JPH0458205A - Multifiber connector and its production - Google Patents

Abstract

PURPOSE:To prevent the influence of production deviation of minute holes of an optical connector member upon the disalignment loss of an optical connector by arranging and fixing optical fiber, which have coatings removed, in longitudinal and transverse directions so that they closely come into contact with one another and heating the front ends of arranged optical fibers to diffuse a dopant of cores of optical fibers by heat. CONSTITUTION:After the coating of a ribbon structure multifiber 1 is removed to exposed optical fibers 3, optical fibers 3 are inserted into an optical fiber arranging member 7 and are arranged in longitudinal and transverse directions from longitudinal and transverse reference faces of the member 7. Thereafter, the front ends of optical fibers 3 are heated to an about softening point and are continuously or inter-ruptedly held for a certain time to extend the mode field diameter. After thermal expansion of the mode field diameter, optical fibers are fixed with an adhesive or the like, and end faces are polished. Thus, the connection loss due to surface diffusion of the dopant is reduced.

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to a method of manufacturing an optical connector that connects a large number of optical fibers to each other with low loss.

[Conventional technology]

In the conventional multi-fiber optical fiber connector, as shown in FIG. 6a, after removing the coating 2 of the multi-fiber optical fiber tape 1 to expose the optical fibers 3, as shown in FIG. The optical fiber 3 is inserted into an optical connector member 5 having fine holes 4 arranged linearly in pairs, and then an adhesive 6 is applied to the fine holes 4 as shown in FIG. 6C. A method has been used for fixing optical fibers by filling the adhesive dropwise and curing the adhesive 6 as shown in FIG. 6d.

[Problem to be solved by the invention]

The diameter of the microhole 4 of the optical connector member 5 is determined based on the average diameter of the optical fiber, because there is a manufacturing deviation of about 1 μm in the diameter of the optical fiber to be inserted, and in order to improve workability during insertion. A margin of several μm or more is provided for the diameter of 125 μm. Therefore, in the end face of the completed optical connector shown in FIG. 7, the center position of the microhole and the center position of the optical fiber inevitably deviate from each other. Furthermore, the M-coat member is generally made by plastic molding, drilling and lapping of ceramics, etc. Therefore, as shown in FIG. 8, it was inevitable that the micropores themselves would be geometrically misaligned. When optical connectors produced by this method are connected to each other, connection loss occurs due to misalignment of the axes of the optical fibers. According to Marcuse's well-known theory, when using a general single-mode fiber, the splice loss with respect to the amount of axis misalignment is 0.2 dB at 1 μm,
It reaches 0.75 dB at 2 μm and 1.7 dB at 3 μm. Therefore, the connection loss of a 50-fiber-bundled multi-fiber optical fiber connector made according to the conventional technology is:
The average was 1.2 dB and the maximum was 5 dB. In addition, the average splice loss of a 200-fiber bundled multi-fiber optical fiber connector is 1. ．．
It was 4 dB, and the maximum was 9 dB. When the connection loss is large as described above, the transmission distance cannot be increased, so a large number of relay devices may be required, or the signal may not be transmitted over a predetermined distance. Furthermore, if an attempt is made to minimize manufacturing deviations in order to reduce geometric axis misalignment, there is a problem in that the manufacturing yield decreases and the price of the connector itself increases significantly. Now, as explained above, in the conventional method for manufacturing a multi-core optical fiber connector, the position of the optical fiber is determined by inserting the optical fiber into the microhole of the connector member, fixing it with adhesive, etc. is its biggest feature. Therefore, in the manufacturing method of multi-core optical fiber connectors using conventional technology, in order to ensure the strength of the connector itself and manufacturing workability, it is essential to use connector members that are much larger in size than the optical fibers, as is well known. When connecting a large number of optical fibers, in addition to the problem of axis misalignment of the optical fibers, problems arise with the size of the connector itself. 50 created according to the conventional method
The dimensions of the core-branched multi-core optical fiber connector are 6mm x
The dimensions of the 4mm, 200-fiber-bundled multi-core optical fiber connector are 8mm x 11mm. Currently, optical cables with up to about 1000 fibers are in practical use, and it is thought that a large bundle of about several thousand optical cables is required to realize fiber optics. As described above, it has been considered nearly impossible to connect optical cables with an extremely large number of fibers using connectors based on the conventional technology due to dimensional limitations. The purpose of the present invention is to solve the problem of axis misalignment of optical fibers that occurred due to the conventional purpose, and to provide a compact multi-core optical fiber connector that can connect a much larger number of optical fibers at once than before. It's about doing.

[Means to solve the problem]

The present invention involves arranging and fixing uncoated optical fibers vertically and horizontally so that their outer diameters are in close contact with each other, and heating the tips of the arranged optical fibers to thermally diffuse the dopants in the cores of the fibers. This is what I did.

[Effect]

With the above configuration, optical fibers can be arranged without using fine holes, and since the mode field diameter is enlarged, loss due to axis misalignment is reduced.

【Example】

FIG. 1 is a block diagram showing an embodiment of the present invention, in which symbol 2 is a multi-core optical fiber tape, 2 is a coating of the multi-core optical fiber tape, 3 is an optical fiber, and 7 is an optical fiber arrangement member. In this method, first, the coating of the multi-core optical fiber tape is removed to expose the optical fibers, and then the optical fibers are inserted into the optical fiber array member, and the optical fibers are inserted from the longitudinal and horizontal reference planes of the array member. , the optical fibers are arranged vertically and horizontally. The longitudinal and lateral positions of the optical fibers are determined by the mutually tangential fibers of the optical fibers. FIG. 2 shows the positional relationship of the arranged optical fibers. In the conventional connector manufacturing method, the amount of axial deviation of the optical fiber is uniquely determined by the geometric precision of the microhole into which the fiber is inserted. However, the amount of axial deviation of the optical fiber according to the present invention is statistically determined by the statistical amount of outer diameter deviation during optical fiber manufacturing and the number of optical fibers to be housed in a desired connector. Here, consider a 256-fiber connector in which 16 layers of optical fiber tapes containing 16 optical fibers are stacked one on top of the other. A survey of a total of 3,000 optical fibers revealed that the outer diameters of single mode optical fibers currently used for boat fishing are normally distributed with an average value of 124.91 μm and a dispersion of exactly 0,052 μm. I understand. When 16 optical fibers are extracted from this population by non-recovery extraction, the average value can be calculated as 124.91 μl, and the variance can be calculated as 0.003 μl. Further, the dispersion when 32 optical fibers are extracted by non-recovery extraction is 0.0014 μm. In other words, when 16 or 32 optical fibers are arranged with their outer diameters touching in the vertical or horizontal direction,
On average, the outer diameter deviation during optical fiber manufacturing can be ignored. In this way, if a large number of optical fibers are assembled into a connector, average axis misalignment will not occur, making it possible to create a low-loss multi-core optical fiber connector. The connectors can be connected to each other by aligning the vertical and horizontal reference planes on which the optical fibers are arranged using guides (not shown) or the like. When the reference planes match, the axes of the fibers match. However, when focusing on the optical fibers near the reference plane, it is the same as extracting a small number of optical fibers, so the influence of the outer diameter deviation still exists. Another problem in manufacturing optical fibers is the eccentricity of the core. Generally used single mode optical fiber has an average diameter of 1 μm.
There is an eccentricity of the core. Therefore, even when a large number of optical fibers are assembled as in the embodiment of the present invention, the connection state is such that there is an axis misalignment of 1 μm on average, that is,
The average connection loss will be 0.2 dB. Therefore, even when this axis misalignment occurs, it is necessary to devise a method for realizing a low-loss connection, but this problem can be solved by the mode field diameter thermal diffusion method described below. After the optical fibers are arranged vertically and horizontally, the optical fiber tips are heated to about the softening point and held continuously or intermittently for a certain period of time to expand the mode field diameter. After thermal diffusion of the mode field diameter, the optical fiber is fixed using an adhesive or the like, and then the end face is polished using a known technique. Alternatively, optical fibers whose mode field diameter has been thermally diffused in advance may be arranged. Next, the effect of thermal diffusion of the dopant will be explained. This phenomenon can be easily understood from the phenomenon of thermal diffusion of atoms or molecules due to heating. FIG. 3 shows the results of actually measuring the near-field pattern of the optical fiber before and after heating. (a) is the near field pattern before heating,
The mode field diameter was 9.6 μm. (b) is a near-field pattern after heating for 30 minutes. It can be seen that after heating, the mode field diameter expands to 15 μm. When connecting optical fibers under conditions of a certain axis misalignment, according to the well-known 1llarcuse theory, the larger the mode field diameter, the smaller the connection loss. To,
Even in the presence of 1 μm misalignment, the average splice loss is 0.07 d due to thermal diffusion of the mode field diameter.
It can be easily reduced to about B. Next, we will show the results of actually confirming this effect. FIG. 4 is a diagram illustrating the effect of reducing connection loss due to thermal diffusion of dopant. In order to explain this effect more clearly, the figure shows a well-known fusion spliced part heated to the softening point temperature of the optical fiber and held continuously or intermittently for a certain period of time, and the splice loss measured over time. The results are shown below. The vertical axis is the relative fusion splicing loss, and the horizontal axis is the heating time. When the heating time is 5 minutes to 30 minutes, the fusion splicing loss approaches almost zero. Thus, it can be seen that expanding the mode field diameter by heating the optical fibers has a remarkable effect even if the optical fibers to be connected are misaligned with each other. FIG. 5 shows the splice loss distribution of a 256-fiber multi-fiber optical fiber connector with 16 fibers x 16 fibers. Average connection loss is 0.0
The maximum connection loss was 0.2 dB. As described above, according to the present invention, it is possible to connect extremely multi-core optical fibers with low loss. Regarding the size of the connector, the size of the optical fiber part is 2mm x 2m.
m, and the outer diameter of the connector is 4mm x 4mm. In the case of a 1024-fiber connector with 32 fibers x 32 fibers, the end fiber part is 4mm x 4mm, and the outer diameter of the connector is 6mm.
It was possible to create an extremely small multi-core optical fiber connector with dimensions of mm x 6 mm.

【Effect of the invention】

As explained above, according to the present invention, it is possible to prevent the influence of manufacturing a deviation of the microholes of the optical connector member on the optical connector on the misalignment loss, and also to connect a significantly larger number of optical fibers compared to the conventional technology. This method has the advantage that it is possible to manufacture a multi-fiber optical connector that can be connected all at once with low loss.

[Brief explanation of the drawing]

Fig. 1 is a configuration diagram showing an embodiment of the present invention, Fig. 2 is a conceptual diagram showing the positional relationship of arranged optical fibers, and Fig. 3 is a result of determining near-field patterns before and after heating.
Figure 4 is a drawing explaining the splice loss reduction effect due to thermal diffusion of dopants, Figure 5 is the splice loss distribution of a 256-fiber multi-fiber optical fiber connector, and Figure 6 is the manufacture of a multi-fiber optical fiber connector using conventional technology. A conceptual diagram showing the method, Figure 7 is a conceptual diagram showing the misalignment of optical fibers on the end face of a multi-fiber optical fiber connector according to the prior art, and Fig. 8 is a conceptual diagram showing the misalignment of the micro holes used in the multi-fiber optical fiber connector. FIG. 1. Multi-core optical fiber tape, 2... Coating of multi-core optical fiber tape, 3... Optical fiber 4... Fine hole, 5.
... Optical connector member, 6... Adhesive, 7... Optical fiber arrangement member.

Claims (2)

[Claims] (1) A multi-core fiber array consisting of a large number of optical fibers arranged vertically and horizontally with their outer diameters in contact with each other in an optical fiber array member having reference planes vertically and horizontally, and whose mode field diameter at the tip portion is enlarged. fiber optic connector. (2) Insert optical fibers into an optical fiber array member that has reference planes vertically and horizontally, arrange the optical fibers vertically and horizontally with their outer diameters touching, and heat and expand the mode field diameter at the tip of the optical fibers. A method for manufacturing a multi-core optical fiber connector.