Optical waveguides – With optical coupler – Plural
Reexamination Certificate
2002-03-22
2004-10-26
Healy, Brian M. (Department: 2874)
Optical waveguides
With optical coupler
Plural
C385S037000, C385S042000, C385S129000, C385S130000, C385S132000, C385S043000, C385S045000, C398S082000, C398S087000
Reexamination Certificate
active
06810167
ABSTRACT:
BACKGROUND OF THE INVENTION
1) Field of the Invention
This invention relates to a wavelength division demultiplexing apparatus particularly suitable for use with a wavelength division multiplexing and demultiplexing apparatus of the arrayed waveguide grating (AWG) type, which is used for wavelength division multiplex communication.
2) Description of the Related Art
FIG. 28
is a block diagram showing a configuration of a common wavelength division multiplexing and demultiplexing apparatus of the AWG type. The wavelength division multiplexing and demultiplexing apparatus can function as any of a wavelength division multiplexing apparatus and a wavelength division demultiplexing apparatus. In the following description, a wavelength division multiplexing and demultiplexing apparatus is referred to as MUX/DEMUX and is used as a term signifying a wavelength division multiplexing apparatus or a wavelength demultiplexing apparatus unless otherwise specified. Further, description is given of a case wherein, taking notice principally of the demultiplexing function from between the multiplexing function and the demultiplexing function the MUX/DEMUX has, the MUX/DEMUX functions as a wavelength division demultiplexing apparatus. It is to be noted that the inputting and outputting directions of light when the wavelength division multiplexing function of the MUX/DEMUX operates are reverse to those when the wavelength division demultiplexing function of the MUX/DEMUX operates.
Referring to
FIG. 28
, the MUX/DEMUX
106
shown includes a single input waveguide
101
, an input slab
102
, a plurality of channel waveguides
103
, an output slab
104
, and n output waveguides
105
all formed on a substrate
100
such that the input waveguide
101
, input slab
102
, channel waveguides
103
, output slab
104
and output waveguides
105
may have a relatively high refractive index or indexes when compared with that of a surrounding region
100
A.
It is to be noted that, in the following description, a portion formed from a material which has a relatively high refractive index when compared with that of the region
100
A is sometimes referred to as “core”, and another portion formed from a material which has a relatively low refractive index and surrounding the core such as the region
100
A is sometimes referred to as “clad”. The input waveguide
1
, input slab
2
, channel waveguides
3
, output slab
4
and output waveguide
5
correspond to the core, and the region
100
A surrounding the input waveguide
1
, input slab
2
, channel waveguides
3
, output slab
4
and output waveguide
5
corresponds to the clad.
In the MUX/DEMUX
106
shown in
FIG. 28
, when light multiplexed in a wavelength region is inputted to the input waveguide
101
of the MUX/DEMUX
106
, light split for different wavelengths is outputted from channels #
1
to #n of the output waveguides
105
. On the other hand, when light of a plurality of different wavelengths is inputted to the channels #
1
to #n of the output waveguides
105
, light in which the light of all of the wavelengths is bunched and multiplexed in a wavelength region is outputted from the input waveguide
101
.
In the following, the configuration of the MUX/DEMUX
106
is described in comparison with the configuration of a conventional spectroscope (monochro-meter). The functions of the MUX/DEMUX
106
are implemented, for example, by not only AWG type devices shown in FIGS.
28
and
29
(
a
) but also spectroscope type devices shown in FIGS.
35
and
29
(
b
) and other devices.
FIG. 35
is a view showing an example of a configuration of a conventional spectroscope. Referring to
FIG. 35
, the spectroscope shown is of the bulk diffraction grating type, and it is generally difficult to reduce the pitch of a diffraction grating. In contrast, a spectroscope of the AWG type does not require the pitch, and it is only necessary to design the differences in length among waveguides which compose the AWG.
Meanwhile, FIG.
29
(
a
) is a schematic view showing a core pattern of the waveguides of the MUX/DEMUX
106
of the AWG type and particularly shows core portions of the MUX/DEMUX
106
. The components (elements or parts)
101
to
105
of the MUX/DEMUX
106
shown in FIG.
29
(
a
) individually correspond to components of a spectroscope.
FIG.
29
(
c
) is a view illustrating a corresponding relationship between the components of a wavelength division multiplexing and demultiplexing apparatus configured using waveguides and a conventional spectroscope. The corresponding relationship is described with reference to FIG.
35
. The spectroscope
110
shown in
FIG. 35
includes, in addition to a diffraction grating
113
with an uneven or rough surface, a single input optical fiber
111
, an input collimate lens
112
, a condenser lens
114
, and n output optical fibers
115
.
The input waveguide
101
which is a component of the MUX/DEMUX
106
(refer to FIG.
29
(
a
)) diffuses and outputs wavelength division multiplexed laser light, which is an object of wavelength division demultiplexing, to the input slab
102
in the following stage. Further, as seen in FIG.
29
(
c
), the input waveguide
101
functionally corresponds to the input optical fiber
111
of the spectroscope
110
in that it has a role of an incidence slit for spreading light. It is to be noted that FIG.
29
(
a
) is a schematic view particularly showing core elements in the MUX/DEMUX
106
.
Similarly, the input slab
102
diffuses light incoming to the input waveguide
101
and couples the diffused light to the channel waveguide
103
in the following stage. The input slab
102
corresponds to a function of the input collimate lens
112
in the spectroscope
110
(a function of aligning incoming light powers from the input optical fiber
111
and irradiating them upon the diffraction grating
113
in the following stage).
Meanwhile, the channel waveguides
103
which correspond to the diffraction grating
113
of the spectroscope
110
deflect light to a predetermined angle for each of wavelengths as hereinafter described, and the output slab
104
which corresponds to the condenser lens
114
condenses the lights outputted (outgoing or radiated) from and diffracted by the channel waveguides
103
. The output waveguides
105
which correspond to the output optical fibers
115
cut part of a spectrum of the light outgoing from the output slab
104
.
Here, the channel waveguides
103
are formed with different lengths such that the channel waveguide at the lowermost position of the MUX/DEMUX
106
shown in FIGS.
28
and
29
(
a
) has the smallest length and any other channel waveguide at a higher position has a successively increasing length. The differences in length between adjacent ones of the channel waveguides are equal to one another. The channel waveguides perform significant operation in wavelength division (splitting of light for each wavelength) or wavelength division multiplexing. In the following, operation of the channel waveguides
103
is described.
FIGS.
30
(
a
) and
30
(
b
) are views showing three neighboring channel waveguides of a plurality of channel waveguides
103
of the MUX/DEMUXs
106
shown in FIGS.
28
and
29
(
a
), respectively. Each of the channel waveguides
131
to
133
shown in FIGS.
30
(
a
) and
30
(
b
) has positions (dark points) of a “crest” and positions (blank points) of a “hollow” of a light wave. Here, where a light wave propagating in the channel waveguides
131
to
133
is represented by cos(&agr;) (&agr; represents the phase), the “crest” represents the position at which the phase &agr; is 2×n×&pgr; and the “hollow” represents the position at which the phase &agr; is (2n+1)×&pgr;. It is to be noted that n and &pgr; represent a positive integer and the number &pgr;, respectively.
Accordingly, in each of FIGS.
31
(
a
) and
31
(
b
), the length between two adjacent “crests” is equal to the wavelength of the light wave propagating in the channel waveguides
131
to
133
. In particular, the light wavelength
Naruse Terukazu
Tabuchi Haruhiko
Fujitsu Limited
Healy Brian M.
Staas & Halsey , LLP
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