Passive Optical Networks (PONs) are becoming a mature concept for the provision of enormous bandwidth to end-users with low cost. In this paper we study the call-level performance of two PON configurations: the OCDMA-PON and the Hybrid WDM-OCDMA PON. We propose analytical models for calculating connection failure probabilities (due to unavailability of a wavelength) and call blocking probabilities (due to the total interference on a call that may exceed a permissible threshold) in the upstream direction. The PONs are described/modeled by onedimensional Markov chains. Bysolving them, we derive recurrent formulas for the blocking probabilities. The proposed analytical models are validated through simulation; their accuracy was found to be absolutely satisfactory.