Modulation device for generating optical signal with quadruple frequency and method thereof

A modulation device for generating an optical signal with multiple frequency, which is used to be implemented in a wavelength-division-multiplexer (WDM) system, said modulation device comprising:

• an electrical signal generator for generating a first modulation signal and a second modulation signal, wherein a phase difference between said first modulation signal and said second modulation signal is 90 degree;
• an optical signal generator for generating an optical signal;
• and
• a first integrated modulator for receiving said optical signal and modulating said optical signal to a first output optical signal with multiple frequency, said first integrated modulator comprising:
• a first modulation unit for receiving said optical signal and said first modulation signal, and modulating said optical signal according to said first modulation signal while said first modulation unit is biased to transmit said optical signal in maximum value;
• a second modulation unit for receiving said optical signal and said second modulation signal, and modulating said optical signal according to said second modulation signal while said first modulation unit is biased to transmit said optical signal in maximum value;
• and
• a third modulation unit for receiving said first modulation signal and said second modulation signal, and generating said first output optical signal with multiple frequency while said third modulation unit is biased to transmit said first optical signal and said second optical signal in minimum value.