Patent ID: 7006723

Claim:
An optical add/drop multiplexer comprising: a multiplexing/demultiplexing unit including an input multiplexing port, an output multiplexing port and a plurality of demultiplexing ports; connected to respective ones of the plural demultiplexing ports, a plurality of optical circulators each including a first port for internally inputting an added channel, a second port for outputting the added channel over the connection to the output multiplexing port and for receiving a channel over the connection from the input multiplexing port, and a third port for externally outputting the channel received over the connection; and associated with a first one and a second one of the plural optical circulators, an optical switch that includes: a first input port, coupled to the third port of said first one, for receiving said channel received by said first one; a second input port for receiving said added channel to be outputted by said second one; a first output port, coupled to said first port of said second one, for outputting said added channel to said first port of the second one; and a second output port for externally outputting said channel received by said first one according to a dropping operation.