300-Gb/s/λ IM/DD Transmission Using Integrated SiP OTDM Transmitter

We fabricate an integrated silicon-photonic (SiP) 2-channel optical-time-division-multiplexing (OTDM) transmitter, which is operable with a sinusoidally modulated input light source. This SiP transmitter consists of two Mach-Zehnder modulators (MZMs), two
$1 \times 2$
multimode interferometer (MMI) couplers, a time-delay line (TDL), and a thermo-optic phase shifter (TOPS). The 3-dB bandwidth of these MZMs is measured to be as large as 60 GHz. However, due to the limited bandwidths of the various components used in our experiment, the overall bandwidth of each OTDM channel is reduced to
$\sim $
35 GHz. Nevertheless, by using this SiP transmitter, we could demonstrate the transmission of a 300-Gb/s OTDM pulse-amplitude modulation 8-level (PAM8) signal over 500 m of the standard single-mode fiber (SSMF). We also confirm that the fabricated SiP OTDM transmitter can be utilized even with the fabrication fluctuations of the TDL.