Pattern dependency comparison of four different 40-Gb/s optical duobinary transmitters using low-bandwidth modulators

Abstract

We investigate the pattern dependency of the 40-Gb/s optical duobinary signals generated by a 10-Gb/s-rated Mach-Zehnder modulator with four different configurations. These configurations correspond to all possible combinations of a 15-GHz-bandwidth low-pass filter and a 0.24-nm bandwidth optical filter used to shape up the duobinary signals. We compare through experiment the back-to-back sensitivities and transmission performances of the duobinary signals for pseudorandom bit sequence lengths of 2(7)-1 and 2(31)-1. The results show that the combination of the 10-Gb/s-rated modulator and the 0.24-nm optical filter exhibits the best performance in terms of both the receiver sensitivity and pattern dependency owing to the good frequency response of the optical filter. (C) 2008 Elsevier B.V. All rights reserved.