JP2773522B2 - Optical fiber airtight terminal structure - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical fiber hermetic terminal structure.

[0002]

2. Description of the Related Art Conventionally, this type of optical fiber hermetic terminal structure has a structure shown in FIG.
A groove 8 and a welding lip 10 are provided at a part of the outer peripheral part of the cylindrical cored bar 6 in which is sealed and fixed, and a groove 5 and an end thereof are provided at a part of the inner surface of the other metal pipe 21. A welding lip 10 is provided, and a cylindrical metal core 6 in which an optical fiber 13 is hermetically sealed is inserted into the metal pipe 21, and a C-shaped ring 4 having elasticity engaging with both grooves 5, 8 is provided. In order to protect the optical fiber 13 from external pressure, a pressure-resistant tube 2 as a protective sleeve is air-tightly connected to the lip portion at the end of the tube.

[0003]

In the above-mentioned conventional optical fiber hermetic terminal structure, the optical fiber is housed in a pressure-resistant protective sleeve that is hermetically brazed to a metal pipe, and the distal end of the optical fiber is connected to an optical submarine cable. It is connected. Some external force is applied to this pressure-resistant protective sleeve,
If the protective sleeve is broken, high water pressure (eg, 800
kg / cm ² ), an attempt is made to push the cylindrical core metal in which the fiber is sealed and fixed into the housing. At this time, a large amount of shearing force is applied to the inserted elastic C-shaped ring through the groove between the cylindrical metal core in which the metal pipe and the optical fiber are hermetically sealed, so as to endure high pressure. When high pressure is applied, the elastic C-shaped ring expands into the space of the groove of the metal pipe without trying to follow the cylindrical core, and comes off the cylindrical core to form an optical fiber hermetic terminal structure. There was a risk of destruction.

An object of the present invention is to prevent an elastic C-shaped ring inserted between a metal pipe and a cylindrical core from falling off even when an optical fiber protective sleeve is broken under high water pressure. To provide an optical fiber hermetic terminal structure.

[0005]

According to the present invention, there is provided a cylindrical metal core in which a plurality of optical fibers are hermetically fixed, a metal pipe into which the cylindrical metal core is inserted and fitted, the cylindrical metal core and the metal pipe. The optical fiber hermetic terminal structure comprises a structure inserted into grooves provided on both sides and fixed through a C-shaped ring having elasticity, wherein a ring-shaped stepped shoulder is provided in a part of the groove of the metal pipe. ing.

[0006]

Next, the present invention will be described with reference to the drawings.

FIG. 1 is a sectional view of one embodiment of the present invention.

In this embodiment, a cylindrical metal core 6 in which a plurality of optical fibers 13 are sealed and fixed, a metal pipe 1 into which the cylindrical metal core 6 is inserted and fitted, a cylindrical metal core 6 and a metal pipe 1
And has a C-shaped ring 4 having elasticity inserted into the groove portions 5 and 8 provided on both sides, and fixed.
A ring-shaped stepped shoulder 9 is provided in a part of the groove 5 of the metal pipe 1.

First, after inserting the pressure-resistant tube 2 into the metal pipe 1 and performing airtight brazing 3, the airtightness of the connection portion is checked in this state. The C-shaped ring 4 having elasticity is inserted into a groove 5 provided on the inner surface of the metal pipe 1 after the metal pipe 1 is assembled. Further, the cylindrical metal core 6 in which a plurality of optical fibers 13 are hermetically sealed is pushed into the metal pipe 1 in which the C-shaped ring 4 is incorporated. At this time, the C-shaped ring 4 having elasticity comes into contact with a chamfered portion 7 provided at an end portion of the cylindrical cored bar 6 and is expanded.
After being further pushed and inserted and fitted into the groove 8 of the cylindrical core 6, the cylindrical core 6 is pulled back, and a C-shaped shoulder 9 is provided on a ring-shaped stepped shoulder 9 provided in the groove 5 on the inner surface of the metal pipe 1. Install the ring 4. Thereafter, the metal pipe 1 at the end and the welding lip 10 at the end of the cylindrical cored bar 6 are hermetically welded 11 to complete the assembly. Thereafter, the airtightness of the welded portion is checked using the flange surface 12 of the metal pipe 1. With this structure, sufficient strength and reliability can be ensured even when the pressure-resistant tube 2 for protecting the fiber is broken under high water pressure.

[0010]

As described above, in the optical fiber hermetic terminal structure according to the present invention, the optical fiber hermetic terminal structure is provided on both the cylindrical metal core in which a plurality of optical fibers are hermetically sealed and the metal pipe into which the optical fiber is inserted and fitted. In the fixing structure via the elastic C-shaped ring inserted into the groove, by giving a ring-shaped stepped shoulder to a part of the groove of the metal pipe,
It is possible to prevent the C-shaped ring from spreading and improve the reliability of the optical fiber hermetic terminal structure under high water pressure.

[Brief description of the drawings]

FIG. 1 is a sectional view of one embodiment of the present invention.

FIG. 2 is a cross-sectional view of an example of a conventional structure.

[Explanation of symbols]

 Reference Signs List 1, 21 metal pipe 2 pressure-resistant tube 3 brazing 4 C-shaped ring 5 groove 6 cylindrical core 7 chamfered portion 8 groove 9 ring-shaped stepped shoulder 10 welding lip 11 airtight welding 12 flange surface 13 optical fiber

Claims (1)

(57) [Claims] 1. A cylindrical metal core in which a plurality of optical fibers are hermetically fixed, a metal pipe into which the cylindrical metal core is inserted and fitted, and grooves provided in both the cylindrical metal core and the metal pipe. An optical fiber hermetic terminal structure comprising a structure inserted into a metal pipe and fixed through an elastic C-shaped ring, wherein a ring-shaped stepped shoulder is provided in a part of the groove of the metal pipe. Airtight terminal structure.