JP2003337248A - Method of fusion splicing polyimide-coated optical fiber and fused fiber - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of fusion splicing a polyimide-coated optical fiber and a fused fiber in which a strong release agent or a mechanical means need not be used to remove a polyimide coating, a wiping with a solvent is unnecessary, the strength of an optical fiber is not reduced, a strong fusion splicing is realized, and the fusion splicing is automated. <P>SOLUTION: The fused fiber is made by a cutting process of optical fiber in which the fiber is cut without removing the coating of the polyimide-coated optical fiber on which the polyimide is coated on the circumference of a bare fiber composed of a core and a clad, a coating removing process in which two coating-removed optical fibers are prepared by exposing the bare fiber part by removing the coating in the vicinity of the cut part with an electric discharge, a fusion splicing process in which the cut faces of both bore bare fibers mutually butted, and the bare fibers are fused and spliced together with the electric discharge, and a protecting process of connected part in which the fused and spliced part is protected. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fusion splicing method for a polyimide coated optical fiber and a fusion splicing fiber.

[0002]

2. Description of the Related Art A coated optical fiber is often used for protection of the optical fiber, insulation and the like. In order to improve high strength, heat resistance, fire resistance, etc., as shown in Fig. 2, a bare fiber (part) consisting of a core 1 and a clad 2
A polyimide-coated optical fiber 5 having a polyimide coating 4 on the outer periphery of 3 is used. When it is necessary to connect the polyimide-coated optical fibers 5 to each other, conventionally, fusion-splicing is performed by the following method. This will be described with reference to FIG. (1) The polyimide coating on the end of the polyimide-coated optical fiber 5 is removed using a strong release agent or mechanical means to form a coating-removed optical fiber 5a ', and the bare fiber portion 3 of the coating-removed portion is wiped with a solvent. . Then bare fiber part 3
Is cut into a predetermined length with a cutter c (FIG. 4 (a)). (2) Optical fiber 5 with coating removed by cutting the bare fiber
Two pieces of a'are set in a fusion machine (not shown) so that the cut surfaces d of the bare fiber portions 3 of the coating removal portion face in a straight line and with a gap therebetween. Pre-discharging is performed on both the cut surfaces d and the vicinity thereof, and the bare fiber portions 3 and 3 near the both cut surfaces are heated (FIG. 4B). (3) Next, the cut surfaces d of the two bare fiber portions 3 of the two optical fibers 5 ′, 5 ′ are butted (FIG. 4 (c)). (4) In the vicinity of the cut surfaces abutting, the bare fiber portions 3 fused and discharged from the discharge electrodes e, e and abutted are heat-fused and connected to each other to provide a fusion-bonded bare fiber portion 3a (FIG. 4). (d)). (5) The fusion splicing bare fiber portion 3a is reinforced with a reinforcing sleeve f.
And the fused fiber 30 is completed (FIG. 4).
(e)). The length of the fusion splicing bare fiber portion 3a is, for example, about 30 mm.

[0003]

The above-described conventional fusion splicing method for polyimide-coated optical fibers has the following problems. First, the polyimide coating must be removed prior to fusion splicing, but because the polyimide coating is strong, it was necessary to remove it with a strong release agent or mechanical means. In the case of the above-mentioned stripping agent, it takes a long time to remove and is strongly acidic, so there is a danger.In the case of mechanical means, the bare fiber is scratched when the coating is removed, so that the strength of the optical fiber deteriorates. Oops. Also, wiping with a solvent deteriorates the strength of the optical fiber. In addition, the length of the portion of the polyimide-coated optical fiber where the coating is removed needs to be, for example, 40 mm, and it is necessary to cut the bare fiber portion to a predetermined length, for example, 15 mm after removing the coating. The length of the connection bare fiber portion after the connection is about 30
Since the length was about mm, the probability of breakage was high. Also,
When the bare fiber part was set in the fusion machine, it was scratched and the strength of the optical fiber deteriorated. In the fusion splicing of the polyimide-coated optical fiber, the splicing portion has high strength, and has low transmission loss characteristics, that is, high-strength fusion splicing is required. It was difficult. Further, the removal of the polyimide coating is carried out manually, and each step of cutting and fusing the bare fiber portion is also carried out independently, which requires man-hours, resulting in an increase in cost. Moreover, the fusion splicing could not be automated.

The present invention has been made in order to solve various problems of the above-mentioned prior art, and it is not necessary to use a strong release agent or mechanical means for removing the polyimide coating, and wiping with a solvent is not required. The purpose of the present invention is to provide a fusion splicing method of a polyimide-coated optical fiber and a fusion splicing fiber, which does not require deterioration of the strength of the optical fiber, can perform high-strength fusion splicing, and can also automate fusion splicing. To do.

[0005]

As a first aspect, the present invention is to cut a fiber without removing the coating of a polyimide-coated optical fiber having a polyimide coating on the outer periphery of a bare fiber portion consisting of a core and a clad, Then, the coating in the vicinity of the cut portion is removed by discharge to expose the bare fiber portion to form two coating-removed optical fibers, and then the cut surfaces of both bare fiber portions of the coated-removed optical fiber are butted to each other before the bare fiber portions are joined together. Is fusion-spliced by electric discharge, and the fusion-spliced portion is further protected to form a fusion-bonded fiber. In the fusion splicing method of the first aspect, the polyimide-coated optical fiber (hereinafter,
(Also referred to as polyimide fiber) The fiber is cut without removing the coating, and the coating in the vicinity of the cut portion of the cut fiber is removed by discharge, so there is no danger of removal of the coating without degrading the strength of the optical fiber, It will be easy to do. Further, since the bare fiber portions of the cut portions are fusion-spliced by discharge following the removal of the coating, the fusion-splicing can be automated. In addition, since the jig does not touch the bare fiber portion during removal of the polyimide coating and fusion, the strength of the optical fiber does not deteriorate, and high strength fusion splicing becomes possible. Further, since the bare fiber portion of the fusion splicing portion can be shortened, the breakage probability is reduced.

As a second aspect, the present invention is to cut a fiber without removing the coating of a polyimide-coated optical fiber having a polyimide coating on the outer circumference of a bare fiber portion consisting of a core and a clad, and then coating the fiber near the cut portion. Of the coating-removed optical fiber by exposing the bare fiber portion to two exposed coating-free optical fibers, and then the cut surfaces of both bare-fiber portions of the coating-removed optical fiber are abutted, and then the bare-fiber portions are fusion-spliced by discharge. The method of fusion splicing of a polyimide-coated optical fiber to further protect the fusion-splicing part to form a fusion-bonded fiber, without removing the coating of the polyimide-coated optical fiber, in a state where tension is applied to the fiber. An optical fiber cutting step of cutting the fiber perpendicularly to the length direction of the fiber; and a cut surface of the cut two polyimide-coated optical fibers. After arranging them so that they face each other and with a gap between them, preliminary discharge is performed near the cut portions of both cut fibers, the coating near the cut portions is removed to expose the bare fiber portion, and the coated fiber is removed. Coating removal step;
And, after abutting the cut surface of the bare fiber portion of the coating removal optical fiber, fusion discharge near the abutting portion,
A fusion splicing step of fusion-splicing the bare fiber portions of the butt portion; and a splicing portion protection step of protecting the fusion-spliced bare fiber portion with a reinforcing sleeve; This is a method for fusion splicing of polyimide-coated optical fibers. In the fusion splicing method of the second aspect,
By using each of the above steps, the fusion splicing of the polyimide fibers can be efficiently performed, and the same action and effect as the first aspect can be obtained.

A third aspect of the present invention is the fusion splicing method for a polyimide-coated optical fiber, wherein the polyimide coating is a semi-cured polyimide coating that has not been sufficiently cured. In the fusion splicing method according to the third aspect, the polyimide coating is a semi-cured polyimide coating, whereby the coating can be efficiently removed by preliminary discharge.

As a fourth aspect, the present invention resides in a fusion splicing fiber obtained by the fusion splicing method. Since the fusion splicing fiber according to the fourth aspect is obtained by the fusion splicing method, the fusion splicing fiber has low cost and improved strength.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The contents of the present invention will be described below in more detail with reference to the embodiments shown in the drawings. The present invention is not limited to this. FIG. 1 is a schematic diagram for explaining a fusion splicing method of a polyimide-coated optical fiber of the present invention. The figure (a) is a state before the polyimide fiber is vertically cut by the cutter. In the same figure (b), two polyimide fibers cut vertically are set in a fusion machine (not shown) so that the cut surfaces face each other in a straight line and with a gap, and near the cut surface from the discharge electrode. The state where the polyimide coating is removed by pre-discharging. Figure (c) shows
A state in which the cut surfaces of the bare fiber part where the polyimide coating is removed are to be butted. (Fig. (D)) shows a state in which the bare fibers of the abutting portion are heated and fused by fusion discharge from the discharge electrode near the abutting portion of the cut surface of the bare fiber portion.
In addition, (Fig. (E)) shows a state in which a fusion spliced bare fiber portion is covered with a polyimide coating and protected by a reinforcing sleeve to obtain a fused fiber as a finished product. FIG. 2 is a sectional view showing an example of the structure of a polyimide-coated optical fiber. Figure 3
It is a chart which shows the fusion splicing method of the polyimide coating optical fiber of this invention. FIG. 4 is a schematic diagram for explaining a conventional fusion splicing method for optical fibers.

In these figures, 1 is a core 1, 2 is a clad, 3 is a bare fiber (part), 3a is a fusion splicing bare fiber (part), 4 is a polyimide coating, 5 is a polyimide coating optical fiber, and 5a is Coating removal optical fiber, 5b fusion splicing optical fiber, 10 fusion bonding fiber, c cutter, d
Is a cut surface, d'is a fusion splicing portion (butting portion), e is a discharge electrode, f is a reinforcing sleeve, and g is an iron rod.

-First Embodiment (Example 1) -A first embodiment of the fusion splicing method of the present invention is shown in FIGS.
Will be explained. First, as shown in FIG. 2, for example, a polyimide coating 4 is applied to the outer periphery of a bare fiber (part) 3 having a core 1 having a diameter of 50 μm and a cladding 2 having a diameter of 125 μm, and a polyimide coating optical fiber having an outer diameter of 140 μm. 5
Is drawn and manufactured. During the production, the temperature of the curing oven was adjusted so that the polyimide coating was semi-cured, that is, the curing did not proceed sufficiently and there were many uncured portions. Next, as shown in FIG. 1 (a), the polyimide fiber 5 is set on a holding jig (not shown) of a fusion machine that can also cut the fiber while applying tension, for example, 10 g, and the fiber 5 is cut by a cutter. Cut vertically with c. Next, as shown in FIG. 1 (b), two vertically cut polyimide fibers are set so that the cut surfaces d, d face each other in a straight line and with a gap, and cut from the discharge electrodes e, e. Preliminary discharge is performed in the vicinity of the surface to remove the polyimide coating for a predetermined length, for example, about 1 mm. The discharge electrodes e, e have a diameter of 2.5 mm, for example. The distance between the discharge electrodes e is 6 mm, for example. In addition, the pre-discharge time was three times with one discharge being one second. Then, as shown in FIG. 1 (c), the sheath-removed polyimide fiber is moved in the direction of the arrow to leave the bare fiber portion 3
The cut surfaces d, d of are abutted. Next, as shown in FIG. 1 (d), discharge discharges e, e are generated from the discharge electrodes e, e near the abutting portions of the cut surfaces d, d, and the bare fibers at the abutting portions are heat-fused to fuse and splice the joints d. 'Is provided. The discharge electrode used for the fusion discharge is the same as the discharge electrode used for the preliminary discharge. The distance between the discharge electrodes e is also the same. It should be noted that the fusion discharge time is set to 2 for one second.
Discharged twice. Then, as shown in FIG. 1 (e), the fusion-bonded bare fiber portion 3a to the polyimide coating 4 are protected by a reinforcing sleeve f to obtain a fused fiber 10. The length of the fusion splicing bare fiber portion is, for example, about 2 m.
m. The reinforcing sleeve f is made of, for example, an EVA (ethylene vinyl acetate copolymer) resin tube, a reinforcing iron bar g is embedded inside, and an adhesive (not shown) is contained inside.

Tensile strength characteristics after fusion of the fusion splicing method of the present invention and the conventional fusion splicing method were compared. The test results are shown in Table 1 below. In addition, the conventional normal fusion splicing method uses a normal fiber strand (250 μm UV coated fiber (bare fiber (part) 125
μm)), mechanical strip, wiping,
The cutting and fusion discharge were performed in this order.

[0013]

[Table 1]

As is clear from the results of the characteristic comparison test shown in Table 1, the fused fiber obtained by the fusion splicing method of the present invention is compared with the fused fiber obtained by the conventional ordinary fusion method. The tensile strength after fusion was strong.

-Second Embodiment- A second embodiment of the fusion splicing method of the present invention will be described with reference to the chart of FIG. The fusion splicing method of the present invention is an optical fiber cutting step f1 in which the fiber is cut perpendicularly to the length direction of the fiber while tension is applied to the fiber without removing the coating of the polyimide-coated optical fiber. ;
And the two cut polyimide-coated optical fibers are arranged such that the cut surfaces face each other in a straight line and with a gap, and then pre-discharged in the vicinity of the cut surfaces of both cut fibers, and near the cut surfaces. A coating removing step f2 in which the coating is removed to expose the bare fiber portion, and the cut surfaces of both cut fibers from which the coating has been removed are butted, and then fusion discharge is performed near the butted portion, and the bare fiber portion of the butted portion is Fusion splicing step f3 for fusion splicing each other; and splicing step protection step f for protecting the fusion spliced bare fiber portion with a reinforcing sleeve.
4; and the fusion splicing method of a polyimide-coated optical fiber to be a fusion fiber.

[0016]

According to the fusion splicing method of the present invention, the fusion splicing of polyimide fibers can be easily performed, and the fusion can be automated. In addition, since the jig does not touch the bare fiber portion during removal of the polyimide coating and fusion, high strength fusion splicing is possible. Further, the length of the bare fiber portion of the fusion spliced portion can be shortened to, for example, about 2 mm, so that the probability of breakage becomes low. Therefore, the fused fiber obtained by the fusion splicing method of the present invention has improved strength. Therefore, the present invention is extremely effective in contributing to the industry.

[Brief description of drawings]

FIG. 1 is a schematic diagram for explaining a fusion splicing method of a polyimide-coated optical fiber of the present invention. (A) is a state before the polyimide fiber is cut vertically by a cutter. In (b), two polyimide fibers cut vertically are set in a fusion machine (not shown) so that the cut surfaces face each other in a straight line and with a gap, and a spare is placed near the cut surface from the discharge electrode. In this state, the polyimide coating is removed by discharging. (C) is a state in which the cut surfaces of the bare fiber portion from which the polyimide coating has been removed are to be butted.
(D) shows a state in which the bare fibers of the abutting portions are heated and fused by fusion discharge from the discharge electrode near the abutting portions of the cut surfaces of the bare fibers. (E) shows a state in which the fusion spliced bare fiber portion is protected by a reinforcing sleeve to obtain a fused fiber as a finished product.

FIG. 2 is a sectional view showing an example of the structure of a polyimide-coated optical fiber.

FIG. 3 is a chart showing a fusion splicing method for a polyimide-coated optical fiber of the present invention.

FIG. 4 is a schematic diagram for explaining a conventional fusion splicing method for optical fibers. (a) is the state before the optical fiber with the coating removed is cut vertically with a cutter. (b) is
Set two vertically cut polyimide fibers in a fusion machine (not shown) so that the cut surfaces face each other in a straight line and with a gap between them, and preheat and discharge the discharge electrodes near the cut surface. It is in a state of being. (c) is a state in which the cut surfaces of the bare fiber portion with the coating removed are butted.
(d) is a state in which the bare fibers in the abutting portion are heated and fused by fusion-discharging from the discharge electrode near the abutting portion of the bare fiber portion. (e) shows a state in which the fusion spliced bare fiber portion is protected by a reinforcing sleeve to form a fused fiber as a finished product.

[Explanation of symbols]

1 core 2 clad 3 Bare fiber (part) 3a Fusion spliced bare fiber (part) 4 Polyimide coating 5 Polyimide coated optical fiber 5a Coating-removed optical fiber 5b Fusion splicing optical fiber 10 fused fiber c cutter d Cut surface d'fusion connection part (butting part) e Discharge electrode f Reinforcing sleeve g iron rod

Claims (4)

[Claims] 1. A bare fiber portion comprising a core and a clad, the outer periphery of which is coated with a polyimide coating, the fiber is cut without removing the coating of the polyimide-coated optical fiber, and the coating near the cut portion is then discharged to remove the bare The fiber portion is exposed to form two coating-removed optical fibers, the cut surfaces of both bare fiber portions of the coating-removed optical fiber are then abutted, and the bare fiber portions are fusion-spliced by discharge, and further the fusion-spliced portion. A method for fusion splicing of a polyimide-coated optical fiber, which is characterized in that a fused fiber is protected. 2. A bare fiber portion comprising a core and a clad, the outer periphery of which is provided with a polyimide coating, the polyimide coated optical fiber is cut without removing the coating, and then the coating near the cut portion is removed by electric discharge to leave the bare fiber. The fiber portion is exposed to form two coating-removed optical fibers, the cut surfaces of both bare fiber portions of the coating-removed optical fiber are then abutted, and the bare fiber portions are fusion-spliced by discharge, and further the fusion-spliced portion. Is a fusion splicing method of a polyimide-coated optical fiber to protect the fused fiber, without removing the coating of the polyimide-coated optical fiber, in a state in which tension is applied to the fiber, in the length direction of the fiber. An optical fiber cutting step of cutting a fiber perpendicularly to the optical fiber;
After arranging the polyimide-coated optical fiber so that the cut surfaces face each other straight and with a gap, pre-discharge near the cut parts of both cut fibers, remove the coating near the cut parts, and leave it bare. A coating removal step of exposing the fiber portion to form a coating-removed optical fiber; and a cut surface of the bare fiber portion of the coating-removed optical fiber are abutted with each other, and then fusion discharge is performed in the vicinity of the abutted portion, and the bare fiber of the abutted portion A fusion-splicing step of fusion-splicing the sections; and a splicing step protecting step of protecting the fusion-spliced bare fiber section with a reinforcing sleeve; Fusion splicing method. 3. The fusion splicing method for a polyimide-coated optical fiber according to claim 1, wherein the polyimide coating is a semi-cured polyimide coating that is not sufficiently cured. 4. A fusion splicing fiber obtained by the fusion splicing method according to claim 1, 2 or 3.