Impact of Chromatic Dispersion on NRZ, RZ and DPSK Modulation Formats in Different Optical Links of a 402 km Metropolitan Optical Backbone

Abstract

The use of optical fiber has revolutionized the optical telecommunications sector. Optical fiber enables faster data transmission in telecommunications networks. Data transmitted in fiber optic systems are affected by several phenomena during their propagation such as chromatic dispersion (CD). This phenomenon causes signal broadening and inter symbol interferences, resulting in signal distortion and data loss. This reduces the data transmission capacity in the optical fiber. The transmitted data is modulated according to a specific modulation format before being sent into the fiber. It is therefore important to choose a good modulation format in order to reduce the dispersion effect. In this article we aim to present a comparative analysis of CD effect on signals modulated with NRZ, RZ and DPSK modulation formats respectively. The study is carried out by simulation with OPTISYSTEM software, considering a 402 km metropolitan backbone of a telecommunication operator in Togo (West Africa). The study takes into account both the full 402 km link and individual sections of the backbone using an ITU-T G.652.D optical fiber at 10 Gbps and 100 Gbps bits rate with a wavelength of 1550 nm. In order to evaluate the quality of transmission we used performance indicators such as Min BER and Q-Factor. The results show that chromatic dispersion reduces signal quality during transmission and that the NRZ modulation format outperforms RZ and DPSK formats in terms of signal quality at 10 Gbps but all formats fail at 100 Gbps.