Hybrid radio over fiber system for generation and distribution of UWB signals

The authors investigate a hybrid radio over fiber system for the generation and distribution of UWB signals. This system is based on gain-switched laser, which is used to generate short optical pulses. The position of these pulses is modulated using electrical data before transmitting them to the remote antenna unit (RAU). At the RAU, the optical signal is detected and undergoes spectral shaping (according to UWB requirements). The resulting pulse position modulated (PPM) electrical impulses are then down-converted to baseband using an electrical mixer. After strong low pass filtering, bit error rate measurements are carried out in order to verify the performance of the system. Error free operation is achieved for optical power levels as low as -16 dBm falling at the detector in RAU. The impact of fiber transmission on the generated UWB signal is also investigated via a simulation model. The evolution of the pulse- and spectral width of the UWB pulses, as the signal travels over different lengths of fiber, is recorded. Results achieved show that the pulse- and spectral width are strongly affected by chromatic dispersion of the fiber. However, these changes can be easily reverted using standard dispersion compensation techniques.