JPS63168606A - Splicing method for optical fiber - Google Patents

Abstract

PURPOSE:To obtain a splicing part of small loss by setting the extent of forcing-in of optical fibers to <=10mum in the case of fusion-splicing between optical fibers of less eccentricity. CONSTITUTION:Single mode optical fibers are put along V grooves to face each other and are forced in and spliced while heated and fused by discharge heating. In this method, the extent of forcing-in for splicing is set to <=10mum when the extent of eccentricity of optical fiber cores of optical fibers is <=0.5%. Thus, fixing V grooves are used and only clads are aligned to splice optical fibers with a small loss of about 0.01dB average, and therefore, the quality of an optical fiber communication line is improved and the splicing device is simplified.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for splicing single mode optical fibers with low loss.

(Prior Art) Conventionally, when fusion splicing a single mode optical fiber, the center 2 of the core 1 is separated from the center 4 of the cladding 3 by ε= δ/R=2
%, so as shown in Figure 3, the X direction,
■Groove 5.5 movable in the Y direction and the Z direction perpendicular to these
After aligning the optical fiber 6.6' along the V-grooves 5, 5' and aligning the cores 1, 1' with each other, the optical fiber 6. .6' was heated, the optical fiber was butted against it, and the fiber was further pushed in to perform fusion splicing.

At this time, as shown in FIG. 4, which shows the relationship between the amount of push-in of the optical fiber and the connection loss, it was thought that the best push-in amount was about 20 μm (Y-Kato et al.

”Arc-fusion splicing of s
ingle-mode fibers 1: Opti
mum 5price conditions” Ap
pl, Opt, 21pp, 1332-1336.
1982).

In the case of such a large eccentricity, deformation of the core during fusion splicing is considered to be the reason why the splice loss varies depending on the amount of pushing of the optical fiber. FIG. 5 shows how the core deforms when the amount of push of the optical fiber is changed. Figure 5(a) shows the core 1.1' immediately after the end surfaces of the optical fibers come into contact during fusion splicing of optical fibers with eccentricity of 2%.
and cladding 3.3', but core 1,1'
They are connected to each other in a straight line. However, when the optical fiber is pushed in only a small amount, the outer diameters of the claddings 3 and 3' match due to surface tension, resulting in extreme deformation of the tip of the core as shown in Figure 5(b), resulting in splice loss. increases. On the other hand, when the optical fiber is pushed in by a large amount, the influence of surface tension is small, but the core is deformed into a waveform as shown in FIG. 5(c), and the splice loss increases. Therefore, it was necessary to appropriately select the amount of push-in of the optical fiber.

In order to be able to connect optical fibers with large eccentricities, the grooves for aligning the optical fiber axes must also be movable in the x, y, and z directions, which complicates the mechanism when building equipment. Another disadvantage is that within the range of the amount of pushing of the optical fiber, the splice loss can only be reduced to about 0.07 dB.

In addition, with conventional technology, it was difficult to manufacture optical fibers with small eccentricities, so keeping in mind the connection of optical fibers with large eccentricities, the amount of push-in of the optical fibers was determined at a rate of about 20 μm. was. Therefore, even optical fibers with small eccentricities are unavoidably pushed in excessively, resulting in an increase in connection loss.

Therefore, depending on the conventional technology, there has been a drawback that the relay distance is limited to some extent due to the construction of the optical fiber communication line.

(Problems to be Solved by the Invention) The present invention clarifies the optimal optical fiber push amount to connect single-mode optical fibers with small eccentricity with low loss, and realizes extremely low-loss connections. The object of the present invention is to provide an optical fiber connection method for

(Means for Solving the Problems) The present invention fuses a single mode optical fiber with an eccentricity of 0.5% or less by aligning its outer diameter only, without actively aligning its core. When connecting, after the end surfaces of a pair of optical fibers to be connected abut each other, the amount of pushing of the optical fibers is set to 10 μm or less.

The difference is that in the conventional optical fiber connection method, the set value for the amount of pushing of the optical fiber is 20 μm.

(Example) FIG. 1 is a diagram for explaining the present invention in detail, and shows experimental data showing the relationship between the pushing amount and splicing loss of an optical fiber with small eccentricity (ε=0.5%).

Note that this data is based on a single mode optical fiber connected along a fixed V-groove without aligning the core. As shown in Figure 1, by setting the optical fiber push depth to 10 μm or less, the splice loss can be reduced to 0.01 dB on average.
It is possible to reduce the splice loss to 177, which is 0.07 dB by the conventional optical fiber fusion splicing method. For optical fibers with small eccentricity (epsilon = 0.5%, for example), as shown in Figure 1, even if the optical fiber is pushed in a small amount, the core deformation due to surface tension is small, so the splice loss can be reduced. This is because it is possible to do so.

Therefore, there are almost no restrictions on the construction of optical fiber communication lines, and it becomes possible to significantly increase the relay distance.

Furthermore, since the above-described low-loss splicing is possible without using the movable V-groove of the conventional optical fiber fusion splicing method, there is also the advantage that the device configuration is simple.

As explained above, according to the optical fiber splicing method of the present invention, when fusion splicing optical fibers with small eccentricity (ε=0.5% or less), the pushing amount of the optical fibers is reduced to 10
By setting the diameter to less than μm, it is possible to achieve a low-loss connection of about 0.01 dB on average by using a fixed V-groove and aligning the cladding without aligning the core using a movable V-groove. Therefore, there are advantages in that the quality of the optical fiber communication line can be improved and the connection device can be simplified.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing the relationship between the pushing amount of the optical fiber and the splicing loss for detailed explanation of the present invention, Fig. 2 is a schematic diagram showing the eccentricity of the core, and Fig. 3 is a diagram of the conventional optical fiber fusion splicing. Fig. 5(a) is an explanatory diagram of the method, and a whistle diagram is a diagram showing the relationship between the amount of pushing of the optical fiber and the splicing loss in the conventional optical fiber fusion splicing method. (B), (C1 is a diagram showing how the core deforms when the amount of pushing of the optical fiber is changed during conventional optical fiber fusion splicing. 1.1'...Core 2...Core center of 3.3
'Clad 4...Center of clad 5.5'...
・Movable V groove 6,6'...Optical fiber 7.7'...
・Discharge electrode 8... Discharge patent applicant Nippon Telegraph and Telephone Corporation Fig. 1 F7P lever push-in location (method) Fig. 2 Fig. 3 Beniuchi

Claims (1)

[Claims] 1. A method in which single mode optical fibers are placed facing each other along a V-groove, the optical fibers are heated and melted by discharge heating, and the optical fibers are pressed and connected to each other,
An optical fiber connecting method, characterized in that for an optical fiber whose optical fiber core has an eccentricity of 0.5% or less, the pushing amount at the time of connection is 10 μm or less.