Optical communications – Optical repeater system – Regenerative
Reexamination Certificate
2000-05-09
2004-10-12
Chan, Jason (Department: 2733)
Optical communications
Optical repeater system
Regenerative
C398S155000
Reexamination Certificate
active
06804468
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to a WDM optical transmission system, and more particularly, to a WDM optical transmission system in which jitter compression is realized and an optical transceiver is commonly used in different transfer rates and different coding formats.
BACKGROUND OF THE INVENTION
FIG. 1
shows a conventional WDM (Wavelength Division Multiplexing) optical transmission system. In this conventional WDM optical transmission system, the reference numerals
1
and
2
indicate WDM optical transmission apparatus,
3
,
4
,
3
′ and
4
′ indicate optional optical transmission apparatus,
5
and
6
indicate optical transceivers,
7
indicates an electrical to optical converter for wavelength &lgr;
1
,
8
indicates an optical to electrical converter for wavelength &lgr;
2
,
9
indicates an optical to electrical converter for wavelength &lgr;
1
,
10
indicates an electrical to optical converter for wavelength &lgr;
2
,
11
indicates an electrical to optical converter for wavelength &lgr;
3
,
12
indicates an optical to electrical converter for wavelength &lgr;
4
,
13
indicates an optical to electrical converter for wavelength &lgr;
3
,
14
indicates an electrical to optical converter for wavelength &lgr;
4
,
15
and
16
indicate optical multiplexers/demultiplexers.
The optical transceivers
5
and
6
include optical signal receiving units
5
-
1
and
6
-
1
, optical signal supplying units
5
-
2
and
6
-
2
, and retiming units
5
-
3
and
6
-
3
, respectively, while the optical transmission apparatus
3
,
4
,
3
′ and
4
′ include electrical to optical converters
3
-
1
,
4
-
1
,
3
′-
1
and
4
′-
1
and optical to electrical converters
3
-
2
,
4
-
2
,
3
′-
2
and
4
′-
2
, respectively.
In this WDM optical transmission system, an optical signal of wavelength &lgr;
1
sent from the electrical to optical converter
3
-
1
of the optical transmission apparatus
3
is received by the optical signal receiving unit
5
-
1
of the optical transceiver
5
of the WDM optical transmission apparatus
1
. The optical signal is converted into an electrical signal by the optical signal receiving unit
5
-
1
and outputted to the retiming unit
5
-
3
, by which the pulse width distortion generated between the optical transmission apparatus
3
and the WDM optical transmission apparatus
1
is corrected to effect jitter compression.
The electrical signal outputted from the retiming unit
5
-
3
is converted by the electrical to optical converter
7
into an optical signal of wavelength &lgr;
1
and inputted to the optical multiplexers/demultiplexers
15
. The optical signal is multiplexed with another optical signal of wavelength &lgr;
3
outputted from the electrical to optical converter
11
to generate a WDM signal which is transmitted via an optical fiber
20
to the WDM optical transmission apparatus
2
.
In this WDM optical transmission apparatus
2
, the WDM signal inputted is demultiplexed by the optical multiplexers/demultiplexers
16
into optical signals of wavelength &lgr;
1
and wavelength &lgr;
3
. The optical signal of wavelength &lgr;
1
is converted into an electrical signal by the optical to electrical converter
9
and inputted to the optical transceiver
5
. The electrical signal inputted to the optical transceiver
5
is converted into an optical signal by the optical signal supplying unit
5
-
2
and supplied to the optical transmission apparatus
3
′, where the optical signal of wavelength &lgr;
1
is converted into an electrical signal by the optical to electrical converter
3
′-
2
.
Thus, communication from the optical transmission apparatus
3
to the optical transmission apparatus
3
′ is performed. Communication from the optical transmission apparatus
3
′ to the optical transmission apparatus
3
using an optical signal of wavelength &lgr;
2
, communication from the optical transmission apparatus
4
to the optical transmission apparatus
4
′ using an optical signal of wavelength &lgr;
3
, and communication from the optical transmission apparatus
4
′ to the optical transmission apparatus
4
using an optical signal of wavelength &lgr;
4
are conducted in the same way.
In this WDM optical transmission system, optical transceivers
5
and
6
use a transfer rate and a coding format which are the same as those of the optical transmission apparatus
3
,
4
,
3
′ and
4
′. and the clocks are sampled in the retiming units
5
-
3
and
6
-
3
from the electrical signals generated by optical to electrical conversion, and the clocks are phase-synchronized with use of PLL (Phase Locked Loop) or narrow band filter, so that the pulse width distortion is corrected to effect jitter compression.
In the conventional WDM optical transmission system, however, there is a disadvantage in that the jitter generated in optical transmission between the WDM optical transmission apparatus
1
and
2
is transmitted without being corrected and is increased to deteriorate the quality of transmission signals, although jitter generated in optical transmission via the optical transceivers
5
and
6
among the optical transmission apparatus
3
,
4
,
3
′ and
4
′ and may be compressed. Also, since the optical transceivers use the same transfer rate and coding format, respectively, as that used in each individual optical transmission apparatus, types of transceivers required increase.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the invention to provide a WDM optical transmission system in which pulse width distortion generated in optical transmission between two WDM optical transmission apparatus is corrected so that jitter between them is compressed.
It is another object of this invention to provide a WDM optical transmission system comprising an optical transceiver which is used in common to various optical transmission apparatus having different transfer rates and coding formats.
According to the invention, a WDM optical transmission system performing communication in accordance with transmission and receipt of an optical wavelength division multiplexed (WDM) signal obtained by multiplexing optical signals of plural wavelengths having same or different transfer rates and coding formats, comprises:
a demultiplexer for demultiplexing a WDM signal to output the optical signals of plural wavelengths,
an optical to electrical converter for converting at least one of the optical signals of plural wavelengths into an electrical signal,
a retiming unit for correcting pulse width distortion of the electrical signal, and
an optical signal supplying unit for converting the electrical signal of which distortion of pulse width has been corrected into an optical signal to be outputted to an optical signal transmission medium.
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patent: 5773345 (1998-06-01), Ota
patent: 5784184 (1998-07-01), Alexander et al.
patent: 5838475 (1998-11-01), Takeyari et al.
patent: 6041066 (2000-03-01), Meki et al.
patent: 6178212 (2001-01-01), Akashi
patent: 6252692 (2001-06-01), Roberts
patent: 6373608 (2002-04-01), Desurvire et al.
M. Ushirozawa et al., “Bit-rate-Independent SDH/SONET Regenerator for Optical Network”, ECOC 97, IEE, Sep. 1997.*
M. Ushirozawa et al. “Bit-rate-Independent SDH/SONET Regenerator for Optical Network” ECOC 97, pp. 25-28, Sep. 1997, Conference Publication No. 448, IEE, 1997.
Jinnai Kuniaki
Kuramochi Fumito
Takano Toshihiiko
Ukaji Hiroshi
Antonelli Terry Stout & Kraus LLP
Chan Jason
Hirakawa Hewtech Corporation Mitsubishi Gas Chemical Company, In
Li Shi K.
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