JPS6042922B2 - How to make optical connector plugs - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a highly accurate and simple method for manufacturing an optical connector plug.

(Prior technology) In optical connectors that connect optical fibers, the optical fiber must be accurately fixed in the center of the plug, and because the core of the optical fiber is small, this fixation requires high precision. do.

The process of aligning and fixing the optical fiber to the central axis of the plug is called centering.

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(2) Make a hole slightly larger than the outer diameter of the optical fiber at the tip of the plug, insert the optical fiber into this hole, and fix it. be.

(1) requires a lot of adjustment, but (2) is advantageous in that it does not require such adjustment. In addition to the positional accuracy of the guide hole (or gap) for positioning the cal fiber wire,
There is an error factor called ``backlash'' when the optical fiber is inserted. In order to eliminate this "backlash," it has been considered in the past to make the tip of the optical fiber thicker so that it comes into contact with the inner surface of the tapered optical fiber guide hole machined at the tip of the plug. Figure 1
As shown in the figure. 1 is an optical fiber wire, 2 is an optical fiber jacket portion, and 3 is a plug.

This method involves passing an optical fiber through a plug, making the tip of the optical fiber thicker, and then pulling the optical fiber in the direction of the arrow in Figure 1 to open a tapered guide hole in the tip of the plug. The optical fiber is brought into contact with the inner surface and automatically fixed at the center of the guide hole. Another method for centering an optical fiber with a thickened tip at the center of the plug is to set three or more balls at the tip of the plug as centering members, and the gap surrounded by the balls to center the optical fiber. The ball is designed to have an outer diameter substantially equal to or larger than the outer diameter of the plug, and the optical fiber is fixed at the center of the plug by pulling up until the thickened part of the tip of the optical fiber comes into contact with this ball. was attempted (Japanese Unexamined Patent Publication No. 187-1987)
No. 61).

(Problems to be Solved by the Invention) In the above method, the axial symmetry of the thickened portion of the optical fiber directly affects the positional deviation of the optical fiber, so high precision is required for this processing.

The following methods are available to thicken the tip of an optical fiber.

(a) A method in which the tip of an optical fiber is heated and melted using an arc discharge, a CO2 laser, an oxyhydrogen flame, etc., and a ball is created using surface tension.

(b) A dipping method in which another liquid is attached to the optical fiber and solidified.

(c) A method of processing optical fiber by changing its thickness during spinning.

In (a), the tip of the optical fiber during melting tends to move due to air currents, vibrations, etc., making it difficult to improve the axial symmetry accuracy of the optical fiber outer shape.

Furthermore, since the core of the processed portion of the optical fiber flows and changes significantly, that portion cannot be used as the end face of an optical connector plug. In (b), the shape is easily distorted due to non-uniformity of the liquid, dirt on the surface of the optical fiber, etc., and it is difficult to achieve high precision.

In (c), a large-scale apparatus is required, and it is difficult to control sudden changes in the fiber outer diameter.

Due to the above-mentioned drawbacks, even if these methods were actually applied to the production of optical fiber ends, highly accurate plugs could not be produced. The present invention enables processing to thicken the outer diameter and core diameter of a part of the fiber while maintaining concentricity, and uses this to perform high-precision centering without adjustment, leaving the thickened part. The present invention is characterized in that an optical connector plug is manufactured by polishing the end portion, and its purpose is to provide a method for manufacturing a highly accurate optical connector plug with good workability.

(Means for solving the problem) In the present invention, an optical fiber is supported at at least two places and held vertically, and the middle part of the held optical fiber is fed in the axial direction while being partially heated to a softening temperature. By this,
The heating part is made thicker while maintaining the core and cladding structure of the optical fiber, and the process of using this thickened part to center and fix the plug at the center is a conventional method. It is used as is.

(Operation) Since a part of the optical fiber is made thicker by the above method, the structure of the cladding and core of the optical fiber is maintained as is.

After centering and fixing the optical fiber in the center of the plug, polish the end of the plug so that this thickened part remains, and you will see a connection end where the core radius of the optical fiber has expanded at the tip of the plug. is obtained.

The effects of producing an optical connector using a plug having such a connection end will be described below. FIG. 3 shows the relationship between the normalized frequency v that provides a constant amount of shaft rubbing loss and the normalized shaft sliding amount Jx.

Here v=KOaVnl2-Rl22, kO=2? r/
λ, x is the amount of axis deviation, λ is the wavelength of light, n1 is the refractive index of the core, N2 is the refractive index of the ground, a is the radius of the core, Δ
is the relative refractive index difference, Δ=(n1-Rl2)/n1.

As is clear from FIG. 3, the allowable amount of axis deviation becomes the minimum near v=1.7, and it can be seen that it is improved before and after that. For example, relative refractive index difference Δ=0.2%, wavelength used λ
=0.85μm1If the allowable connection loss is 0.5dB,
The allowable axis deviation amount is 1.3 μm when v=2.4, whereas it is improved to 1.7 μm when v=3.8. v
Since the value is proportional to the core radius a, this effect can be obtained by increasing a. That is, if a plug manufactured by the method of the present invention is used, connection loss will not increase even if there is some axis misalignment. (Example) An example of the process of thickening an optical fiber is shown below.

FIG. 5 is a schematic perspective view of the equipment used in this step,
8 is a vacuum chuck, 9 is a vacuum pump, 10 is a discharge electrode,
11 is a high voltage power supply.

To operate this, first, the inclination of the vacuum chuck 8 is adjusted so that the vacuum chuck 8 can support the optical fiber in the vertical direction.

The vacuum chuck 8 has a structure in which two parts are glued together, and a vacuum pump 9 is used to suck air through a narrow groove (not shown) in the joint. Since this narrow groove is made sufficiently smaller than the fiber radius, the optical fiber is supported along the right-angled groove of the vacuum chuck. The jacket portion of the optical fiber is attached to a fiber feeding device (not shown). A discharge electrode 10 is inserted into the center of the vacuum chuck, and the jacket portion of the optical fiber is automatically fed downward by a fiber feeding device while the optical fiber is heated by generating a discharge between the electrodes. As a result of this operation, the optical fiber is supplied to the heating section from above, and as a result, the heating section becomes thicker. This method is different from the conventional method (a) in which the tip of the optical fiber is heated and melted.Since the fused portion of the optical fiber is supported at two points, the upper and lower points, the fused portion is difficult to move, and therefore the core and the outer shape of the fiber are It also becomes thicker while maintaining high-precision axial symmetry.

FIG. 2A shows a first embodiment of the centering process of the present invention, in which 1 is an optical fiber, 2 is an optical fiber coating, and 3 is a plug. The effect of centering the thickened part of the optical fiber by inscribing it in the tapered hole at the tip of the plug is the same as in the prior art shown in FIG.

FIG. 2B shows a cross section of the end of the plug manufactured by this method after polishing, where 4 is the core of the optical fiber and 5 is the adhesive layer. In the method of the present invention, the structure of the core and cladding is maintained during the process of thickening the optical fiber, so a plug with the core 4 expanded at the tip can be obtained.

The effect is as described above. FIG. 4 shows a second embodiment of the centering process of the present invention.

Instead of machining a tapered hole at the tip of the plug, the plug 3 is machined into a cylindrical vibe shape whose inner diameter is much larger than the fiber diameter, and three steel balls 6 as center setting members are inserted into the steel ball support vibe 7 in the inner hole. The gap formed in the center is used in place of the tapered hole in the previous embodiment. FIG. 4A is a schematic cross-sectional view of the plug during centering, and FIG. 4B is a schematic enlarged cross-sectional view of the tip of the plug after the plug is manufactured. Easy centering without adjustment,
As in the previous embodiment, the core diameter of the optical fiber can be increased at the plug end. The differences include:
(1) Hole position accuracy is higher than when drilling a small tapered hole at the plug setting position.

(2) Since the inner diameter of the steel ball supporting vibe is larger than the maximum diameter of the optical fiber processing section, the optical fiber can be processed in advance before passing it through the plug.

The steel ball is attached after passing the optical fiber through it. (3)
Since the optical fiber and the steel ball are in point contact and there are many gaps, it is easy to pour the adhesive while keeping the optical fiber in contact with the steel ball.

In the above embodiment, the plug has a double-vib structure, but if there is no problem with machining accuracy, the steel ball support vibrator may be integrated with the plug and machined, and three steel balls may be used. The above method may be used to fix the portion of the optical fiber where the outer diameter is increased. Further, the ball is not limited to a steel ball, and any hard ball may be used.
The fact that this method can be applied to multi-pair connections was disclosed in Japanese Patent Application Laid-open No. 5
As shown in No. 4-18761. Regarding the dimensions of each part, the following conditions hold true. In other words, the diameter of the steel ball 6 is DL.The inner diameter of the plug 3 in which the steel ball is inscribed is DL.
, the inner diameter of the central through hole is D, and the diameter of the optical fiber is D
If the maximum diameter of the thickened part of the Fl optical fiber is d''2, the condition for three or more spheres to be inscribed in the plug 3 is also that the thickened part of the optical fiber is drawn into the gap in the center of the spheres. In order to use it, the following conditions are necessary.

Regarding the central through-hole, the following conditions apply.

As mentioned above, in practical terms, D,>Dp''. (Effects of the Invention) As explained above, according to the method for manufacturing an optical connector plug of the present invention, the following can be achieved in a simple process. High-precision plugs can be manufactured, mass production is possible, and low-cost optical connectors can be supplied.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram of a conventional method for centering a plug for an optical connector, Fig. 2 shows an embodiment of the present invention, A is a schematic cross-sectional view of the plug during centering, and B is a plug after the plug is manufactured. Figure 3 is an enlarged sectional view of the tip of the
The figures show other embodiments of the present invention, A is a schematic cross-sectional view of the plug during centering, B is an enlarged cross-sectional view of the tip, and Fig. 5 is an optical fiber used in the process of thickening the optical fiber of the present invention. FIG. 2 is a schematic perspective view of a processing device. 1...Optical fiber wire, 2...Optical fiber jacket part, 3...Plug, 4...
...Optical fiber core, 5...Adhesive layer, 6...
... Steel ball, 7 ... Fiber holding vibe, 8
...Vacuum chuck, 9...Vacuum pump, 10...Discharge electrode, 11...High voltage power supply.

Claims (1)

[Claims] 1. A process of passing an optical fiber through a through hole provided at the center of the plug, a process of thickening the heated part by holding the optical fiber vertically and sending it in the axial direction while locally heating it, and a process of thickening the heated part. A process of centering and fixing the part to the center of the plug by inscribing the part into the inner wall of the tapered through-hole at the tip of the plug or by inscribing it in a centering member installed at the tip of the plug, and fixing the tip of the plug to the center of the plug. A method of manufacturing a plug for an optical connector, comprising the steps of: leaving a part of the thickened portion of the optical fiber so that the end face of the plug and the end face of the optical fiber are flush with each other.