Enhancing of optical spectrum efficiency through reducing the baud rate for advanced modulation techniques

Abstract An essential consideration for an optical network design engineer when starting a wavelength division multiplexing (WDM) network is to improve spectrum efficiency by selecting the optimal baud rate (symbol rate). In this paper will provide a concise overview of the rising baud rates and modulation types, highlighting the key advantages and issues associated with their increments and elucidating the reciprocal correlation that binds them together. Two systems for phase shift keying (PSK) modulations and quadrature shift keying (QAM) modulations are designed and simulated. The results show that the best type of modulation to use for the capacity 100G and 200G is quadrature phase shift keying (QPSK) for different fiber lengths (5, 10, 80, 400, 800 and 6,400 km) depending on the comparison of the type of modulation with received optical signal to noise ratio (OSNR) and log of bit error rate (BER). In this case higher order modulation can be used, but that will direcvtly affect optical reach and that is what will highlight by studying the effect of changing the types of modulation for many of the distances that mentioned to get better modulation order than QPSK for required capacity 100G and 200G within those lengths that provide smaller baud rate and better spectrum efficiency.