The interest of implementation of advanced modulation formats in metro and access networks has experienced a steady increase under the influence of exponentially increasing data amount from multimedia services like videoconferencing, high definition television, video on demand, interactive games and others. The transition period to advanced modulation formats requires a solution for efficient all-optical modulation format conversion to avoid replacement of the existing end-user hardware with the more expensive and complex devices capable of processing of advanced modulation formats. In this paper the authors have investigated the opportunity of all-optical modulation format conversion from binary polarization shift keying to intensity on-off keying in optical metro and access network using a single-pump fiber optical parametric amplifier. This preamplifier ensures up to 30 dB of gain and provides efficient modulation format conversion in the access network. Such additional functionality of single-pump parametric amplifiers in optical access networks has not been demonstrated so far.