JP2001021757A - Plastic ferrule - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance molding dimension precision of a plastic ferrule for an optical connector to reduce relative eccentricity between fellow ferrules butted against each other inside a split sleeve. SOLUTION: This plastic ferrule 10 is provided with a strand holding part 18 having the first penetrated through hole 16 of a small diameter opened in a front end face 12 to have a common center axial line, and a core wire holding part 22 having the second penetrated through hole 20 of a large diameter arranged adjacently to the first hole 16 to have the common center axial line. The core wire holding part 22 is provided with a centering portion 32 having a cylindrical outer circumferentail face 32a with the common center axial line between a flange 28 and the strand holding part 18. The centering part 32 has a substantially uniform wall-thickness ranging over its axis-directional full length. The holding part 18 has a cylindrical outer circumferential face 18a with the common center axial line having a diameter smaller than that of the centering prtion 32, ranging over its full length of the first through hole 16. A wall-thickness equal or thinner to/than that of the centering portion 32 is imparted in the strand holding part 18.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plastic ferrule for an optical connector.

[0002]

2. Description of the Related Art In recent years, in the field of optical connectors, a plastic ferrule integrally formed of a resin material has been developed from the viewpoint of promoting mass production and cost reduction. Generally, the plastic ferrule is concentrically disposed adjacent to the first through-hole in the cylindrical through-hole holding portion for accommodating the uncoated optical fiber in the first through-hole opened at the front end face in the axial direction. A cylindrical core holding portion for accommodating the coated optical fiber core is provided in the second through hole having a diameter larger than the first through hole, and the element holding portion and the core holding portion are formed by molding. It is formed by integrally molding a resin material having excellent properties through an injection molding process and a transfer molding process.

[0003] In this type of plastic ferrule, it is an issue how to improve the dimensional accuracy and mechanical strength of a molded product to a level at which there is no practical problem. An optical connector usually includes a cylindrical positioning member called a split sleeve, and a pair of ferrules each having an optical fiber attached thereto are aligned in the axial direction in one split sleeve and then butted to connect the optical fibers to each other. Can be connected concentrically. At this time, in order to reduce the relative eccentricity of the pair of ferrules in the split sleeve as much as possible,
It is necessary to improve the dimensional accuracy (outer diameter dimensional tolerance, cylindricity, roundness, eccentricity of the first through hole, etc.) of the ferrule.
In particular, in an optical connector used for connecting a single mode optical fiber, the ferrule is required to have extremely high dimensional accuracy of the order of 1 μm. For the purpose of ensuring such a high level of molding dimensional accuracy, various compositions suitable as resin materials for ferrules have been conventionally proposed (see, for example, JP-A-8-59965 and JP-A-10-293232). ).

[0004]

As disclosed in the above publications, the conventional plastic ferrule has a cylindrical outer peripheral surface continuously formed on both the wire holding portion and the core wire holding portion. Then, the ferrule is centered by bringing the cylindrical outer peripheral surface into contact with the inner surface of the split sleeve under pressure. Under such a configuration, the thickness of the ferrule inevitably changes in a region where the core holding portion having the large-diameter second through hole shifts to the wire holding portion having the small-diameter first through hole. . Then, due to the change in the thickness, there is a tendency that imbalance occurs in the molding shrinkage of the resin material of the ferrule. As a result, in the conventional plastic ferrule, regardless of the composition of the resin material, there is a concern that the various dimensional accuracy described above is likely to be deteriorated particularly in a region near the front end in the axial direction of the ferrule. Such a deterioration in the dimensional accuracy of the ferrule can be a factor that increases the relative eccentricity of the ferrule of the connection partner supported by the split sleeve.

SUMMARY OF THE INVENTION An object of the present invention is to provide a plastic ferrule for an optical connector, which has a shape capable of relatively easily ensuring a high level of molding dimensional accuracy, and allows relative eccentricity with respect to a mating ferrule connected within a split sleeve. An object of the present invention is to provide a plastic ferrule that can be reduced as much as possible.

[0006]

According to a first aspect of the present invention, there is provided an optical fiber device comprising: a first through hole having a small diameter which is opened at a front end face in an axial direction; A wire holding portion for accommodating the wire, and a core wire holding portion having a large-diameter second through hole concentrically arranged adjacent to the first through hole and accommodating the optical fiber core wire in the second through hole. A plastic ferrule in which the strand holding portion and the core holding portion are integrally formed from a resin material, wherein the core holding portion includes a centering portion having a cylindrical outer peripheral surface; The wire holding portion has a substantially uniform thickness over the entire length in the axial direction, and the wire holding portion has an outer peripheral contour shape reduced in the radial direction from the centering portion over the entire length of the first through hole. Provide a plastic ferrule with features.

According to a second aspect of the present invention, there is provided the plastic ferrule according to the first aspect, wherein the wire holding portion has a cylindrical outer peripheral surface having a diameter smaller than that of the centering portion. According to a third aspect of the present invention, in the plastic ferrule according to the second aspect, the cylindrical outer peripheral surface of the centering portion and the cylindrical outer peripheral surface of the element wire holding portion are provided via an annular shoulder surface that expands in a radial direction. Provide a plastic ferrule to be connected.

According to a fourth aspect of the present invention, in the plastic ferrule according to the third aspect, the annular shoulder surface is formed of the first ferrule.
A plastic ferrule formed at a position corresponding to a boundary between a through hole and a second through hole is provided. According to a fifth aspect of the present invention, there is provided the plastic ferrule according to the first aspect, wherein the wire holding portion has a truncated conical outer peripheral surface whose diameter is continuously reduced toward the front end surface.

According to a sixth aspect of the present invention, in the plastic ferrule of the fifth aspect, the cylindrical outer peripheral surface of the centering portion and the truncated conical outer peripheral surface of the wire holding portion are conical from the cylindrical outer peripheral surface. Provided is a plastic ferrule connected via a truncated conical outer peripheral portion of a core wire holding portion that continuously reduces in diameter toward the trapezoidal outer peripheral surface. According to a seventh aspect of the present invention, there is provided the plastic ferrule according to any one of the first to sixth aspects, wherein the wire holding portion has a thickness smaller than a thickness of the centering portion. .

[0010]

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings. In the drawings, the same or similar components are denoted by common reference numerals. FIG. 1 is a sectional view of a plastic ferrule 10 according to a first embodiment of the present invention, FIG. 2 is a front view of the plastic ferrule 10, and FIG. 3 is an end view of the plastic ferrule 10.

The plastic ferrule 10 is a hollow cylindrical integrally molded product having a center axis 10a, an axial front end face 12, and an axial rear end face 14, and has a first axis opening to the front end face 12 sharing the center axis 10a. A wire holding portion 18 having a through hole 16, a second axis which is disposed adjacent to the first through hole 16 while sharing the center axis 10 a, has a larger diameter than the first through hole 16, and opens to the rear end face 14. And a cord holding portion 22 having a through hole 20. The wire holding portion 18 and the core wire holding portion 22 are integrally formed from a resin material having excellent moldability as described later through a well-known resin molding process such as injection molding or transfer molding.

The first through hole 16 of the wire holding portion 18 has a slightly larger diameter than the diameter of the wire (optical fiber wire 26) of the optical fiber core wire 24 (FIG. 4) to be connected. A cylindrical portion 16a and a guide portion 16b concentrically extending rearward in the axial direction of the cylindrical portion 16a and tapering toward the second through hole 20 of the core wire holding portion 22 so as to expand (that is, expand in diameter) and extend. Is provided. Second through hole 2 of core wire holding portion 22
Numeral 0 is a cylindrical hole having a diameter slightly larger than the coating outer diameter of the optical fiber core wire 24 to be connected, and has a front end in the axial direction and a rear end in the axial direction of the guide portion 16b of the first through hole 16. Connected.

The core wire holding portion 22 is provided with a flange 28 protruding radially outward in a substantially disk shape substantially at the center in the axial direction. The flange 28 is provided with a plurality of (four in the figure) rectangular notches 30 at equal intervals in the circumferential direction. Flange 28
Acts to receive an urging force in the optical connector (not shown) forward in the axial direction by a spring. Further, the plurality of notches 30 function as rotary tool receivers for finely adjusting the eccentricity between optical fibers after the optical fibers are connected.

The core holder 22 further includes a centering portion 32 having a cylindrical outer peripheral surface 32a sharing the central axis 10a between the flange 28 and the strand holder 18. Centering portion 32 has a substantially uniform wall thickness over the entire axial length. The wire holding portion 18 is provided with a centering portion 32 of the core wire holding portion 22 over the entire length of the first through hole 16.
The outer peripheral shape is smaller in the radial direction than the outer peripheral shape. That is, the wire holding portion 18 has a smaller diameter than the centering portion 32,
It has a cylindrical outer peripheral surface 18a sharing the central axis 10a. As a result, the wire holding portion 18 is given a thickness less than the thickness of the centering portion 32.

In the illustrated embodiment, the cylindrical outer peripheral surface 32a of the centering portion 32 and the cylindrical outer peripheral surface
Is connected via an annular shoulder surface 34 which extends substantially perpendicularly to the central axis 10a in the radial direction. The annular shoulder surface 34 is formed at a position corresponding to a boundary between the first through hole 16 (guide portion 16 b) of the wire holding portion 18 and the second through hole 20 of the core wire holding portion 22.

As described above, the plastic ferrule 10
Since the centering portion 32 of the core holding portion 22 has a substantially uniform thickness over the entire length in the axial direction, the molding shrinkage of the resin material particularly at the centering portion 32 in the integral molding process from the resin material is reduced. Thus, high dimensional accuracy (outside diameter tolerance of the outer peripheral surface 32a, cylindricity and roundness, eccentricity of the second through hole 20 with respect to the center axis 10a, and the like) can be secured in the centering portion 32. . The wire holding unit 18
Has a thickness equal to or less than the thickness of the centering portion 32, so that the dimensional accuracy of the wire holding portion 18 due to molding shrinkage (the outer peripheral surface 18a
Of the first through-hole 16 with respect to the center axis 10a) is reduced. Therefore, the plastic ferrule 10 as a resin molded product has an eccentric amount of the first through hole 16 of the strand holding portion 18 and a cylindricity and a trueness of the outer peripheral surface 32a of the centering portion 32 which particularly affect the connection loss of the optical fiber. Circularity can be maintained at a high accuracy level on the order of 1 μm applicable to single mode optical fibers.

One mode of use of the plastic ferrule 10 having the above configuration will be described with reference to FIGS. The optical fiber core wire 24 to which the plastic ferrule 10 is attached is prepared such that the resin coating is removed at a predetermined length (about 3 to 5 mm) at the end and the optical fiber wire 26 is exposed. The length of the exposed portion of each optical fiber wire 26 is set slightly longer than the length of the first through hole 16 of the wire holding portion 18 of the ferrule 10. The optical fiber core wire 24 is inserted into the second through hole 20 from the rear end face 14 of the ferrule 10, the exposed optical fiber wire 26 is arranged in the first through hole 16 of the wire holding portion 18, and the coating is performed. A portion near the end of the optical fiber core wire 24 is disposed in the second through hole 20 of the core wire holding part 22. At this time, the optical fiber 26 and the optical fiber 24 are fixed to the first through hole 16 and the second through hole 20 via an adhesive (not shown), respectively. After that, the surplus portion of the optical fiber 26 protruding from the front end face 12 of the ferrule 10 is polished or heated and the end face is processed to complete the mounting.

A pair of optical fiber cores 24 each having a plastic ferrule 10 attached thereto are connected to a split sleeve 3 incorporated in an optical connector (not shown) in the following manner.
6 are interconnected. Each ferrule 10 is arranged at a predetermined position in the split sleeve 36 with the cylindrical outer peripheral surface 32 a of the centering portion 32 of the core wire holding portion 22 being in close contact with the cylindrical inner peripheral surface 36 a of the split sleeve 36. At this time, the split sleeve 36 is expanded by the centering portion 32 of each ferrule 10 to exhibit elastic restoring force, and supports each ferrule 10 at a predetermined position under the pressure. In this state, the front end faces 12 of the two ferrules 10 are aligned with each other in the axial direction and abutted against each other, whereby the optical fiber wires 26 fixedly held by the ferrules 10 are connected to each other.

Here, as described above, the plastic ferrule 10 has a high accuracy, particularly with respect to the amount of eccentricity of the first through hole 16 of the wire holding portion 18 and the cylindricality and roundness of the outer peripheral surface 32a of the centering portion 32. Since the level can be secured, when the pair of plastic ferrules 10 are centered and supported in the split sleeve 36 as described above, the relative eccentricity of the pair of ferrules 10 (that is, the center axis 10a)
) Can be reduced to such an extent that the connection loss of the optical fiber can be maintained at a desired low level.

The plastic ferrule according to the present invention comprises:
It can have various shapes other than the above, which can relatively easily ensure a high level of molding dimensional accuracy. 6 and 7
Shows a plastic ferrule 40 according to a second embodiment of the present invention having such other shapes. The plastic ferrule 40 is the same as the plastic ferrule 1 described above except for the outer peripheral shape of the wire holding portion and the core wire holding portion.
Since it has substantially the same configuration as 0, the corresponding components are denoted by the same reference numerals and description thereof will be omitted.

The plastic ferrule 40 has a first through hole 16 that opens in the front end face 12 while sharing the central axis 40 a.
And a core wire holding portion 44 having the second through hole 20 that opens to the rear end face 14 by sharing the central axis 40a. The core wire holding portion 44 includes a centering portion 46 having a cylindrical outer peripheral surface 46a sharing the central axis 40a between the flange 28 and the wire holding portion 42. The centering portion 46 has a substantially uniform thickness over the entire axial length. Then, the wire holding portion 42 extends over the entire length of the first through hole 16,
The outer peripheral shape is smaller in the radial direction than the outer peripheral shape. That is, the strand holding portion 42 has a truncated cone-shaped outer peripheral surface 42a that continuously extends toward the front end face 12 with a reduced diameter (that is, a reduced diameter dimension). As a result, the wire holding portion 42 is given a thickness less than the thickness of the centering portion 46.

In the illustrated embodiment, the cylindrical outer peripheral surface 46a of the centering portion 46 and the truncated conical outer surface 42 of the strand holding portion 42
a is a cylindrical outer peripheral surface 46a to a frustoconical outer surface 42a
Are connected to each other via a truncated cone-shaped outer peripheral surface portion 44a of a core wire holding portion 44 which continuously extends in a reduced diameter toward. In this case, the truncated cone-shaped outer peripheral surface 42a of the strand holding portion 42 and the truncated cone-shaped outer peripheral portion 44a of the core wire holding portion 44 are inclined at the same angle with respect to the center axis 40a to form a smooth tapered surface. I do. Further, the cylindrical outer peripheral surface 4 of the core wire holding portion 44
A boundary line 48 between 6 a and the truncated cone outer peripheral surface portion 44 a corresponds to a boundary between the first through hole 16 (guide portion 16 b) of the wire holding portion 42 and the second through hole 20 of the core wire holding portion 44. It is formed at a position slightly closer to the flange 28 from the position.

As described above, the plastic ferrule 40
Since the centering portion 46 of the core holding portion 44 has a substantially uniform thickness over its entire length in the axial direction, the molding shrinkage of the resin material particularly at the centering portion 46 in the integral molding process from the resin material is reduced. Therefore, high dimensional accuracy (outside diameter tolerance of the outer peripheral surface 46a, cylindricity and roundness, the amount of eccentricity of the second through hole 20 with respect to the center axis 40a, etc.) can be secured in the centering portion 46. . The wire holding unit 42
Has a thickness equal to or less than the thickness of the centering portion 46, so that the dimensional accuracy of the wire holding portion 42 due to molding shrinkage (the outer peripheral surface 42a
Of the first through-hole 16 with respect to the central axis 40a). Therefore, plastic ferrule 4 as a resin molded product
0 is the amount of eccentricity of the first through hole 16 of the wire holding portion 42 and the centering portion 4 which particularly affect the connection loss of the optical fiber.
6 can maintain the cylindricity and roundness of the outer peripheral surface 46a at a high accuracy level on the order of 1 μm.

If a pair of optical fiber cores 24 each having a plastic ferrule 40 attached thereto are connected to each other by the method already described with reference to FIGS.
When the pair of ferrules 40 are centered and supported in the split sleeve 36, the relative eccentricity of the pair of ferrules 40 (i.e., the displacement of the center axis 40a) can be maintained at a desired low level of the optical fiber connection loss. To the extent possible.

In addition, as shown in FIG. 8A, the annular shoulder surface 34 of the plastic ferrule 10 is moved from a position corresponding to the boundary between the first through hole 16 (guide portion 16b) and the second through hole 20 from the position corresponding to the boundary. As shown in FIG. 8B, the shape is arranged at a position slightly close to the flange 28 (FIG. 1) (that is, the cylindrical outer peripheral surface 32a of the centering portion is reduced).
The boundary line 48 of the plastic ferrule 40 is disposed at a position corresponding to the boundary between the first through hole 16 (guide portion 16b) and the second through hole 20 (that is, the truncated cone-shaped outer peripheral surface portion 44a of the core wire holding portion). Figure 8)
As shown in (c), a shape or the like in which the outer peripheral surface of the wire holding portion is constituted by a combination of the cylindrical outer peripheral surface 18a and the truncated conical outer surface 42a can be implemented. In either case, the cylindrical outer peripheral surfaces 32a, 46 of the centering portions 32, 46
In order to achieve a sufficient centering function in the split sleeve 36 (FIG. 4), the front ends 12a of the ferrules 10, 40 are used.
At least 2/3 of the length of the part from
Preferably, it has a length of the order of magnitude.

The plastic ferrule according to the present invention comprises:
It can be manufactured from various resin materials excellent in moldability, such as various engineering plastics. In particular,
A material containing a cyclic polyolefin resin (for example, “ZEONEX (trade name)” of Nippon Zeon Co., Ltd.) from the viewpoint of low hygroscopicity and a reduction in shape change over time as much as possible.
It is advantageous to make from Furthermore, by mixing additives such as glass beads into such a material,
The orientation at the time of molding can be adjusted.

[0027]

As is apparent from the above description, the plastic ferrule for an optical connector according to the present invention is particularly suitable for the first wire holding portion which affects the connection loss of an optical fiber.
With respect to the amount of eccentricity of the through hole and the cylindricity and roundness of the outer peripheral surface of the centering portion, the molding dimensional accuracy can be maintained at a high level. Therefore, according to the present invention, the relative eccentricity of a pair of ferrules abutted in the split sleeve of the optical connector can be reduced as much as possible, and the connection loss of the optical fiber can be maintained at a desired low level. Become.

[Brief description of the drawings]

FIG. 1 is a sectional view of a plastic ferrule according to a first embodiment of the present invention.

FIG. 2 is a front view of the plastic ferrule of FIG.

FIG. 3 is an end view of the plastic ferrule of FIG. 1 as viewed from an arrow III.

FIG. 4 is a sectional view showing a usage form of the plastic ferrule of FIG. 1;

FIG. 5 is a sectional view taken along line VV in FIG. 4;

FIG. 6 is a sectional view of a plastic ferrule according to a second embodiment of the present invention.

FIG. 7 is a front view of the plastic ferrule of FIG. 6;

FIGS. 8A to 8C are cross-sectional views showing the tip of a plastic ferrule according to various modifications.

[Explanation of symbols]

 10, 40 ... plastic ferrule 12 ... front end face 14 ... rear end face 16 ... first through hole 18, 42 ... strand holding part 20 ... second through hole 22, 44 ... core holding part 24 ... optical fiber core 26 ... Optical fiber 32, 46 ... Centering part 34 ... Circular shoulder surface 36 ... Split sleeve

Claims (7)

[Claims] A first through-hole having a small diameter which is opened at a front end face in an axial direction; a wire holding portion for accommodating an optical fiber in the first through-hole; and a concentrically adjacent to the first through-hole. A second core through-hole having a large diameter disposed therein, and a core holding part for accommodating an optical fiber core in the second through-hole, wherein the strand holding part and the core holding part are made of a resin material. In a plastic ferrule integrally molded from the above, the center wire holding portion has a centering portion having a cylindrical outer peripheral surface, and has a substantially uniform thickness over the entire axial length of the centering portion. The plastic ferrule, wherein the wire holding portion has an outer peripheral shape that is smaller in the radial direction than the centering portion over the entire length of the first through hole. 2. The plastic ferrule according to claim 1, wherein the strand holding portion has a cylindrical outer peripheral surface having a smaller diameter than the centering portion. 3. The plastic ferrule according to claim 2, wherein the cylindrical outer peripheral surface of the centering portion and the cylindrical outer peripheral surface of the wire holding portion are connected via a radially extending annular shoulder surface. 4. The plastic ferrule according to claim 3, wherein the annular shoulder surface is formed at a position corresponding to a boundary between the first through hole and the second through hole. 5. The plastic ferrule according to claim 1, wherein the wire holding portion has a truncated cone-shaped outer peripheral surface whose diameter continuously decreases toward the front end surface. 6. The cylindrical outer peripheral surface of the centering portion and the truncated conical outer surface of the strand holding portion continuously decrease in diameter from the cylindrical outer peripheral surface toward the truncated conical outer peripheral surface. 6. A connection via a truncated conical outer peripheral portion of the core wire holding portion.
Plastic ferrule described in. 7. The plastic ferrule according to claim 1, wherein the wire holding portion has a thickness smaller than a thickness of the centering portion.