JP2001166175A - Fusion splicing method for optical fiber - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fusion splicing method for an optical fiber, capable of reducing connecting loss without using the original mode field diameter for each of first and second optical fibers to be fusion-spliced and the diffusion coefficient of additives. SOLUTION: After an optical fiber A and B are fusion-spliced by using the fusion splicing method 1 for optical fibers, the fusion-spliced part is heated by electrical discharge. In this heating by discharge, an inert gas is supplied from a gas feeding port 10a into the housing 10 to form an inert gas state inside the housing 10. A pair of electrodes 13, 14 heats the fusion-spliced part by electrical discharge while moving at least in the longitudinal direction of the fiber (in a direction parallel to the Z axis) by electrode moving stages 15, 16. Heat distribution in the fusion-spliced part in the discharge heating process is determined by the electric current (i.e., heating quantity) supplied to the pair of electrodes 13, 14 and by the moving pattern (i.e., heating time at each position) of the pair of electrodes 13, 14.

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 end faces of a first optical fiber and a second optical fiber to each other.

[0002]

2. Description of the Related Art As a method of optically connecting the end faces of a first optical fiber and a second optical fiber, there is a connection by fusion in addition to a connection by an optical connector. In the fusion splicing, the end faces of the first optical fiber and the second optical fiber are preheated and pushed into each other, and further heated and fused to connect the two optical fibers to each other. This fusion splicing is said to be suitable in that the splice loss is small.

However, if the mode field diameters of the first and second optical fibers to be fusion spliced are different from each other, the mode field diameter becomes discontinuous at the fusion spliced portion, thereby increasing the splice loss. . Therefore, in order to solve such a problem, by heating the vicinity of the fusion splicing portion after the fusion splicing, the additive near the fusion splicing portion of each of the first and second optical fibers is diffused. In order to reduce the connection loss, the mode field diameter is continuously changed at the fusion spliced portion.

[0004]

However, the heating of the fusion spliced portion for reducing the splice loss as described above has the following problems. That is, when heating the vicinity of the fusion splicing section, two parameters of the heating amount and the heating time can be changed. However, even if these two parameters are changed, the heat distribution in the fusion splicing section due to the heating can be changed. Are always similar and symmetrical.

As shown in FIG. 8, when the heating amount is large and the heating time is long, when the heating amount is medium and the heating time is medium, and when the heating amount is small and the heating time is short,
In either case, the heat distribution in the fusion spliced part is similar to each other. As described above, there is a correlation between the heating range and the maximum heating temperature in the vicinity of the fusion splicing portion, and only a limited heat distribution can be given to the fusion splicing portion. Therefore, it is difficult to heat a wide range at a low temperature, and it is also difficult to heat a narrow range at a high temperature. This limits the combination of the first and second optical fibers that can reduce the connection loss by heating the fusion spliced part.

Further, as shown in FIG. 8, the heat distribution at the fusion spliced portion due to heating is always symmetrical.
When the symmetric center position of the heat distribution coincides with the fusion splicing position, the same heat is applied to each of the first and second optical fibers. Therefore, depending on the initial mode field diameter and the additive diffusion coefficient of each of the first and second optical fibers, the mode field diameter of each optical fiber cannot be matched by heating, and the connection loss can be reduced. Can not. For example, as shown in FIG. 9, an optical fiber A having a large initial mode field diameter and a small additive diffusion coefficient and an optical fiber B having a small initial mode field diameter and a large additive diffusion coefficient are fusion-spliced portions. Is heated, the respective mode field diameters can match each other. However, the optical fibers A and C having the same initial additive concentration do not have the same mode field diameter even when the fusion spliced portion is heated.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and is based on the initial mode field diameter and additive diffusion coefficient of each of the first and second optical fibers to be fusion spliced. An object of the present invention is to provide an optical fiber fusion splicing method capable of reducing splice loss.

[0008]

An optical fiber fusion splicing method according to the present invention comprises: (1) a fusion splicing step of fusion splicing end faces of a first optical fiber and a second optical fiber to each other; (2) While moving a pair of electrode rods provided opposite each other with the fusion splicing part to be fusion spliced in this fusion splicing step at least in the longitudinal direction of the fiber,
A discharge heating step of discharging and heating the fusion spliced portion with the pair of electrode rods.

[0009] According to this optical fiber fusion splicing method, the fusion splicing portion which is fusion spliced in the fusion splicing step is interposed between the two.
A pair of electrode rods are provided facing each other, and in the discharge heating step, the fusion spliced portion is discharge-heated by the pair of electrode rods while moving the pair of electrode rods at least in the longitudinal direction of the fiber. . Either the fusion splicing step or the discharge heating step may be performed first. By performing the discharge heating of the fusion spliced portion in this way, an arbitrary heat distribution can be realized, and the initial mode field diameter and additive diffusion coefficient of each of the first and second optical fibers to be fusion spliced. Accordingly, the mode field diameter can be matched at the fusion spliced portion, and the connection loss can be reduced.

[0010] In the discharge heating step of the optical fiber fusion splicing method according to the present invention, the discharge heating of the fusion spliced portion by a pair of electrode rods is performed in an inert gas atmosphere. In this case, since the fusion heating of the fusion spliced portion by the pair of electrode rods is performed in an inert gas atmosphere, the breaking strength of the fusion spliced portion can be improved.

An optical fiber fusion splicing method according to the present invention comprises:
A diffusion coefficient obtaining step of obtaining a diffusion coefficient of an additive of each of the first optical fiber and the second optical fiber;
The discharge heating step is characterized in that a heating distribution at the time of discharge heating of the fusion spliced portion by the pair of electrode rods is set based on the diffusion coefficient obtained in the diffusion coefficient obtaining step.
In this case, since the heating distribution at the time of electric discharge heating is set based on the diffusion coefficient of the additive of each of the first and second optical fibers obtained in the diffusion coefficient obtaining step, the mode at the fusion spliced portion is set. Field diameter matching and connection loss can be suitably reduced.

[0012]

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, an optical fiber fusion splicing apparatus to which the optical fiber fusion splicing method according to the present embodiment can be suitably applied will be described. FIG. 1 is an explanatory diagram of the optical fiber fusion splicing apparatus 1. The optical fiber fusion splicing apparatus 1 shown in FIG. 1 includes a holding portion 11 for holding one optical fiber A, a holding portion 12 for holding the other optical fiber B, a pair of electrode rods 13 and 14, an electrode rod moving stage 15 for moving the electrode rod 13, and an electrode rod 14
And an electrode rod moving stage 16 for moving the electrodes. Also,
The housing 10 has a gas supply port 10a for supplying an inert gas to the inside and a gas exhaust port 10b for exhausting the inside gas to the outside. Here, considering a rectangular coordinate system (xyz) as shown in FIG.
A direction parallel to each optical axis is defined as a z-axis.

An optical fiber fusion splicing method using the optical fiber fusion splicing apparatus 1 will be described. FIG. 2 is a flowchart illustrating the optical fiber fusion splicing method according to the present embodiment. First, the optical fiber A to be fusion spliced
The diffusion coefficient of each of the additives B and B is obtained by calculation or measurement based on the type of the additive or the like (step S11). Next, the coating of each of the optical fibers A and B is partially removed (step S12), and cut at the coating removing portion (step S13). Then, the optical fiber A is gripped by the gripper 11 and the optical fiber B is gripped by the gripper 12 (step S14). At this time, each of the optical fibers A and B is arranged so that the end faces of which the coating has been removed face each other, and the positions are adjusted so that the respective optical axes coincide.

Subsequently, the optical fibers A and B are fusion-spliced (step S15). At this time, the vicinity of each end face of the optical fibers A and B is a pair of electrode rods 13 and 14.
Melted by the discharge heating by the optical fibers A and B
The respective end faces are pressed into each other by the holding parts 11 and 12 and are fused. Thus, the optical fibers A,
B is fusion spliced.

Subsequently, the fusion spliced portion is heated by electric discharge (step S16). At this time, the housing 10 is connected to the gas supply port 10a.
An inert gas is supplied to the inside, and the inside of the housing 10 is set to an inert gas atmosphere. Then, the pair of electrode rods 13 and 14
While being moved by the electrode rod moving stages 15 and 16 at least in the fiber longitudinal direction (direction parallel to the z-axis), the fusion spliced portion is heated by discharge. In addition, a pair of electrode rods 13 and 14
Is the x-axis or y by the electrode rod moving stages 15 and 16.
It may also move in a direction parallel to the axis. At this time, the movement pattern of the pair of electrode rods 13 and 14 (that is, the heating time at each position) and the current supplied to the pair of electrode rods 13 and 14 (that is, the amount of heating) are each determined in step S11. The determination is made based on the obtained diffusion coefficients of the additives of the optical fibers A and B. Thereafter, the fusion spliced portion is heated at a low temperature while moving the pair of electrode rods 13 and 14 in the x-axis direction or the y-axis direction to remove thermal distortion of the fusion spliced portion (step S17).

FIG. 3 is a diagram for explaining in more detail one example of the discharge heating step in the optical fiber fusion splicing method according to the present embodiment. This figure shows ON / OFF of an electromagnetic valve provided at the gas supply port 10a, and a pair of electrode rods 13 and 14.
And the positions of the pair of electrode rods 13 and 14 in the z-axis direction are shown. The time when the discharge heating is disclosed is set as the reference time. The electromagnetic valve is turned on three seconds before the start of the discharge heating, and the supply of the inert gas into the housing 10 is started. The current supplied to the pair of electrode rods 13 and 14 is greatest immediately after the start of discharge, and thereafter gradually decreases. In addition, the pair of electrode rods 13 and 14 reciprocate in a direction parallel to the z-axis, and their amplitude gradually decreases immediately after the start of discharge. At time 20 seconds, the discharge heating ends and the movement of the pair of electrode rods 13 and 14 also ends. Then, at time 22 seconds, the electromagnetic valve is turned off, and the supply of the inert gas into the housing 10 is stopped.

According to the optical fiber fusion splicing method according to this embodiment, the pair of electrode rods 13 and 14 used for fusion splicing can be used for discharge heating, and the discharge heating is performed by burner heating. Local heating is possible as compared to other methods.
The heat distribution in the fusion spliced portion during the discharge heating step includes the current supplied to the pair of electrode rods 13 and 14 (that is, the amount of heating) and the movement pattern of the pair of electrode rods 13 and 14 (that is, Heating time at the position). Therefore, it is possible to realize an arbitrary heat distribution such as a wide range of low temperature, a narrow range of high temperature, and a left-right asymmetric one as a heat distribution in the fusion splicing part in the discharge heating step.

FIGS. 4 to 6 are diagrams showing examples of the heat distribution in the fusion spliced portion during the discharge heating step in the optical fiber fusion splicing method according to the present embodiment. According to the optical fiber fusion splicing method according to this embodiment, as shown in FIG. 4, it is possible to realize a heat distribution at the highest temperature at the fusion splicing point, but different heating ranges. As shown in FIG. 5, it is possible to realize a heat distribution in which the maximum temperature is different at the fusion splicing point but the heating range is the same. Further, as shown in FIG. 6, a heat distribution that is asymmetrical in the left-right direction can be realized.

As described above, according to the optical fiber fusion splicing method according to the present embodiment, an arbitrary heat distribution can be realized, so that the initial mode of each of the optical fibers A and B to be fusion spliced is Depending on the field diameter and the additive diffusion coefficient, the mode field diameter can be matched at the fusion spliced portion, and the connection loss can be reduced. Further, in the present embodiment, since the discharge heating of the fusion spliced portion by the pair of electrode rods 13 and 14 is performed in an inert gas atmosphere, the breaking strength of the fusion spliced portion can be improved. Further, in the present embodiment, the diffusion coefficient of the additive for each of the optical fibers A and B is determined in advance, and the heating distribution at the time of discharge heating is set based on the determined diffusion coefficient. , The matching of the mode field diameter and the reduction of the connection loss can be suitably performed.

In the above description, the discharge heating step is provided after the fusion splicing step. However, the discharge heating step may be provided before the fusion splicing step. In particular, optical fibers A and B
By adding an asymmetrical heat distribution (FIG. 6) to the fusion spliced portion as in the case where the respective initial mode field diameters are different and the additive diffusion coefficients are equal, matching and connection of the mode field diameter at the fusion spliced portion In order to reduce the loss, it is preferable to provide the discharge heating step before the fusion splicing step. FIG. 7 is a flowchart illustrating an optical fiber fusion splicing method according to another embodiment.

In the optical fiber fusion splicing method shown in this figure, the diffusion coefficient of each additive of the optical fibers A and B to be fusion spliced is determined (step S21), and the coating of each of the optical fibers A and B is partially removed. Remove (Step S2
2) And, here, the respective portions of the optical fibers A and B to be the fusion spliced portions after fusion splicing are heated by electric discharge (step S23). Also at this time, discharge heating is performed by the pair of moving electrode rods 13 and 14 in an inert gas atmosphere. At this time, the movement pattern of the pair of electrode rods 13 and 14 (that is, the heating time at each position) and the current supplied to the pair of electrode rods 13 and 14 (that is, the amount of heating) are each determined in step S21. The determination is made based on the obtained diffusion coefficients of the additives of the optical fibers A and B.

After the discharge heating, each of the optical fibers A and B is cut at the coating removing section (step S2).
4). Then, the optical fiber A is gripped by the gripper 11 and the optical fiber B is gripped by the gripper 12 (step S2).
5) The optical fibers A and B are fusion-spliced (step S26). Thereafter, the fusion spliced portion is heated at a low temperature while moving the pair of electrode rods 13 and 14 in the x-axis direction or the y-axis direction to remove thermal distortion of the fusion spliced portion (step S2).
7).

In this case, an arbitrary heat distribution can be realized, so that the fusion splicing is performed according to the initial mode field diameter and the additive diffusion coefficient of each of the optical fibers A and B to be fusion spliced. The mode field diameter can be matched at the connection portion, and the connection loss can be reduced. Further, since the discharge heating of the fusion spliced portion by the pair of electrode rods 13 and 14 is performed in an inert gas atmosphere, the breaking strength of the fusion spliced portion can be improved. Further, since the diffusion coefficient of each additive of the optical fibers A and B is determined in advance, and the heating distribution at the time of discharge heating is set based on the determined diffusion coefficient, the mode field diameter at the fusion spliced portion is determined. Matching and connection loss can be suitably reduced.

[0025]

As described above in detail, according to the present invention, a pair of electrode rods are provided opposite to each other with a fusion splicing portion to be fusion spliced in the fusion splicing step interposed therebetween. In the discharge heating step, the fusion spliced portion is discharge-heated by the pair of electrode rods while moving the pair of electrode rods at least in the longitudinal direction of the fiber. By performing the discharge heating of the fusion spliced portion in this way, an arbitrary heat distribution can be realized, and the initial mode field diameter and additive diffusion coefficient of each of the first and second optical fibers to be fusion spliced. Accordingly, the mode field diameter can be matched at the fusion spliced portion, and the connection loss can be reduced.

When the discharge heating step is performed in an inert gas atmosphere, the breaking strength of the fusion spliced portion can be improved. When the heating distribution at the time of discharge heating is set based on the diffusion coefficient of the additive of each of the first and second optical fibers obtained in the diffusion coefficient obtaining step, the mode field diameter at the fusion spliced portion is set. And the connection loss can be suitably reduced.

[Brief description of the drawings]

FIG. 1 is an explanatory view of an optical fiber fusion splicing apparatus.

FIG. 2 is a flowchart illustrating an optical fiber fusion splicing method according to the embodiment.

FIG. 3 is a diagram illustrating an example of a discharge heating step in the optical fiber fusion splicing method according to the embodiment in more detail.

FIG. 4 is a view showing an example of a heat distribution in a fusion splicing part in a discharge heating step in the optical fiber fusion splicing method according to the present embodiment.

FIG. 5 is a diagram showing an example of a heat distribution in a fusion splicing part in a discharge heating step in the optical fiber fusion splicing method according to the present embodiment.

FIG. 6 is a diagram showing an example of a heat distribution in a fusion splicing part in a discharge heating step in the optical fiber fusion splicing method according to the present embodiment.

FIG. 7 is a flowchart illustrating an optical fiber fusion splicing method according to the embodiment.

FIG. 8 is a graph showing a heat distribution when heating the vicinity of a conventional fusion splicing part.

FIG. 9 is a graph showing how a mode field diameter changes when heating the vicinity of a conventional fusion splicing part.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Optical fiber fusion splicing apparatus, 10 ... Housing | casing, 10a ... Gas supply port, 10b ... Gas exhaust port, 11, 12 ... Grip part,
13, 14 ... electrode rods, 15, 16 ... electrode rod moving stage.

Claims (3)

[Claims] 1. A fusion splicing step of fusion splicing end faces of a first optical fiber and a second optical fiber to each other, and opposing each other with a fusion spliced portion fusion spliced in the fusion splicing step. A discharge heating step of discharging and heating the fusion spliced portion by the pair of electrode rods while moving the pair of electrode rods provided at least in the longitudinal direction of the fiber. Fusion splicing method. 2. The optical fiber fusion splicing method according to claim 1, wherein, in the discharge heating step, discharge heating of the fusion splicing portion by the pair of electrode rods is performed in an inert gas atmosphere. . 3. The method according to claim 1, further comprising a step of obtaining a diffusion coefficient of an additive of each of the first optical fiber and the second optical fiber, wherein the discharge heating step is performed by the diffusion coefficient obtaining step. The optical fiber fusion splicing method according to claim 1, wherein a heating distribution at the time of electric discharge heating of the fusion spliced portion by the pair of electrode rods is set based on the diffusion coefficient.