A simple pulse shape randomization scheme is considered in this paper for improving the performance of Ultra Wide band (UWB) communication systems using On Off Keying (OOK) or Pulse Position Modulation (PPM) formats. The advantage of the proposed scheme, which can be either employed for Impulse Radio (IR) or for carrier-based systems, is first theoretically studied based on closed-form derivations of power spectral densities. Then, we investigate an application to an IR-UWB over optical fiber system, by utilizing the 4-th and 5-th orders of Gaussian derivatives. Our approach proves to be effective for 1 Gbps-PPM and 2 Gbps-OOK transmissions, with an advantage in terms of power efficiency for short distances. We also examine the performance for a system employing an in-line Semiconductor Optical Amplifier (SOA) with the view to achieve a reach extension, while limiting the cost and system complexity.