JP2000121872A - Plastic ferrule for optical connector and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thin-diameter plastic ferrule for to be used in an optical connector which has high size precision, high mechanical strength, high connection reliability, and superior economy as a plastic ferrule as an optical connector which is used to connect a single-mode optical fiber. SOLUTION: In this optical connector plastic ferrule which has an optical fiber insertion hole 33 and also has a cylinder part 34 regarding connection of an optical fiber, a hold part 35 for stably holding the cylinder part 34 and a coated optical fiber guide hole 32 into which the optical fiber is inserted, the length 33a of the optical fiber insertion hole 33 is formed to a 5 to 6 mm, and the border part 37 between the cylinder part 34 and hold part 35 is formed not at right angle so as to avoid concentration of stress.

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plastic ferrule for an optical connector and a method of manufacturing the same, and particularly useful for connecting a single mode fiber. 2. Description of the Related Art With the development of optical communication technology, it has become possible to introduce various types of communication services by introducing an optical fiber to each home. To realize such a subscriber communication network, an economical optical connector is required. Conventionally, in order to connect an optical fiber used for optical communication, as shown in FIG. 7, two ferrules 01A and 01B into which an optical fiber is inserted are divided into split sleeves 02A and 01B.
This is done by aligning the inside. In the drawings, reference numerals 03A and 03B indicate optical fiber cords. FIG. 8 is a vertical sectional view showing a ferrule used for such a purpose. As shown in the figure, the ferrule 01 has an optical fiber core wire guide hole 04 and one optical fiber insertion hole 05 at the tip. Further, it has a cylindrical portion 06 directly related to the connection, a holding portion 07 for stably holding the ferrule 01 in the optical connector, and an insertion portion 08 for inserting an optical fiber into the ferrule 01. In the ferrule 01, extremely high dimensional accuracy is required for the amount of eccentricity of the optical fiber insertion hole 05, the outer diameter of the ferrule 01, and the roundness of the outer diameter. [0004] The ferrule 01 according to the prior art cuts ceramics and metal with high precision.
It was produced by polishing. Here, ferrule 0 used for a MU type connector capable of high-density mounting
1 is a commonly used SC having an outer diameter of 1.25 mm.
Since the diameter is smaller than that of a connector or the like, there is a problem that a more advanced processing technique is required, the production efficiency is poor, and the production cost is increased. The present invention has been made in view of the above-mentioned problems of the prior art,
Plastic ferrule for optical connector used for connection of single mode optical fiber, high dimensional accuracy,
An object of the present invention is to provide a small-diameter plastic ferrule for an optical connector having excellent mechanical strength, connection reliability, and economy, and a method for manufacturing the same. [0006] The present invention that achieves the above object has the following features. 1) a cylindrical portion having one optical fiber insertion hole for fixing an optical fiber and relating to the connection of the optical fiber, a holding portion for stably holding the cylindrical portion in the optical connector, and In a plastic ferrule for an optical connector having an optical fiber core guide hole for inserting an optical fiber, the length of the optical fiber insertion hole is 5 mm or more,
6 mm or less. 2) In the plastic ferrule for an optical connector described in 1) above, the boundary is formed at a non-perpendicular angle so that stress does not concentrate on the boundary between the ferrule cylindrical portion and the holding portion. 3) A cylindrical portion having one optical fiber insertion hole for fixing an optical fiber and directly relating to the connection of the optical fiber, and a holding portion for stably holding the cylindrical portion in the optical connector. And a method of manufacturing a plastic ferrule for an optical connector having an optical fiber core guide hole into which an optical fiber is inserted, wherein the cavity of the mold that does not move with the mold clamping of the mold for forming the ferrule cylindrical portion. In the distal end portion, a small-diameter pin forming the optical fiber insertion hole is provided, and in the cavity of the mold that moves with the mold clamping, the tip portion of the small-diameter pin is closed at the time of mold clamping. In a mold having a pin receiving member having a pin receiving hole, at least the thermotropic liquid crystalline wholly aromatic polyester and the orientation of the thermotropic liquid crystalline wholly aromatic polyester And manufacturing by injection molding a resin composition containing an additive that reduces the viscosity. 4) In the method of manufacturing a plastic ferrule for an optical connector described in 3) above, a mechanism for controlling the flow of resin is provided in a part of the resin flow passage of the mold. 5) In the method of manufacturing a plastic ferrule for an optical connector described in 3) above, the cylindrical center position of the cavity portion that does not move with the mold clamping for forming the ferrule cylindrical portion of the mold is , Being relatively movable with respect to the center position of the small diameter pin forming the optical fiber insertion hole. 6) The method of manufacturing a plastic ferrule for an optical connector described in 3) above, wherein the resin composition is caused to flow into a mold from a resin inflow portion located inside a side surface of the holding portion. To do. DETAILED DESCRIPTION OF THE INVENTION The present inventors have studied the prior art and its problems in detail, and as a result, completed the present invention in the following manner. 1) Reduction of the amount of eccentricity in the mold structure plastic ferrule is the greatest technical problem. The amount of eccentricity depends most on the employed mold structure. 9 and 10 show typical mold structures according to the prior art. In the mold structure 11 shown in FIG. 9, a core pin 12a forming an optical fiber core wire guide hole 04 (see FIG. 8) and an optical fiber insertion hole 05 (see FIG. 8) is provided in the movable mold 13, and the mold is clamped. Thus, the pin is held by the pin receiving portion 16 in the cavity. Here, the tip of the core pin 12a and the pin receiving portion 16 have at least several μm.
m clearance is required. For this reason, the core pin 12a vibrates due to the flow of the resin during molding, and an eccentricity of several μm occurs. In order to solve such a problem, the mold structure 21 shown in FIG. 10 fixes the core pin 26a. As shown in the figure, in this structure, the fixed core pin 26a does not move at the time of molding, and the small-diameter pin 26 does not vibrate. A small number of molded products can be obtained. Here, if the length of the optical fiber insertion hole 05 (see FIG. 8) exceeds 6 mm, the small diameter pin
May be damaged. If it is less than 5 mm, the strength of the boundary 09 (see FIG. 8) where the cylindrical portion 06 (see FIG. 8) and the holding portion 07 (see FIG. 8) of the ferrule 01 (see FIG. 8) intersect at right angles. There is a problem that becomes weak.
This is because stress is concentrated on the boundary 09 when the cylinder 06 and the holding part 07 intersect at a right angle at the boundary 09. This problem is particularly prominent in small-diameter ferrules. In FIG. 9, 12 is a core pin,
Reference numeral 14 denotes a fixed mold, 15 denotes a cavity, 17 denotes a resin inflow portion, 18 denotes a parting line.
2 is a pin catcher, 22a is a core pin holding hole, 23 is a movable mold, 24 is a fixed mold, 25 is a cavity, 27 is a resin inflow section, and 28 is a parting line. In order to prevent the strength of the boundary portion between the cylindrical portion and the holding portion of such a small diameter ferrule from decreasing, the boundary portion 37 of the ferrule 31 is inclined as shown in FIG.
The boundary portion 37 may be made non-perpendicular to avoid stress concentration and increase the mechanical strength. However, when the length 33a of the optical fiber insertion hole 33 is less than 5 mm, the cylindrical portion 34 is provided. The thickness of the resin at the boundary 37 between the metal and the holding portion 35 becomes thin, and it becomes impossible to obtain sufficient mechanical strength.
In FIG. 1, reference numeral 32 denotes an optical fiber core wire guide hole, and reference numeral 36 denotes an insertion portion. After the ferrule is attached with the optical fiber,
Although it is inserted into the plug and attached, if the clearance between the plug and the holding portion is small and the resin inflow portion (gate) is located on the holding side surface, post-processing after gate cutting is required. However, as shown in FIG. 2, the plastic ferrule molded by positioning the gate position 39 inside the side surface of the holding portion 35 can eliminate the post-processing step after the gate cut, and can be economically manufactured. Becomes In the figure, the same parts as those in FIG. Reference numeral 38 denotes a runner. By using the mold structure 21 shown in FIG. 10, a small-diameter plastic ferrule having an eccentricity of 1 μm or less having sufficient mechanical strength can be economically manufactured. Fixed core pin 26a
Since a gap of several μm is required between the tip of the pin catcher 22 and the pin catcher 22, the resin wraps around during molding to generate burrs, and the continuous optical fiber guide hole 04 (see FIG. 8) and the optical fiber insertion hole 05 (see FIG. 8) cannot be formed. Such a burr problem can be solved by selecting the molding material described below. 2) Selection of molding material In molding technology, selection of a molding material is the most important issue. For example, when a thermosetting resin such as a phenol resin or an epoxy resin is used, a mold structure 2 shown in FIG.
The above-mentioned burrs are particularly remarkably generated in No. 1 and post-processing is required, and the purpose of obtaining an economical ferrule cannot be realized. Since the thermoplastic resin has a high viscosity at the time of melting, it is considered to be advantageous for the burr problem. As a result of examining various thermoplastic resins, it has been found that, when the thermotropic liquid crystalline wholly aromatic polyester is used, there is no problem of burr generation and the roundness and cylindricity of 1 μm or less shown in Table 1 can be realized. [Table 1] The liquid crystal polymer (LCP) generally exhibits liquid crystallinity in a molten state, and therefore has extremely good fluidity during molding. Therefore, the transferability of the resin to the mold is good, and high dimensional accuracy is realized. Also, during molding, the small diameter pin 26
a (see FIG. 10), and the length 33a of the optical fiber insertion hole 33 (see FIG. 1) can be reduced.
Can be prevented from being bent or bent even when the diameter of the pin 26a is about 6 mm. On the other hand, since the viscosity largely depends on the shear stress, it flows into the mold and rapidly solidifies when the flow stops. For this reason, even if there is a gap of several μm between the tip of the small diameter pin 26a and the pin catcher 22, the resin is prevented from wrapping around, and the problem of burr generation does not occur. As shown in Table 2, the liquid crystal polymers can be conveniently classified into three types according to their deflection temperatures under load. [Table 2] In the present invention, type I having a wholly aromatic structure is used.
And a type II structure. This is because the resin having the type III structure has poor heat resistance and is inferior in various reliability described later. In the present invention, an additive for reducing the orientation of the thermotropic liquid crystalline wholly aromatic polyester is used as an additive for the resin. That is, fibrous additives such as glass fibers and carbon fibers are not used. Specifically, glass beads, quartz beads, graphite, zinc oxide, potassium titanate,
Various inorganic additives such as magnesium oxide, titanium oxide, aluminum oxide, silicon carbide, silicon nitride, graphite, calcium carbide, zinc carbide, and magnesium hydroxide are exemplified. The amount of addition is determined within a range that does not reduce the fluidity of the resin, and is preferably 20% to 70%, more preferably 30% to 60%.
It can be appropriately selected within the range of percentage. 3) Control of the amount of eccentricity By employing the mold structure 21 shown in FIG. 10, fluctuation of eccentricity during molding can be suppressed. However, the absolute value of the eccentric amount is not always zero. In other words, in order to increase the processing accuracy of each mold part as much as possible and to combine the mold parts even if the eccentricity is set to zero as the part level,
A minimum clearance of 1-2 μm is required. Therefore, the amount of eccentricity that can be expected depending on the assembly state of the mold is not always at the zero level, and a certain eccentricity occurs. Therefore, regarding the eccentricity, it is necessary to provide a mechanism for controlling the amount of eccentricity in order to make the present invention more effective. In the present invention, the eccentricity is reduced by using the following two eccentricity adjusting mechanisms. A mechanism for controlling the flow of the resin is provided in a part of the runner, which is the passage of the resin in the mold. Specifically, as shown in FIG.
Can be applied. Here, FIG. 3A shows a state in which the pin 41 is not inserted, and the pin 41 is inserted deeply into the runner 42 in the order of FIGS. 3B and 3C, and the flow of the resin is affected. In this method, the eccentricity can be controlled in a range of ± 3 μm. A mechanism for changing the relative position between the cavity and the core pin is provided. Specifically, in order to fix the position of the core pin and change the position of the cavity, the cavity component 52 is configured as shown in FIG. Here, by changing the thickness of the gauge 51 to be inserted, the position of the cavity center 53 can be changed. ± 10
Eccentricity adjustment is possible in the range of μm. In the present invention, both methods can be used together. Incidentally, in FIG.
Is an adjustment space, and 55 is a mold base. Next, a specific embodiment will be described. A small-diameter plastic ferrule having an outer diameter of 1.249 mm was molded using the injection mold shown in FIGS. 7 and 8. Here, the length of the optical fiber insertion hole is 5.5 mm.
And In the clamped state, a cavity 25 is formed between the movable mold 23 and the fixed mold 24, and a small-diameter pin 26 a of a fixed core pin is fitted into one end of a through hole of the pin catcher 22 and both ends are fitted. Provide support. If the process shifts to the injection step from this state, the molten resin is injected into the cavity 25 from the gate. The resin is divided into both,
The holding portion 35 and the insertion portion 36 (see FIG. 1) of the ferrule 31 (see FIG. 1) are formed by the molten resin filled in the second cavities 25b and 25c.
A cylindrical portion 34 (see FIG. 1) of the ferrule 31 (see FIG. 1) is formed by the molten resin filled in the inside 5a, and an optical fiber insertion hole 33 and an optical fiber core wire guide hole 32 are provided at the center.
(See FIG. 1) is formed. Here, the movable mold 23 and the fixed mold 24 are fixed to a mold clamping machine of an injection molding machine (not shown) via a movable mounting plate 62 and a fixed mounting plate 61, respectively. The following were used as molding agents. 60 parts by weight of wholly aromatic thermotropic liquid crystal polyester (type II) 40 parts by weight of glass beads (average particle diameter 30 μm) 40 parts by weight The injection conditions at this time are shown in Table 3. [Table 3] The plastic ferrule manufactured under the above conditions has the same dimensions as the ferrule for the MU type optical connector, and is applicable to the MU type optical connector. The ferrule used for the MU-type connector is made of ceramic and has high mechanical strength.
Even with such a small outer diameter, sufficient strength can be obtained. on the other hand,
Plastic materials have lower mechanical strength than ceramics, and may have a small outer diameter of 1.249 mm, and may be damaged during polishing, insertion and removal, and the like. On the other hand, the small-diameter plastic ferrule according to the present embodiment can be polished by the same polishing method of the ceramic ferrule, and there is no problem that the ferrule is broken during polishing, and
PC polishing can be used. In addition, 20
Even after repeated insertion / removal of zero times, the boundary between the cylindrical portion 34 (see FIG. 1) and the holding portion 35 (see FIG. 1) is not damaged, and exhibits practically sufficient mechanical strength. By using the eccentricity control of this embodiment,
A plastic ferrule with an eccentricity of 1 μm or less is obtained.
The theoretical connection loss at an eccentricity of 1 μm is about 0.2 dB, and achieves dimensional accuracy applicable to single mode fiber connection. Further, since the gate is located inside the side surface of the holding portion 35 (see FIG. 1), it can be mounted in the plug without performing post-processing after the gate cut. As described in detail with the above embodiments, according to the present invention, the present invention can be used for connecting a single mode optical fiber, and has high dimensional accuracy, mechanical strength, connection reliability, and economy. An excellent small-diameter plastic ferrule can be obtained.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a longitudinal sectional view showing a plastic ferrule according to an embodiment of the present invention. FIG. 2 is an explanatory diagram showing a resin inflow portion of a mold used in the embodiment of the present invention. FIG. 3 is an explanatory view conceptually showing a mechanism for controlling a flow amount of a resin used in the embodiment of the present invention. FIG. 4 is an explanatory view showing a fixed-side mold structure for eccentricity control in the embodiment of the present invention. FIG. 5 is a cross-sectional view showing a main part of a ferrule injection molding die used in the embodiment of the present invention. FIG. 6 is a sectional view showing the entire ferrule injection molding die used in the embodiment of the present invention. FIG. 7 is a vertical cross-sectional view showing a fitting state of a ferrule in a split sleeve. 8 is a vertical sectional view showing the ferrule of FIG. 7 in an extracted and enlarged manner. FIG. 9 is a structural sectional view of a ferrule molding die. FIG. 10 is a structural sectional view of another ferrule molding die. [Description of Signs] 21 Mold structure 22 Pin catcher 23 Movable mold 24 Moving mold 25 Cavity 26 Fixed core pin 26a Small diameter pin 27 Resin inflow section 28 Parting line 31 Ferrule 32 Optical fiber guide hole 33 Fiber Insertion hole 33a Length of fiber insertion hole 34 Cylindrical part 35 Holding part 36 Insertion part 37 Boundary part 38 Runner 39 Gate part 41 Pin 42 Runner 51 Gauge 52 Cavity component 53 Cavity center 54 Adjustment space 55 Mold base 61 Fixed side mounting Plate 62 Moving side mounting plate

Continuation of front page    (72) Inventor Yoshito Shuto             3-19-2 Nishi Shinjuku, Shinjuku-ku, Tokyo Japan             Telegraph and Telephone Corporation (72) Inventor Masayoshi Ohno             3-19-2 Nishi Shinjuku, Shinjuku-ku, Tokyo Japan             Telegraph and Telephone Corporation (72) Inventor Shunichi Higashino             3-19-2 Nishi Shinjuku, Shinjuku-ku, Tokyo Japan             Telegraph and Telephone Corporation (72) Inventor Shinichi Iwano             3-19-2 Nishi Shinjuku, Shinjuku-ku, Tokyo Japan             Telegraph and Telephone Corporation (72) Inventor Makoto Sumita             3-19-2 Nishi Shinjuku, Shinjuku-ku, Tokyo Japan             Telegraph and Telephone Corporation F-term (reference) 2H036 QA18 QA20

Claims (1)

Claims: 1. An optical fiber insertion hole for fixing an optical fiber, and a cylindrical portion related to the connection of the optical fiber, and the cylindrical portion stably held in an optical connector. A plastic ferrule for an optical connector having a holding portion for inserting the optical fiber and an optical fiber guide hole for inserting the optical fiber, wherein the length of the optical fiber insertion hole is 5 mm or more and 6 mm or less. For plastic ferrule. 2. The plastic ferrule for an optical connector according to claim 1, wherein the boundary is formed at a non-perpendicular angle so that stress is not concentrated on a boundary between the ferrule cylindrical portion and the holding portion. A plastic ferrule for an optical connector. 3. A cylindrical portion having one optical fiber insertion hole for fixing an optical fiber and directly connected to the connection of the optical fiber, and a holding portion for stably holding the cylindrical portion in the optical connector. And a method of manufacturing a plastic ferrule for an optical connector having an optical fiber core guide hole into which an optical fiber is inserted, wherein a cavity of the mold that does not move with the mold clamping of the mold for forming the ferrule cylindrical portion is formed. In the distal end portion, a small-diameter pin forming the optical fiber insertion hole is provided, and in the cavity of the mold that moves with the mold clamping, the tip portion of the small-diameter pin is closed at the time of mold clamping. At least the thermotropic liquid crystalline wholly aromatic polyester and the orientation of the thermotropic liquid crystalline wholly aromatic polyester are placed in a mold having a pin receiving member having a pin receiving hole. Method of producing an optical connector plastic ferrule, characterized by prepared by molding a resin composition, an injection comprising a additive to Gensa. 4. A method for manufacturing a plastic ferrule for an optical connector according to claim 3, wherein a mechanism for controlling the flow of resin is provided in a part of the resin flow passage of the mold. Manufacturing method of plastic ferrule for connector. 5. The method of manufacturing a plastic ferrule for an optical connector according to claim 3, wherein the center of the cylindrical portion of the cavity portion does not move with the mold clamping for forming the ferrule cylindrical portion of the mold. The position is
A method of manufacturing a plastic ferrule for an optical connector, wherein said plastic ferrule is movable relative to a center position of said small diameter pin forming said optical fiber insertion hole. 6. The method of manufacturing a plastic ferrule for an optical connector according to claim 3, wherein the resin composition is caused to flow into a mold from a resin inflow portion located inside a side surface of the holding portion. A method for producing a plastic ferrule for an optical connector, characterized by comprising: