Optical waveguides – With optical coupler – Input/output coupler
Reexamination Certificate
1999-04-20
2002-12-31
Sanghavi, Hemang (Department: 2874)
Optical waveguides
With optical coupler
Input/output coupler
C385S050000, C385S088000, C359S199200
Reexamination Certificate
active
06501876
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a bidirectional (two-way) optical communication device and a bidirectional optical communication apparatus which can carry out bidirectional optical communication simultaneously by using a single optical fiber.
BACKGROUND OF THE INVENTION
With respect to conventional bidirectional optical communication devices used for bidirectional optical communication links (bidirectional optical communication apparatuses), Japanese Laid-Open Patent Application No. 279627/1988 (Tokukaishou 63-279627) discloses such a device (first prior art). As illustrated in
FIG. 9
, this bidirectional optical communication device is provided with a first optical communication module
32
and a second optical communication module
36
. The first optical communication module
32
and the second optical communication module
36
are respectively connected to one end and the other end of a single polarization-maintaining optical fiber
31
.
Moreover, the first optical communication module
32
is provided with a first wave guide polarizing beam splitter
33
, a first semiconductor laser
34
and a first photo-detector
35
. The second optical communication module
36
is provided with a second wave guide polarizing beam splitter
37
, a second semiconductor laser
38
and a second photo-detector
39
. Here, the wave guide polarizing beam splitters
33
and
37
, which are made from a birefringence substance such as LiNbO
3
, function to transmit TE (Transverse Electric) mode light projected from the semiconductor lasers
34
and
38
so as to project TM (Transverse Magnetic) mode light on the lower faces of substrates
40
and
40
′.
The TE mode light, projected from the first semiconductor laser
34
of the first optical communication module
32
, is transmitted through the first wave guide polarizing beam splitter
33
, coupled to the polarization-maintaining optical fiber
31
, transferred through the polarization-maintaining optical fiber
31
while maintaining its plane of polarization, emitted from the other end of the polarization-maintaining optical fiber
31
and guided to the second optical communication module
36
.
As illustrated in
FIG. 10
, the first optical communication module
32
and the second optical communication module
36
, connected to the polarization-maintaining optical fiber
31
, are installed so that planes of polarization of the respective output lights are aligned orthogonal to each other. For this reason, the output light of the first optical communication module
32
forms TM mode light in the second optical communication module
36
, with the result that it is not transmitted through the second wave guide polarizing beam splitter
37
, and detected by the second photo-detector
39
installed on the lower surface of the substrate
40
′. In the same manner, the output light from the second optical communication module
36
is also detected by the first photo-detector
35
in the first optical communication module
32
.
Moreover, with respect to another conventional bidirectional optical communication link, Japanese Laid-Open Patent Application No. 262276/1996 (Tokukaihei 8-262276) discloses such a link (second prior art). As illustrated in
FIG. 11
, this bidirectional optical communication link is constituted by a light-emitting element
41
and a light-receiving element
42
, two lenses
45
and
46
, a wavelength filter
43
that transmits light having the first wavelength &lgr;
1
and reflects light having the second wavelength &lgr;
2
, and an optical fiber
44
whose light inputting and outputting end face
44
a is diagonally polished. Here, the light-emitting element
41
, the light-receiving element
42
, two lenses
45
and
46
and the waveform filter
43
constitute a bidirectional optical communication device.
Light having the first wavelength &lgr;
1
released from the light emitting element
41
is converged by the first lens
45
, and coupled to the optical fiber
44
through the wavelength filter
43
. Light having the second wavelength &lgr;
2
, which is an inputted light from the optical fiber
44
, is reflected by the wavelength filter
43
, converged by the second lens
46
and coupled to the light-receiving element
42
.
In the case when the end face
44
a
is placed so as to be orthogonal to the inputted light, a portion of the light having the first wavelength &lgr;
1
is reflected by the end face
44
a
, and the reflected light is again reflected by the wavelength filter
43
and directed to the light-receiving element
42
, with the result that cross talk tends to occur. However, in this second prior art, since the end face
44
a
is tilted, the reflected light from the end face
44
a
of the optical fiber
44
is not allowed to enter the second lens
46
, thereby reducing cross talk.
Here, the first and second prior arts have the following problems: In the first prior art, expensive members, such as the polarization-maintaining optical fiber
31
and the wave guide polarizing beam splitters
33
and
37
, are required, resulting in high costs, and since the polarization-maintaining optical fiber
31
is a single-mode optical fiber with a small core diameter of several &mgr;m, with the result that time-consuming tasks are required in positioning the respective optical communication modules
32
and
36
and the polarization-maintaining optical fiber
31
to each other.
In the second prior art, the light-emitting elements
41
such as semiconductors, etc., having mutually different generating waveforms and the bidirectional optical communication devices provided with the wavelength filters
43
having mutually different transmitting wavelengths have to be installed at both of the ends of the optical fiber
44
, and the characteristics of the respective bidirectional optical communication devices have to be changed. This makes the construction of bidirectional optical communication links complex, and results in difficulty in reducing the costs of the bidirectional optical communication device and the bidirectional optical communication link using those parts.
SUMMARY OF THE INVENTION
In order to address the above-mentioned problems, the objective of the present invention is to provide a bidirectional optical communication device and a bidirectional optical communication link using the device in which the bidirectional optical communication device and an optical fiber are easily positioned at low costs.
In order to solve the above-mentioned problems, a bidirectional optical communication device in accordance with the present invention is provided with: a light-emitting element for generating signal light in accordance with a data signal, a light-receiving element for receiving the signal light and for generating a data signal in accordance with the signal light, a transmitting light wave guide for projecting transmission light that is the signal light from the light-emitting element to an optical fiber outside, a received light wave guide for guiding received light that is signal light from the optical fiber outside, and a positioning means for positioning the transmitting light wave guide, the received light wave guide and the optical fiber so as to optically connect with one another, wherein: the transmitting light wave guide and the received light wave guide are mutually optically separated from each other, and the light axis of the transmission light is set so as to tilt with respect to the normal to the end face of the optical fiber.
With the above-mentioned arrangement, in the case when the above-mentioned arrangements are connected to both of the ends of an optical fiber so as to form a bidirectional optical communication apparatus, signal light from the light-emitting element is coupled to the optical fiber through the transmitting light wave guide, and transferred to one end to the other end of the optical fiber, while signal light from the optical fiber is sent through the received light wave guide, and received by the light-receiving element at which the corresponding data i
Fujita Hideaki
Ishii Yorishige
Kurata Yukio
Matsushima Toshiyuki
Okada Kuniaki
Conlin David G.
Edwards & Angell LLP
Jensen Steven M.
Rojas Omar
Sanghavi Hemang
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