Electrical Equalization Analysis of PAM-4 Transmission in Short-Reach Optical Systems

Inclusive and intensive performance analysis of electrical equalizers in a short-reach optical system using four-level pulse amplitude modulation (PAM-4) is presented in this paper. Two equalizers are used—a feedforward equalizer and decision feedback equalizer using the least mean square algorithm. The sensitivity to cut-off frequency for the transmitter and receiver filters, fiber length and number of equalizers taps in the means of the bit error rate vs. optical input power are shown. The analysis reveals the considerable impact of the filters’ bandwidth, particularly in the receiver, on the equalizer performance. These results and their reasons are analyzed and broadly discussed