Pulse amplitude modulation communication in terahertz-band using asymmetric Mach-Zehnder interferometer-type optical signal emulator

We report on pulse amplitude modulation (PAM) communication in the terahertz (THz)-band using an integrated-optic PAM signal emulator, which consists of asymmetric Mach-Zehnder interferometer (MZI). The asymmetric MZI, whose edge couplers are composed of symmetric MZIs (coupling ratio tunable couplers), produces an optical PAM signals from an input optical on-off keying signal by adjusting each phase shift at each interferometer arm. We generated an optical 25 Gsymbol/s three-level PAM (PAM3) signal with this emulator and converted the generated optical signal into a PAM3 signal in the 300 GHz band with high-speed photo-mixing. We show obtained results on the THz-wave 25 Gsymbol/s PAM3 communication.