Patent ID: 7199921

Claim:
A system comprising a pair of two stage amplifiers arranged at two spatially separate modules, for respectively serving two opposite directions of bi-directional optical transmission comprising one or more informational channels each serving exclusively for transmitting optical traffic and not performing supervisory channel functions, wherein each of the two-stage optical amplifiers comprises a 1 st stage, a 2 nd stage and a mid-stage formed between said two stages, and serves one of the two opposite transmission directions, and wherein each stage of said two stages is formed by at least one optical amplifying unit and is located at a spatially separate module, so that each of the two spatially separate modules accommodates the 1 st stage of one of said amplifiers and the 2 nd stage of the other of said amplifiers; the system comprises at least two Optical Add Drop Multiplexers (OADMs) connected in the mid-stages of said two-stage optical amplifiers and adapted to add and drop said one or more informational channels.