Abstract

In this work, based on a conventional silicon photonic travelling-wave Mach-Zehnder modulator (MZM) with a 3-dB bandwidth of 22.5 GHz, we experimentally demonstrate ultra-high speed optical interconnects with Nyquist shaped pulse amplitude modulation (PAM) signals. For bandwidth-limited systems, a two-tap digital post filter is employed to suppress the equalization-enhanced high frequency noise. The post filter induced inter-symbol interference (ISI) is subsequently eliminated by maximum likelihood sequence detection (MLSD). Enabled by the post filter and MLSD, we achieve 200 Gb/s (80 Gbaud) PAM-6 signal direct detection (DD) transmission over 1 km standard single-mode fiber (SSMF) with a bit-error rate (BER) below the 20% hard-decision forward error correction (HD-FEC) threshold of 1.5 × 10⁻². For PAM-4 format, we successfully transmit 192 Gb/s (96 Gbaud) and 176 Gb/s (88 Gbaud) signals over 1 km and 2 km SSMF, respectively, with BERs lower than the 20% HD-FEC threshold. For PAM-8 format, 192 Gb/s (64 Gbaud) and 168 Gb/s (56 Gbaud) signals are generated at back-to-back (BTB) and transmitted over 1 km SSMF, respectively. To our best knowledge, we achieve the highest single lane bitrates ever reported for single polarization PAM-4/6/8 signal generation and DD transmission with all-silicon MZM. The flexible receiver-side digital signal processing (DSP) can significantly enhance the performance of silicon MZM, which provides a promising solution for future single lane 200 G data-center interconnects.

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