This paper presents investigation of the impact of electro-absorption modulator integrated laser (EML) on performance of multiband-orthogonal frequency-division-multiplexing (MB-OFDM) ultra wideband (UWB) signal over single-mode fiber transmission by theoretical and experimental analysis, considering various parameters, such as fiber length, bias voltage, modulation power, bias current, and temperature of EML. The effect of the EML modulation nonlinearities on the OFDM subcarriers in MB-OFDM UWB over fiber system is investigated considering intermodulation distortion (IMD) and adjacent channel power ratio. It is shown that MB-OFDM UWB over fiber is limited by SNR for small modulation power and EML modulation nonlinearities induced IMD for high modulation power. Fiber transmission length is mainly degraded by EML phase noise converted relative intensity noise and power fading. The developed theory is verified by experiments.