Multi-value modulation apparatus

摘要

In the multi-value modulation apparatus, one optical intensity detecting unit (13) detects optical intensity of a modulation optical signal generated by one optical modulation signal generating unit (10) and output from the variable optical attenuator (12). The detected optical intensity is provided to the comparator (16). Another optical intensity detecting unit (14) detects optical intensity of a modulation optical signal output from another optical modulation signal generating unit (11). The attenuator (15) attenuates the optical intensity detected by the another optical intensity detecting unit (14), and provides it to the comparator (16). The output of the comparator is provided to the optical variable attenuator as a control signal. The variable optical attenuator (12) controls optical intensity of the modulation optical signal based on the control signal.