The aim of this work is to offer different alternatives for an OFDM PON networks, studying and analyzing many systems with their pros and cons and proposing news schematics for a multiuser scenario for the uplink. The systems analyzed are composed by an optical I/Q transmitter and two types of receivers, a DD and a hybrid 90º coherent receiver. A new technique, called predistortion, that improves the drawbacks of the conventional oIQ systems is studied. The idea to perform the multiuser scenario is shifting the user data, allowing allocation of each user in a given optical spectral band. All the simulations have been done using the commercial software VPItransmissionMakerTM and VPIphotonicsAnalyzerTM, (VPI) in combination with a code in Matlab for the OFDM coder and decoder. Also the performance of the optical OFDM systems is measured by means of a script in TCL/TK language that allows changing many parameters, in order to test and obtain results of the systems performance in terms of sensitivity vs. length for a threshold minimum quality BER value of 10-3.