Burst-Mode Multi-Level-CPFSK Signal Detection Using DD-LMS Based Adaptive Equalizer for High-Speed TDM-PON Upstream

This paper evaluates the link budget for burst-mode single wavelength 50-Gbps 4-level continuous phase frequency shift keying (CPFSK) signal reception in time domain multiplexing (TDM) based digital coherent optical access networks. The key advances of the burst-mode CPFSK transmitter and receiver are as follows; simple EA-DFB-SOA based transmitter that suppresses the intensity modulation component generated by direct modulation of the DFB-LD, a burst-mode DSP that reduces convergence time of the adaptive finite impulse response (FIR) filter-based equalizer by using the tap coefficient handover method with simple decision-directed least mean square (DD-LMS) algorithm. The results of burst-mode experiments show the proposal offers high link budget of 40.7 dB with 32.8 ns short preamble. In addition, we calculate and compare the BER characteristics for higher baud rate 4-level CPFSK signals (37.5 Gbaud, and 50 Gbaud) and higher level CPFSK signals (8- and 16- level CPFSK signals) detection as a feasibility study for beyond 50-Gbps optical access networks.