Simulation study of the self-phase modulation effect in 30km optical link of a metropolitan backbone network

This study investigates the impact of Self Phase Modulation (SPM) on optical signals under varying input power levels, different modulation formats and fiber parameters in a 30km optical link, representative of a typical metropolitan backbone network. The increasing intensity of light signals in fiber networks introduces nonlinear optical effects and can significantly impair signal quality. Among these nonlinear phenomena, the Self Phase Modulation (SPM) effect induced by nonlinear refraction, results from the interaction between the optical pulses transmitted and the nonlinear response of the propagation medium. It causes phase and frequency distortions and produces a broadening of the signal spectrum. In this paper, through numerical simulations we analyse the evolution of optical pulses under the influence of SPM effect propagating in a single mode fiber. We consider a 30km optical link of a metropolitan backbone network with its real-parameters. The results reveal critical thresholds for signal degradation and demonstrate the interplay between SPM-induced spectral broadening and dispersion. We observe the broadening of the signal spectrum as the injected power increases independently of the modulation format. The findings provide valuable insights into optimizing metropolitan optical networks, ensuring robust performance under high data rates traffic conditions.