US Patent 7110674 Optical add/drop device

Disclosed herein is an optical add/drop device including an optical demultiplexer for separating WDM signal light into n optical signals where n is an integer not less than 2, n first optical switches to which the n optical signals output from the optical demultiplexer are supplied, respectively, a second optical switch for adding provided on the input side of the first optical switches, a third optical switch for dropping provided on the output side of the first optical switches, n regenerators for wavelength converting the optical signals passed through the first optical switches, and an optical multiplexer for wavelength division multiplexing the wavelength-converted optical signals. A transmission distance between nodes can be increased by using this device.