Orthogonal Frequency Division Multiplexing, OFDM, is an emerging modulation technique which is now used in most broadband wired and wireless communication systems. Its narrow multi-carrier nature provides a very effective solution to the undesirable effects caused by dispersive channels. The OFDM applied to optical systems has been studied recently concluding that it is an appropriate solution to the chromatic dispersion, the most stringent impairment in single mode optical systems. This Master Thesis presents a study of optical OFDM techniques applied to optical networks. From the many different strategies presently available for optical OFDM, here we focus in the most simple and cost-effective Intensity Modulation / Direct Detection with RF upconversion. The Virtual Photonics software is used to simulate point-to-point OFDM links in the presence of signals coming from other users in order to see the effect of Optical Beat Interference (OBI), one of the more detrimental effects in optical OFDMA networks. Mathematical models are used to help to understand the results of simulations and based on that, strategies to overcome OBI are proposed. A multiuser uplink simulation scenario has been built up, taking advantage of the VPI functionalities such as Cosimulation, definition of global variables that can automatically be updated, etc. The result has been a user-friendly and scalable simulation platform that allows for easy setup of simulations of the uplink of OFDMA networks, ready for the testing of the different OBI cancellation strategies also identified in this work.