240 Gbit/s Silicon Photonic Mach-Zehnder Modulator Enabled by Two 2.3-Vpp Drivers

We recently reported for the first time 200 Gbit/s/λ net rate data transmission with a single silicon photonic modulator in an intensity modulation direct detection link. Our demonstration relied on an in-house designed, O-band segmented-electrode MZM. In this article, we detail the optimization of the modulator driving scheme, bandwidth/efficiency trade-off and modulation format enabling this result. We use two single-ended RF signals, each having 2.3-Vpp amplitude only, to drive two 1.5-mm modulator segments and transmit data at 80 Gbaud PAM-8 (240 Gbit/s) across 2 km under the 20% soft-decision forward error correction BER threshold of 2E-02. We further decrease the BER using maximum likelihood sequence detection (MLSD), and discuss the related implications. Additionally, we present the system margins regarding modulator drive voltage, received optical power and equalizer taps. At 240 Gbit/s line rate, the modulator energy consumption is only 73 fJ/bit at the SD-FEC threshold. We finally discuss practical implementation considerations for our system.