LAUSR

100 G/λ amplifier-free direct detection (DD) systems beyond 40-km reach are desirable to enable the next generation cost- and power-efficient 800 G-ER optical modules. Though such systems in the O-band have been demonstrated, an interest remains to leverage the investment in long haul C-band transceivers. To our knowledge, this article reports the first C-band amplifier-free DD system at beyond 100 G throughput over reaches of 40 and 60-km using a high-power single-sideband transmitter (HPSSBT). This transmitter configuration allows for a cost-efficient 100 G transceiver for the datacenter interconnect requiring only a single digital-to-analog converter (DAC), a Mach–Zehnder modulator, a single-ended photodiode with integrated trans-impedance amplifier (PD+TIA), and an analog-to-digital converter (ADC). In this article, we studied the performance impact of key system parameters including the digitally regenerated DC component of the photocurrent, the driving voltage, and the launch power. We also characterized the sensitivity impact of the system nonlinearity and demonstrated the transmission of 155.14 Gb/s and 104.67 Gb/s net rate single sideband (SSB) PAM-4 signals over 40-km and 60-km of single-mode fiber (SMF) below the HD-FEC threshold of 3.8 × 10−3, respectively. Due to the colored SNR, we further approached the system capacity by transmitting a probabilistically-shaped multi-subcarrier (PS-MSC) signal, allowing a throughput of 176 Gb/s over a 40-km SMF assuming an SD-FEC with a normalized general mutual information (NGMI) threshold of 0.88.