Beyond 100-Gbps IM/DD Optical Interconnects at 2-Micron Waveband Under Severe Bandwidth Limitation Enabled by Advanced DSP

The 2-micron waveband has attracted significant attention for its potential of expanding bandwidth in fiber optic communication systems from its current Tele- and Data-communication wavelength windows. However, unlike C-band equipment with mature fabrication techniques and ecosystem, devices such as modulator and photodetector at 2-micron waveband suffer from limited electronic bandwidth and pronounced nonlinearities, introducing severe inter-symbol interference (ISI) that constrains transmission capacity. In this paper, we propose an improved Volterra nonlinear equalizer (VNLE) for a high-speed intensity-modulated direct detection (IM/DD) transmission system achieving a net-bitrate beyond 100 Gbps at 2-micron waveband under severe bandwidth limitation. Experimental results from a transceiver system with an end-to-end 3-dB (20-dB) bandwidth of only <5 GHz (19 GHz) show that, the proposed improved VNLE reduces multiplication computations by 22% compared to the traditional scheme, while enhancing BER performance and receiver power sensitivity. Additionally, we achieve line-rates of 104/105.7/132.2 Gbps and the corresponding net-rates of 97.2/98.1/102.4 Gbps over 100-m solid core fiber (SCF) using PAM4, PCS-PAM8, PCS-PAM16 modulation formats, respectively, with the help of the look-up table (LUT) based nonlinear pre-distortion at the transmitter and the proposed improved VNLE at the receiver. To the best of our knowledge, these experimental results set new records for transmission capacity of single-lane demonstrations at 2-micron waveband, presenting a promising high-speed and short-reach optical interconnect scheme for this promising spectral region.