FIELD: optical communication. SUBSTANCE: invention is related to multiwave bi-directional optical amplifiers carrying four-port communication device for spectral multiplexing. Four-port communication device for spectral multiplexing has dichroic filter to reflect signals of first range of length of waves coming into device and to output of device designed for output of signals of specified first range of length of waves and to let signals of second range of length of waves coming into device pass to output of device meant for output of specified second range of length of waves in which portion of signal of first three-decibel length of wave of first range of length of waves islet by mentioned filter pass and in which portion of signal of second three-decibel length of waves of second range of length of waves is reflected by said filter. Device also has additional dichroic filter that shows such filtering characteristic which differs from characteristic of filter of spectral multiplexing of device and secures value of introduced loss for at least one of first and second three-decibel lengths of waves sufficient correspondingly in substance to at least one of first and second three-decibel lengths of waves sufficient for reflection and transmission of whole signal of first and second three-decibel lengths of waves. Dichroic filters are additionally used to suppress light of three-decibel length of wave in order to prevent Q-modulation in amplification resonator formed in multiwave bi-directional amplifier of optical signal due to presence of reflection point in optical path connected to amplifier. EFFECT: enhanced efficiency of device and procedure. 14 cl, 11 dwg
