ABSTRACT
We experimentally demonstrate PAM-8 generation from binary electrical signals driving a silicon multi-electrode Mach-Zehnder modulator acting as an optical digital-to-analog converter. Measured BER in back-to-back configuration is used to evaluate signal quality. We demonstrate 38 GBd PAM-8 transmission below the forward error correction (FEC) threshold using minimum mean square error (MMSE) equalization. The results show that modulators with segmented phase shifters can be advantageously used to eliminate the need for high bandwidth electronic digital-to-analog converters in the generation of multilevel signals. These modulators, that can be designed and fabricated with standard CMOS compatible tools and processes, are of high interest for short range high-speed data links.
ABSTRACT
We demonstrate PAM-4 and OOK operation of a novel silicon photonic modulator. The modulator design is based on two phase-shifts in a Bragg Grating structure driven in a push pull configuration. Back-to-back PAM-4 modulation is demonstrated below the FEC threshold at up to 60 Gb/s. OOK modulation is also shown up to 55 Gb/s with MMSE equalization and up to 50 Gb/s without equalization. Eye diagrams and BER curves at different bit rates are provided for both PAM-4 and OOK modulations. To our knowledge, this structure is the fastest silicon photonic modulator based on Bragg gratings, reaching modulation speed comparable to the fastest Mach-Zehnder modulators and micro-ring modulators.