In this work, a VCSEL simulator has been developed. Starting from a single-mode rate-equation model, several characteristics have been studied and implemented: DC characteristics (steady state), small signal response, Relative Intensity Noise (RIN). Later on, also the effects of electrical parasitics have been taken into account. Based on experimental data extracted from a VCSEL sample (provied by OptiGOT), parameters have been fine-tuned to match a realistic scenario. After this preliminary work, a complete transmission link has been implemented, to check the impact of RIN (Relative Intensity Noise) when a modulated signal is sent as input to the VCSEL. Both binary and PAM-4 modulations have been analyzed.