Optically restorable WDM ring network using simple add/drop circuitry

An apparatus for restoring a parallel optical ring network, said network comprising a first optical fiber, a central transmitter coupled to one end of said first optical fiber, a second optical fiber, a central receiver coupled to one end of said second optical fiber, at least one local station, said at least one local station comprising a local receiver and a local transmitter, said apparatus comprising:

• central sensing means for sensing a fiber failure centrally and providing a central alarm;
• coupling means for coupling another end of said first optical fiber to said central receiver and coupling another end of said second optical fiber to said central transmitter in response to said central alarm signal;
• local sensing means for sensing a fiber failure locally and providing a local alarm;
• local switching means for switching having a first position and a second position, said local switching means moving from said first position to said second position in response to said local alarm;
• wherein said local transmitter is coupled to said second optical fiber and said local receiver is coupled to said first optical fiber when said local switching means is in said first position, said local transmitter is coupled to said first optical fiber and said local receiver is coupled to said second optical fiber when said local switching means is in said second position, and said central transmitter momentarily stops transmitting a signal to each of said at least one local station from which a signal has not been received by said central receiver.

A method for restoring a parallel ring network, said network comprising a first transmission medium, a central transmitter coupled to one end of said first transmission medium, a second transmission medium, a central receiver coupled to one end of said second transmission medium, at least one local station, said at least one local station comprising a local receiver and a local transmitter, said method comprising the steps of:

• sensing a transmission medium failure centrally;
• providing a central alarm signal in response to said transmission medium failure centrally;
• coupling another end of said first transmission medium to said central receiver in response to said central alarm signal;
• coupling another end of said second transmission medium to said central transmitter in response to said central alarm signal;
• sensing a transmission medium failure locally;
• providing a local alarm signal in response to said transmission medium failure locally;
• switching said local transmitter from said second transmission medium to said first transmission medium in response to said local alarm signal;
• switching said local receiver from said first transmission medium to said second transmission medium in response to said local alarm signal;
• and,
• stopping said central transmitter momentarily from transmitting a signal to each of said at least one local station from which a signal has not been received by said central receive.

A central apparatus for restoring a parallel ring network, said network comprising a first transmission medium, a second transmission medium, at least one local station, said at least one local station comprising a local receiver and a local transmitter, said apparatus comprising:

• a central transmitter coupled to one end of said first transmission medium;
• a central receiver coupled to one end of said second transmission medium;
• central sensing means for sensing a transmission medium failure centrally and providing a central alarm;
• coupling means for coupling another end of said first transmission medium to said central receiver and coupling another end of said second transmission medium to said central transmitter in response to said central alarm,
• wherein said central transmitter momentarily stops transmitting a signal to each of said at least one local station from which a signal has not been received by said central receiver.