Patent ID: 6952308

Claim:
A multi-stage bidirectional optical amplifier with two input/output ports (p 1 , p 2 ) for amplifying counter-propagating upstream and downstream signals, comprising: two input/output ports (p 1 , p 2 ) for amplifying upstream/downstream optical signals proceeding bidirectionally; two single-stage bidirectional optical amplifiers ( 30 a , 30 b ), connected to said input/output ports (p 1 , p 2 ) respectively, each amplifying the counter-propagating upstream and downstream signals optical signals proceeding bidirectionally at the same time; two multiple reflection suppression means ( 28 a , 28 b ) connected to the single-stage bidirectional optical amplifiers ( 30 a or 30 b ) respectively, and arranged to transmit optical signals with specific wavelengths only to one direction and to block the signals in the other direction; and a mid-stage element component ( 42 ), installed between said two multiple reflection suppressing means multiple reflection suppression means ( 28 a , 28 b ) and between said two single-stage bidirectional optical amplifiers, said mid-stage element comprising a means for chromatic dispersion-compensation, a means for widening optical amplifier gain bandwidth, optical amplifier gain-flattening means, a means for minimizing accumulation of optical amplifier noise, a means for add/drop multiplexing, or a combination of these means.