This MSc dissertation presents a theoretical analysis that evaluates the distortion experienced by the power spectrum density of OFDM signals when they are transmitted through a non-linear channel. The complex envelope of the OFDM signals are modeled as a complex proper gaussian random process and the channel non-linearity is characterized through a power series expansion of its AM/AM and AM/PM distortion curves. Using the Moment Theorem for complex gaussian random processes, closed form expressions for the autocorrelation function and the power spectrum density of the signal produced at the non-linear channel output are obtained. These expressions are applied to specific situations in which 1, 2 and 3 OFDM signals share the nonlinear channel, producing results that quantify the distortions corresponding to intermodulation products of different orders and the effect of varying the signal input back-off value.