Impact of cascaded optical filters on 100 Gb/s PM-QPSK and 400 Gb/s PM-16QAM coherent communication systems

In this paper, the impact of cascading optical filters on 100 Gb/s and 400 Gb/s systems has been studied using two types of filters: fiber Bragg grating (FBG) and thin-film filters (TFF). Simulation results indicate a smaller eye closure penalty (ECP) for TFF cascade relative to FBG filter cascade. At 3-dB ECP, the number of cascaded filters for single-carrier 100 Gb/s polarization-multiplexed quadrature phase shift keying (PM-QPSK) system is 4 TFF and 2 FBG with 3-dB bandwidth of 43 GHz at 50 GHz channel spacing. Also simulation results indicate that at 3-dB ECP, the number of cascaded filters for single-carrier 400 Gb/s polarization-multiplexed 16-ary quadrature amplitude modulation (PM-16QAM) system is 2 TFF with 3-dB bandwidth of 90 GHz at 100 GHz channel spacing. A single FBG with 3-dB bandwidth of 90 GHz at 100 GHz channel spacing results in an ECP of 4-dB for 400 Gb/s PM-16QAM system.