850-nm VCSEL-Based Single-Lane 200-Gbps PAM-4 Transmission for Datacenter Intra-Connections

A demonstration of an 850-nm vertical cavity surface emitting laser (VCSEL) based 200-Gb/s PAM-4 transmission over 100-m OM4 multimode fiber (MMF) is presented. To overcome the large Inter-symbol Interference (ISI) caused by bandwidth limitation and to compensate the non-linearity caused by optics, we propose to combine noise cancellation algorithm, partial response signaling and simplified Volterra nonlinear equalizer (NLE) in the digital signal processing (DSP). A power margin about 4 dB for 50-m MMF transmission and 3 dB for 100-m MMF transmission is observed. Different DSP configurations are also experimentally evaluated. The use of the simplified Volterra NLE enables the BER to be improved from
$2\times 10^{- {2}}$
to
$1.1\times 10^{- {3}}$
. A 2.5 dB power margin improvement is also achieved by employing the noise cancellation module.