JP2807721B2 - Multi-core optical fiber connector and method of manufacturing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial technical field]

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

2. Description of the Related Art As shown in FIG. 6A, a conventional multi-core optical fiber connector has a structure in which a coating 2 of a multi-core optical fiber tape 1 is removed to expose an optical fiber 3, and then as shown in FIG. 6B. Next, the optical fiber 3 is inserted into the optical connector member 5 having the fine holes 4 linearly arranged so as to form a pair with the number of the optical fibers, and further, as shown in FIG. Adhesive 6
A method has been used in which the optical fiber is fixed by dropping and filling, and curing the adhesive 6 as shown in FIG. 6d.

[Problems to be solved by the invention]

The diameter of the micro-holes 4 of the optical connector member 5 is set to about 1 μm due to the manufacturing deviation of the diameter of the optical fiber to be inserted and to improve the workability at the time of insertion. A margin of several μm or more is provided for a 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 are inevitably shifted. Further, generally, the connector member is formed by plastic molding, punching / lapping of ceramics, or the like. Therefore, as shown in FIG. 8, occurrence of geometrical displacement of the microhole itself was inevitable. When the optical connectors produced by this method are connected to each other, a connection loss occurs due to misalignment between the optical fibers. According to Marcuse's well-known theory,
When a general single mode optical fiber is used, the connection loss with respect to the amount of axis deviation is 0.2 dB at 1 μm and 0.75 d at 2 μm.
B, and reaches 1.7 dB at 3 μm. Accordingly, the connection loss of the 50-fiber bundled multi-fiber optical fiber connector made according to the prior art was 1.2 dB on average and 5 dB at maximum.
The connection loss of a 200-fiber multi-fiber optical fiber connector was 1.4 dB on average and 9 dB at maximum. When the connection loss is large as described above, the transmission distance cannot be increased, so that a large number of relay devices are required, or a signal cannot be transmitted to a predetermined distance. Further, if the deviation in manufacturing is to be suppressed to a small extent in order to reduce the geometrical axis deviation, there has been a problem that the yield at the time of manufacturing is reduced and the price of the connector itself is significantly increased. As described above, in the method for manufacturing a multi-core optical fiber connector according to the related art, the optical fiber is inserted into the fine hole of the connector member, and then fixed with an adhesive or the like to determine the position of the optical fiber. Is the most significant feature. Therefore, in the method of manufacturing a multi-core optical fiber connector according to the prior art, as is well known, a connector member having a size much larger than that of an optical fiber is indispensable in order to secure the strength of the connector itself and workability. However, when many optical fibers are connected, in addition to the problem of misalignment of the optical fibers, a problem of the size of the connector itself occurs. 50 created according to the conventional method
Multi-core optical fiber connector with 6 cores × 4 mm, 200
The dimensions of the multicore optical fiber connector are 8 mm x 11 mm. Currently, optical cables of up to about 1000 fibers are in practical use, but it is considered that a large bundle of optical cables of about several thousand is required to realize Fiber to the home.
As described above, it is almost impossible to connect an optical cable having an extremely large number of cores with a connector according to the prior art because of dimensional restrictions. An object of the present invention is to solve the problem of misalignment of optical fibers caused by the conventional object and to provide a small-sized multi-core optical fiber connector capable of connecting a much larger number of optical fibers at a time than before. Is to do.

[Means for Solving the Problems]

The present invention is to arrange and fix the coated optical fibers vertically and horizontally so that their outer diameters are in close contact, and heat the tip of the arranged optical fibers to thermally diffuse the dopant of the core of the fibers. It was made.

[Action]

According to the above configuration, the optical fibers can be arranged without using fine holes, and the mode field diameter is enlarged, so that the loss due to axial misalignment is reduced.

【Example】

FIG. 1 is a block diagram showing an embodiment of the present invention.
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 array member. In this method, first, after removing the coating of the multi-core optical fiber tape to expose the optical fiber, the optical fiber is inserted into the optical fiber array member, and the vertical and horizontal reference planes of the array member are used. The optical fibers are arranged vertically and horizontally.
The vertical and horizontal positions of the optical fiber are positioned by the fibers that touch each other. FIG. 2 shows the positional relationship between the arranged optical fibers. In the method of manufacturing a connector according to the related art, the amount of axial deviation of the optical fiber is uniquely determined by the geometric accuracy of the microhole into which the optical 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 the deviation of the outer diameter during the production of the optical fiber and the number of optical fibers housed in a desired connector. Here, consider a 256-fiber connector in which 16 optical fiber tapes each containing 16 optical fibers are stacked. The outer diameter of the currently used single mode optical fiber was found to have a normal distribution with an average value of 124.91 μm and a dispersion of 0.052 μm by examining the outer diameter of a total of 3000 optical fibers. Was. The average value when extracting 16 optical fibers from this population by non-restoration extraction is 124.
The dispersion can be calculated to be 91 μm and the dispersion to be 0.003 μm. Also, when 32 optical fibers were extracted by non-restoration extraction, the dispersion was 0.0014.
μm. In other words, when 16 or 32 optical fibers are arranged with their outer diameters in contact with each other in the vertical or horizontal direction, the outer diameter deviation in the optical fiber manufacturing can be ignored on average in both the vertical and horizontal directions. Become. If a large number of optical fibers are assembled into a connector as described above, an average axial deviation does not occur, and a low-loss multi-core optical fiber connector can be manufactured. The connectors may be connected to each other by aligning the vertical and horizontal reference planes on which the optical fibers are arranged with a guide or the like (not shown). When the reference planes match, the axes of the fibers match. However, when focusing on the optical fiber near the reference plane, it is the same as extracting a small number of optical fibers, so that the influence of the outer diameter deviation still exists. Further, there is an eccentricity of the core as a problem in manufacturing the optical fiber. In a commonly used single mode optical fiber, an average of 1 μm
There is m core eccentricity. Therefore, even when a large number of optical fibers are assembled as in the embodiment according to the present invention, the connection state with an axis deviation of 1 μm on average, that is, the average connection loss is 0.2 dB. Therefore, it is necessary to devise a method for realizing low-loss connection even when this axis deviation occurs. However, this problem can be solved by a heat diffusion method having a mode field diameter described below. After arranging the optical fibers vertically and horizontally, the mode field diameter is enlarged by heating the optical fiber tip to about the softening point and holding it continuously or intermittently for a certain period of time. After the thermal diffusion of the mode field diameter, the optical fiber is fixed using an adhesive or the like, and the end face is polished by a known technique. Alternatively, optical fibers having a mode field diameter thermally diffused in advance may be arranged. Next, the effect of thermal diffusion of the dopant will be described. This phenomenon can be easily understood by a thermal diffusion phenomenon of atoms or molecules due to heating. FIG. 3 shows the results of actually measuring the near-field pattern before and after heating the optical fiber. (A) is a near field pattern before heating, and 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 has expanded to 15 μm. According to the well-known Marcuse theory, when the optical fibers are connected to each other under a condition of a certain axis shift, the connection loss can be reduced as the mode field diameter increases. Therefore, as described above, even when there is an axis deviation of 1 μm, the average connection loss can be easily reduced to about 0.07 dB by thermal diffusion of the mode field diameter. Next, the result of actually confirming this effect will be shown. FIG. 4 is a drawing for explaining the effect of reducing connection loss due to thermal diffusion of the dopant. In the figure, in order to explain this effect more clearly, a known fusion spliced part is heated to the softening point temperature of the optical fiber and held continuously or intermittently for a certain period of time to measure the splice loss over time. The results are shown. The vertical axis represents relative fusion splice loss, and the horizontal axis represents heating time. With a heating time of 5 to 30 minutes, the fusion splice loss approaches zero.
Thus, it can be seen that the expansion of the mode field diameter due to the heating of the optical fiber has a remarkable effect even if the optical fibers to be connected are off-axis. FIG. 5 shows the connection loss distribution of a 16-core × 16-core 256-core multicore optical fiber connector. The average splice loss was 0.08 dB and the maximum splice loss was 0.2 dB. As described above, according to the present invention, an extremely large number of optical fibers can be connected with low loss. As for the size of the connector, the size of the optical fiber portion is 2 mm × 2 mm, and the outer diameter of the connector is 4 mm × 4 mm. In the case of a 32-core x 32-core 1024-fiber connector, the optical fiber part was 4 mm x 4 mm and the connector outer diameter was 6 mm x 6 mm, and an extremely small multi-core optical fiber connector could be made.

【The invention's effect】

As described above, according to the present invention, it is possible to prevent the optical connector from being affected by the manufacturing deviation of the fine hole of the optical connector member with respect to the axial deviation loss, and to bundle a significantly larger number of optical fibers as compared with the conventional technology. Thus, there is an advantage that a multi-core optical connector which can be connected with low loss can be manufactured.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is a conceptual diagram showing a positional relationship between arranged optical fibers, FIG. 3 is a result of measuring near-field patterns before and after heating, and FIG. And FIG. 5 are diagrams for explaining the effect of reducing the connection loss due to thermal diffusion of Dobant, FIG. 5 is a connection loss distribution of a 256-core multi-core optical fiber connector, and FIG. FIG. 7 is a conceptual diagram showing a positional shift of an optical fiber at an end face of a conventional multi-core optical fiber connector. FIG. 8 is a conceptual diagram showing a positional shift of a fine hole used in the multi-core optical fiber connector. It is. 1 ... multi-core optical fiber tape, 2 ... multi-core optical fiber tape coating, 3 ... optical fiber, 4 ... micropore, 5 ...
Optical connector member 6 Adhesive 7 Optical fiber array member

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Claims (2)

(57) [Claims] 1. An optical fiber arrangement member comprising a plurality of optical fibers arranged in an optical fiber arrangement member having reference planes in the vertical and horizontal directions with an outer diameter in the vertical and horizontal directions and having a mode field diameter at a tip end portion enlarged. Multi-core optical fiber connector. 2. An optical fiber is inserted into an optical fiber arranging member having reference planes in the vertical and horizontal directions, the outer diameter of the optical fiber is arranged in the vertical and horizontal directions in contact with each other, and the mode field diameter at the tip portion of the optical fiber is heated. A method for manufacturing a multi-core optical fiber connector, comprising: