Improving the performance of NRZ‐DPSK optical fiber networks using adaptive FSR in the receiver

Abstract

In this work, we consider the impact of spectral narrowing of 43Gb/s NRZ-DPSK signals on the system performance. NRZ-DPSK signals passing through reconfigurable optical add/drop multiplexer (ROADM) devices are subject to spectral narrowing due to the narrow bandwidth of ROADMs. For a system level analysis of this phenomenon, we model the ROADM devices as a bandpass filter, the bandwidth of which is deliberately decreased. The dependence of the system performance on the delay time between adjacent bits in the receiver is also investigated. It is shown that the performance of signals passing through ROADM devices can be improved with an appropriate delay line interferometer (DLI) for any amount of devices. These results were obtained by simulating the whole system performance using different values of the BPF bandwidth and FSR. We present a technique for finding the optimal FSR of DLI that allows for improving the performance of NRZ-DPSK systems in the presence of spectral narrowing of the channel. Improved bit error ratio is achieved by using optimized FSR for each BW.