Optical waveguides – With optical coupler – Switch
Reexamination Certificate
2000-06-13
2002-08-13
Kim, Ellen E. (Department: 2874)
Optical waveguides
With optical coupler
Switch
C359S199200, C370S216000
Reexamination Certificate
active
06434288
ABSTRACT:
This application is the national phase under 35 U.S.C. § 371 of PCT International Application No. PCT/JP99/04682 which has an International filing date of Aug. 30, 1999, which designated the United States of America.
1. Technical Field
The present invention relates to an optical switching system for carrying out path switching on a network that interconnects a plurality of nodes through a working path and a preparatory path using optical signals.
2. Background of the Invention
FIG. 1
is a block diagram showing a partially redrawn conventionally studied optical switching system as disclosed under the title of “WDM four fiber ring experiment”, B-10-230, page 739, Proceedings of the 1997 IEICE (the Institute of Electronics, Information and Communication Engineers of Japan) General Conference; and
FIG. 2
is a partially redrawn operational diagram illustrating a path switching operation in case of a fault described in this paper.
In
FIG. 1
, a reference numeral
101
designates an acoustooptic filter for isolating any desired wavelength component;
102
designates a 4×4 optical space switch for connecting four optical inputs to four output ports in any desired pattern;
103
designates a recombining element for recombining optical signals;
104
designates an optical amplifier for collectively amplifying wavelength multiplexed optical signals;
105
designates a terminal unit for transmitting and receiving optical signals;
106
designates an east side (denoted as “East side” from now on) working input/output port (denoted as “WRK in/out port” from now on) for interconnecting a working path between nodes;
107
designates a west side (denoted as “West side” from now on) WRK in/out port for interconnecting the working path between nodes;
108
designates an East side preparatory input/output port (denoted as “PRT in/out port” from now on) for interconnecting a preparatory path between the nodes; and
109
designates a west side PRT in/out port for interconnecting the preparatory path between the nodes.
In
FIG. 2
, reference numerals
111
-
114
each designate a node corresponding to the optical switching system as shown in
FIG. 1
;
115
designates an inside transmission path for transmitting optical signals in both directions used as the working path for interconnecting the nodes. The reference numeral
116
designates an outside path for transmitting optical signals in both directions used as the preparatory path for interconnecting the nodes. Reference numerals
117
each designate a 4×4 optical space switch in the node;
118
each designate a working terminal unit connected to the node; and
119
each designate a preparatory terminal unit.
Next, the operation will be described.
In
FIG. 2
, the transmission paths
115
and
116
that interconnect the nodes
111
-
114
are wavelength multiplexed, and are connected to the WRK in/out ports
106
and
107
and PRT in/out ports
108
and
109
of the optical switching system of FIG.
1
. Each acoustooptic filter
101
, receiving a drive signal, isolates a particular wavelength signal to be connected to the optical space switch
102
, and passes the remaining wavelength signals without change. Without the drive signal, all the wavelength optical signals pass through the acoustooptic filters
101
. Thus, each acoustooptic filter
101
is used as a switch for switching whether to remove (denoted as “Drop” from now on) the wavelength from the transmission path or not by the drive signal.
The isolated signals output from the acoustooptic filters
101
are connected to appropriate terminal units
105
via the optical space switches
102
to be received. The individual nodes are each connected to four terminal units
105
, so that they are connected to East side and West side WRK in/out ports and PRT in/out ports.
The optical signals input to the optical switching system through the terminal units
105
are distributed to the appropriate recombining elements
103
at the output ports by the optical space switches
102
, recombined with the optical signals of other wavelengths passing through the acoustooptic filters
101
, and transmitted to adjacent nodes through the output ports as wavelength multiplex signals.
The optical space switches
102
switch, if some fault takes place on the transmission path, the communications on the working system to the recombining elements
103
on the same or reverse direction preparatory path in accordance with the fault pattern, thereby saving the communications on the working system at the cost of the communications on the preparatory system.
Thus, the network is constructed by providing the nodes of the transmission paths with the optical switching system with the foregoing functions and by connecting the transmission paths in a ring-like pattern.
Next, an example of the switching operation in case of a network fault will be described with reference to FIG.
2
.
In a normal operation mode in which no fault takes place, communications can be carried out using the working path and preparatory path as shown in FIG.
2
(
1
). For example, the working terminal units
118
connected to the node
111
and to the node
113
are bidirectionally interconnected through the working path
115
, and the terminal units
119
connected to the node
113
and to the node
114
are bidirectionally interconnected through the preparatory paths
116
.
If a fault takes place on the working path
115
interconnecting the nodes
111
and
113
, and the preparatory path passing through the same route is in a faultless state, the optical space. switches
117
of the nodes
111
and
113
that carry out transmission and reception are switched to the preparatory paths of the same direction as shown in FIG.
2
(
2
), so that the communication path used by the working terminal unit
118
is switched to the preparatory path passing through the same route, thereby detouring the signal flowing through the transmission path
115
to the transmission path
116
, and preventing the transmission path from being disconnected.
If a fault takes place simultaneously on both transmission paths
115
and
116
interconnecting the nodes, the optical space switches
117
of the nodes
111
and
113
switch the input/output ports for transmission and reception to the opposite preparatory path side as shown in FIG.
2
(
3
), thereby detouring the signals to the transmission path
116
passing through the network in the opposite direction, and preventing the working path from being disconnected. In this case, the communications carried out between the nodes
113
and
114
using the transmission path
116
in the faultless state are disconnected to prevent the disconnection of the working transmission path.
FIG. 3
is a block diagram showing another partially redrawn conventionally studied optical switching system as disclosed under the title of “Node configuration on OADM ring system”, B-10-85, page 384, Proceedings of the 1997 Society Conference of the Institute of Electronics, Information and Communication Engineers of Japan.
In
FIG. 3
, reference numerals
121
each designate an optical switching system that receives currently working signals, and switches, in case of a transmission path fault, an optical signal path to an unimpaired transmission path; the reference numeral
122
designates a backup optical switching system used in place of one of the optical switching systems
121
when it is faulty; &lgr;(1)−&lgr;(n+1) each designate an optical signal with a different wavelength; reference numerals
127
-
128
each designate a terminal unit connected to the optical switching system
121
and
122
for transmitting and receiving the optical signals &lgr;(1)−&lgr;(n+1);
123
and
124
each designate a wavelength multiplexer for wavelength multiplexing the optical signals &lgr;(1)−&lgr;(n+1) with different wavelengths transmitted from the terminal units
127
-
128
, and for sending them out to transmitting paths;
125
and
126
each designate a wavelength demultiplexer for demultiplexing the wa
Ichibangase Hiroshi
Kabashima Takatomi
Kitayama Tadayoshi
Kobayashi Naoki
Miyazaki Tetsuya
KDD Corporation
Kim Ellen E.
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