With the view to achieve a reach extension, the use of a Semiconductor Optical Amplifier (SOA) is investigated here for Impulse Radio Ultra Wide Band (IR-UWB) over fiber systems. Due to the nonlinear effects occurring when the amplifier operates in its saturated region, designing pulse shapes appears to be challenging for such systems. By calibrating the key parameters of some Gaussian pulses based on the photo-detected spectrum, and by considering a highly accurate SOA model, we show that a significant power efficiency improvement can be achieved. In particular, it is demonstrated that an efficiency greater than 50% can be reached with Abraha's linear sum of modified doublets, while operating at a strongly saturated point (0 dBm input power). Moreover, we examine the benefits of the proposed pre-distortion scheme in presence of 1.6 Gbps-OOK and 0.8 Gbps-PPM modulation formats, significant performance gains being obtained over a large transmission distance.