In this paper we present results from the study of optical signal amplification using Raman assisted fiber optical parametric amplifier with considerable benefits for S-band telecommunication systems where the use of widely used erbium-doped fiber amplifier is limited. We have created de-tailed models and performed computer simulations of combined Raman and fiber optical parametric amplification in a 16-channel 40 Gbps/channel wavelength division multiplexed transmission system. Achieved gain bandwidth, as well as transmission system parameters—signal-to-noise ratio and bit-error-ratio—were analyzed by comparing the Raman assisted fiber optical parametric amplifier to the single pump fiber optical parametric amplifier. Results show that the 3 dB gain bandwidth in the case of combined amplification is up to 0.2 THz wider with 1.9 dB difference between the lowest and highest gain.