JPS59228218A - Welding connection method of optical fiber - Google Patents

Abstract

PURPOSE:To minimize the influence of an error in initial end surface interval even when there is an error by specifying the moving speed of an optical fiber end part when the optical fiber end parts are set in abutting relation and connected together by welding by being thrust against each other. CONSTITUTION:The couple of optical fiber end surfaces 8A and 8B are set facing each other at the initial end surface interval L2; and then one optical fiber end part 7B is moved to the other optical fiber end part 7A and heating is started almost synchronously with the movement. Both optical fiber end surfaces 8A and 8B abut on each other a time (t) after the starting point of the heating, and thrusting operation starts. In this case, the moving speed of the optical fiber end part is so set that T2/T1<=0.9, where T2 is the time from the heating starting point to the time when the end surface moves by the initial end surface interval L2 plus an extent L3 of thrusting and T1 is the time from the heating starting point to the ending point of the thrusting. Thus, an optical-fiber welding connection is made with a little failure.

Description

[Detailed description of the invention] The present invention relates to improvements in optical fiber fusion splicing methods.

The fusion splicing method, which has been adopted as a permanent splicing method for optical fibers, is said to have advantages such as low splicing loss and high tensile strength at the optical fiber joint. Among the fusion splicing methods, the technically advanced one is as shown in Fig. 1 f-1')i, which includes a shaft joining base 1, an end face spacing setting plate 2, a pair of slip holders 3A,
3B, a pair of discharge electrodes 4M, 4N, etc., is used, and the upper surface of the shafting table 1 is formed with straight ■-shaped concave grooves 18, 1b. Tomo f
On the upper surface of each of the slip holders 3A and 3B, support pins a, -a4, and b1-b4 are respectively provided.

On the other hand, the pair of optical fibers 5A and 5B have coating parts 6A and 6B.
, but its end 7A.

7B has the covering removed, and is the covering portion 6A.

Length from 6B to end faces 8A and 8B, that is, end 7A
, 7B are constant (aligned).

When fusion splicing the above-mentioned pair of optical fibers 6A, 5B, first, as shown in FIG.
~b4 respectively, and the optical fiber ends 7A,
7B is fitted into each of the grooves 1a and Ib of the shafting base 1.

Next, the slip holder 3A is connected to the slip holder 3A via a drive system (not shown).
3B is moved in the direction of the arrow in FIG. 2i reaches the end, resulting in the state shown in Figure 1 (b).

At this point, the slip holders 3A and 3B are temporarily stopped, but even if the end faces 8A and 8B are strongly abutted against the end face spacing setting plate 2 due to the above-mentioned excessive feeding,
Each support pin a, ~a4, b1~b4 and each covering part 6A, 6
Since mutual slip occurs with B, the optical fiber end face 8
A, 8Bt There is no impact force that would damage it.

The end face spacing setting plate 2 has each end face 8A.

8B, the distance between the end faces 8A and 8B is confirmed using a microscope, etc., and if this is appropriate, the next step is carried out.

Also, in the case of single mode optical fibers, apart from the case of multimode optical fibers, more precise alignment is performed at this point.

After the end face spacing setting plate 2 leaves, both optical fiber ends 7A
, 7B is moved toward the other, and when the distance between the end faces 8A and 8B is narrowed to this point (as shown in the first figure), the discharge from the pair of discharge electrodes 4M and 4Nl begins. The optical fiber ends 7A and 7B are fusion-spliced by moving the optical fiber ends, which also serves as end-face butting and end-pushing, and discharge heating, as shown in Figure ←) (E), and the connection is completed. After that, the discharge stops as shown in the same figure (f).

Here, the end face spacing caused by the above-mentioned space setting plate 2i (the state shown in FIG. 1 (b)) is called the digit spacing L1, and the end face spacing suitable for the subsequent start of discharge is called the initial end face spacing L2. The pushing amount (distance) is assumed to be L3.

Normally, the end face spacing setting plate 2 is set to have a thickness of 0.5 mm in consideration of its mechanical strength, processing accuracy, etc., and therefore the digit spacing L1 is 0.5 tran.

On the other hand, the initial end face spacing L2 is determined by setting the optical fiber end moving speed (butting speed) after setting the distance to 5'Opm/se.
c, it is generally said that about 2011 m is good, and the indentation ML3 is also about 20A71.

In other words, if you set L2 above 20 pm and start discharging as described above, the end of the optical fiber will melt too much,
On the other hand, if discharge is started with L2 set to less than 20 mm, the end of the optical fiber will not be sufficiently melted, and the indentation amount L3i will also vary, resulting in problems of splice loss and a decrease in the strength of the fusion bond at the joint. By the way, since the digit spacing L1 and the moving speed of the optical fiber end in the above are both known matters, it is necessary to move the original fiber end by a predetermined amount after setting the digit spacing L2 (
From this, it seems that the initial end face spacing L2 can be easily set and L3 can also be easily obtained based on the setting of L2, but in reality L2 cannot be set accurately, causing the above-mentioned problem. There is.

In other words, when the optical fiber ends 7A and 7B are set on the axis combining table 1, the distance between these end faces is quite wide, and each end face 8A and 8B is separated from the line connecting the discharge electrodes 4M and 4N.
Since the distances at t are also unequal, these end faces 8A, 8
By hitting B against the end face spacing setting plate 2 at a fairly high speed, G
Setting 1 must be performed with good workability, and it is necessary to press the end of the optical fiber to ensure the above-mentioned abutment state. In such cases, slip holders 3A and 3B are used. However, each optical fiber end 7A, γB (deflection occurs, and after the end face spacing setting plate 2 is removed, each optical fiber end 7A, 7B in the bent state returns to a straight state. An error occurs in the coarse interval Ll.

On the other hand, if the end faces are abutted against the end face spacing setting plate 2 with a weak force (slow speed) for fear of the problem of deflection, not only will the work efficiency be reduced, but the abutment will be insufficient (this will cause the rough spacing L1 to be at the predetermined interval). An error that tends to be wider than that occurs.

Of course, after setting the group interval L1, the corresponding L is determined by microscopic observation.
1, but this also has an error of about 104, so high reliability cannot be obtained.

Therefore, by using the rough spacing L1 as a reference ζ, the initial end face spacing L
2, and when performing fusion splicing of optical fibers through subsequent operations, a good splicing condition may not be obtained.

The present invention enables fusion splicing with a high success rate by minimizing the influence of errors in the initial end face spacing when fusion splicing a pair of optical fibers in a process similar to the conventional method described above. The specific means to achieve this will be explained below with reference to the drawings.

Figure 2 shows the time lapse from (c) to (f) in the process of fusion splicing optical fibers IA and IB in Fig. 1 (a) to (f) described above. (horizontal axis) and the relative distance change (vertical axis) between the end faces 8A, 8B due to the movement of the optical fiber ends (vertical axis). discharge heating time).

In FIG. 2, the solid line shows the optical fiber end faces 8A and 8B in the standard state (this state is 1), and the initial end face distance L in this state is 1.
2 has no error, so the entire state of L2±0 is maintained.

In a state where the initial end face spacing is L2±0 (here, one optical fiber end 7B is moved toward the other optical fiber end 7A 110 at a speed V, and heating is started almost in synchronization with this).

When time t (preheating period) has elapsed from the above heating start point, the optical fiber end surfaces 8A and 8B come into contact with each other, and immediately after that, pushing begins.

The pushing amount (distance) at this time is L3, and when 12 hours have passed from the time when the aforementioned optical fiber end 7B started moving, in other words, when T1 time has passed from the time when heating started, the end 7B is pushed in to the correct size, heating continues, and heating here also stops after a predetermined time.

By the way, as mentioned above, there is no problem when fusion splicing of optical fibers is performed as standard, but if the initial end face spacing is L2±△d (
If this goes wrong, the preheating time becomes t±△t, and the pushing amount becomes L3±△d').
errors occur, and as pointed out above, a good fusion splicing condition cannot be obtained.

Here, the moving speed of the optical fiber end 7B is set to v, and the above △
The relationship between d and Δt is determined by the following equation.

■-△d/△t...(1) Calculating the rate of change between t and t±△t is as follows: 0 △1 / 1-△d / vt ''・(21 Above (2 ]
In order to absorb the variation in △d in the formula f (this can be done by increasing the denominator on the right-hand side), when the values of v and t are large, the quotient of △d divided by ■.

In reality, it is difficult to measure V and t because these values are small, but increasing the speed of ■ will result in shortening T2, and increasing t will result in lengthening T1. Therefore, for some songs, T2' may be shortened or T1 may be lengthened.

However, when increasing T1, even if discharge heating or laser heating is used, the heat source intensity must be adjusted to a low level (there is a limit to this, and the longer T1 causes the optical fiber ends 7A and 7B to melt too much). It is expected that.

Therefore, leaving T1 unchanged and increasing ■, that is, shortening T2, can be said to be a safety measure to reduce the influence of Δd.

In this case, T2 is relative to T1, and T2/T1≦0
, 9 must be satisfied < , T2 /TI≦
If V is set to 0.9, T2/
The fact that T1≦0.9 is valid will be explained with reference to FIG.

FIG. 3 shows the relationship between Δd and T2/T in which fusion splicing is performed ten times and the range in which the splicing is successful all ten times.

As is clear from FIG. 3, in the present invention T2/'[,=
When Q, 9, even if the error △d of the initial end face spacing L2 (201tn1) is +3.71Lm to +14.8/ltr+, that is, for the above spacing L2 = 20mm, △d is within the range of 11/LIn. 10 successes even if there are variations within the
A 100% success rate has been achieved with 10 connections.

Also, when T2/T, (0,9, Δd is 11 p
The same 10 as above, even though m'r exceeds
A success rate of 0% has been obtained.

The range of △d generated by the average song number using existing equipment is 1
Since it is about 0.0, T2/T+≦0.9 (
Therefore, the error Δd when setting the initial end face spacing L2 can be sufficiently absorbed.

On the other hand, when T2/T, )0.9, the allowable range of Δd becomes quite strict, and existing equipment cannot achieve a high success rate.

The results shown in Figure 3 were obtained under the following conditions.

Optical fiber diquartz, clad outer diameter 125S Fusion heating means: Discharge current 17 mks Discharge time 1 sec Optical fiber end moving speed: 7411 m1 sec Initial end face spacing: 20Prn Pushing amount: 20,1471 Required time for T1: 06 As explained above, in the present invention, after the end portions of a pair of optical fibers are opposed to each other and the initial end face spacing of the two optical fibers is escaped, the end portions of the optical fibers are heated, and each end of the optical fibers is heated. A method of fusion splicing a pair of optical fibers by relatively moving the fibers in the mating direction, and then butting the end faces of both optical fibers against each other, and pushing the ends of both optical fibers relatively. Here, the time taken for the end of the optical fiber to move by the above-mentioned initial end face distance + the above-mentioned pushing amount (distance) is defined as T2, and the pushing of the end ends from the time when the heating of the optical fiber end starts. If the time taken to reach the end is T1, then the moving speed of the optical fiber end is set to satisfy T2/T, ≦09. Therefore, when setting the initial end face spacing, this ( Even if considerable variation occurs, the influence of the error can be eliminated and optical fiber fusion splicing with fewer failures can be realized.

[Brief explanation of the drawing]

Figure 1 A) to Figure 1) are explanatory diagrams showing the optical fiber fusion splicing method in the order of its steps, and Figure 2 explains the fusion splicing method of the present invention from the relationship between the moving distance of the optical fiber end and time. Figure 3 shows the range of success during optical fiber fusion splicing by Δ
d and T2. /T. It is a diagram showing the relationship number. 5A, 5B... Optical fibers 7A, 7B... Optical fiber ends 8A, 8B...
... Optical fiber end face L2 ... Initial end face spacing L3 ... Indentation amount Δd ... Initial end face spacing error Patent applicant's agent Patent attorney Makoto Ifuji No. 21:1 Figure 3 yr7 Shirane 162, Nippon Telegraph and Telephone Public Corporation, Ibaraki Telecommunications Research Laboratory Inventor: Yutaka Usui - Sumitomo Electric Industries, Ltd., Yokohama Works, 1, Taya-cho, Totsuka-ku, Yokohama City, Japan Telegraph and Telephone Public Corporation ■Applicant Sumitomo Electric Industries Co., Ltd. 5-15-1 Kitahama, Higashi-ku, Osaka Applicant Fujikura Electric Wire Co., Ltd. 1-5-1 Kiba, Koto-ku, Tokyo

Claims (1)

[Claims] After setting the initial distance between the end faces of the two optical fibers by arranging the end portions of the pair of optical fibers to face each other, the end portions of the optical fibers are heated and the respective end portions are moved relative to each other in the direction of abutment. In the method of fusion splicing a pair of optical fibers by pushing the ends of the optical fibers relative to each other,
The end of the optical fiber is pushed in the above initial end face distance 10 times the above indentation amount (
If T2 is the time taken to move the optical fiber (distance), and T1 is the time from the time when heating the end of the optical fiber starts until the end of pressing the end, then T2/T1≦0.
A method for fusion splicing optical fibers, in which the moving speed of the end of the optical fiber is set so as to satisfy the condition 9.