JPH0815568A - Plastic ferrule for optical connector and its production - Google Patents

Abstract

PURPOSE:To produce a plastic ferrule excellent in high dimentional accuracy, mechanical strength, connecting reliability, cost effectiveness, etc. CONSTITUTION:In the ferrule for an optical fiber connector having a putting hole fixing an optical fiber, the ferrule 11 is formed by subjecting a resin composition containing at least thermotropic liquid crystalline total aromatic polyester and carbon fiber to an injection molding under pressure.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ferrule for an optical connector used for connecting a single mode optical fiber and a method for manufacturing the ferrule, and more particularly to a ferrule designed to be economically manufactured. is there.

[0002]

2. Description of the Related Art With the development of optical communication technology, it has become possible to introduce optical fibers to each home and provide various communication services. In order to realize such an optical subscriber communication network, an economical optical connector is necessary.

Conventionally, in order to connect an optical fiber used for optical communication, as shown in FIG. 1, two ferrules 11A and 11B in which the optical fiber is inserted are split sleeves 1.
It is performed by aligning and joining in 2. In addition,
Reference numerals 13A and 13B in the figure denote optical fiber cords. In the ferrule used for such a purpose, an extremely high dimensional accuracy is required for the optical fiber guide hole diameter, the optical fiber guide hole diameter eccentricity, the ferrule outer diameter, the circularity of the outer diameter, and the like. Conventionally, a ferrule has been produced by cutting and polishing ceramics or metal with high precision. Therefore, the manufacturing efficiency is low,
There is a problem that the manufacturing cost becomes high.

In order to solve these problems, attempts have been made to produce a ferrule by plastic molding. For example, Yoshizawa et al. Have proposed a plastic ferrule prepared by transfer molding of phenol (Research Practical Report, Vol. 32, No. 3, 831-).
842 (1983)). However, as the optical fiber at that time, a so-called multimode fiber with a large outer diameter of the core of about 50 μm was mainly used, and although a plastic ferrule was applicable to the connection of such a fiber, it was proved in the present situation. The outer diameter of the core is 8
There is a problem that it cannot be applied to a so-called single mode fiber of -10 μm. Further, as a molding method, transfer molding requires post-treatment such as deburring and post-molding heat treatment, which is not sufficient in terms of economy.

Attempts have also been made to produce plastic ferrules using an economical injection molding technique. It is known that PPS (polyphenylene sulfide) or the like, which has relatively excellent heat resistance and fluidity, has been studied as the resin. However, there has not been obtained one that can withstand the connection of a single mode fiber and that satisfies dimensional accuracy, mechanical strength, various types of reliability, and the like.

FIG. 2 is a structural sectional view of the ferrule 11, in which an optical fiber core wire guide hole 14 and an optical fiber guide hole 15 are formed, and the dimensional accuracy of the ferrule required for connecting a single mode fiber is [ The values in Table 1] are required.

[Table 1]

However, the conventional method could not realize a highly accurate ferrule as shown in [Table 1]. On the other hand, the connection characteristics of the optical connector can be evaluated by the connection loss and the return loss of the end face, but the former requires a value of 0.5 dB or less and the latter a value of 25 dB or more.

Further, in the reliability test, it has been pointed out that the connection characteristics are deteriorated when exposed to a high temperature and humidity environment. The reason for this is that in the plastic ferrule, the length of the optical fiber guide hole 15 shown in FIG. 2 is 1-2 mm (about 8 mm for the zirconia ferrule) due to the molding method, and the optical fiber and the ferrule under high temperature and high humidity. It is presumed that this is because the adhesive strength is insufficient. That is, there is a large difference in the coefficient of thermal expansion between the optical fiber and the plastic ferrule (the former; 7 × 10 ⁻⁷ , the latter; 2 × 10 ⁻⁵ ), and the contact between the optical fibers due to stress in a high temperature and high humidity atmosphere ( It is considered that PC (physical contact) deteriorates.

In view of the above problems, the present invention provides a plastic ferrule for an optical connector used for connecting a single mode fiber, which has high dimensional accuracy, mechanical strength,
It is an object of the present invention to provide a plastic ferrule excellent in connection reliability and economy, and a method for manufacturing the same.

[0010]

The structure of the ferrule according to the present invention for achieving the above object is a ferrule for an optical fiber connector having an insertion hole for fixing an optical fiber, wherein the ferrule is at least the thermotropic liquid crystalline wholly aromatic compound. It is characterized by comprising a resin composition containing polyester and carbon fibers. Further, the above resin composition is characterized in that carbon fibers are contained in an amount of 10 to 40% by weight with respect to the thermotropic liquid crystalline wholly aromatic polyester.

Further, the manufacturing method of the present invention is a method for manufacturing a ferrule for an optical fiber connector having an insertion hole for fixing an optical fiber, wherein the resin composition contains at least the thermotropic liquid crystalline wholly aromatic polyester and carbon fiber. It is characterized by being manufactured by injection compression molding.

The contents of the present invention will be described below.

In the present invention, a ferrule for an optical connector is formed from a resin composition containing a thermotropic liquid crystalline wholly aromatic polyester and carbon fibers, and injection compression molding is carried out during the production of the ferrule. It is possible to form a ferrule with excellent economical efficiency.

That is, in the present invention, the resin composition containing the thermotropic liquid crystalline wholly aromatic polyester (hereinafter referred to as "liquid crystal polymer") and carbon fiber has an extremely small thermal expansion coefficient of about 2 × 10 ^-6. Pay attention to
Therefore, even if the length of the optical fiber guide hole is as short as about 2-3 mm, the problem of reliability of the adhesive strength between the optical fiber and the ferrule is unlikely to occur.

Further, since carbon fiber generally has the effect of improving the slidability, it is also an excellent reinforcing agent from the viewpoint of inserting and removing the ferrule and the sleeve.

On the other hand, in the present invention, the injection compression molding technique is used, and the operation of pressing a part of the resin after molding is added. That is, a carbon fiber reinforced liquid crystal polymer in which carbon fibers are mixed with a liquid crystal polymer has a large anisotropy between the flow direction and the other directions, and deformation such as "warp" and "sink" occurs when ordinary injection molding is performed. Although there was a problem that occurred, this operation can prevent the deformation of the molded product due to the cooling of the resin.

In addition, the above-mentioned operation is generally performed by using a liquid crystal polymer.
It also plays the role of preventing the decrease in weld strength (a phenomenon in which the mechanical strength at the portion where the resin flows merge significantly decreases). "This is because the flow of resin is induced in the weld. The injection molding technique has been confirmed to be effective in molding a lens or a compact disc (CD), mainly in molding a non-crystalline resin, but molding a crystalline polymer such as a liquid crystal polymer. There is no known example in which a remarkable effect was found.

The present invention has been made by finding an extremely effective and remarkable effect when the above-mentioned technique is applied to an optical connector ferrule. The injection compression is suitably performed partially using an ejector pin or the like, and at this time, the compression operation can be performed periodically (5-10 Hz). In addition, liquid crystal polymer has a "burr" at the time of molding compared to PPS (polyphenylene sulfide).
It also has the advantage that it does not come out easily.

The content of carbon fiber added to the above liquid crystal polymer is preferably 10 to 40% by weight. This is 10% by weight
If it is less than 40% by weight, there is no effect of addition, and if it exceeds 40% by weight, the effect of increasing the amount is not exhibited. Also,
In addition to this, various ferrule-forming additives as necessary,
For example, a surface treatment agent, a coloring agent or the like may be added.

In injection molding, the design of the molding die is important, and it is necessary to pay attention to the surface precision of the die surface and the alignment precision on the paring surface. In order to increase the alignment accuracy, there are a structure having a spigot portion, a method of providing a taper pin or a cotter block, and these may be appropriately selected.

The shape of the gate for introducing the resin into the mold may be a pin point gate, a ring gate, a film gate, etc., and may be appropriately selected according to the position of the gate.

As the injection conditions, "high-speed injection technology (injection pressure may be different)" in which the injection speed is made higher, or conversely, the injection speed is reduced as much as possible to reduce the distortion after molding. "Low-speed injection molding" technology, etc. can be appropriately used.

As a molding machine to be used, a small injection molding machine having a very small mold clamping pressure (about 50 t or less) can be used.

A conventionally known hydraulic traverse molding machine, an electric injection molding machine using a servo motor as a drive source, or a hybrid type apparatus using hydraulic / electric type on the injection side / mold clamping side can be used.

A particular point to note in the molding machine is the parallelism between the movable plate and the fixed plate, which are moved by mounting the mold. If this value is bad, the positioning of the mold will decrease, making it unsuitable for precision molding. The value of parallelism is defined by the error in the distance between the quantity plates and should be at least 50 μm, more preferably within 30 μm.

[0026]

EXAMPLES Preferred examples will be described below.

Example 1 A liquid crystal polymer containing 30% by weight of carbon fiber was used to injection-mold a plastic ferrule having a structure as shown in FIG. The injection conditions are shown in "Table 2" below. Also, injection compression is performed from the tip side of the ferrule using an ejector pin to 1500 Kgf / c.
It was carried out at a pressure of m ² for 10 seconds. The characteristics of the obtained molded product are shown in "Table 3".

[0028]

[Table 2]

[0029]

[Table 3]

As can be seen from Table 3, the dimensional conditions applicable to the single mode fiber were satisfied. An optical connector (SC
Type) was assembled and the splice loss and return loss were measured.
The polishing condition was PC polishing.

The results are shown in FIGS. 3 and 4, respectively.
As can be seen from these drawings, the characteristics were sufficient for splicing single mode fibers. In addition, "Table 4" below
The results of various mechanical characteristics and reliability tests are shown in Table 1. In all cases, the target characteristics were satisfied.

[0032]

[Table 4]

Comparative Example 1 A ferrule was prepared in the same manner as in Example 1 except that the liquid crystal polymer containing 30% of glass beads was used instead of the carbon fiber. Regarding the dimensional accuracy, the characteristics were almost the same as those of Example 1, but in the accelerated deterioration test, the splice loss was changed from 0.3 dB to 1.5 dB, and the return loss was 26 d.
It changed from B to 18 dB, and it was found that there was a problem in connection reliability.

[Comparative Example 2] A ferrule was prepared in the same manner as in Example 1 except that the injection compression step was not performed. The obtained ferrule has a sink mark at the tip of the ferrule, and the fiber hole eccentricity is 2 μm.
It became a value of the age.

[0035]

As described above, according to the present invention, since the ferrule is made of the resin composition containing at least the thermotropic liquid crystalline wholly aromatic polyester and the carbon fiber, the ferrule can be used for connecting the single mode fiber. There is an advantage that a plastic ferrule for an optical connector having excellent characteristics, reliability and economy can be obtained.

[Brief description of drawings]

FIG. 1 is a view showing a fitted state of a ferrule in a split sleeve.

FIG. 2 is a sectional view of a plastic ferrule.

FIG. 3 is a graph showing a connection loss characteristic of an optical connector using the plastic ferrule obtained in Example 1.

FIG. 4 is a graph showing return loss characteristics of an optical connector using the plastic ferrule obtained in Example 1.

[Explanation of Codes] 11, 11A, 11B Ferrule 12 Split sleeve 13A, 13B Optical fiber cord 14 Optical fiber core wire guide hole 15 Optical fiber guide hole

Claims (3)

[Claims] 1. A ferrule for an optical fiber connector having an insertion hole for fixing an optical fiber, wherein the ferrule comprises a resin composition containing at least thermotropic liquid crystalline wholly aromatic polyester and carbon fiber. Plastic ferrule for connector. 2. The ferrule for an optical connector according to claim 1, wherein the resin composition contains 10 to 40% by weight of carbon fiber with respect to the thermotropic liquid crystalline wholly aromatic polyester. Plastic ferrule. 3. A method for manufacturing an optical fiber connector ferrule having an insertion hole for fixing an optical fiber, which is manufactured by injection compression molding a resin composition containing at least the thermotropic liquid crystalline wholly aromatic polyester and carbon fiber. A method of manufacturing a plastic ferrule for an optical connector, comprising: