Optical waveguides – With optical coupler – Plural
Reexamination Certificate
2002-01-23
2004-07-06
Font, Frank G. (Department: 2877)
Optical waveguides
With optical coupler
Plural
C398S082000
Reexamination Certificate
active
06760510
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to a wavelength multiplex optical communication module for use in various communication networks, and more particularly to a wavelength multiplex optical communication module for use in multiplexing/demultiplexing or transmission/reception of light with different wavelengths.
BACKGROUND OF THE INVENTION
Various wavelength multiplex optical communication modules for use in multiplexing/demultiplexing or transmission/reception of light with different wavelengths have been developed.
FIG. 1
is a side view of a conventional wavelength multiplex optical communication module disclosed in Japanese Patent Laid-Open No. 133069/1998. This wavelength multiplex optical communication module
11
comprises a silicon substrate
12
and an optical waveguide
14
mounted on the silicon substrate
12
in its upper surface
13
. An input/output (hereinafter often referred to as “I/O”) port optical fiber
16
is provided on the left side of the optical waveguide
14
in the drawing so that one end of the I/O port optical fiber
16
is connected to a port
15
in the optical circuit. An optical fiber
17
, a photodiode (PD) module
18
, and a laser diode module
19
are provided on the right side of the optical waveguide
14
in the drawing. In
FIG. 1
, the photodiode module
18
is hidden by the laser diode module
19
. Numeral
21
designates a core of the I/O port optical fiber, numeral
22
a core of the optical fiber
17
, and numeral
25
an I/O port.
FIG. 2
shows the upper surface of this conventional wavelength multiplex optical communication module. As shown in
FIG. 2
, the core
21
of the I/O port optical fiber
16
and the core
22
of the optical fiber
17
are provided on an extension line of an identical optical axis. Light with different wavelengths &lgr;
1
and &lgr;
2
is incident through the I/O port optical fiber
16
on the port
15
. The incident light is demultiplxed in a multiplexing/demultiplexing section
24
in the optical circuit within the optical waveguide
14
, and the demultiplexed light with wavelength &lgr;
1
as such travels straight and is sent to the optical output port
25
. One end of the optical fiber
17
is optically coupled to the optical output port
25
, and the light with wavelength &lgr;
1
is guided through the core
22
of the optical fiber
17
.
On the other hand, the light with wavelength &lgr;
2
demultiplexed in the multiplexing/demultiplexing section
24
is branched in a branching section
26
into two parts which travel in two respective directions. One of the branched light parts reaches a port
27
and is input into a photodetector
18
where the optical signal is converted to an electrical signal. The other branched light part reaches a port
28
. A laser diode (LD) module
19
is connected to the port
28
. The laser diode module
19
is constructed so as to output the light with wavelength &lgr;
2
. This light travels in the reverse direction through the branching section
26
and reaches the multiplexing/demultiplexing section
24
for multiplexing. The multiplexed light is input through the port
15
into the I/O port optical fiber
16
and is guided through the core
21
in the reverse direction.
The wavelength multiplex optical communication module
11
shown in
FIGS. 1 and 2
has a structure such that the optical waveguide
14
, the photodiode module
18
for receiving an optical signal, and the laser diode module
19
for sending an optical signal are mounted on the upper surface
13
of one silicon substrate
12
. By virtue of this structure, the wavelength multiplex optical communication module
11
can be prepared at low cost.
In this wavelength multiplex optical communication module
11
, two optical fibers
16
,
17
are provided respectively on both sides of the optical waveguide
14
so as to sandwich the optical waveguide
14
therebetween. Therefore, in order to prevent the optical fibers
16
,
17
from contacting with other electrical components (not shown), a certain space should be provided on both sides of the wavelength multiplex optical communication module
11
. This disadvantageously makes it difficult to realize high density packaging of the wavelength multiplex optical communication module
11
.
Japanese Patent No. 2919329 and Japanese Patent Laid-Open No. 333243/1993 also disclose wavelength multiplex optical communication modules. Also in these techniques, optical fibers are connected to an optical waveguide respectively in its end faces opposite to each other. Therefore, these techniques involve the same problem as the technique shown in
FIGS. 1 and 2
.
FIG. 3
shows a wavelength multiplex optical communication module which has been proposed in Japanese Patent Laid-Open No. 190026/1996 for solving the problem of packaging density of the above wavelength multiplex optical communication modules. In this conventional wavelength multiplex optical communication module
31
, one end of an input single mode optical fiber
32
and one end of an output optical fiber
33
are coupled through a glass block
34
respectively to corresponding I/O ports
36
,
37
of the optical waveguide
35
. Light with different wavelengths &lgr;
1
and &lgr;
2
is incident through the input single mode optical fiber
32
on the I/O port
36
. The light with wavelengths &lgr;
1
and &lgr;
2
is incident on a dielectric multi-layer film
39
disposed in a groove
38
formed in the center portion of the optical waveguide
35
. Light with wavelength &lgr;
1
as such passes through the dielectric multi-layer film
39
and, in a branching section
41
, is branched into two parts which travel through two respective paths. A laser diode module
42
is optically connected to the end of one of the paths, and a photodiode module
43
is optically connected to the end of the other path.
In this conventional wavelength multiplex optical communication module
31
, the dielectric multi-layer film
39
is disposed perpendicularly to a reference plane
45
in a planar optical waveguide circuit to simplify the structure and thus to prepare a compact module. In the prior art technique shown in
FIGS. 1 and 2
, since two optical fibers
16
,
17
are mounted respectively on different end faces of the optical waveguide, high density packaging of the wavelength multiplex optical communication module
11
cannot be realized. On the other hand, the wavelength multiplex optical communication module
31
shown in
FIG. 3
solves this problem by connecting the optical fibers
32
,
33
to an identical end face.
FIG. 4
shows a wavelength multiplex optical communication module disclosed in Japanese Patent Laid-Open No. 160952/1998 which is another example of the wavelength multiplex optical communication module wherein, as with the prior art technique shown in
FIG. 3
, two optical fibers are connected to one end face of an optical waveguide. In this wavelength multiplex optical communication module
51
, a difference in level is provided in an optical waveguide substrate
52
, and the end of a first optical fiber
53
and the end of a second optical fiber
54
are disposed in this portion of the difference in level. Light with different wavelengths &lgr;
1
and &lgr;
2
is incident through the first optical fiber
53
on a corresponding first port
55
, is guided through a first optical waveguide
56
, and is incident on a wavelength demultiplexing element
58
disposed on a second port
57
which is located opposite to the first port
55
of the optical waveguide substrate
52
.
The wavelength demultiplexing element
58
substantially completely reflects light with wavelength &lgr;
1
. Therefore, the light with wavelength &lgr;
1
is guided through a second optical waveguide
59
, reaches a third port
61
, and then is incident on the second optical fiber
54
. Further, the wavelength demultiplexing element
58
permits a part of light with wavelength &lgr;
2
to pass therethrough, and this light is received in a photodetector
66
for an optical output monitor provided behind the wavelength demultiplexing ele
Font Frank G.
Lyons Michael A.
McGinn & Gibb PLLC
NEC Corporation
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