Phase modulation apparatus, transmitting apparatus, receiving apparatus, and phase modulation method

Abstract

It is aimed to provide a phase modulation apparatus that realizes high-precision phase modulation in high-speed phase modulation of dual optical pulses. A phase modulatorincluded in the phase modulation apparatus, when a dual optical pulse with a time difference composed of a signal optical pulse SP and a reference optical pulse RP passes therethrough, phase-modulates this dual optical pulse in proportion to an applied voltage of an electrical pulse. As a result, a phase-modulated SP' and a phase-modulated RP′ are output. A modulation signal generatoroutputs an electrical pulse of a predetermined bias at an input timing of a trigger signal, according to an input of a four-valued data signal, for example. The modulation signal generatoroutputs, for one input of the trigger signal, a dual electrical pulse having a time difference and having opposite polarities. The time difference of this dual electrical pulse corresponds to the time difference of the dual optical pulse that passes through the phase modulator