Optical waveguides – With disengagable mechanical connector – Structure surrounding optical fiber-to-fiber connection
Reexamination Certificate
2000-03-28
2002-12-10
Spyrou, Cassandra (Department: 2872)
Optical waveguides
With disengagable mechanical connector
Structure surrounding optical fiber-to-fiber connection
C385S033000
Reexamination Certificate
active
06491443
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a sleeve for an optical connector which is arranged between an optical fiber and an optical element module and serves to transmit light emitted from one to the other. The present invention also relates to a receptacle constituting an optical connector together with an optical plug and provided with the sleeve for the optical connector.
2. Description of the Related Art
A typical sleeve for an optical connector (hereinafter referred to as “sleeve”) located between the optical fiber and the optical element module is disclosed in J-UM-
6-33443
by the inventors of the invention.
FIG. 12
is a horizontal sectional view of a conventional optical connector, and
FIG. 13
is a horizontal sectional view of the receptacle shown in FIG.
12
. In
FIGS. 12 and 13
, reference numeral
1
denotes a sleeve, and reference numeral
2
denotes an optical connector.
Sleeves
1
are attached to a receptacle (connector on the side of a device) constituting the optical connector
2
. These sleeves
1
are arranged between optical element modules
4
(consisting of a light receiving element module and a light emitting element module) and a pair of optical fibers
6
which are attached to an optical plug (connector on the side of the optical fiber) constituting the optical connector
2
, respectively. The sleeves
1
serve to make an optical connection between the optical element modules
4
and optical fibers
6
.
A more detailed explanation will be given of the optical connector
2
as well as the sleeves
1
.
The optical connector
2
includes the receptacle
3
and the optical plug
5
fit into the receptacle
3
.
The receptacle
3
, as shown in
FIGS. 12 and 13
, has a housing
7
made of synthetic resin and having a pair of housing chambers
8
. The housing chambers
8
each houses an optical element module
4
which is supported by a back sheet
9
made of elastic material such as rubber. The rear of the housing chambers
8
is covered with a cap
10
. The receptacle
3
has a pair of receiving cylinders
12
which are arranged in front of the housing chambers
8
, and extended forward so as to accord with the respective axes of lenses
11
. The sleeves
1
are inserted in the receiving cylinders
12
, respectively.
The sleeve
1
can be formed by grinding both end surfaces of the optical fiber composed of a core and a cladding (not shown) after it has been secured to a cylindrical holder
14
.
On the other hand, the optical plug
5
fit in the receptacle
3
, as seen from
FIG. 12 and 14
which is a horizontal sectional view of the optical plug shown in
FIG. 12
, includes a pair of ferule assemblies
15
each covering the optical fiber with its end face exposed at the tip of the assembly, a plug housing
17
with a pair of cylindrical partitions
16
for protecting the ferule assemblies
15
housed therein, a spring cap
17
fit over the plug housing
18
and a boot
19
fit over the rear of the spring cap
18
.
The plug housing
17
has shoulders
17
a
each to be engaged with a flange
15
a
formed on the rear half of the periphery of each ferule assembly
15
. The ferule
15
is urged forward normally by a spring
20
which is located between the flange
15
a
and inner cylinder
18
a
of the spring cap
18
.
As shown in
FIG. 14
, by engagement between the flange
15
a
and shoulder
17
a
, the tip A of the ferule assembly is always pulled more internally than the tip of the plug housing
17
. The tip A of the ferule assembly
15
corresponds to the light-incident/emitting face of the optical fiber
6
.
As regards the above configuration, referring to
FIG. 12
, an explanation will be given of connection between the receptacle
3
and the optical plug
5
.
When the receptacle
3
is fit over the optical plug
5
, the receiving cylinders
12
advance into the plug housing
17
, and the ferule assemblies
15
also advance into the receiving cylinders
12
. At this time, the ferule assembly
15
is brought into contact with the tip of the receiving cylinder
12
and a suitable contact pressure is kept by the elastic force by the spring
20
.
In this state, the tip A (
FIG. 14
) and sleeve
1
are arranged with a minimum gap (not shown) kept. Therefore, the loss of the gap can be minimized.
The prior art described above, in which the sleeve
1
has an optical fiber
13
and is formed in a ring-shape, presents the following problems.
As shown in
FIG. 15
, with respect to a light beam c
1
(within a range of a critical angle) which is propagated through an optical fiber
6
and sleeve
1
along an optical path indicated by arrow in
FIG. 15
, when the light receiving face
4
a
of the light receiving element module
4
is smaller than the light-emitting face
1
a
of the sleeve
1
(the width of the module
4
is smaller by d than that of the optical fiber
13
on the one side with respect to a center line), the light beam c
1
may not be received by the light receiving element module
4
. This is one of causes reducing the transmission efficiency.
Although not shown, when the light beam emitted from the light emitting face (not shown) of the light emitting element module is diffusive-LED light, part of the light cannot enter the sleeve
1
. This is one cause reducing the transmission efficiency. Even if such a light beam is incident on the sleeve
1
, it becomes a light beam c
2
out of the critical angle range. Therefore, the light c
2
does not reflect totally but permeates through the sleevel. The light c
2
will be not be propagated.
Further, the prior art intends to minimize the gap loss to improve the transmission efficiency. However, a slight gap between the optical fiber
6
and sleeve
1
and axis displacement therebetween may influence the transmission efficiency.
There is also a problem relative to productivity of the sleeve
1
as well as the problem of the transmission efficiency.
Specifically, as described above, in order to improve the optical characteristic (transmission efficiency of light) of the sleeve
1
, after the optical fiber
13
is inserted in and attached to the holder
14
, both end surfaces of the optical fiber
13
as well as the holder
14
must be ground using abrasives of plural grain sizes. Thus, production of the sleeve
1
requires many manufacturing steps inclusive of necessary previous steps of making its components, and is inferior in productivity.
Further, production of the sleeve
1
, which requires monitoring the production status of its components and testing the size, is involved with complicate production management. This deteriorates the productivity of the sleeve and increases the production cost.
It is also demanded to assemble the sleeve with a receptacle smoothly.
SUMMARY OF THE INVENTION
A first object of the invention is to provide a sleeve for an optical connector, capable of improving the transmission efficiency and improving the productivity to reduce the production cost.
A second object of the invention is to provide an improved receptacle which can be smoothly assembled with the sleeve.
In order to attain the first object, in accordance with the invention, there is provided a sleeve comprising: a core of transparent synthetic resin; and a cladding of transparent synthetic resin and having a smaller refractive index than the core, wherein the core includes an optical waveguide extending in an optical axial direction with an outer wall to taper in a conical shape and a lens formed at the large diameter end of the waveguide, the lens receiving light and converging it, and the cladding is formed concentrically with the core in intimate contact with an side wall of the core.
In this configuration, the light outgoing from one of the optical fiber and optical element module is received and converged by the lens. The light is propagated through the waveguide while repeating total reflection and gradually converged. Thus, the transmission efficiency of light is improved.
The discrepancy of the optical axis from the sleeve can be relaxed by the lens. The out
Matsushita Junichi
Serizawa Naoshi
Armstrong Westerman & Hattori, LLP
Cherry Euncha
Spyrou Cassandra
Yazaki -Corporation
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