Comparison of post-equalizers for beyond 100-Gb/s/λ C-band signal transmission over a 100-km dispersion-uncompensated SSMF

A comprehensive comparison among different post-equalizers with relatively low complexity is studied for C-band 100-km dispersion-uncompensated standard single-mode fiber (SSMF) intensity modulation and direct detection (IM/DD) transmission systems with data rate beyond 100 Gb/s/λ. These representative post-equalizers include feed-forward equalizer (FFE), polynomial-based nonlinear FFE (P-NFFE), absolute-term based nonlinear FFE (AT-NFFE), FFE combined with decision-feedback equalizer (FFE-DFE), polynomial based nonlinear FFE-DFE (P-NLE), absolute-term based nonlinear FFE-DFE (AT-NLE), and their lower-complexity versions of FFE-DFE-WS, P-NLE-WS, and AT-NLE-WS which use weight sharing (WS) to eliminate weight redundancy. We demonstrate 100-Gb/s/λ and 112-Gb/s/λ on-off keying (OOK) transmissions over a 100-km SSMF. For 112-Gb/s transmission, BERs of FFE-DFE(-WS), P-NLE(-WS), and AT-NLE(-WS) can reach 7% hard-decision forward error correction (HD-FEC) limit at 3.8 × 10−3. Under 7% HD-FEC limit, AT-NLE-WS with 32 real-valued multiplications shows similar BER performance as P-NLE and AT-NLE with a small power penalty of < 0.4 dB, but outperforms P-NLE-WS, AT-NLE, and P-NLE in huge complexity reduction of approximately 83.2%, 92.4%, and 92.7%, respectively. Therefore, taking both the BER performance and the operation complexity into account, AT-NLE-WS is the optimal equalizer and is a strong candidate to be applied in low-cost C-band IM/DD interconnections with data rates beyond 100 Gb/s/λ and transmission distance up to 100 km.