Patent ID: 7058313

Claim:
A multi-value modulation apparatus comprising: N+1 (N≧1) number of optical modulation signal generating units, each optical modulation signal generating unit generating a binary modulation optical signal based on amplitude-modulation of an input electric signal; N number of optical intensity control units, each optical intensity control unit controlling an optical intensity of modulation optical signal output from a corresponding one of said optical modulation signal generating units based on a control signal; N+1 number of optical intensity detecting units, each one of N optical intensity detecting units detecting an optical intensity of modulation optical signal output from a corresponding one of said optical intensity control unit, and N+1-th optical intensity detecting unit detecting an optical intensity of modulation optical signal output from said optical modulation signal generating unit that does not have a corresponding optical intensity control unit; a control unit which receives detection signals output from said optical intensity detecting units, and outputs the control signal to each said optical intensity control unit so that the optical intensity of modulation optical signal controlled by each said optical intensity control unit becomes a predetermined value, based on the optical intensity of modulation optical signal output from said optical modulation signal generating unit that does not have a corresponding optical intensity control unit; and an optical combining unit which combines the 5 modulation optical signal output from said optical modulation signal generating unit that does not have a corresponding optical intensity control unit and the modulation optical signals controlled by each said optical intensity control unit to output a multi-valued modulation optical signal.