Optical communications – Multiplex – Optical switching
Reexamination Certificate
2001-02-15
2004-05-25
Chan, Jason (Department: 2633)
Optical communications
Multiplex
Optical switching
C398S043000, C398S074000, C398S075000, C398S052000, C398S053000, C398S098000
Reexamination Certificate
active
06741810
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a signal demultiplexing device and a signal routing device in a high speed transmission system, for time division demultiplexing a series of high speed multiplexed signal lights in which signal lights with a prescribed identical frequency, i.e., identical wavelength, are time division multiplexed in terms of time-slots, by converting them into low speed wavelength division multiplexed signal lights, and outputting signal lights of desired wavelengths that constitute the low speed wavelength division multiplexed signals by distributing them in desired time-slots.
2. Description of the Background Art
A conventional signal demultiplexing device of this type is as shown in
FIG. 11
, for example. In this conventional signal demultiplexing device of
FIG. 11
, high speed multiplexed signal lights constituting a series of signal lights that are time division multiplexed in terms of time-slots T
1
, T
2
, T
3
and T
4
are distributed by a distributor
61
and a plurality of distributed signal lights are respectively supplied to a plurality of separators
63
a
,
63
b
,
63
c
and
63
d.
On the other hand, a prescribed phase difference &Dgr;T corresponding to a time interval between adjacent time-slots is sequentially given by phase difference giving elements
67
a
,
67
b
and
67
c
such as delay lines, with respect to a series of signals sequentially outputted from an oscillator
65
, so as to sequentially generate time division demultiplexing signals with phases coinciding with those of the time-slots. This series of time division demultiplexing signals are respectively supplied to the plurality of separators
63
d
,
63
c
,
63
b
and
63
a
where signal lights of the respective time-slots are extracted by using the time division demultiplexing signals, and the signal lights of the respective time-slots T
1
, T
2
, T
3
and T
4
are received by a plurality of receivers
69
a
,
69
b
,
69
c
and
69
d
respectively.
The conventional signal demultiplexing device in such a configuration requires a plurality of separators
63
a
to
63
d
which are time division demultiplexing elements for the purpose of extracting the respective time-slots, and there is a need to align phases of the respective time-slots with phases at respective separators, while the time-slot demultiplexing speed is limited by the separators
63
a
to
63
d
that are the time division demultiplexing elements.
FIG. 2
shows a configuration of a signal demultiplexing device using a wavelength converter. This signal demultiplexing device of
FIG. 2
has a wavelength converter
1
into which signal lights with a prescribed identical wavelength &lgr;s that are high speed time division multiplexed signal lights multiplexed in terms of time-slots T
1
, T
2
, T
3
and T
4
are inputted, and probe lights that are low speed wavelength division multiplexed signal lights comprising a series of sub-probe lights with prescribed different wavelengths &lgr;
1
, &lgr;
2
, &lgr;
3
and &lgr;
4
for respective time-slots T
1
, T
2
, T
3
and T
4
that are synchronized with the high speed time division multiplexed signal lights are also inputted. In this wavelength converter
1
, the prescribed wavelength &lgr;s of each signal light in each time-slot is converted into a desired wavelength &lgr;i (i=1, 2, 3, 4) of the probe light in the corresponding time-slot Ti (i=1, 2, 3, 4), and resulting wavelength division multiplexed signal lights are supplied to a wavelength demultiplexer
9
.
Then, at the wavelength demultiplexer
9
, the wavelength division multiplexed signal lights from the wavelength converter
1
are demultiplexed, and as outputs of the wavelength demultiplexer
9
shown in
FIG. 2
, a signal light with a wavelength &lgr;
1
is outputted to the time-slot T
1
from a first port of the wavelength demultiplexer
9
and received by a receiver
11
a
, a signal light with a wavelength &lgr;
2
is outputted to the time-slot T
2
from a second port of the wavelength demultiplexer
9
and received by a receiver
11
b
, a signal light with a wavelength &lgr;
3
is outputted to the time-slot T
3
from a third port of the wavelength demultiplexer
9
and received by a receiver
11
c
, and a signal light with a wavelength &lgr;
4
is outputted to the time-slot T
4
from a fourth port of the wavelength demultiplexer
9
and received by a receiver
11
d.
Note that the probe lights constituting the low speed wavelength division multiplexed signal lights are applied with a clock modulation at a divided frequency of the high speed time division multiplexed signal lights, and a phase relationship adjustment such that bits are in complementary relationship, thereby converting the high speed time division multiplexed signal lights into the wavelength division multiplexed signal lights which are them wavelength demultiplexed and received by the respective receivers
11
a
,
11
b
,
11
c
and
11
d.
In the signal demultiplexing device using the wavelength converter described above, the probe lights that are low speed signals can be generated conventionally by an individual modulation scheme using electrically generated phase differences, an individual modulation scheme using optically generated phase differences, or a collective modulation scheme, and each of these schemes will be described next.
FIG. 12
shows a circuit configuration of a conventional probe light source for realizing the individual modulation scheme using electrically generated phase difference mentioned above. The probe light source of
FIG. 12
has a plurality of sub-probe light sources
13
a
,
13
b
,
13
c
and
13
d
for respectively generating sub-probe lights with prescribed different wavelengths &lgr;
1
, &lgr;
2
, &lgr;
3
and &lgr;
4
for respective time-slots T
1
, T
2
, T
3
and T
4
, and the sub-probe lights with wavelengths &lgr;
1
, &lgr;
2
, &lgr;
3
and &lgr;
4
outputted from these sub-probe light sources
13
a
,
13
b
,
13
c
and
13
d
are respectively supplied to modulators
71
a
,
71
b
,
71
c
and
71
d.
On the other hand, a prescribed phase difference &Dgr;T corresponding to a time interval between adjacent time-slots is sequentially given by electric phase difference giving elements
67
a
,
67
b
and
67
c
such as delay lines, with respect to a series of signals sequentially outputted from an oscillator
65
, so as to sequentially generate phase adjustment signals with phases coinciding with those of the time-slots. This series of phase adjustment signals are supplied to the respective modulators
71
a
,
71
b
,
71
c
and
71
d
where phases of the sub-probe lights from the sub-probe light sources
13
a
,
13
b
,
13
c
and
13
d
are adjusted, and the phase adjusted sub-probe lights are multiplexed by a multiplexer
73
, and the probe lights comprising a series of sub-probe lights with different wavelengths &lgr;
1
, &lgr;
2
, &lgr;
3
and &lgr;
4
for the respective time-slots T
1
, T
2
, T
3
and T
4
which are synchronized with the respective time-slots T
1
, T
2
, T
3
and T
4
are outputted from the multiplexer
73
.
FIG. 13
shows a circuit configuration of a conventional probe light source for realizing the individual modulation scheme using optically generated phase difference mentioned above. The probe light source of
FIG. 13
uses a plurality of optical fibers
75
a
,
75
b
,
75
c
and
75
d
with different lengths for optically generating phase differences, instead of the electric phase difference giving elements
67
a
,
67
b
and
67
c
used in the conventional probe light source shown in
FIG. 12
, such that a sub-probe light with a wavelength &lgr;
1
transmitted from the sub-probe light source
13
a
through the modulator
71
a
is inputted into the multiplexer
73
without any delay by an optical fiber
75
a
, a sub-probe light with a wavelength &lgr;
2
transmitted from the sub-probe light source
13
b
through the modulator
71
b
is inputted into the multiplexer
73
with a delay of &Dgr;T by an optical fiber
75
b
, a
Miyazaki Tetsuya
Otani Tomohiro
Yamamoto Shu
Chan Jason
DDI Corporation
Olson & Hierl Ltd.
Payne David C.
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