Optical waveguides – With optical coupler – Input/output coupler
Reexamination Certificate
2000-11-30
2002-09-17
Kim, Ellen E. (Department: 2874)
Optical waveguides
With optical coupler
Input/output coupler
C385S093000
Reexamination Certificate
active
06453091
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to an optical system unit for optical transceiver and particularly an optical system unit for optical transceiver arranged of receptacle type for coupling with a plurality of optical fibers and transmitting and receiving optical signal over the optical fibers.
BACKGROUND OF THE INVENTION
It is contemplated that an optical system unit for optical transceiver for coupling with a plurality of optical fibers and transmitting and receiving optical signals over the optical fibers is equivalent to a connection hub (a cable coupler) for coupling a group of LAN (local area network) cables for a local network such as in an office.
Any LAN cable for transmission of electric signals can be joined at one end to a relatively smaller connector and also can transmit and receive a signal over a single line. Accordingly, the hub for coupling the LAN cables for electric signals is common available of a compact size.
On the contrary, a conventional optical system unit for optical transceiver is designed having a desired number of connectors, each connector joined with a fiber optic cable accommodating a transmission optical fiber and a fiber optic cable accommodating a reception optical fiber.
FIG. 9
schematically illustrates a primary part of such a conventional optical system unit for optical transceiver. The conventional optical system unit for optical transceiver
101
may be coupled with two or more connectors
102
. The connector
102
is joined with one end of a transmission fiber optic cable
103
and one end of a reception fiber optic cable
104
. The optical system unit for optical transceiver
101
includes a transmission lens
107
located opposite to and spaced by a certain distance from the end of a transmission optical fiber
106
accommodated in the transmission fiber optic cable
103
of the connector
102
. Similarly, it includes a reception lens
109
located opposite to and spaced by a certain distance from the end of a reception optical fiber
108
accommodated in the reception fiber optic cable
104
. Provided on the other side of the lenses
107
and
109
opposite to the connector
102
side is a lead frame
111
. A light emitting diode
112
and a photo diode
113
are mounted on the lead frame
111
to face the transmission lens
107
and the reception lens
109
respectively.
In
FIG. 9
, the connector
102
is illustrated as a single unit. It is understood that the optical system unit
101
for optical transceiver when coupled with two or more of the connectors
102
includes a corresponding number of such optical systems.
As the connector
102
is joined with the two fiber optic cables
103
and
104
, the conventional optical system unit for optical transceiver
101
is relatively large in the overall size. This allows the transmission lens
107
and the reception lens
109
to be used of large size. Also, this permits the light emitting diode
112
and the photo diode
113
to be generously spaced from each other, thus improving the separation between a transmission signal and a received signal.
However, as its connector
102
is large, the conventional optical system unit for optical transceiver
101
becomes bulky in the dimensions. As compared with the LAN cable joined hub as a like unit for transmission and reception of electric signals, the conventional optical system unit for optical transceiver
101
may be too large. It is hence proposed to provide a modified optical system unit for optical transceiver which can be coupled with a smaller connector accompanied with a single fiber optic cable for transmission and reception of optical signals.
FIG. 10
is an enlarged view showing schematically a modified optical system unit for optical transceiver coupled with one end of the fiber optic cable. The fiber optic cable
121
includes a transmission optical fiber
122
and a reception optical fiber
123
joined closely to each other by a distance L. The distance L may be as short as 0.75 mm. As a result, a connector
124
joined with the fiber optic cable
121
can be decreased to a size equal to that of the common LAN cable connector for electric signals. Consequently, the modified optical system unit for optical transceiver
125
coupled with the connector
124
will be minimized in the size.
However, when the distance L between the two optical fibers
122
and
123
is very small, their corresponding lenses
126
and
127
, the light emitting diode
128
. and the photo diode
129
may hardly be aligned with the two optical fibers
122
and
123
. For compensation, a group of mirrors
131
to
134
are utilized to separate the two optical paths
135
and
136
, denoted by the one-dot chain lines, from each other in directions orthogonal to the axes of the optical fibers
122
and
123
as shown in FIG.
10
. Such a technique is disclosed in “Opto-com”, pp. 60, April 1998.
As the modified optical system unit for optical transceiver
125
shown in
FIG. 10
includes the mirrors
131
to
134
for transmitting and receiving a pair of optical signals, its price will unfavorably be increased. Accordingly, some attempts for forming the lenses and the mirrors integrally by molding of an optically transparent material have been proposed. One of the attempts is depicted in the Electric Components & Technology Conference 1998 proceeding, “Low Wave Length Transparent Epoxy Mold Optical Data Link” by Ichiro Tonai et al.
FIG. 11
is a view of the connector coupling end of such a modified optical system unit for optical transceiver described in the above proceeding, seen from the connector side.
FIG. 12
is a cross sectional view of the modified optical system unit for optical transceiver
101
taken along the line A—A of
FIG. 11
vertical to the sheet of paper. As shown in
FIG. 12
, the optical system unit for optical transceiver
141
is coupled with a connector
142
.
The connector
142
shown in
FIG. 12
is joined with a two-core fiber optic cable
145
having a transmission optical fiber
143
and a reception optical fiber
144
. The connector
142
has two M type ferrule positioning holes
146
and
147
provided in the front side thereof. When its M type ferrule positioning holes
146
and
147
are in engagement with a pair of corresponding M type ferrule positioning pins
148
and
149
mounted at the opposite positions on the front side of the optical system unit for optical transceiver
141
, the connector
142
is correctly coupled with the optical system unit for optical transceiver
141
.
The optical system unit for optical transceiver
141
incorporates a resin body
151
in which the two M type ferrule positioning pins
148
and
149
are implanted. In the resin body
151
, each of the opposite position of the transmission optical fiber
143
and the reception optical fiber
144
project hemispherically, and the resin body
151
construct the convex lens
152
and
153
, respectively. The resin body
151
is made of a transparent resin material which is transparent for both a mode of light transmitted to the transmission optical fiber
143
and a mode of light received from the reception optical fiber
144
. Also, a lead frame
155
of a sheet form is embedded in the resin material
151
to extend on a plane orthogonal to the M type ferrule positioning pins
148
and
149
. A light emitting device
156
for emitting light via the lens
152
to the transmission optical fiber
143
is mounted on the lead frame
155
to face the transmission optical fiber
143
. Also, a light receiving device
157
for receiving light transmitted via the lens
153
from reception optical fiber
144
is mounted on the lead frame
155
to face the bet reception optical fiber
144
. The light emitting device
156
is connected by a wire
161
to a transmission signal line
158
which is provided flush with the lead frame
155
. Similarly, the light receiving device
157
is connected by a wire
162
to a reception signal line
159
which is provided flush with the leaf frame
155
.
In the optical system unit for optical transc
Kim Ellen E.
McGinn & Gibb PLLC
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