Impact of cascaded thin-film filters on metro networks employing NRZ, LPF-DB, and CSRZ formats

We studied the transmission performance of metro networks employing cascaded thin-film filters (TFFs) for three modulation formats including non-return-to-zero (NRZ), duobinary, and carrier-suppressed RZ (CSRZ). The effects caused by TFFs' dispersion and passband characteristics are investigated for 10- and 40-Gb/s signals, respectively. Simulation results show that the penalty resulted from dispersion can be partially compensated by the passband effects of the cascaded filters. CSRZ is shown to be a preferred format compared with NRZ and duobinary primarily originating from its good back-to-back performance.