Improved filter concatenation tolerance using duobinary modulation format for metropolitan area networks

In this paper a simulation study of a metropolitan area networks (MAN) scenario is carried out. The MAN is incorporating a number of nodes with optical add-drop-multiplexers (OADMs) each one incorporating two filters. The work focuses on the filter concatenation using standard nonreturn-to-zero (NRZ) and DBR modulation formats and compares their system performance. The filters used in the simulations were 3/sup rd/ order Bessel (AWG transfer function) and Butterworth (TTF transfer function) filters. Results are taken for 10 Gb/s systems with 100, 50 and 25 GHz channel spacing. The 3 dB filter bandwidth in all cases is assumed to be 65% of the channel spacing, which is consistent with commercially available components.