Spectral compression of pulses due to self-phase modulation and group velocity dispersion on direct detection optical transmission system

The performance of optical transmission system, which operates at data rates above 10 Gb/s is limited by fiber nonlinearity and group velocity dispersion (GVD). In this paper we have solved the nonlinear Schrödinger equation analytically using Volterra series for studying the impact of self-phase modulation (SPM) and GVD only on direct detection fiber-optic transmission system. In the anomalous dispersion regime of standard single mode fiber (SSMF), the SPM induced chirp is positive and GVD induced chirp is negative and as a result at relatively short distance the propagating pulse spectrally get compressed. It is found that increasing the peak input power in the range 70 – 80 mW, the bit distance product is nearly 1.28 times higher at a distance of 8.5 km when operating in the anomalous-dispersion regime at 1550 nm for constant unchirped Gaussian input pulse width of 25 ps.