FIELD: optical amplifiers. SUBSTANCE: optical amplifier incorporating several amplifier channels has first amplifier channel for transmitting and amplifying first in-band optical-coupling signal including wavelength-selective filter essentially used for disabling propagation and amplification of out-of-band optical- coupling signal in first amplifier channel; second amplifier channel for transmitting and amplifying second in-band optical-coupling signal including wavelength-selective filter used essentially for disabling propagation and amplification of out-of-band optical-coupling signal in second amplifier channel; wavelength-selective filters are disposed in respective amplifier channels so as to ensure desired noise and output power in device. EFFECT: reliable suppression of cross-color or optical loss that might otherwise cause multibeam interference, return loss, and self-oscillations. 14 cl, 5 dwg
