JPS6341808A - Terminal part for optical fiber - Google Patents

Abstract

PURPOSE:To prevent an optical fiber from extruding by calking and fixing a ferrule on a thin thickness part of a plastic clad to be inserted into an optical fiber positioning hole. CONSTITUTION:The thickness of plastic 3 is thinned at the end part of the optical fiber 1. The ferrule 4 is made of metal and its tip part has the positioning hole 5 into which thin thickness part of the clad 3 of the optical fiber 1 is to be inserted. The inner diameter of the hole 5 is smaller than the outer diameter of the clad 3 of the optical fiber 1 and slightly larger than the thin thickness part of the clad 3. When the thin thickness part of the optical fiber 1 is inserted into the hole 5, the end part of the optical fiber 1 is positioned coaxially with the ferrule 4 and the ferrule 4 is calked and fixed on the thin thickness part. Consequently, the core 2 can be prevented from its extruding phenomenon.

Description

[Detailed Description of the Invention] [Technical Field] The present invention relates to a terminal part of an optical fiber, which is formed by attaching a ferrule of an optical connector to the end of a plastic clad glass core optical fiber [Prior art and its problems] Plastic clad glass core optical fibers have a core made of pure silica glass, doped quartz glass, or multi-component glass, and a cladding made of plastic with a lower refractive index, but in general: ■ A quartz core and a silicone cladding. ■ Those consisting of a quartz core and a fluororesin gland (t
J S P 4511209), etc. are known.

In both cases, the clat' is a single layer made of one type of polymer.

Conventionally, as a means for attaching a ferrule of an optical connector to the terminal of this type of optical fiber, a method is known in which the end of the optical fiber is inserted into the ferrule with the clad attached, and the two are fixed with adhesive. However, the plastic cladding has a certain thickness and is softer than the core and ferrule, so the above method cannot reliably fix the core and ferrule, and when subjected to heat cycles, the core There is a problem in that a protrusion phenomenon occurs and a good connection cannot be obtained.

An improved version of this is to remove the plastic cladding from the optical fiber terminal, then cover the core with a thin layer of fluororesin, water glass, etc. with a lower refractive index, and fix it inside the ferrule with adhesive. As is well known (Japanese Patent Publication No. 56-41973), in such a structure, installing the ferrule not only makes the work complicated, but also damages the core surface when removing the cladding, which may cause breakage. there were.

[Means for solving problems and their effects]

The present invention provides an end portion of a plastic clad optical fiber which solves the above-mentioned problems of the prior art. In the terminal part of the optical fiber having a ferrule attached to the end of the optical fiber, the ferrule has a positioning hole at least at its tip part with an inner diameter smaller than the outer diameter of the plastic cladding of the optical fiber, and the ferrule has a positioning hole in the positioning hole of the optical fiber. The plastic cladding in the inserted part is thinner than the other parts, and the ferrule is fixed to the thinner part of the plastic cladding by caulking.

In other words, the present invention aims to make the plastic cladding at the end of the optical fiber as thin as possible to ensure that the ferrule's crimp engages the hard glass core, thereby firmly integrating the end of the optical fiber and the ferrule. It is something to do.

〔Example〕

FIG. 1 shows an embodiment of the invention. In the figure, 1 is an optical fiber consisting of a glass core 2 and a plastic craft 3, and 4 is a ferrule attached to its end.

The glass core 2 is made of quartz glass, and the cladding 3 is made of fluorine resin (polyvinylidene fluoride, trifluoroethylene copolymer, fluoroalkyl methacrylate polymer,
(fluoroalkyl acrylate polymer, etc.).

The thickness of the cladding 3 is thin at the end of the optical fiber 1. To form the cladding 3 into this shape, the cladding 3 at the end is melted or swollen with a solvent and the required thickness is made. Just leave it and remove it.

The ferrule 4 is made of metal, and has a positioning hole 5 at its tip, into which a thinned portion of the plastic cladding 3 of the optical fiber 1 is inserted. This positioning hole 5
The inner diameter of the plastic cladding 3 of the optical fiber 1 is smaller than the outer diameter of the plastic cladding 3 of the optical fiber 1, and slightly larger than the thin part of the cladding 7 of the optical fiber 1. Therefore, when the thin cladding part of the optical fiber 1 is inserted into the hole 5, the end of the optical fiber 1 is positioned coaxially with the ferrule 4.

The ferrule 4 is fixed to the thin part of the optical fiber 1 by caulking.

6 is the caulking part. In this part, the thickness of the crand 3 is thinner, and a hard glass core 2 is placed just below it.
is present, the caulking mechanism works effectively and the optical fiber 1
The ferrule 4 can be firmly attached to the ferrule 4.

Next, experimental results using this structure will be explained. Optical fiber 1 has a 200 μm pure silica glass core with a 5-thickness cladding.
It is coated with 0 μm polyvinylidene fluoride.

A positioning hole 5 with an inner diameter of 215 μm was formed at the tip of the ferrule 4. Dimethylacetamide was applied to about 25 mm of the end of the optical fiber 1 to swell the cladding. This softened the outer layer of the cladding, so that portion of the cladding was removed so that a thin inner layer remained and was dried. The cladding remaining at the end had a thickness of 5 μm.The end of the optical fiber treated with 0 or more was inserted into the ferrule 4 of the optical connector, and the ferrule was caulked and fixed to the end of the optical fiber.

The end portion of the optical fiber thus obtained has a pull-out strength of 1 kg or more, and the increase in loss due to end treatment is 0.
It was less than 1 dB. Further, no protrusion of the optical fiber from the ferrule was observed even after 10 heat cycles of -30°C to +80°C.

For comparison, we made a prototype by inserting the cladding at the end of the optical fiber into a ferrule (tip inner diameter: 320 μm) and fixing it with a ferrule, and heat cycled it 10 times. An optical fiber protrusion phenomenon occurred.

FIG. 2 shows another embodiment of the present invention. The optical fiber 1 in this embodiment has a cladding 3 made of a soft silicone resin on a glass core 2, and a protective coating 7. The protective coating 7 is stripped from the end of the optical fiber 1. Further, a positioning hole 5 having an inner diameter smaller than the outer diameter of the craft 3 is formed at the tip of the ferrule 4.

The end portion of the optical fiber 1 from which the protective coating 7 has been stripped is not subjected to any treatment to reduce the thickness of the cladding 3 as in the previous embodiment, but is directly pushed into the ferrule 4 to reduce the thickness of the cladding. Since the craft 3 is soft, such pushing is possible. Note that a tapered hole 8 is formed on the entrance side of the positioning hole 5 in the ferrule 4 to facilitate pushing. Fixing the tip of the ferrule 4 to the optical fiber 1 by caulking is the same as in the previous embodiment.

Even with such a configuration, the same results as in the above embodiment can be obtained.

〔Effect of the invention〕

As is clear from the above description, the present invention has the following effects.

■ The ferrule is fixed to the end of the optical fiber by caulking, but since the thickness of the plastic crimp is thinner at the caulking part, the caulking mechanism is reliably transmitted to the hard glass core, and the ferrule can be firmly fixed. , the core protrusion phenomenon can be prevented.

■ Since a thin plastic crimp is left at the end of the optical fiber, there is no risk of damaging the glass core, improving reliability in terms of strength.

[Brief explanation of drawings]

FIG. 1 and FIG. 2 are sectional views each showing an embodiment of an optical fiber terminal portion according to the present invention. 1-Optical fiber, 2-Glass core, 3-Plastic gland, 4-Ferrule, 5-Positioning hole, 6-Force-sealing part. Tribute; Figure 1 (A 2, -2

Claims (1)

[Claims] In the terminal portion of an optical fiber in which a ferrule is attached to the end of an optical fiber having a glass core coated with a single layer of plastic cladding, the ferrule is positioned at least at its tip portion with an inner diameter smaller than the outer diameter of the plastic cladding of the optical fiber. The optical fiber has a hole, and the part of the optical fiber that enters the positioning hole has a plastic cladding that is thinner than other parts, and the ferrule is fixed to the thinner part of the plastic cladding by caulking. An optical fiber terminal section characterized by: