Patent ID: 7398022

Claim:
A device 120 for modulating a digital optical signal 160 , said device 120 comprising: a) an optical modulator with dual-drive design 104 , having at input a substantially continuous flow of optical radiation, to modulate the optical power in said optical signal 160 with a train of optical pulses with repetition rate R (GHz) and to simultaneously modulate the optical phase in said optical signal 160 with a M-levels phase driving signal V φ 141 at symbol rate R (Gsymbol/s) and symbol period T B =1/R (s), representative of n=log 2 M input binary electrical tributaries 108 , having each the bit rate R, b) a clock signal 106 at frequency R/2 (GHz), delayed by (h+½)T B , respect to said phase signal 141 , being h an integer number, and suitably amplified to produce the amplitude driving signal V A 140 , c) an electrical pre-encoding circuit 130 , having at input the n electrical tributaries 108 , generating the M-ary phase driving signal V φ 141 , d) electrical circuits to analogically add 144 and subtract 145 said driving signals, according to the equations V 1 ( t )= V A ( t )+ V φ ( t )+ V bias V 2 ( t )=− V A ( t )+ V φ ( t ) (7) whereas V 1 , V 2 and V bias are respectively the two driving voltages and the bias voltage applied to the modulator 104 .