Patent ID: 7787772

Claim:
An optical line amplifier for bi-directional optical transmission system comprising a first input/output port, a second input/output port, an optical amplifying means, a first wavelength division multiplexing means, a second wavelength multiplexing means, a third wavelength multiplexing means, a fourth wavelength multiplexing means, a first variable optical signal attenuating means, and a second variable optical signal attenuating means: wherein, (a) an optical signal of a first wavelength inputted from said first input/output port is transmitted to said second input/output port through said first wavelength division multiplexing means, said first variable optical signal attenuating means, said second wavelength division multiplexing means, said optical amplifying means, said third wavelength division multiplexing means, and said fourth wavelength division multiplexing means; and (b) an optical signal of a second wavelength inputted from said second input/output port is transmitted to said first input/output port through said fourth wavelength division multiplexing means, said second variable optical signal attenuating means, said second wavelength division multiplexing means, said optical amplifying means, said third wavelength division multiplexing means, and said first wavelength division multiplexing means.