PERFORMANCE EVALUATION OF SPECTRAL EFFICIENCY IN LINEAR REGIME FOR HIGH RATE WDM SYSTEM

This paper addresses the effect of various system parameters on the spectral efficiency of wavelength division multiplexing (WDM) systems. Three types of WDM systems wereinvestigated: unconstrained modulation with coherent detection (UMCD) system, constantintensitymodulation with coherent detection (CIMCD) system, and unconstrained modulation with the direct detection (UMDD) system. Expressions are derived and presented to assess the spectral efficiency of these systems in the linear regime only. Simulation results are presented to assess the effect of various system parameters such as amplifier noise figure, number of spans and span length on the spectral efficiency. The results indicate clearly that the spectral efficiency increases almost linearly with both optical signal-to-noise ratio (SNR) and input power, and this effect is more pronounced at high SNR. The UMCD system offers the highest spectral efficiency followed by CIMCD system. The UMDD system shows the lowest efficiency compared with other systems. The efficiency decreases with increasing number of spans, and this effect is more pronounced for the UMCD system.