JP2895654B2 - High strength connection method of optical fiber - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for fusion splicing an optical fiber for communication, and more particularly to a method for splicing an optical fiber having a hermetic layer on an optical fiber glass.

[0002]

BACKGROUND OF THE INVENTION On the outer periphery of an optical fiber glass, for example, aluminum, tin, titanium,
A so-called hermetic optical fiber having a carbon-based thin film coating layer (hermetic layer) such as silicon carbide, titanium nitride, or zirconia has a hermetic layer formed on the surface as compared with a normal optical fiber.
Special care must be taken when connecting. In other words, if an attempt is made to connect without removing the hermetic layer, the core portion of the optical fiber cannot be observed from the side depending on the material of the hermetic film, so that a widely used core direct-view fusion splicer cannot be used. LI / LD (Loca
l Injection / Local Detect
It is also difficult to use a light injection type fusion splicer called ion). For this reason, only the conventional optical power monitoring method can be used, and the efficiency of the connection work is greatly reduced. If discharge fusion is performed without removing the hermetic layer, a discharge current may flow through the hermetic layer depending on the material of the hermetic film, resulting in surface deterioration. For this reason, the strength after connection of the optical fiber is greatly reduced.

[0003] For connection of an optical fiber having a hermetic layer mainly for the above-mentioned reasons, it is effective to remove the hermetic layer in advance and perform fusion splicing.
As a means for removing the hermetic layer, a method of thermally decomposing the carbon-based thin film coating layer by using heat such as arc discharge has been proposed by the present applicant earlier (filed on January 23, 1989, No. 1-14638).

On the other hand, as a high-strength connection method of an optical fiber, a coating portion of a coated optical fiber is heated, the coating is slightly shifted in a longitudinal direction to expose the optical fiber glass portion, and then the exposed optical fiber glass is damaged. The optical fiber glass is cut by applying bending and tensile stress without contacting the optical fiber glass part, and then the coating is removed again to expose a predetermined length of the optical fiber glass, and the exposed surface of the optical fiber is discharged. A method of applying a thin film coating to this portion, setting it in a V-groove and fusion-splicing the portion, and reinforcing the connection portion has been proposed by the present applicant (September 3, 1987). Application, Japanese Patent Application No. 62-221
677).

However, the inventor of the present application has proposed a connection method disclosed in Japanese Patent Application No. 62-221677.
In an experiment including a method for removing a hermetic layer according to No. 638, as shown in Table 1 below, a hermetic optical fiber having an initial strength of 6 kg could only achieve a post-connection strength of 2 kg or less.

[0006]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems and provides a method for connecting a high-strength optical fiber without unnecessarily reducing the initial strength of the hermetic optical fiber. The step of removing at least the coating layer, the step of removing the hermetic layer by air discharge, the step of cutting the exposed optical fiber glass, the step of cleaning the optical fiber glass, the step of exposing the exposed optical fiber glass and the
-With the tip of optical fiber glass on the outer periphery of the
After the steps of forming the thin film coat layer are performed in this order except in the vicinity, fusion bonding is performed to reinforce the connection portion.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIGS. 1A to 1G are explanatory views of the working procedure of a specific example of the high-strength connection method of the present invention. The working steps will be described below with reference to FIG. (A) After a cut is made in a predetermined position of the coating layer 2 of the optical fiber core wire 1 having the coating layer 2, the hermetic layer 3 is exposed by extracting the coating layer 2 while heating the coating layer 2 with a heater 11. Let it. The removal length is about 3 cm . (B) The optical fiber core wire 1 is moved in the direction of the optical axis while aerial discharge is performed using a pair of discharge electrode rods 5 arranged in a direction perpendicular to the optical axis, and the predetermined length (10 to 15 mm) is set. The hermetic layer 3 is removed by thermal decomposition to expose the optical fiber glass 4. (C) The covering portion of the optical fiber core wire 1 is gripped by the fixed clamp 6, the tip hermetic layer 3 is pulled, gripped by the clamp 7, and the tension clamp 7 is moved in the direction of the arrow to the optical fiber glass 4 portion. While applying tension, the surface of the optical fiber glass 4 is scratched initially with a flaw blade 8, and the optical fiber glass 4 is cut by bending it with a cutting pillow 9. Cutting length is 1
2 to 16 mm. (D) Four parts of the optical fiber glass 4 are immersed in sulfuric acid 10 heated by a heater or immersed in acetone, and ultrasonic waves 16 are applied thereto to remove the adhered substances adhered to the surface of the optical fiber glass 4 by washing. I do. At this time, the above 2
Two methods may be used in combination. (E) A thin film resin is applied on the exposed outer periphery of the optical fiber glass 4 and the hermetic layer 3 and cured to form the thin film coat layer 12. (F) The two optical fiber glasses 4 processed in (a) to (e) above are positioned on the V-groove base 13 with their end faces facing each other, and fixed with the V-groove clamp 14. In this state, fusion welding is performed by discharge heating of the discharge electrode rod 5 using a core direct-view fusion splicer or the like. (G) The connecting portions are set in a pair of molds each having a semicircular cross section, and the resin is filled and cured to form a mold reinforcing layer 15 having the same outer shape as the coating layer of the optical fiber 1.

[0008]

EXPERIMENTAL EXAMPLE A hermetic optical fiber having an initial breaking strength of about 6 kg was fusion-spliced in the process shown in FIG. 1, and the breaking strength after connection was determined. As a result, as shown in FIG. 2, an average breaking strength of 2.5 kg was obtained. The connection loss at this time is as shown in FIG. 3, and the average connection loss was 0.03 dB, and a good value equivalent to that of a normal connection was obtained.

[0009] For comparison, when the work was performed by changing the order of the steps as shown in Table 1, it was confirmed that the breaking strength was lowered in all cases and the order according to the method of the present invention was excellent.

[0010]

[Table 1]

The connection method of the present invention defines the order of the steps as described above, and particularly limits the technical contents of each step, the fusion splicing method, and the method of forming the reinforcing layer. Not something. Further, after the step of forming the thin film coating layer, it is possible to further improve the strength by, for example, clamping and fusion-splicing the coated portion of the optical fiber or washing with hydrofluoric acid after the connection.

[0012]

As described above, according to the connecting method of the present invention, it is possible to obtain a high-strength fusion spliced portion without unnecessarily reducing the initial strength of the hermetic optical fiber.

[Brief description of the drawings]

FIGS. 1A to 1G are explanatory diagrams of a working procedure of a specific example of a connection method according to the present invention.

FIG. 2 is a data diagram of the breaking strength of an optical fiber connection portion according to the connection method of the present invention.

FIG. 3 is a data diagram of a connection loss of an optical fiber connection portion according to the connection method of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Optical fiber core wire 2 Coating layer 3 Hermetic layer 4 Optical fiber glass 5 Electrode rod 6 Fixed clamp 7 Pull clamp 8 Scratching blade 9 Cutting pillow
DESCRIPTION OF SYMBOLS 10 Sulfuric acid 11 Heater 12 Thin film coating layer 13 V groove base 14 V groove clamp 15 Mold reinforcement layer 16 Ultrasonic source

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-2-87106 (JP, A) JP-A-64-63905 (JP, A) JP-A-2-195304 (JP, A) JP-A 63-63 282707 (JP, A) JP-A-2-199411 (JP, A) JP-A-58-42013 (JP, A) JP-A-60-232513 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) G02B 6/24

Claims (1)

(57) [Claims] 1. A method of connecting an optical fiber comprising a hermetic layer on an optical fiber glass and a coating layer provided thereon, comprising: at least a step of removing the coating layer; a step of removing the hermetic layer by air discharge; more Engineering for cutting the exposed optical fiber glass, washing the optical fiber glass, dew
On the outer periphery of the exposed optical fiber glass and hermetic layer
Thin-film coating except for the tip of the optical fiber glass
A high-strength connection method for an optical fiber, comprising performing a step of forming a layer in this order, fusion-splicing, and reinforcing the joint.