In this paper, fibers and transmission system designs using nonlinear optical amplification and frequency conversion in single-mode fibers (SMF) are discussed. Optical amplification of signals issued from laser diodes in the first and second optical transmission windows is reported. Raman gains of 40 dB have been obtained for 1.32 um laser diode light at the rate of 11 dB/W in a 2.5 km long SMF. Parametric amplification of laser diode signals at 1.57µm in a 30 m long SMF pumped in the low dispersion region at 1.32 um is presented. Gain values in excess of 30 dB are measured. Up and down frequency conver-sions using stimulated four-photon mixing experiments are also demonstrated.