O-Band 10-km PAM Transmission Using Nonlinear-Spectrum-Shaping Encoder and Transition-Likelihood-Based Decoder with Symbol- and Likelihood-Domain Feedbacks

We show that a nonlinear-spectral-shaping scheme with transition-likelihood-based decoder including symbol- and likelihood-domain feedbacks enhances the tolerance to bandwidth limitation and achieves KP4-FEC threshold in 10-km O-band transmission of 93-Gbaud PAM4 with very severe bandwidth limitation in which the 20-dB bandwidth is 40 GHz.