Optical: systems and elements – Deflection using a moving element – Using a periodically moving element
Reexamination Certificate
1998-10-22
2002-10-15
Chan, Jason (Department: 2633)
Optical: systems and elements
Deflection using a moving element
Using a periodically moving element
C359S199200
Reexamination Certificate
active
06466348
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a trunk apparatus and a terminal apparatus used in a wavelength-division-multiplexing communication system and a monitoring and controlling method for the wavelength-division-multiplexing communication system.
2. Description of the Related Art
In a recent optical communication, an optical transmission system using a WDM (wavelength-division-multiplexing) technology has been put to practical use.
FIGS. 1A
,
1
B and
1
C show structures of such a system.
FIG. 1A
shows a case of a simplified structure;
FIG. 1B
shows a case in which an ADM (add/drop multiplexer) is used in the system; and
FIG. 1C
shows a case of a ring-type structure.
In the case of the simplified structure shown in
FIG. 1A
, a transmitting terminal
101
wavelength-division-multiplexes a transmission signal, and sends the signal to an optical cable. Trunk apparatuses
102
to
104
relay the signal so as to transmit the signal to a receiver terminal
105
.
In the case of
FIG. 1B
in which ADMs are present, a WDM communication system (a) and a WDM communication system (b) are interconnected by ADMs
108
and
113
. The ADM
108
drops a part of a signal from the transmitter terminal
106
to the ADM
113
, and adds a signal from the ADM
113
. The ADM
113
drops a part of a signal from the transmitter terminal
111
to the ADM
108
, and adds a signal from the ADM
108
. Thereby, intercommunication between the WDM communication system (a) and the WDM communication system (b) is achieved.
In the case of the ring-type structure shown in
FIG. 1C
, nodes
116
A to
116
D to which a terminal apparatus can be connected and ADMs
118
A to
118
D together form a ring-type network.
It should be noted that although the transmitter terminal apparatus or the receiver terminal apparatus is represented as a terminal apparatus, a single terminal apparatus may serve as both a transmitter terminal apparatus and a receiver terminal apparatus.
FIG. 2
shows a structure of a terminal apparatus of a WDM communication system. The terminal apparatus
119
wavelength-division-multiplexes signals sent from apparatuses
120
to
122
, each apparatus being a SDH (synchronous digital hierarchy) terminal multiplexing apparatus or a SONET (synchronous optical network) terminal multiplexing apparatus, and sends the signals to a transmission path
135
. The terminal apparatus
119
also wavelength-division-demultiplexes signals received via a transmission path
136
, and sends the signals to the apparatuses
120
to
122
. In the terminal apparatus
119
, signals of wavelengths &lgr;
1
to &lgr;n are multiplexed by the transmitter-side wavelength division multiplexing apparatus
125
via a variable light attenuating apparatus
124
. The multiplexed signal is amplified by a transmitter-side multi-wavelength amplifier
127
, and is output to the transmitter-side transmission path
135
. A WDM signal received via the receiver-side transmission path
136
is amplified by a receiver-side multi-wavelength amplifier
133
. The amplified signal is demultiplexed into signals of each wavelength and is transmitted to the apparatuses
120
to
122
. It should be noted that dispersion compensation fiber modules
126
and
134
are provided for compensating for a dispersion in an optical cable. Boosters
128
and
132
are booster units for additional exiting-light sources. An analyzer
129
is for a spectrum analysis. Each part in the terminal apparatus
119
is controlled by a central monitoring and controlling apparatus
123
.
FIG. 3
shows an example of a structure which does not includes an ADM. A signal transmitted via a transmission path
152
is amplified by a multi-wavelength amplifier
143
, and the amplified signal is sent to a transmission path
153
. Similarly, a signal transmitted via a transmission path
154
is amplified by a multi-wavelength amplifier
146
, and the amplified signal is sent to a transmission path
155
. A monitoring and controlling apparatus
151
including monitoring and controlling units
144
and
145
is connected to the multi-wavelength amplifiers
143
and
146
so as to monitor and control the WDM communication system.
FIG. 4
shows an example of a structure which includes an ADM. A signal transmitted via the transmission path
152
is amplified by a multi-wavelength amplifier
159
, and input to an ADM
158
. An output signal of the ADM
158
is amplified by a multi-wavelength amplifier
161
, and the amplified signal is sent to the transmission path
153
. Similarly, a signal transmitted via the transmission path
154
is amplified by a multi-wavelength amplifier
162
, and input to the ADM
158
. An output signal of the ADM
158
is amplified by a multi-wavelength amplifier
160
, and the amplified signal is sent to the transmission path
155
. A signal of a wavelength &lgr;a on a transmission path
156
is added by the ADM
158
, and a signal of a wavelength &lgr;d is dropped to a transmission path
157
by the ADM
158
. It should be noted that dispersion compensation fiber modules
140
and
148
are provided for compensating for dispersion in an optical cable. BST boosters
141
and
147
are booster units for additional exiting-light sources. Each part in the apparatus is controlled by a central monitoring and controlling apparatus
149
.
FIG. 5
shows an example of a structure of an ADM (passive) having no switch circuit. A wavelength-division-multiplex signal transmitted through a transmission path
163
is wavelength-division-demultiplexed by a wavelength-division-demultiplexing apparatus
164
. A signal of a wavelength &lgr;d is dropped from among the demultiplexed wavelengths, and the rest of the wavelengths are input to a wavelength-division-multiplexing apparatus
165
. Additionally, a signal of a wavelength &lgr;a is added to the wavelength-division-multiplexing apparatus
165
. Signals of the wavelengths including the wavelength &lgr;a are wavelength-division-multiplexed by the wavelength-division-multiplexer
165
, and the multiplexed signal is output to a transmission path
166
.
FIG. 6
shows an example of a structure of an ADM (active) having a switch circuit. A plurality of switch circuits
172
to
177
are provided so as to select wavelengths to be dropped. The remaining structure is the same as the ADM shown in FIG.
5
.
FIG. 7
shows an example of a structure of a monitoring and controlling apparatus
180
. A monitoring and controlling signal having
1
to n channels is input via a transmission path
181
, and is converted into an electric signal by an optoelectric converter
183
. The signal is input to a serial/parallel converter
187
via a frame end unit
186
, and is subjected to a serial/parallel conversion so as to obtain a monitoring and controlling signal
193
. On the other hand, a monitoring and controlling signal
194
having 1 to n channels is input to a parallel/serial converter
189
and is converted into a serial signal. Then, a frame for synchronization is added to the serial signal by a frame generating unit
188
, and the serial signal is converted into an optical signal by an electrooptic converter
184
. The optical signal is transmitted through a transmission path
182
.
It should be noted that a clock received by the optoelectric converter
183
is supplied to the frame synchronization circuit
185
, and a frame pulse is supplied from the frame synchronization circuit
185
to the frame end unit
186
. Additionally, the clock received by the optoelectric converter
183
is also supplied to a selector
192
. The selector
192
selects one of the clock, an output of an oscillator
191
and clocks
195
received from outside. The selected clock is supplied to a pulse-generating unit
190
. An output of the pulse-generating unit
190
is supplied to the parallel/serial conversion circuit
189
and the frame-generating unit
188
.
FIG. 8
is an illustration of a simplified structure shown in
FIG. 1A
which is further simplified and represented in view of a wavelength. A plural
Chan Jason
Fujitsu Limited
Leung Christina Y
Staas & Halsey , LLP
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