JPH01201612A - Manufacture of connector for optical fiber - Google Patents

Abstract

PURPOSE:To generate no optical transmission loss, and also, to strengthen coupling force to an optical fiber by forming a connector by injecting a specific forming material into a mold, in a state that a temperature in a forming mold has been set to below a softening temperature of the optical fiber. CONSTITUTION:In order to form a connector 22, a supporting member 29 is provided on a forming mold 28, a temperature of its forming mold 28 is set to below a softening temperature of an optical fiber 21a, and also, a forming material whose temperature is below said softening temperature + 150 deg.C and whose melt flow rate is >=5g/min is used. Therefore, an optical fiber 21 is supported and fixed so as not to become eccentric, and also, the forming material which has been injected at a high speed into the forming mold 28 is cooled and solidified quickly by a high dissipation of the forming mold 28 of a low temperature and the supporting member 29. In such a way, it can be prevented that the optical fiber 21 becomes eccentric, a melt and a deformation are generated in the forming mold 22 and the forming material due to a high temperature, etc., and an optical transmission loss of the optical fiber 21 becomes large, and also, coupling force to the optical fiber is strengthened by the injection molding.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for manufacturing an optical fiber connector that is attached to the end of a plastic optical fiber and is used to connect the ends of the optical fiber.

[Conventional technology]

In recent years, optical fibers have been used as communication cables in information communication systems, and plastic optical fibers are being used instead of glass fiber optical fibers from the viewpoint of cost and the like. Since such optical fibers are laid over long distances, they are used to connect optical fibers to each other or to other devices. A connector 1 as shown in FIG. 5 is used to connect such optical fibers. That is, this connector 1 is composed of a main body 4 consisting of a fixing part 2 and a connecting part 3, and a lid part 6 that can fit into a recess 5 provided on the upper surface of the fixing part 2. Reference numeral 7 designates engaging protrusions provided alternately at predetermined intervals on both side walls along the longitudinal direction of the recess 5, and reference numeral 8 represents a hole that penetrates into the recess 5 from one end 2a of the fixing part 2. The optical fiber core 9 can be inserted into the hole 8, and the fixing part 2
A hole (not visible in the figure) having the same diameter as the hole 8 is also drilled from the recess 5 to the connecting portion 3. 10
is a cylindrical protrusion protruding from the other end 3a of the connecting part 3, the center hole 10a of which communicates with the hole drilled from the four parts 5 to the connecting part 3, and the optical fiber core 9 The core, which is the central part of the optical fiber, and the cladding part 9a (consisting of a core part with a high refractive index of light surrounded by a cladding part with a low refractive index, which is the strand part of the optical fiber) can be inserted. . Reference numeral 11 denotes a plurality of engagements protruding from the back surface of the lid 6 so as to fit into the gaps between the retaining protrusions 70 along the longitudinal direction of the recess 5 when the lid 6 is fitted into the recess 5. It is a joint. On both sides of the tip of this engaging portion 11,
Engaging pawls 12 are provided to protrude toward the inside of the lid portion 6, respectively.

For this purpose, the outer sheath 9b at one end of the optical fiber core 9 is removed, and the one end is inserted into the 8° recess 5 and the hole in the main body 4, and the core at the tip thereof is inserted.

The cladding part 9a is inserted into the center hole 10a of the cylindrical projection 10. Next, by fitting the lid 6 into the recess 5 of the fixing part 2 in this state, the outer skin 9b of the optical fiber core 9 is clamped and fixed by the engaging claws 12 of the lid 6, as shown in FIG. It is now possible to do so. Therefore, by connecting the connecting portion 3 of the main body 4 to other equipment, etc. in this state, the core and cladding portions 9a can be connected to the above-mentioned equipment, etc.

[Problem that the invention seeks to solve]

However, since the above-mentioned connector is attached to the optical fiber core 9 by clamping and fixing the outer cover 9b of the optical fiber core 9 with the engaging claws 12 provided on the lid 6, the coupling force is weak and it is easy to come off. There is a problem. Further, in order to insert the core and cladding portion 9a through the center hole 10a of the cylindrical projection 10, the diameter of the center hole 10a is set to be slightly larger than the diameter of the core and cladding portion 9a. Therefore, the core and cladding portion 9a are eccentrically positioned in the center hole 10a, and when connecting the optical fibers, there is a problem that the axis misalignment becomes large and the optical transmission loss becomes large. Furthermore, there is another problem in that moisture enters the gap between the core, cladding portion 9a, and cylindrical protrusion 10, which adversely affects optical transmission. Another problem is that the number of parts increases and the connector itself becomes large. For this reason, the inventors believe that the binding force is strong and
In addition, in order to create a connector that has no gaps between the optical fibers and can be further miniaturized, the outer sheath 9b of the optical fiber core 9 in the area where the connector is to be formed is peeled off to expose the core and cladding 9a, and the remaining portion of the outer sheath is removed. The boundary between the core and the exposed cladding part is shown in Figures 7, 8 and 9.
It was devised that the connector is disposed in a mold 13 as shown in the figure, and in that state, a liquid resin material 14 is injected into the mold 13 from an injection port 15, thereby integrally molding the connector with the boundary portion. However, since the above-mentioned connector also requires the function of covering and protecting the optical fiber core wire 9, it requires a heat resistance temperature higher than that of the optical fiber core wire 9. Therefore, when forming the above-mentioned connector, the melting temperature of the core and cladding portion 9a of the nine optical fibers is approximately 80°C.
In contrast, the liquid resin material 14 is the core thereof.

A material with a melting temperature higher than that of the cladding part 9a and the outer skin part 9b is used, and the material is heated at a temperature of approximately 180°C (lower temperature causes poor fluidity of the resin in the mold, so It is necessary to inject it into the mold 13 at a setting of Furthermore, in order to improve the fluidity of the resin material 14, it is necessary to heat the mold 13 to a certain temperature or higher. Under such conditions, the present inventor conducted a series of studies based on methods devised by himself. During the course of this research, we discovered the following problems. That is, in the above molding method, when the temperature of the mold 13 is higher than the softening point of the optical fiber core 9, the shaded portions a and b of the optical fiber core 9 shown in FIG. 7 may melt due to the heat of the mold 13, The portion C of the core and cladding portion 9a melts due to the heat of the mold 13 before the resin material 14 is injected, resulting in a thin state as shown in the figure. Furthermore, if the temperature of the resin material 14 exceeds the softening point of the core and cladding portions 9a by 150° C., the core and cladding portions 9a will melt and breakage as shown in FIG. 8 will occur. Melt flow rate (JIS-7210.190℃, 2,16
If the flow (flow at a kg load) is 5 g/min or less, the filling of the resin material into the mold 13 will be slow;
As a result, the flowability of the resin material 14 flowing inside the mold 13 differs between the upper side and the lower side, creating a pressure difference.

Deformation such as bending as shown in FIG. 9 occurs in the cladding portion 9a. This causes problems such as an increase in optical transmission loss of the optical fiber core wire 9 or an unusable state.

This invention was developed in consideration of these circumstances, and it does not cause the optical fiber to melt or deform due to the heat of the resin material used for connector molding, does not cause eccentricity, and has a small number of parts (it is small and can be used for optical fibers). The purpose of this invention is to provide a method for manufacturing an optical fiber connector that has a high bonding force and high temperature resistance.

[Means for solving problems]

In order to achieve the above object, the method for manufacturing an optical fiber connector of the present invention involves removing the outer sheath at one end of a plastic optical fiber whose periphery is covered with an outer sheath,
The boundary between the remaining part of the outer skin and the removed part of the outer skin is
The optical fiber is placed in a mold having a support member that supports and fixes the optical fiber so that it is not eccentric, and the temperature inside the mold is set to a temperature equal to or lower than the softening temperature of the optical fiber. The connector is formed on the outer periphery of the boundary by casting a molding material at a temperature of .degree. C. or lower and a melt flow rate of 5 g/min or higher.

[Function] That is, the optical fiber connector of the present invention is obtained by an improved method of connector integral molding devised by the present inventor, and in order to form the connector,
A supporting member is provided in a molding mold, and the temperature of the molding mold is set to below the softening temperature of the optical fiber, and as a molding material, the temperature is below the above softening temperature + 150°C and the melt flow rate is 5 g/min or more. I'm using the one from Therefore, the optical fiber is supported and fixed so as not to be eccentric, and the molding material injected into the mold at high speed is quickly cooled and solidified by heat dissipation from the low-temperature mold and supporting member. Therefore, it is possible to prevent the optical fiber from becoming eccentric, or from being melted or deformed due to the high temperature of the mold or the molding material, and it is possible to prevent the optical fiber from increasing optical transmission loss. Furthermore, a material with a higher melting temperature than the optical fiber can be used as a molding material for the connector, resulting in a connector with high heat resistance. Furthermore, since it is molded integrally with the optical fiber by injection molding, the bonding force with the optical fiber is strong, and the number of parts is small (miniaturization is possible).

Next, the present invention will be explained in detail based on examples.

〔Example〕

FIG. 1 shows an embodiment of the invention. In the figure, reference numeral 21 denotes an optical fiber core formed by covering an optical fiber with an outer skin part 21b, which includes a core made of methacrylic resin with a diameter of 980 μm, and a cladding made of fluoride resin with a thickness of 20 μm surrounding the core, and the cladding. 21a (optical fiber) is covered with a polyethylene outer cover 21b. This optical fiber core wire 21 has the outer skin portion 21b removed from one end side, and the core and
The cladding portion 24a is exposed. 22 is a connector made of polyacetal, which is connected to the remaining side of the outer skin portion 21b of the optical fiber core 21 and the core.

It is formed so as to cover the boundary portion with the exposed side of the cladding portion 21a. The connector 22 has a connecting portion 23 having a small diameter at its distal end, and a concave portion 23a is coaxially provided at the distal end of the connecting portion 23. A cylindrical protrusion 24 into which the core and cladding portion 21a are fitted protrudes from the center of the bottom surface of the recess 23a. A pair of cylindrical holes 25 are provided on the outer periphery of the rear end of the connector 22 at right angles to the axis, and face each other from above and below. Further, reference numeral 26 denotes a rubber boot part for protecting the connector attached to the outer periphery of the remaining outer skin part 21b of the optical fiber core wire 21 from the rear end side of the connector 22, and two boots protruding from the inner peripheral surface. The cylindrical projection 27 of the connector 22 is fitted into the cylindrical hole 25 of the connector 22 and is detachably attached.

Such a connector can be obtained as follows.

That is, first, the outer skin portion 11b on one end side of the optical fiber core wire 21 is removed to expose the core and cladding portion 21a. Next, a mold 28 as shown in FIG.
Temperature below the softening temperature of the cladding part 21a (outer skin part 21b
The softening temperature of the core and the cladding part 21a is set to be higher than that of the core and the cladding part 21a), and the boundary part between the remaining part of the outer skin part 21b of the optical fiber core wire 21 and the exposed part of the core and the cladding part 21a is placed in the mold 28. Place.

Then, the remaining portion of the outer skin portion is sandwiched between pins 29 provided on the mold 28 and supported and fixed so as not to be eccentric. The cylindrical pin 29 serves to fix the optical fiber core 21 and at the same time release the heat inside the mold 28 to the outside.
It passes through the mold 28 and its tip protrudes outside the mold 28. Next, in this state, the injection port 30 is inserted into the molding space 28a of the molding die 28 at the softening temperature +150.
The temperature is set to below ℃, and the melt flow rate is 5 g/
Liquid polyacetal in an amount of min. Note that during this formation, when the liquid polyacetal solidifies, it shrinks (molding shrinkage rate of 2.5 or more), so that the optical fiber core 21 is firmly fixed to the connector 22. Next, connector 22
The core and cladding portion 2 protrude from the cylindrical protrusion 24 of the
1a and a pre-formed rubber boot part 2
6, the boot part 2 as shown in FIG.
6. A protected connector is obtained. By connecting the connecting portion 23 of this connector to another connector, device, etc., the tip of the core/cladding portion 21a can be connected to the core, cladding, etc. of the optical fiber. Note that during the connector molding process, the temperature of the mold 28 rises due to the heat of the polyacecool, but this is cooled down by water cooling or the like in preparation for the next use, thereby constantly maintaining the temperature below the softening temperature of the optical fiber core 21. Ru.

The output fluctuation (dB) of the optical fiber core 21 when the connector protected by the boot part 26 thus obtained is repeatedly connected to and disconnected from equipment, etc.
As shown in the figure. As shown in the figure, almost no output fluctuation was observed even after repeated attachment and detachment 500 times. Further, when a pullout test was conducted by pulling the connector and the optical fiber core 21 in opposite directions, the results shown in FIG. 4 were obtained. That is, first, a load of just over 4 kg was applied and maintained for 1 minute, then the load was increased to 7 kg.
and maintained for 1 minute. Next, as the load is increased, the optical fiber core 21 starts to stretch at 13 kg, but the optical fiber core 21 does not come off from the connector.

Since the conventional connector 1 shown in FIG. 5 separates from the optical fiber core 9 when a load of 7.5 kg is applied, it is believed that the connector of the present invention has sufficient pull-out strength to withstand use. I can say that.

In this way, in this connector, the optical fiber is installed without eccentricity in the mold 28 in which pins 29 for fixing and heat dissipation are arranged, and the temperature of the mold 28 is adjusted to the core of the optical fiber core 21. The temperature is set below the softening temperature of the cladding part 21a, and the temperature is set to the above softening temperature +1.
Below 50℃, melt flow rate is 5 g/m
It is manufactured by injecting polyacetal of i n or more. Therefore, the polyacetal injected into the mold 28 at high speed is quickly cooled and solidified by heat dissipation from the mold 28 and pins 29. Therefore, the optical fiber core 21
The fibers do not become eccentric, and the optical transmission rate improves when optical fibers are connected. Furthermore, the core and cladding portions 2 of the optical fiber core 21 are further damaged due to the high temperatures of the mold 28 and the polyester.
It is possible to prevent the optical fiber core 21 from being melted and deformed before it is filled with polyacetal due to the slow injection speed of polyacetal, and the optical transmission of the optical fiber core 21 can be prevented. Increased losses can be prevented. Moreover, for this reason, a material with a high melting temperature can be used as the molding material for the connector 22,
The heat resistance temperature of the connector 22 can be increased. Furthermore, the optical fiber core 2 is made by injection molding the connector.
Since it is integrally molded with the optical fiber core wire 21, the bonding force with the optical fiber core wire 21 is strong, making it difficult to separate, and since no gaps are created, no moisture can enter. Therefore, even if the connector is repeatedly connected to and disconnected from other devices, the optical fiber core 21
Almost no output fluctuation occurs. Furthermore, the number of parts is small, making it possible to downsize and making manufacturing easier. Furthermore, the cylindrical hole 2 of the connector 22 formed by this pin 29
5 is used to attach the boot portion 26 to the outer periphery of the connector 22, the connection between the connector 22 and the boot portion 26 is made stronger.

Note that the materials constituting the core and cladding 21a are as follows:
Plastics such as acrylic and polycarbonate, and glass fibers can be used. In addition, the material for the connector 22 is polyethylene terephthalate (molding shrinkage rate 1 to 2).
, polypropylene (molding shrinkage rate 1 to 1.5), polyamide (shrinkage rate 0.3 to 0.8), geothermally cured resins thereof, etc. can be used. Furthermore, the boundary between the remaining outer skin portion of the optical fiber core 21, the core, and the cladding portion 21a may be coated with a thermosetting resin, etc. This prevents turbulence from occurring at the boundary, especially in connector molding. The connector can be obtained in a stable and uniform state.

(Effects of the Invention) As described above, according to the present invention, almost no optical transmission loss occurs, the coupling force with the optical fiber is strong (and the number of parts is small, making it possible to downsize. Since the optical fiber is not melted and deformed by the heat of the molding material, a highly heat-resistant material can be used as the connector molding material.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view of an embodiment of the present invention, FIG. 2 is a longitudinal sectional view explaining the manufacturing method thereof, FIG. 3 is a curve diagram showing the relationship between the number of repetitions of attachment and detachment and output fluctuation, and FIG. Fig. 4 is a curve diagram showing the pull-out strength, Fig. 5 is an exploded perspective view of the conventional example, Fig. 6 is a vertical sectional view of the main part, and Figs. 7, 8, and 9 are diagrams of other conventional examples. It is a longitudinal cross-sectional view explaining a manufacturing method. 21... Optical fiber core wire 21a... Core, clad part 21b... Outer skin part 22... Connector
29... bottle

Claims (1)

[Claims] (1) Remove the outer skin from one end of a plastic optical fiber whose periphery is covered with an outer skin, and support the boundary between the remaining outer skin and the removed outer skin so that the optical fiber does not become eccentric. The optical fiber is placed in a mold having a support member to be fixed, and the temperature inside the mold is set to a temperature equal to or lower than the softening temperature of the optical fiber, and the melt flow is performed at a temperature equal to or lower than the softening temperature +150°C. A method for manufacturing an optical fiber connector, characterized in that the connector is formed on the outer periphery of the boundary by casting a molding material having a rate of 5 g/min or more.