Transmission of 28-Gb/s Duobinary and PAM-4 Signals Using DML for Optical Access Network

Abstract

We explore the possibility of utilizing 1.55-μm directly modulated lasers (DMLs) for optical access networks operating at 28 Gb/s per wavelength. For this purpose, we attempt to maximize the power budgets of 28-Gb/s duobinary and four-level pulse amplitude modulation (PAM-4) signals generated from a DML without using optical amplifiers or optical dispersion compensation modules. For experimental investigation, we set the bias current of the DML far above the threshold current, optimize the extinction ratio of the signals, and utilize the electrical equalization at the receiver. The experimental results show that we can secure power margins of 9.6 and 10 dB after transmission over 40-km long standard single-mode fiber for the duobinary and PAM-4 signals, respectively.