In this article, we propose the generation of a microwave signal through a VCSEL Based Optoelectronic Oscillator (VBO) for free space communication applications. This system is implemented using VCSELs in the O-band and C-band. The signals generated at 1.25 GHz and 2.49 GHz are used to produce experimentally Return-to-Zero On Off Keying (RZ-OOK) and Return-to-Zero Differential Phase Shift Keying (RZ-DPSK) modulations for free space optical communication.