Fiber optic connector ferrule and method of making the same

Details Fiber optic connector ferrule and method of making the same Fiber optic connector ferrule and method of making the same

1999-10-05

2001-07-24

Palmer, Phan T. H. (Department: 2874)

Optical waveguides

With disengagable mechanical connector

Optical fiber/optical fiber cable termination structure

C385S060000, C385S072000, C264S001250

Reexamination Certificate

active

06264375

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a fiber optic connector ferrule for arranging optical fibers, and a method of making the same.
2. Related Background Art
In general, when optical fiber ribbons are to be connected to each other, the coating is removed from an end portion of optical fiber ribbons so as to expose each optical fiber, and a fiber optic connector ferrule made of a synthetic resin for arranging the optical fibers is attached to this end portion, thereby establishing the connection. The connector ferrule is used for accurately arranging the optical fibers.
FIG. 11
shows the configuration of a typical fiber optic connector ferrule manufactured to JIS C 5981.
The fiber optic connector ferrule
102
shown in
FIG. 11
has a plurality of parallel fiber-arranging holes
120
for arranging the respective optical fibers therewithin. Disposed on the inside or the fiber insertion side of each fiber-arranging hole
120
is a tapered portion
121
whose inside diameter gradually increases so as to continue to a groove portion
122
. The connector ferrule
102
also has an open portion
123
used for receiving an adhesive for securing an optical fiber ribbon
103
(see FIGS.
13
and
14
), a pin hole
124
into which a guide pin is inserted at the time of connecting with the other fiber optic connector ferrule to be paired.
While the connector ferrule
102
is being molded by transfer molding or injection molding, each fiber-arranging hole
120
is formed by an axially-slidable mold pin
101
(see
FIG. 12
) disposed within a mold (not shown) adapted to open vertically. For easier understanding of the structure, only two mold pins
101
are shown in FIG.
12
. Each mold pin
101
is a round pin having a circular cross section, and is constituted by a first columnar portion
101
a
, a second columnar portion
101
c
having an outside diameter greater than that of the first columnar portion
101
a
, and a tapered portion
101
b
connecting the first and second columnar portions
110
a
,
101
c
, all of which are concentric. The mold pins
101
are held by holding members
113
on the proximal end side thereof. At this time, a plurality of mold pins
101
are accurately positioned by V-shaped grooves
114
of one of the holding members
113
.
SUMMARY OF THE INVENTION
When the connector ferrule
102
is molded by use of the mold pins
101
, a certain extent of thickness H is necessary in the holding member
113
on the V-shaped groove
114
side since the mold pins
101
are held by the V-shaped grooves
114
. Then, since the connector ferrule
102
is formed while the holding members
113
are being inserted into the mold, a step may be formed behind the groove portions
122
, i.e., further on the fiber insertion side, as shown in FIG.
13
.
Consequently, as shown in
FIG. 13
, when an optical fiber ribbon
103
is inserted into the connector ferrule
102
, coated portion
131
of the optical fiber ribbon
103
may not be supported from the lower side, whereby optical fibers
130
in the optical fiber ribbon
103
may bend. This case has been problematic in that transmission characteristics deteriorate due to a bending stress and, at worst, the optical fibers
130
may break while being used. Similar problems may also occur in the case where a fiber optic connector ferrule without the open portion
123
is manufactured.
Also, although not usually done, the coated portion
131
may be inserted to the inner end of the connector ferrule
102
in order to be supported from the lower side as shown in FIG.
14
. Though the coated portion
131
is positioned on the groove portion
122
in this case, the lower face of the coated portion
131
would align with the axis of the optical fiber
130
within the fiber-arranging hole
120
. As a consequence, the optical fibers
130
may also bend. For eliminating the above-mentioned problems and stably connecting optical fiber ribbons
103
to each other, there has been a demand for further improvements in making a fiber optic connector ferrule which can securely hold not only the optical fibers
130
but also the coated portion
131
.
Therefore, it is an object of the present invention to provide a fiber optic connector ferrule which prevents transmission characteristics of an optical fiber from deteriorating and has no danger of damaging the optical fiber, and a method of making the same.
For achieving the above-mentioned object, the method of making a fiber optic connector ferrule in accordance with the present invention is a method of making a fiber optic connector ferrule in which one or a plurality of fiber-arranging holes for arranging and securing respective optical fibers are provided, the method comprising the steps of: (1) disposing one or a plurality of mold pins each having a columnar portion formed on a distal end side thereof and a prismatic portion, disposed on a proximal end side thereof, having substantially a quadrangular cross section, with side faces of the prismatic portions being in contact with each other, within a mold such that each mold pin is slidable in an axial direction of the columnar and prismatic portions; and (2) filling the mold with a resin, and axially pulling off each mold pin after the resin is cured, thereby each of fiber-arranging holes being formed and a coating-accommodating portion for mounting a coated portion of the respective optical fibers being formed.
In the fiber optic connector ferrule made by this method, the coating-accommodating portion can maintain the axis of the optical fiber substantially straight to the front end in the respective fiber-arranging hole. This fiber optic connector ferrule securely holds the optical fibers at the portion that are likely to bend, i.e., the area ranging from the front end of the coated portion to the end of the optical fibers.
Also, since the proximal end side of the mold pin is formed as the prismatic portion, it is advantageous in that no burrs would occur on the insertion side of the coating-accommodating portion in the accomplished fiber optic connector ferrule, whereby the optical fiber can be prevented from being damaged by burrs, and that the positioning of the optical fibers in the optical axis direction can be achieved without being prevented by burrs. Conventionally, since the mold pin
101
(see
FIG. 12
) having a circular cross section has been used, there have been cases where a resin immerses into the V-shaped groove
114
. Such immersing resin forms burrs on the insertion side of the groove portion
122
.
At least one side edge of the prismatic portion may be chamfered along the lengthwise direction of the mold pin, and this chamfered portion is disposed, when the mold pins are arranged within the mold, at a part forming the coating-accommodating portion. As a consequence, in the molded fiber optic connector ferrule, the coating-accommodating portion is provided with a guiding projection for guiding the optical fiber to be inserted into the fiber-arranging hole. As a result, a workability of attaching the optical fiber ribbon to the fiber optic connector ferrule will be improved.
It is preferred that a tapered portion whose outside diameter gradually expands in a direction away from the columnar portion is disposed between the columnar portion and the prismatic portion. This tapered portion forms a fiber-guiding portion, at the insertion-side end portion of the fiber-arranging hole in the fiber optic connector ferrule, for guiding the optical fiber to be inserted into the fiber-arranging hole. As a result, when the optical fiber is to be attached to the fiber optic connector ferrule, the optical fiber can be smoothly inserted into the fiber-arranging hole without being damaged. When the tapered portion is used together with the above-mentioned chamfered portion forming the guiding projection, the operation of attaching the optical fiber to the fiber optic connector ferrule can further be smoothed.
The upper or lower side part of the prismatic portion may be provided with a predetermined

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