C-band 200 Gbit/s/λ PAM-4 transmission over 2-km SSMF using look-up-table pre-distortion combined with nonlinear Tomlinson-Harashima pre-coding

Abstract

The performance of high baud-rate intensity modulation direct detection (IM-DD) transmissions is severely degraded by both the linear and nonlinear inter-symbol interference (ISI). Here, we propose and experimentally demonstrate a transmitter-side look-up-table pre-distortion combined with nonlinear Tomlinson-Harashima pre-coding (LUT_PD-NTHP) scheme with the capability of mitigating the linear and nonlinear ISI simultaneously, enabling a C-band 200 Gbit/s/λ PAM-4 transmission over 2-km standard single mode fiber (SSMF), under an end-to-end 10-dB bandwidth of about 20 GHz. The proposed LUT_PD-NTHP scheme is experimentally verified to be superior to the LUT pre-distortion combined with linear THP (LUT_PD-LTHP) scheme, in terms of both the receiver sensitivity and the LUT storage requirement, when only the feed-forward equalization (FFE) is used at the receiver-side. In particular, after the 200 Gbit/s PAM-4 signal transmission over the 2-km SSMF without the chromatic dispersion (CD) compensation, the proposed LUT_PD-NTHP scheme with a LUT pattern length of 3 possesses not only 0.25 dB improvement of the receiver sensitivity but also about 99% LUT pattern reduction, in comparison with the LUT_PD-LTHP scheme with a LUT pattern length of 5.