O-band EML and 4-bits DAC enabled 112 GBaud PAM8 transmission over a 10 km SSMF without optical amplifiers

The increasing traffic of intra-data center networks creates an urgent demand for low-cost and high-speed intensity modulation/direct detection (IM/DD) transmission. In this Letter, we propose a joint scheme combining nonlinear lookup table (NL-LUT) pre-distortion, digital pre-emphasis (DPE), and a digital resolution enhancer (DRE) to achieve high-speed and low-cost IM/DD optical links using a low-resolution digital-to-analog converter (DAC). The NL-LUT and DPE are responsible for the system nonlinear impairments and channel attenuation at high frequency, respectively, while DRE handles the quantization noise (QN) caused by high peak-to-average ratios (PAPRs) and low-resolution DAC. Leveraging the advanced pre-compensation scheme at the transmitter, we experimentally demonstrate the O-band transmission of 124 GBaud and 112 GBaud PAM8 over 2 km and 10 km SSMF, respectively, using only a 4 bits DAC and a simple 5-tap linear equalizer at the receiver-side. To the best of our knowledge, among the reported demonstrations using the low-resolution DAC without an optical amplifier, this work achieves the highest net rates of 310 Gb/s over 2 km and 280 Gb/s over 10 km of SSMF, respectively, which offers a promising solution for low-cost high-speed IM/DD transmission.