Beyond 1.6 Tb/s Net Rate PAM Signal Transmission for Rack-Rack Optical Interconnects With Mode and Wavelength Division Multiplexing
Dongdong Zou, Fan Li, Wei Wang, Zixuan Zhang, Jinkun Hu, Jianping Li, Qi Sui, Chao Lü, Zhaohui Li
Abstract
In this article, a beyond 1.6 Tb/s net rate pulse amplitude modulation (PAM) communication system is experimentally demonstrated for 20 m rack-rack optical interconnects with low cost intensity modulation direct detection (IM-DD) architecture, which is enabled by mode division multiplexing (MDM) and wavelength division multiplexing (WDM). The MDM with three linearly polarized modes is realized by a multiplane light conversion (MPLC) mode multiplexer with the maximum modal crosstalk less than - 20 dB. The experimental results show that 2.01 Tb/s (1.84 Tb/s net rate) PAM-6 signal carried on three modes and four wavelengths is successfully transmitted over 20 m standard OM2 multimode fiber (MMF) with the BERs of received signals from all channels below hard decision forward error correction (HD-FEC) threshold of 3.8 × 10-3. Look-up table (LUT) pre-distortion and Volterra nonlinear equalizer (VNLE) are employed for nonlinear impairment mitigation to improve the system performance. Compared to linear feedforward equalizer (FFE), 0.3 dB and 1 dB receiver sensitivity improvements are obtained by LUT and VNLE, respectively. To the best of our knowledge, our proposed scheme achieves the highest bit rate of 167.5 Gb/s per wavelength in MDM system with IM-DD structure. The experimental results show that our proposed PAM MDM communication scheme is a promising candidate for future 1.6 Tb/s short reach rack-rack optical interconnects.