Optical waveguides – Accessories – External retainer/clamp
Reexamination Certificate
2001-01-22
2003-06-24
Bovernick, Rodney (Department: 2874)
Optical waveguides
Accessories
External retainer/clamp
C385S138000
Reexamination Certificate
active
06584270
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a fixed component which is used in the optical communications or the like and an optical component employing the same.
2. Description of the Related Art
In recent years, in the optical communications, as the technology for making a rapid increase of the transmission capacity, the study and development of the optical wavelength division multiplexing communications have been actively carried out and the practical use thereof is in progress. The optical wavelength division multiplexing communications is such that for example, a plurality of lights having the wavelengths different from one another are wavelength-multiplexed to be transmitted. In such an optical wavelength division multiplexing communications system, there is required the optical multiplexing/demultiplexing device for demultiplexing optically the transmitted wavelength multiplexed light into a plurality of lights having the wavelengths different from one another and for multiplexing optically a plurality of lights having wavelengths different from one another.
As one example of such a optical multiplexing/demultiplexing device, for example, there is an AWG (Arrayed Waveguide Grating) type optical multiplexing/demultiplexing device
11
as shown in FIG.
9
. The AWG type optical multiplexing/demultiplexing device
11
is such that a waveguide structure as shown in
FIG. 9
is formed on a substrate
41
. This waveguide structure is constituted of one or more optical input waveguides
42
, a first slab waveguide
43
, an arrayed waveguide
44
, a second slab waveguide
45
, and a plurality of optical output waveguides
46
. In this waveguide structure, as shown in
FIG. 9
, the first slab waveguide
43
is connected to the output end of the above-mentioned one or more optical input waveguides
42
arranged side by side. The arrayed waveguide
44
is connected to the output end of the first slab waveguide
43
. In addition, the second slab waveguide
45
is connected to the output end of the arrayed waveguide
44
. Furthermore, a plurality of optical output waveguides
46
arranged side by side are connected to the output end of the second slab waveguide
45
.
The above-mentioned arrayed waveguide
44
propagates light output from the first slab waveguide
43
. As shown in
FIG. 9
, the arrayed waveguide
44
consists of a plurality of channel waveguides
44
a
arranged side by side which are formed in lengths different between adjacent channel waveguides. Then, the lengths of the adjacent channel waveguides
44
a
are different from each other with the differences (&Dgr;L) preset. The diffraction grating is constituted by such an arrayed waveguide
44
.
In this connection, the above-mentioned one or more optical input waveguides
42
and optical output waveguides
46
, for example, are provided in correspondence to the number of demultiplexed or multiplexed signal lights (i.e., the number of lights having the wavelengths different from one another which are demultiplexed or multiplexed by the AWG type optical multiplexing/demultiplexing device
11
) which are required for the AWG type optical multiplexing/demultiplexing device
11
. The number of the channel waveguides
44
a
of the arrayed waveguide
44
are provided by
100
for example. In addition, a large number of optical input waveguides
42
, and a large number of optical output waveguides
46
are provided. In
FIG. 9
, however, for the sake of simplicity of the figure, the number of optical input waveguides
42
, the number of channel waveguides
44
a
of the arrayed waveguide
44
, and the number of optical output waveguides
46
are schematically shown.
The above-mentioned AWG type optical multiplexing/demultiplexing device
11
is formed such that an optical waveguide portion
40
made of quartz based glass is laminated on a silicon substrate
41
. Then, the above-mentioned optical waveguide portion
40
is formed such that a under cladding which is formed on the silicon substrate
41
, a core in which the waveguide structure is formed, and a over cladding with which the core is covered are laminated in turn. In the conventional AWG type optical multiplexing/demultiplexing device
11
, the over cladding is made of quartz based glass, for example, in which 5 mol % B
2
O
3
and 5 mol % P
2
O
5
are added to pure quartz.
An optical fiber on the transmission side (not shown) for example is connected to one of one or more optical input waveguides
42
such that the wavelength-multiplexed light is introduced thereinto. The light which has been introduced to the first slab waveguide
43
through one of one or more optical input waveguides
42
is diffracted by the diffraction effect and enters the arrayed waveguide
44
to be propagated through the arrayed waveguide
44
.
The light which has been propagated through the arrayed waveguide
44
reaches the second slab waveguide
45
and then is condensed in the optical output waveguides
46
to be output therefrom. Now, as described above, the lengths of the adjacent channel waveguides
44
a
are different between adjacent channel waveguides by the preset differences (&Dgr;L). Thus, the lights which have been output from the channel waveguides
44
a
to the second slab waveguide
45
are shifted in phase from each other. The phase front of the lights is tilted in correspondence to the differences and then the position where the light is condensed is determined by the angle of this tilt. For this reason, the positions where the lights having the wavelengths different from one another are condensed are different from one another. Then, the optical output waveguides
46
are formed in those condensing positions, whereby the lights having the different wavelengths can be output from the different optical output waveguides
46
for the wavelengths.
In addition, the AWG type optical multiplexing/demultiplexing device
11
utilizes the principle of the reciprocity (the reversibility) of the optical circuit. For this reason, the AWG type optical multiplexing/demultiplexing device
11
has the function as the optical multiplexer as well as the function as the optical demultiplexer. That is, a plurality of lights having the wavelengths different from one another may be input to the respective optical output waveguides
46
for the wavelengths. Then, these lights pass through the reversed propagation path to the above-mentioned propagation path to be multiplexed in the arrayed waveguide
44
to be output from one of one or more optical input waveguides
42
.
In such an AWG type optical multiplexing/demultiplexing device
11
, as described above, the wavelength resolution is proportional to the differences (&Dgr;L) between the lengths of the adjacent channel waveguides
44
a
of the arrayed waveguide. For this reason, the above-mentioned differences &Dgr;L is designed so as to be made large, whereby there becomes possible the optical multiplexing/demultiplexing device for the wavelength multiplexed lights having the narrow wavelength intervals which has not been able to be realized in the conventional optical multiplexer/demultiplexer. As a result, there can be obtained the optical multiplexing/demultiplexing function (i.e., the function of demultiplexing or multiplexing a plurality of light signals having the wavelength intervals of equal to or smaller than 1 nm) for a plurality of signal lights which is required to realize the high density-optical wavelength division multiplexing communications.
In this connection, in the AWG type optical multiplexing/demultiplexing device
11
as described above, in general, one sheet of half waveplate
48
is provided so as to cross the longitudinal center portion of the arrayed waveguide
44
. As a result, the polarization dependence is eliminated. The polarization dependency of the central wavelength is caused by waveguide birefringence which is the effective refractive index differences between the TE mode and the TM mode which is propagated through the arrayed waveguide. The above-mentioned half wav
Kashihara Kazuhisa
Nekado Yoshinobu
Tanaka Kanji
Bovernick Rodney
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Stahl Mike
The Furukawa Electric Co. Ltd.
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