Performance Improvement for OADM based DP-QPSK WDM Optical Networks with 37.5 GHz Channel Spacing

Dual polarization quadrature phase shift keying (DP-QPSK) wavelength division multiplexing (WDM) system with 50 GHz channel spacing is currently providing various high-speed data services. The spectral efficiency (SE) of DP-QPSK WDM systems can further be increased by decreasing the channel spacing to 37.5 GHz. The 37.5 GHz frequency grid promises 33% increase in the throughput. However OADMs located at intermediate nodes in an optical network limit the performance of the 37.5 GHz, DP-QPSK WDM system. The narrowband optical filtering and crosstalk introduced by cascading OADMs limits its performance. In this paper, we presents that if the filter order of WDM multiplexer and demultiplexer is kept different it leads to an improvement in the performance of 37.5 GHz, DP-QPSK WDM optical networks. Further a significant improvement can be achieved by assigning unequal launch power on adjacent channels.