Patent ID: 7853153

Claim:
A fourth harmonic generating system using optical double side-band suppressed carrier modulators, the system comprising: a first optical double side-band suppressed carrier modulator ( 2 ); a second optical double side-band suppressed carrier modulator ( 3 ), the second optical double side-band suppressed carrier modulator ( 3 ) being connected in series to the first optical double side-band suppressed carrier modulator ( 2 ); a signal source ( 4 ) for generating a modulating signal, the modulating signal being applied to the first optical double side-band suppressed carrier modulator ( 2 ) and the second optical double side-band suppressed carrier modulator ( 3 ); and a signal controller ( 5 ) for controlling a modulating signal, the modulating signal being applied to the first optical double side-band suppressed carrier modulator ( 2 ) and the second optical double side-band suppressed carrier modulator ( 3 ) by the signal source ( 4 ), wherein “a lower side-band signal of the second optical double side-band suppressed carrier modulator ( 3 ) which is a modulated signal of an upper side-band signal of the first optical double side-band suppressed carrier modulator ( 2 )” and “an upper side-band signal of the second optical double side-band suppressed carrier modulator ( 3 ) which is a modulated signal of a lower side-band signal of the first optical double side-band suppressed carrier modulator ( 2 )” cancel each other, whereby a fourth harmonic signal is obtained.