The performance of orthogonal frequency division multiplexing ultra wideband (UWB) radio signals distribution in long-reach passive optical networks (LR-PONs) using conventional chirp-less Mach Zehnder (MZ) and linearized (L) Y-fed directional couplers electro-optic modulators (EOMs) is compared. Particularly, the optimum modulation index and the corresponding minimum optical signal-to-noise ratio (OSNR) required to achieve a bit error probability of 10-12are evaluated through numerical simulation for systems operating with single and three UWB sub-bands and different standard single-mode fiber (SSMF) distances indicated for LR-PONs. Both modulators are characterized experimentally and theoretical model parameters are adjusted to correctly describe the power and chirp characteristics of the electro-optic conversion in the simulation process. It is shown that the optimum modulation index and the tolerance to modulation index variations, considering either single or multi band UWB operation, is approximately two times higher for systems employing L-EOM than MZ-EOM. Additionally, with MZ-EOM, the required OSNR may increase considerably when the fiber length increases due to the power fading induced by fiber chromatic dispersion, achieving a penalty of almost 3 dB for systems with 100 km of SSMF and single UWB sub-band operation. Instead, with L-EOM, the required OSNR penalty (when compared with the back-to-back case) is lower for fiber lengths up to 100 km than it is for systems employing the MZ-EOM modulator due to the combined effect of the chirp generated by the modulator and the chromatic dispersion.

A novel photonic analog-to-digital converter (ADC) architecture tailored for the localization of transmitters employing ultra-wide band (UWB) radio technology is proposed and experimentally demonstrated in this paper. The proposed photonic-ADC architecture comprises several parallel branches each including an electro-optic sensor at different spatial locations capturing UWB signals simultaneously (sub-picosecond resolution). A single optical source is required in this architecture for all electro-optic sensors and also a single processing unit is needed to process the optically sampled data, thus simplifying the system implementation. A five-branch photonic-ADC has been developed for the experimental demonstration. The laboratory measurements demonstrate the successful detection and localization of fully-standard UWB transmitters as in WiMedia specification for very-low power radio signals (-65 dBm received power) captured. A mean three-dimensional positioning error of 48.5 cm with 15 cm standard deviation is achieved.

The interference produced by WiMAX mobile wireless transmissions operating in the 3.5 GHz band on a WiMedia-defined ultra-wideband (UWB) wireless link is experimentally analyzed in this paper. The investigation includes standard IEEE 802.16e WiMAX, and ECMA-368 UWB equipment as defined by the WiMedia alliance. A conventional meeting room scenario has been considered for the measurements. The experimental results indicate that WiMAX transmitters must be located at distances larger than 5 m from the UWB receiver to guarantee successful UWB communication.