Abstract: A bi-directional optical communication system. A first optical fiber includes a plurality of pieces, each piece having a first and second end. An optical amplifier for amplifying optical signals transmitted in a first direction is coupled to first and second pieces of the first optical fiber. A second optical fiber is coupled to the first and second pieces, bypasses the optical amplifier and transmits optical signals in a second direction opposite to the first direction. A first optical signal generator apparatus coupled to the first piece of the first optical fiber provides optical signals propagating in the first direction to a optical receiver apparatus coupled to the second piece of the first optical fiber. A second optical signal generator in the optical receiver apparatus provides optical signals propagating in the second direction to the first optical signal generator apparatus.

Abstract: A method for optical switching using an optical directional coupler. In a first step, excitation light is supplied to an interaction region of the coupler having input and output ports. The interaction region is doped with an active ion having the capability for optical amplification. In a second step, signal light is inputted to one of the input ports and amplified in the interaction region. In a third step, the signal light is outputted from one of the output ports depending on whether saturation of optical gain takes place or not.