Reach Extension of a 53.12 Gbps PAM-4 IM/DD Signals With Optimized Extinction Ratio in Amplified Multi-Span O-Band Transmission

This paper explores, through the utilization of analytical models and simulations, the bit error rate (BER) of 400GBASE-LR8/ER8 in back-to-back configuration, considering various extinction ratio (ER) values and photodetector types. Simulation of transmission over fiber is carried out to measure chromatic dispersion (CD) penalty in each scenario. To increase the distance, we simulated a multi-span transmission with inline optical amplifiers (OAs). We mitigated the effects of CD-induced power fading by employing equalization such that the channel under test (CUT) at 1274 nm could reach
$7\times 30$
km. The effects of fiber nonlinearity were also investigated for both single-channel and 3 wavelength division multiplexing (WDM) at various channel spacings. Moreover, the relationship between ER and peak-to-average-power ratio (PAPR) at different distances was investigated. An ER optimization for a highly accumulated CD multi-span fiber link with amplification was effective in improving the BER. Finally, we successfully transmitted a 26.56 GBaud 4-level pulse amplitude modulation (PAM-4) signal up to
$8\times 30$
km with the optimal ER of 5 dB.