The main goal of this paper is to investigate the ability of a single-pump fiber optical parametric amplifier with linearly polarized pumping radiation to provide binary polarization shift keying to intensity on-off keying modulation format conversion in a single channel optical transmission system. The amplifier produced up to 14.8 dB of on-off gain, and it was demonstrated that such level of amplification is sufficient to provide modulation format conversion, while maintaining acceptable quality of the converted signal. It was found that due to fiber birefringence the original state of polarization needs to be recovered at the input of the amplifier, otherwise, drop in amplification and converted signal discrepancies will occur.