Results on computer simulations of a lumped single-pump FOPA (fiber optical parametric amplifier) are presented. We demonstrate optical amplification of a 10 Gbit/s 4-channel S-band DWDM system utilizing a lumped FOPA on a 400 km long link with 80 km long inter-amplifier spans. In most of the recent papers in the field of fiber optical parametric amplifiers research the amount of amplification and the gain bandwidth are considered as the FOPA parameters. We evaluate the effectiveness of FOPA through BER parameter, which depends on both the attenuation of optical signal and the quality degradation due to dispersion, crosstalk and amplifier noise, and therefore is more suitable for evaluation of optical amplifiers in lightwave systems.