Patent ID: 7349636

Claim:
An optical communication system ( 100 ) comprising: a first apparatus ( 110 ) to transmit at least a digital optical signal ( 160 ) with a simultaneous modulation of the amplitude and the phase, the said first apparatus ( 110 ) comprising: a) a laser light source ( 102 ), that furnishes a substantially continuous flow of optical radiation, b) an optical modulator with dual drive design ( 104 ), having at its input a substantially continuous flow of optical radiation, to modulate the optical power in the said optical signal ( 160 ) with an encoded sequence of dark pulses ( 328 ), being representative of a first Non-Return-to-Zero (NRZ) data electrical signal NRZ A , referred below as Amplitude Tributary ( 106 ), and to simultaneously modulate the optical phase in the said optical signal ( 160 ) with a second encoded sequence ( 330 ), representative of a second NRZ data electrical signal NRZ φ , referred below as Phase Tributary ( 108 ), the said two sequences ( 328 , 330 ) having bit rate R and bit period T B =1/R, c) an electrical driving circuit for the said optical modulator ( 104 ), having at its input the said Amplitude and Phase Tributaries ( 106 , 108 ) at bit rate R, and generating two driving electrical signals V 1 ( 148 ) and V 2 ( 150 ) applied to the two electrical inputs of the said dual drive modulator ( 104 ); an optical transmission line ( 170 ), optically connected to the said first apparatus ( 110 ), for the propagation of the said optical signal ( 160 ); a second apparatus ( 180 ), optically connected to the said optical transmission line ( 170 ), to receive the said optical signal ( 160 ), the said second apparatus ( 180 ) comprising: d) an optical filter ( 182 ) to select in frequency the said optical signal ( 160 ), e) a non-polarizing beam splitter ( 184 ) to split the said optical signal ( 160 ) and apply the two portions to respectively an optical intensity receiver ( 186 ) and an optical phase receiver ( 188 ), f) an optical intensity receiver ( 186 ) of type for intensity modulation with direct detection (IM-DD), g) an optical phase receiver ( 188 ), for the phase detection of the said optical signal ( 160 ).