Optical signal switching device for use in an optical protection network

A switching device for a communication node including an optical signal transceiver comprising at least one optical signal transmitting device and at least one optical signal receiving device to transmit and receive an optical signal to and from an opposite communication node, said switching device comprising:

• a first multiplexing and demultiplexing device including a first bi-directional port connected to said optical signal transmitting communication line, and a second multiplexing and demultiplexing device including a second bi-directional port connected to said optical signal receiving communication line;
• and
• a first optical switch which selects one of said first and second multiplexing and demultiplexing devices to be connected to said optical signal transmitting device, and a second optical switch which selects one of said first and second multiplexing and demultiplexing devices to be connected to said optical signal receiving device
• wherein said switching device configured to be connectable to at least one piece of an optical signal transmitting communication line to transmit an optical signal to said opposite communication node, at least one piece of an optical signal receiving communication line to receive an optical signal from said opposite communication node, said optical signal transmitting device and said optical signal receiving device,
• wherein, when no failure has occurred in said optical signal transmitting communication line and in said optical signal receiving communication line, an optical signal fed from said optical signal transmitting device is transmitted to said optical signal transmitting communication line and an optical signal fed from said optical signal receiving communication line is transmitted to said optical signal receiving device, and
• wherein, when a failure has occurred in said optical signal transmitting communication line, switching is done such that said optical signal fed from said optical signal transmitting device is transmitted via said second bi-directional port to said optical signal receiving communication line and, when a failure has occurred in said optical signal receiving communication line, switching is done such that said optical signal to be fed to said optical signal receiving device is received via said first bi-directional port from said optical signal transmitting communication line.

A switching device that transmits a plurality of external optical signals through a plurality of optical signal communication lines, comprising:

• a plurality of optical multiplexing and demultiplexing devices each corresponding to one of said plurality of optical signal communication lines and each device including a bi-directional communicating input port and a bi-directional communicating output port, wherein optical signals of different types are communicated between said bi-directional communicating input and output ports of different devices of said plurality of optical multiplexing and demultiplexing devices through one of said plurality of optical signal communication lines that corresponds to specific optical multiplexing and demultiplexing devices;
• and
• a plurality of optical switches that correspond to and communicates one of said plurality of external optical signals between said plurality of optical signal communication lines and a bi-directional communicating input and a bi-directional communicating output port of one of said specific optical multiplexing and demultiplexing devices, wherein when no failure has occurred in one of said plurality of optical signal communication lines, and when a failure has occurred in one of said plurality of optical signal communication lines, said one of said plurality of external optical signals is communicated to a bi-directional communicating input and a bi-directional communicating output port of an other of said specific optical multiplexing and demultiplexing devices, and
• wherein bidirectional communication are conducted through the input and output ports.

A communication node comprising:

• an optical signal transceiver including an optical signal transmitting device and an optical signal receiving device to transmit and receive an optical signal to and from another communication node;
• an optical signal transmitting communication line to transmit an optical signal to said another communication node;
• an optical signal receiving communication line to receive an optical signal from said another communication node;
• and
• a switching device comprising:
• a first multiplexing and demultiplexing device including a bi-directional port connected to said optical signal transmitting communication line, and a second multiplexing and demultiplexing device including a bi-directional port connected to said optical signal receiving communication line;
• and
• a first optical switch which selects one of said first and second multiplexing and demultiplexing devices to be connected to said optical signal transmitting device, and a second optical switch which selects one of said first and second multiplexing and demultiplexing devices to be connected to said optical signal receiving device.