Patent ID: 8687970

Claim:
A Modulator and Demodulator System for a Differential Optical Modulation Format with Eight Phase Changes (SDPSK) comprising: a modulator comprising three cascade phase modulators ( 5 , 6 , 7 ) and a precoder ( 8 ); and a demodulator comprising three branches with parallel Mach-Zehnder interferometers ( 9 , 10 , 11 ), wherein each interferometer is followed by a conditioning stage and electronic signal processing to recover transmitted signals; wherein the first branch of the demodulator contains a balanced electro-optical detection using two photodetectors ( 12 ), followed by a conditioning and a direct component eliminator ( 15 ) and a limiting amplifier ( 16 ), wherein the conditioning stage consists of a third order 20-GHz low-pass Bessel electronic filter ( 13 ) and an electronic amplifier ( 14 ); wherein the second branch of the demodulator contains a balanced electro-optical detection using two photodetectors( 12 ), followed by a conditioning stage and a direct component eliminator ( 15 ), an absolute value signal extractor ( 17 ), and another direct component eliminator ( 15 ), wherein the conditioning stage consists of a third order 20-GHz low-pass Bessel electronic filter ( 13 ) and an electronic amplifier ( 14 ); wherein the third branch of the demodulator has a balanced electro-optical detection using two photodetectors ( 12 ), followed by a conditioning and a direct component eliminator ( 15 ), an absolute value signal extractor ( 17 ), a second direct component eliminator ( 15 ), a second absolute value signal extractor( 17 ), and a third direct component eliminator( 15 ), wherein the conditioning stage consists of a third order 20-GHz low-pass electronic Bessel filter ( 13 ) and an electronic amplifier ( 14 ).