Optical beam former for cellular CO-OFDM systems

In this paper, design and simulation of optical beam former for cellular coherent optical OFDM (CO-OFDM) system with high data rate is addressed. We first discuss the generation of CO-OFDM symbols and then present the MEMS (micro electro mechanical systems) based optical beam former. The optical OFDM signal destined for a mobile terminal is split into eight equal-intensity signals. Each signal is complex weighted by controlling the phase and amplitude using a pair of micromirrors driven by electrostatic comb drive actuators. The processed optical signal is heterodyned with phase locked local optical signal. The resulting weighted microwave signal is then fed to the corresponding element of the 1 times 8 antenna array. The complex weights are computed using maximum directivity (MD) algorithm for specified directions of arrival of signals and interferences. The radiation patterns of the proposed multi beam forming network are simulated using MATLAB & SIMULINK for different sets of look directions and null directions. The beam steering is found to be satisfactory in a 120deg sector.