Design and analysis of high-speed optical access networks in the O-band with DSP-free ONUs and low-bandwidth optics.

In this paper, we demonstrate and investigate high-speed passive optical networks (PON) in the O-band without using any digital signal processing (DSP) at the ONU side, meanwhile still adopting cost-effective low-bandwidth optics. We show that with commercial 10G-class optics including DML and PIN-TIA, 50Gb/s PAM4 PON with a power budget up to 29dB is achieved under the HD-FEC BER limit. We present the detailed design procedure of the DSP including the downlink Nyquist pulse shaping and pre-equalization and uplink post-equalization, and conduct a comprehensive study on this system including DSP complexity, DAC/ADC sampling rate requirement and tolerance to the response diversity of ONU receivers. We conclude that, 1) 55 and 35 taps are sufficient for downlink and uplink digital filters to approach the BER floor; 2) the minimum required DAC and ADC sampling rate are respectively 33.75GS/s and 32GS/s to achieve the optimal performance; and 3) with 1dB sensitivity penalty at the HD-FEC BER limit, the allowable response diversity of ONU receivers can be from -2.2dB/10GHz to 1.8dB/10GHz. Furthermore, we explore and demonstrate the suitable data rate based on on-off keying and duobinary modulation formats in this system and present corresponding results.