JP2002207138A - Method for manufacturing optical fiber element and optical fiber element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical fiber element in which mechanical strength of a fusion spliced part is secured without depending on reinforcement by a steel wire and a method for manufacturing the optical fiber element. SOLUTION: Two optical fibers 10 and 20 are prepared (Fig. 1 (a)), coatings of resin 12 and 22 at end parts are removed to expose glass fibers 11 and 21 (Fig. 1 (b)), axial alignment is performed (Fig. 1 (c)), and a fusing process for fusing by heating respective end faces of the glass fibers 11 and 21 is performed (Fig. 1 (d)). In an additive diffusing process, a region including the fusion spliced part A is heat-treated at a first temperature T1 and additives which are added to the glass fibers 11 and 21 are diffused (Fig. 1 (e)). In a thermal distortion removing process, the region including the fusion spliced part A is heat-treated at a second temperature T2 lower than the first temperature T1 to remove thermal distortion (Fig. 1 (f)). In a gradual cooling process, the periphery of the fusion spliced part A is cooled from a prescribed initial temperature to 200 deg.C for a specified time or more (Fig. 1 (g)).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical fiber element having a fusion spliced portion in which two optical fibers are fusion spliced,
And a method for manufacturing the optical fiber element.

[0002]

2. Description of the Related Art As a method of cascading two optical fibers, there are a connector connection and a fusion splicing. Among them, the fusion splicing is a technique in which two optical fibers are axially aligned and each end face is heated and fused, and has an advantage that a splice loss is small. However, on the other hand, there is a problem that the mechanical strength of the fusion spliced part is lower than that of other parts of the optical fiber. Therefore, conventionally, in an optical fiber element having a fusion spliced portion, in order to reinforce the strength of the fusion spliced portion, a steel wire is provided along the fusion spliced portion, and the entirety is covered with a resin. Have been done.

[0003]

However, the above-described method of reinforcing a fusion spliced portion using a steel wire has the following problems. That is, as compared with other portions of the optical fiber, the outer diameter of the reinforcing portion (the portion to which the steel wire is attached) including the fusion spliced portion becomes larger. When the outer diameter of the reinforcing portion to which the steel wire is attached becomes large, when two optical fibers including the reinforcing portion and cascaded are formed into a cable, when wound around a bobbin to be modularized, or when other mounting is performed. At this time, stress is applied to the optical fiber in the vicinity of the reinforcing portion, and as a result, the risk of breakage of the optical fiber increases, or the loss of light propagating through the optical fiber increases. Further, when winding two optical fibers including the reinforcing portion around a bobbin, it is difficult to bend the reinforcing portion. As described above, in the optical fiber element having the fusion spliced portion, depending on the mounting mode or the application, the reinforcement of the fusion spliced portion by the steel wire may not be preferable.

An object of the present invention is to solve the above-mentioned problems, and an optical fiber element in which the mechanical strength of a fusion spliced portion is ensured without relying on reinforcement by a steel wire, and an optical fiber An object is to provide a method for manufacturing an element.

[0005]

An optical fiber element manufacturing method according to a first aspect of the present invention is a method for manufacturing an optical fiber element having a fusion spliced portion where each end face of two optical fibers is fusion spliced. And (1) a step of heating each end face of the two optical fibers and fusing them to form a fusion spliced part; and (2) an initial temperature of 500 ° C. or more and 1500 ° C. or less after the fusion step. A cooling step of cooling the fusion spliced portion from the temperature to 200 ° C. over 10 seconds or more.

In the first invention, in the slow cooling step after the fusion step, the fusion spliced portion is cooled from the initial temperature of 500 ° C. or more and 1500 ° C. or less to the temperature of 200 ° C. over 10 seconds or more. In the optical fiber element manufactured by this manufacturing method, the thermal strain generated during the fusion step is removed during the slow cooling step. Is sufficiently secured.

An optical fiber element manufacturing method according to a second aspect of the present invention is a method for manufacturing an optical fiber element having a fusion spliced portion in which respective end faces of two optical fibers are fusion spliced, (1)
A fusion step of heating and fusing each end face of the two optical fibers to form a fusion spliced part;
A heat distortion removing step of heat-treating the region including the fusion spliced portion at a temperature of not more than 1500 ° C. to remove thermal distortion; and (3) after the heat distortion removing step, the heating temperature in the thermal distortion removing step is reduced. A cooling step of cooling the fusion spliced portion to a temperature of 200 ° C. over 2 seconds or more.

[0008] In the second aspect of the present invention, in the thermal distortion removing step after the fusion step, the region including the fusion spliced portion is subjected to heat treatment at a temperature of 500 ° C. or more and 1500 ° C. or less to remove thermal distortion. In the subsequent slow cooling step, the fusion spliced portion is cooled from the heating temperature in the heat distortion removing step to a temperature of 200 ° C. over 2 seconds or more. In the optical fiber element manufactured by this manufacturing method, the thermal strain generated during the fusion step is removed during the slow cooling step and the thermal distortion removal step, so that the fusion is performed without using the reinforcing steel wire. The mechanical strength of the region including the connection portion is sufficiently ensured.

An optical fiber element manufacturing method according to a third aspect of the present invention is a method for manufacturing an optical fiber element having a fusion spliced portion in which respective end faces of two optical fibers are fusion spliced, (1)
(C) a fusion step in which each end face of the two optical fibers is heated and fused to form a fusion spliced part;
An additive diffusion step of performing a heat treatment on the region including the fusion spliced portion at a temperature of not less than 1500 ° C. and diffusing the additive added to the two optical fibers in the region including the fusion spliced portion; 3) After the additive diffusion step, a gradual cooling step of cooling the fusion spliced portion from the heating temperature at the time of the additive diffusion step to a temperature of 200 ° C. over 10 seconds or more is provided.

[0010] In the third aspect of the present invention, in the additive diffusion step after the fusion step, the region including the fusion joint is heated at a temperature of 800 ° C to 1500 ° C to include the fusion joint. In the region, the additive added to the two optical fibers diffuses. In the subsequent slow cooling step, the fusion spliced portion is cooled from the heating temperature in the thermal strain removing step to a temperature of 200 ° C. over 10 seconds or more. In the optical fiber element manufactured by this manufacturing method, the thermal strain generated during the fusion step and the additive diffusion step is removed during the slow cooling step, so that the fusion is performed without reinforcing the steel wire. The mechanical strength of the region including the connection portion is sufficiently ensured.

An optical fiber element manufacturing method according to a fourth aspect of the present invention is a method for manufacturing an optical fiber element having a fusion spliced portion in which respective end faces of two optical fibers are fusion spliced, (1)
(C) a fusion step in which each end face of the two optical fibers is heated and fused to form a fusion spliced part;
An additive diffusion step of heating the region including the fusion spliced portion at a first temperature of not less than 1500 ° C. and diffusing the additive added to the two optical fibers in the region including the fusion spliced portion; And (3) heat-treating the region including the fusion spliced portion at a second temperature of 500 ° C. or more and 1200 ° C. or less and lower than the first temperature after the additive diffusion step to remove thermal distortion. The method is characterized by comprising: a distortion removing step; and (4) a gradual cooling step of cooling the fusion spliced portion from the second temperature to a temperature of 200 ° C. over 2 seconds or more after the thermal distortion removing step.

[0012] In the fourth aspect of the present invention, in the additive diffusion step after the fusion step, the region including the fusion spliced portion is heat-treated at the first temperature of 800 ° C. or more and 1500 ° C. or less, so that In the region including the portion, the additive added to the two optical fibers diffuses. In the subsequent thermal distortion removing step, the region including the fusion spliced portion is subjected to heat treatment at a second temperature of 500 ° C. or more and 1200 ° C. or less and lower than the first temperature to remove thermal distortion. Further, in the subsequent slow cooling step, the fusion spliced portion is cooled from the heating temperature (second temperature) in the heat distortion removing step to a temperature of 200 ° C. over 2 seconds or more. The optical fiber element manufactured by this manufacturing method is:
Since the thermal strain generated during the fusion step and the additive diffusion step has been removed during the slow cooling step and the thermal distortion removal step, the machine in the area including the fusion spliced part without reinforcing with steel wire The target strength is sufficiently secured.

The method for manufacturing an optical fiber element according to any one of the first to fourth inventions, comprises:
The region including the fusion spliced portion is heat-treated by a flame generated by supplying a combustible gas and an oxygen gas to the burner or by a heater. In the method for producing an optical fiber element according to the second or fourth aspect of the present invention, in the thermal distortion removing step, the fusion splicing is performed by an arc discharge, a flame generated by supplying a combustible gas and an oxygen gas to a burner, or a heater. The region including the portion is subjected to a heat treatment. Further, in the method for manufacturing an optical fiber element according to the third or fourth aspect, in the additive diffusion step, the arc is generated by a flame generated by supplying a combustible gas and an oxygen gas to a burner, or by a heater. The heat treatment is performed on a region including the connection part. In any of these cases, in each step, the fusion spliced portion of the optical fiber element and its surroundings are subjected to a heat treatment at an appropriate temperature to remove thermal strain generated during the fusion step. When heat treatment is performed by arc discharge, the fusion splicing apparatus can be used as it is, which is preferable. The heat treatment using a burner is preferable because the fusion spliced portion of the optical fiber element and its periphery can be distributedly heated, and the heating device can be downsized. Further, it is preferable that the heat treatment is performed by the heater because the fusion spliced portion of the optical fiber element and its periphery can be distributedly heated and the heating atmosphere is clean.

In the optical fiber element manufacturing method according to the second or fourth invention, the fusion spliced portion and its periphery are moved in the thermal strain removing step while moving the heating source relatively in the longitudinal direction of the two optical fibers. It is characterized by performing a heat treatment. In this case, the thermal strain in the range heated in the additive diffusion step can be removed in the thermal strain removing step.
In the optical fiber element manufacturing method according to the second or fourth invention, the temperature gradient in the longitudinal direction of the two optical fibers in the thermal strain removing step is 500 ° C./mm or less. In this case, the thermal strain is sufficiently removed because the temperature gradient is small.

An optical fiber element according to the present invention is characterized by being manufactured by the above-described optical fiber element manufacturing method according to the present invention. In this optical fiber element, the thermal strain generated during the fusion step (and the additive diffusion step) is removed during the slow cooling step (and the thermal strain removing step).
The mechanical strength of the fusion spliced portion and its surroundings is sufficiently ensured without relying on steel wire reinforcement. Even if two optical fibers having different mode field diameters are fusion-spliced, the additive is diffused by heat treatment at the first temperature during the additive diffusion step. The difference in field diameter is small, and the connection loss is small.

The optical fiber element referred to here is 2
An optical fiber transmission line (for example, a dispersion compensating optical fiber + single mode optical fiber) to be laid, and a module wound around a bobbin. For example, dispersion compensating optical fiber + single mode optical fiber, E for optical amplification
r element doped optical fiber + single mode optical fiber),
Other forms are included.

[0017]

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings. In the description of the drawings, the same elements will be denoted by the same reference symbols, without redundant description.

First, the history of the present invention will be described. The inventor of the present application has investigated the cause of a decrease in the mechanical strength of the fusion spliced portion compared to the other portion of the optical fiber in the optical fiber element having the fusion spliced portion,
It has been found that the thermal strain caused by locally heating each end face of the two optical fibers and only the vicinity thereof at a high temperature at the time of fusion is caused. That is, when the glass end face of each optical fiber is heated and fused to a temperature at which the glass is sufficiently softened, thermal distortion occurs in the fusion spliced portion, and thereafter, when each optical fiber is cooled, thermal distortion remains. I do. The thermal strain remaining in the fusion spliced portion can be observed using an interference microscope or the like. If the thermal distortion remains in the fusion spliced portion, the fusion spliced portion will break during a later process, and the production yield of the optical fiber element will deteriorate. The present invention has been made on the basis of the above-described findings, and heat-treating a region including a fusion spliced portion at an appropriate temperature after fusion to remove thermal distortion, thereby fusing an optical fiber element. This is to secure the mechanical strength of the connection portion.

Next, first to fourth embodiments of the optical fiber element manufacturing method according to the present invention will be described. The optical fiber element manufacturing method according to the first embodiment includes a fusion bonding step and a slow cooling fixing. The method for manufacturing an optical fiber element according to the second embodiment includes a fusing step, a heat distortion removing step, and a slow cooling fixing. The method for manufacturing an optical fiber element according to the third embodiment includes a fusing step, an additive diffusion step, and a slow cooling fixation. Also,
The method for manufacturing an optical fiber element according to the fourth embodiment includes a fusion bonding step, an additive diffusion step, a thermal strain removing step, and a slow cooling fixing. Although the heat treatment conditions (temperature, slow cooling rate) in each step are different in each of the first to fourth embodiments, items common to the fourth embodiment will be described first, and the first to fourth embodiments will be described below. Matters that differ in each embodiment will be described later.

FIG. 1 is a process diagram illustrating a method for manufacturing an optical fiber element according to this embodiment. First, two optical fibers 10 and 20 to be fusion-spliced are prepared (FIG. 1A). The optical fibers 10 and 20 are obtained by coating glass fibers 11 and 21 based on quartz glass with resins 12 and 22, respectively. Then, the coating of the resin 12, 22 at the end of each of the optical fibers 10, 20 is removed to expose the glass fibers 11, 21 at the end (FIG. 1B). The removal of the coating of the resins 12 and 22 is chemically performed using, for example, hot concentrated sulfuric acid, and then the sulfuric acid is washed away using water or acetone. Then, the glass fibers 11 and 21 at the ends are cut with a fiber cutter,
The optical fibers 10, 20 whose ends are removed are held by the fiber holders 30, 40 of the fusion splicer.
The axes of the glass fibers 11 and 21 are aligned (FIG. 1).
(C)).

After the alignment, the glass fibers 11 and
1 is heated and fused to form a fusion spliced portion A (FIG. 1D). Specifically, the end faces of the glass fibers 11 and 21 are preheated and shaped, and the end faces of the glass fibers 11 and 21 are pushed into each other and connected.
The periphery of the fusion spliced portion A is shaped and heated.

After the fusing step, the third embodiment and the fourth embodiment
In the embodiment, the region including the fusion spliced portion A is subjected to the heat treatment at the first temperature T1 of 800 ° C. or more and 1500 ° C. or less, and the glass fibers 11 and 21 are formed in the region including the fusion spliced portion A.
An additive diffusion step of diffusing the additive added to the substrate is performed (FIG. 1E). The heating temperature range of 800 ° C. to 1500 ° C. in the additive diffusion step is the same as that of the glass fiber 11,
21 or lower and the glass fiber 1
The temperature is sufficient for diffusing the additives added to 1,21. The heating time in the additive diffusion step is preferably about 2 minutes or more and about 10 minutes or less. The higher the heating temperature, the shorter the heating time may be. By diffusing the additive by the heat treatment in the additive diffusion step, the difference in the mode field diameter can be reduced, and the connection loss can be reduced.

After the additive diffusion step, in the second and fourth embodiments, the region including the fusion spliced portion A is heated at a second temperature T2 within a predetermined temperature range and lower than the first temperature T1. A thermal distortion removing step of removing the thermal distortion by processing is performed (FIG. 1F). The heating temperature range in the heat distortion removing step is equal to or lower than the softening temperature of the glass fibers 11 and 21 and is a temperature sufficient to remove the thermal distortion. The heating time in the heat distortion removing step is shorter than the heating time in the additive diffusion step, and a short time of about several seconds to several tens of seconds is sufficient. By the heat treatment in the heat distortion removing step, the thermal distortion around the fusion spliced portion A generated during the fusion step or the additive diffusion step is removed, and the mechanical strength around the fusion spliced portion A is restored. In each of FIGS. 1 (d) and 1 (e), how the mode field diameter of the glass fibers 11 and 21 changes in the longitudinal direction is schematically shown by broken lines.

In the thermal distortion removing step, it is preferable to heat the area including the fusion spliced portion while moving the heating source relatively in the longitudinal direction of the glass fibers 11 and 21. By doing so, the thermal strain in the range heated during the additive diffusion step can be removed in the thermal strain removal step. That is, in order to reduce the radiation loss due to the change in the longitudinal direction of the mode field diameter, it is necessary to moderate the change in the longitudinal direction of the mode field diameter. Is relatively high, the range of heating during the additive diffusion step (that is, the range in which thermal strain occurs) is relatively wide (for example, 10 m
m to about 15 mm). On the other hand, since the second temperature in the thermal strain removing step is relatively low, if the heating source is fixed, the heating range in the thermal strain removing step is relatively narrow (for example, About 5 mm to 10 mm). Therefore,
In the heat distortion removing step, it is preferable to heat-treat the region including the fusion spliced portion while moving the heating source relatively in the longitudinal direction of the two optical fibers. In the thermal strain removing step, the temperature gradient in the longitudinal direction of the two optical fibers is 50.
The temperature is preferably 0 ° C./mm or less. By reducing the temperature gradient in this manner, thermal distortion is sufficiently removed.

After the thermal strain removing step, a slow cooling step of cooling the region including the fusion spliced portion A is performed (FIG. 1).
(G)). In the slow cooling step, the fusion spliced portion A is cooled from a predetermined initial temperature to a temperature of 200 ° C. over a predetermined time. In the slow cooling step, the temperature is changed from the initial temperature to 200 ° C.
The cooling rate to ° C. may be constant, but not necessarily constant. For example, the cooling rate may be initially high and gradually reduced. After cooling, the exposed glass fibers 11 and 21 are re-coated with the resin 52 (FIG. 1).
(H)). The outer diameter of the coating with the resin 52 is substantially equal to the outer diameter of the coating of the optical fibers 10 and 20 with the resins 12 and 22. After that, the optical fibers 10 and 2 including the fusion spliced portion A
The optical fiber element 1 is manufactured by performing predetermined mounting such as winding 0 around a bobbin.

In the optical fiber element 1 manufactured as described above, the thermal strain generated during the fusion step (and the additive diffusion step) is removed during the slow cooling step (and the thermal strain removing step). Therefore, the mechanical strength of the region including the fusion spliced portion A is sufficiently ensured without using the reinforcement by the steel wire. Even if two optical fibers having different mode field diameters are fusion-spliced, the additive is diffused by heat treatment at the first temperature during the additive diffusion step. The difference in field diameter is small, and the connection loss is small.

FIG. 2 is a table summarizing the heat treatment conditions in each step of each of the first to fourth embodiments. In the first embodiment, the annealing step is performed after the fusing step without performing the additive diffusion step and the thermal strain removing step. It takes 10 seconds or more to cool the periphery of the fusion spliced portion A.

In the second embodiment, the heat distortion removing step and the slow cooling step are performed after the fusing step without performing the additive diffusion step. In the thermal strain removing step in the second embodiment, 50
A heat treatment is performed on the periphery of the fusion spliced portion A at a temperature T2 of 0 ° C. or more and 1500 ° C. or less to remove thermal distortion. In the slow cooling step, the heating temperature T2 in the heat distortion removing step is increased from the heating temperature T2 to a temperature of 200 ° C.
The area around the fusion spliced portion A is cooled over a period of at least seconds.

In the third embodiment, the additive diffusion step and the slow cooling step are performed after the fusion step without performing the thermal strain removing step. In the additive diffusion step in the third embodiment, 80
Heat treatment is performed on the periphery of the connection portion A at a temperature T1 of 0 ° C. or more and 1500 ° C. or less. In the slow cooling step, the area around the fusion spliced portion A is cooled from the heating temperature T1 in the additive diffusion step to the temperature of 200 ° C. over 10 seconds or more.

In the fourth embodiment, an additive diffusion step, a thermal strain removing step, and a slow cooling step are performed after the fusion step. 4th
In the additive diffusion step in the embodiment, 800 ° C. or more and 150 ° C.
Heat treatment is performed around the fusion spliced portion A at a temperature T1 of 0 ° C. or less. In the thermal distortion removing step, the periphery of the fusion spliced portion A is subjected to a heat treatment at a temperature T2 which is 500 ° C. or more and 1200 ° C. or less and lower than the temperature T1 to remove thermal distortion. In the slow cooling step, the heating temperature T2 in the heat distortion removing step is increased from the heating temperature T2 to a temperature of 200 ° C.
The area around the fusion spliced portion A is cooled over a period of at least seconds.

FIG. 3 is a block diagram of an apparatus for performing a heat treatment in each step (additive diffusion step, thermal distortion removing step and slow cooling step) in the optical fiber element manufacturing method according to the present embodiment. As shown in this figure, a heating source 60 for heating the fusion splicing portion A and its surroundings, and a radiation thermometer 70 for measuring the temperature of the fusion splicing portion A and its surroundings are provided by fusion splicing. It is provided near the part A. The temperature of the fusion spliced portion A and its surroundings is measured by a radiation thermometer 70, and the temperature of the fusion spliced portion A and its periphery by the heating source 60 is adjusted so that the temperature measured by the radiation thermometer 70 becomes an appropriate value. Control heating.

The heating source 60 includes an electrode for arc discharge,
It is a burner or a heater (electric heater, ceramic heater, or the like), and can reciprocate in the longitudinal direction of the glass fibers 11 and 21. At the time of heating by the burner, a combustible gas (for example, a hydrocarbon gas such as propane gas) and an oxygen gas are supplied to the burner to generate a flame, and the flame heats the fusion spliced portion A and its surroundings. . It is preferable to use an arc discharge as the heating source 60 because the fusion splicing device can be used as it is. When a burner is used as the heating source 60, it is preferable because the fusion spliced portion A and its periphery can be subjected to distributed heating, and the heating device can be downsized. Further, it is preferable to use a heater as the heating source 60 because distributed heating of the fusion spliced portion A and its periphery can be performed, and the heating atmosphere is clean.

The radiation thermometer 70 is a combination of a two-dimensional infrared radiation thermometer and a magnifying lens.
And the temperature distribution around it. Further, the emissivity is set to 0.5 in consideration of the shapes and materials of the glass fibers 11 and 21 to be measured. In each of the additive diffusion step and the thermal strain removal step, the heating source 60 is arranged such that the temperature distribution measured by the radiation thermometer 70 becomes the maximum temperature at or near the fusion spliced portion A or in the longitudinal direction. It is moved, and this maximum temperature is used as the heating temperature in each step. In the slow cooling step, the radiation thermometer 7 is used.
The heating source 60 is arranged so that the temperature distribution measured by zero becomes the maximum temperature at or near the fusion spliced portion A, and the heating source 60 is moved so that the rate of decrease of the maximum temperature falls within the above-mentioned predetermined range. Control.

Next, specific examples of the optical fiber element manufacturing method according to each embodiment will be described.

The first example corresponds to the first embodiment (fusing step + slow cooling step). In the fusion step, the glass fibers 11 and
21 were fusion-spliced to each other. In the subsequent slow cooling process, the amount of gas supplied to the burner was gradually reduced,
Splice A from initial temperature 1500 ° C to 200 ° C
Was gradually cooled. Then, in the slow cooling step, the initial temperature 150
Optical fiber elements were manufactured by changing the annealing time required for gradually cooling from 0 ° C. to a temperature of 200 ° C., and a breaking test was performed on each optical fiber element under the conditions of a weighing distance of 200 mm and a pulling speed of 5 mm / min. Then, the 50% breaking strength was measured. FIG. 4 shows the annealing time and 50% in the first embodiment.
5 is a graph showing a relationship with% breaking strength. As can be seen from this graph, if the annealing time in the annealing step is 10 seconds or more, the 50% breaking strength is 19.6 N (2.00 k
g) or more, and if the slow cooling time in the slow cooling step is 14 seconds or more, the 50% breaking strength is 22.54 N (2.30 N).
kg) or more, and good results were obtained.

The second embodiment corresponds to the second embodiment (fusing step + thermal distortion removing step + gradual cooling step). In the fusion splicing step, the respective end faces of the glass fibers 11 and 21 were fusion-spliced to each other by arc discharge using a fusion splicer.
In the subsequent heat distortion removing step, the fusion spliced portion A is burned using a burner.
And its periphery was heated at a temperature of 1500 ° C. for 0.5 minutes to reduce thermal distortion around the fusion spliced portion A. In the subsequent gradual cooling step, the amount of gas supplied to the burner after the thermal strain removing step is gently reduced, and the heating temperature (initial temperature) in the thermal strain removing step is increased from 1500 ° C. to 200 ° C. A was gradually cooled. Then, in the slow cooling step, an optical fiber element is manufactured by variously changing a slow cooling time required for slowly cooling from an initial temperature of 1500 ° C. to a temperature of 200 ° C., and a weighing distance of 20 for each optical fiber element.
A breaking test was performed under the conditions of 0 mm and a tensile speed of 5 mm / min, and a 50% breaking strength was measured. FIG. 5 is a graph showing the relationship between slow cooling time and 50% breaking strength in the second example. As can be seen from this graph, if the annealing time in the annealing step is 2 seconds or more, the 50% breaking strength is 2%.
If it is 8.42 N (2.90 kg) or more and the slow cooling time in the slow cooling step is 3 seconds or more, the 50% breaking strength is 2
It was 9.4 N (3.00 kg) or more, and good results were obtained.

The third embodiment corresponds to the third embodiment (fusion step + additive diffusion step + slow cooling step). In the fusion splicing step, the respective end faces of the glass fibers 11 and 21 were fusion-spliced to each other by arc discharge using a fusion splicer.
In the additive diffusion step, the fusion spliced portion A and its periphery were heated at 1200 ° C. for 5 minutes using a burner to reduce the splice loss at the fusion spliced portion A. In the subsequent slow cooling step, the amount of gas supplied to the burner after the additive diffusion step is gradually reduced, and the fusion spliced portion A is heated from the heating temperature (initial temperature) of 1200 ° C. to the temperature of 200 ° C. in the additive diffusion step. Was gradually cooled. Then, an optical fiber element is manufactured by variously changing the annealing time required for gradually cooling from the initial temperature of 1200 ° C. to the temperature of 200 ° C. in the annealing step.
For each optical fiber element, a breaking test was performed under the conditions of a weighing distance of 200 mm and a pulling speed of 5 mm / min, and a 50
% Breaking strength was measured. FIG. 6 is a graph showing the relationship between slow cooling time and 50% breaking strength in the third example.
As can be seen from this graph, if the annealing time in the annealing step is 10 seconds or more, the 50% breaking strength is 19.6 N.
(2.00 kg) or more, and if the slow cooling time in the slow cooling step is 14 seconds or more, the 50% breaking strength is 24.5 N.
(2.50 kg) or more, and good results were obtained.

The fourth embodiment corresponds to the fourth embodiment (fusion step + additive diffusion step + thermal strain removal step + gradual cooling step). In the fusion splicing step, the respective end faces of the glass fibers 11 and 21 were fusion-spliced to each other by arc discharge using a fusion splicer. In the additive diffusion step, the fusion spliced portion A and its periphery were heated at 1200 ° C. for 5 minutes using a burner to reduce the splice loss at the fusion spliced portion A. In the subsequent heat distortion removing step, the fusion spliced portion A and its periphery were heated at a temperature of 700 ° C. for 0.5 minutes using a burner to reduce the thermal distortion around the fusion spliced portion A. In the subsequent slow cooling step, the amount of gas supplied to the burner after the thermal strain removing step is gradually reduced, and the heating temperature (initial temperature) 700 in the thermal strain removing step is reduced.
The fusion spliced part A was gradually cooled from a temperature of 200C to a temperature of 200C. Then, in the slow cooling step, the initial temperature from 700 ° C. to 200 ° C.
An optical fiber element was manufactured by changing the annealing time required to gradually cool to 50 ° C., and a breaking test was performed on each optical fiber element under the conditions of a weighing distance of 200 mm and a pulling speed of 5 mm / min, and a 50% fracture was performed. The strength was measured. FIG.
It is a graph which shows the relationship between slow cooling time and 50% breaking strength in 4th Example. As can be seen from this graph, if the annealing time in the annealing step is 2 seconds or more, the 50% breaking strength is 28.42 N (2.90 kg) or more, and the annealing time in the annealing step is 3 seconds or more. , The 50% breaking strength was 29.89 N (3.05 kg) or more, and good results were obtained.

In each of the above embodiments, a burner was used as a heating source in each of the additive diffusion step, the thermal strain removal step, and the slow cooling step. However, any of arc discharge and a heater may be used. Similar results were obtained.

As described above, according to the method for manufacturing an optical fiber element according to the present embodiment, in the fusion step, the end faces of the glass fibers 11 and 21 are heated and fused to form a fusion spliced portion. . Thereafter, in an additive diffusion step performed as necessary, the fusion spliced portion and its periphery are subjected to heat treatment at a first temperature of 800 ° C. or more and 1500 ° C. or less, and the glass fiber 11 is melted at the fusion spliced portion and its periphery. , 21 are diffused. In the subsequent thermal distortion removal step performed as necessary,
At a second temperature that is within a predetermined temperature range and lower than the first temperature, the fusion spliced portion and its surroundings are subjected to heat treatment to remove thermal distortion. Then, in the slow cooling step, the periphery of the fusion spliced portion is cooled from a predetermined initial temperature to a temperature of 200 ° C. for a predetermined time or more.

Therefore, even in the case where the glass fibers 11 and 21 having different mode field diameters are fusion-spliced, the additive is diffused by heating at the first temperature in the additive diffusion step. , The difference in the mode field diameter can be reduced, and the connection loss can be reduced. In addition, during the fusion step (and the additive diffusion step), thermal distortion occurs in the fusion spliced portion and its periphery, and the thermal strain is removed during the slow cooling step (and the thermal distortion removal step). Therefore, the mechanical strength of the fusion spliced portion of the optical fiber element and the periphery thereof is ensured.

[0042]

As described in detail above, according to the first aspect, in the slow cooling step after the fusing step,
The fusion spliced part is cooled from the initial temperature of not less than 150 ° C. to the temperature of 200 ° C. over 10 seconds or more. According to the second invention, in the thermal distortion removing step after the fusing step, 5
The region including the fusion spliced portion is subjected to heat treatment at a temperature of not less than 00 ° C. and not more than 1500 ° C. to remove the thermal distortion.
The fusion splice is cooled to 00 ° C. over 2 seconds. According to the third aspect, in the additive diffusion step after the fusion step, the region including the fusion spliced portion is subjected to heat treatment at a temperature of 800 ° C. or more and 1500 ° C. or less, so that the region including the fusion spliced portion is heated. The additive added to the two optical fibers diffuses, and in the subsequent slow cooling step, the fusion spliced part is cooled from the heating temperature at the time of the thermal strain removing step to a temperature of 200 ° C. over 10 seconds or more. . According to the fourth aspect, in the additive diffusion step after the fusion step, the temperature is set to 800 ° C. or more and 150 ° C.
A region including the fusion spliced portion is subjected to heat treatment at a first temperature of 0 ° C. or less, and the additive added to the two optical fibers is diffused in the region including the fusion spliced portion. In the removing step, the region including the fusion spliced portion is subjected to heat treatment at a second temperature of 500 ° C. or more and 1200 ° C. or less and lower than the first temperature to remove thermal distortion, and further in a subsequent slow cooling step, From the heating temperature during the heat distortion removal step to the temperature 2
The fusion splice is cooled to 00 ° C. over 2 seconds.

In the optical fiber element manufactured by the optical fiber element manufacturing method according to the present invention, the thermal strain generated during the fusion step (and the additive diffusion step) is reduced by the slow cooling step (and the thermal strain removing step). Since it is removed at the time, the mechanical strength of the region including the fusion spliced portion is sufficiently ensured without relying on the reinforcement by the steel wire. Therefore, the outer diameter of the fusion spliced portion does not increase as compared with the other portions of the optical fiber. Therefore, when two optical fibers including the fusion spliced portion are formed into a cable, the module is wound around a bobbin. The stress applied to the optical fiber around the fusion spliced portion during the mounting or other mounting is reduced. Further, the risk of breakage of the optical fiber is reduced, and an increase in loss of light propagating through the optical fiber is suppressed. Further, when two optical fibers including the fusion spliced portion are wound around the bobbin, it is easy to bend the fusion spliced portion. Also,
Even when two optical fibers having different mode field diameters are fusion-spliced, the difference in the mode field diameter is small because the additive is diffused by heat treatment in the additive diffusion step. Low connection loss.

[Brief description of the drawings]

FIG. 1 is a process chart for explaining an optical fiber element manufacturing method according to an embodiment.

FIG. 2 is a table summarizing heat treatment conditions in each step of each of the first to fourth embodiments.

FIG. 3 is a configuration diagram of an apparatus for performing a heat treatment in each step in the optical fiber element manufacturing method according to the embodiment.

FIG. 4 is a graph showing the relationship between slow cooling time and 50% breaking strength in the first example.

FIG. 5 is a graph showing the relationship between slow cooling time and 50% breaking strength in a second example.

FIG. 6 is a graph showing the relationship between slow cooling time and 50% breaking strength in a third example.

FIG. 7 is a graph showing the relationship between slow cooling time and 50% breaking strength in a fourth example.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Optical fiber element, 10 ... Optical fiber, 11 ... Glass fiber, 12 ... Resin, 20 ... Optical fiber, 21 ... Glass fiber, 22 ... Resin, 30, 40 ... Fiber holder, 52 ... Resin, 60 ... Heating source, 70: radiation thermometer, A
... Fused connection.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Osamu Kazuka, Inventor 1 at Tayacho, Sakae-ku, Yokohama, Kanagawa Prefecture Sumitomo Electric Industries, Ltd. Yokohama Works (72) Inventor Daisuke Yokota 1st, Tayacho, Sakae-ku, Yokohama, Kanagawa Prefecture Sumitomo Electric Industry Co., Ltd. Yokohama Works F-term (reference) 2H036 MA12 MA15

Claims (16)

[Claims] 1. A method for manufacturing an optical fiber element having a fusion spliced part in which respective end faces of two optical fibers are fusion spliced, wherein each end face of the two optical fibers is heated and fused. A fusion bonding step of forming a fusion spliced portion; and a slow cooling step of cooling the fusion spliced portion from an initial temperature of 500 ° C. or more and 1500 ° C. or less to a temperature of 200 ° C. over 10 seconds or more after the fusion step. A method for manufacturing an optical fiber element, comprising: 2. A method of manufacturing an optical fiber element having a fusion spliced part in which respective end faces of two optical fibers are fusion spliced, wherein each end face of the two optical fibers is heated and fused. A fusion bonding step of forming a fusion splicing portion; and, after the fusion step, removing a heat distortion by heat-treating a region including the fusion splicing portion at a temperature of 500 ° C. or more and 1500 ° C. or less. And a gradual cooling step of cooling the fusion spliced portion from the heating temperature at the time of the thermal strain removing step to a temperature of 200 ° C. over 2 seconds or more after the thermal strain removing step. Optical fiber element manufacturing method. 3. A method for manufacturing an optical fiber element having a fusion spliced part in which respective end faces of two optical fibers are fusion spliced, wherein each end face of the two optical fibers is fused by heating. A fusion bonding step of forming a fusion splicing portion; and after the fusion step, heat-treating a region including the fusion splicing portion at a temperature of 800 ° C. or more and 1500 ° C. or less to include the fusion splicing portion. An additive diffusion step of diffusing an additive added to the two optical fibers in the region; and after the additive diffusion step, at least 10 seconds from a heating temperature at the time of the additive diffusion step to a temperature of 200 ° C. A cooling step of cooling the fusion spliced portion by cooling. 4. A method for manufacturing an optical fiber element having a fusion spliced part in which respective end faces of two optical fibers are fusion spliced, wherein each end face of the two optical fibers is heated and fused. A fusion bonding step of forming a fusion spliced portion, and after the fusion step, heat-treating a region including the fusion spliced portion at a first temperature of 800 ° C. or more and 1500 ° C. or less,
An additive diffusion step of diffusing an additive added to the two optical fibers in a region including the fusion spliced part; and after the additive diffusion step, the temperature is 500 ° C. or more and 1200 ° C. or less, A heat distortion removing step of heat-treating a region including the fusion spliced portion at a second temperature lower than the first temperature to remove thermal distortion; and, after the thermal distortion removing step, a temperature of 2 from the second temperature.
A cooling step of cooling the fusion spliced portion to 00 ° C. over 2 seconds or more. 5. The method of manufacturing an optical fiber element according to claim 1, wherein a region including the fusion spliced portion is heat-treated by arc discharge in the slow cooling step. 6. The region including the fusion spliced portion is heat-treated by a flame generated by supplying a combustible gas and an oxygen gas to a burner in the slow cooling step. 2. The method for manufacturing an optical fiber element according to claim 1. 7. The method of manufacturing an optical fiber element according to claim 1, wherein in the annealing step, a region including the fusion spliced portion is heat-treated by a heater. 8. The method according to claim 2, wherein in the heat distortion removing step, a region including the fusion spliced portion is heat-treated by arc discharge. 9. The region including the fusion spliced portion is heated by a flame generated by supplying a combustible gas and an oxygen gas to a burner in the thermal distortion removing step. The manufacturing method of the optical fiber element according to the above. 10. The method according to claim 2, wherein in the thermal distortion removing step, a region including the fusion splicing portion is heated by a heater. 11. The method according to claim 3, wherein in the additive diffusion step, a region including the fusion spliced portion is heat-treated by arc discharge. 12. The method according to claim 3, wherein in the additive diffusion step, a region including the fusion spliced portion is heat-treated by a flame generated by supplying a combustible gas and an oxygen gas to a burner. The manufacturing method of the optical fiber element according to the above. 13. The method according to claim 3, wherein in the additive diffusion step, a region including the fusion splicing portion is heated by a heater. 14. In the thermal strain removing step, a region including the fusion spliced portion is heated while a heating source is relatively moved in a longitudinal direction of the two optical fibers. Or the method for manufacturing an optical fiber element according to 4. 15. The method according to claim 2, wherein a temperature gradient in a longitudinal direction of the two optical fibers is 500 ° C./mm or less in the thermal strain removing step. 16. An optical fiber device manufactured by the method for manufacturing an optical fiber device according to claim 1. Description: