. (3) The optical fiber connection structure according to claim (1), wherein the connection means commonly attached to the two ferrules is a single metal cylinder into which the ferrules are inserted.