OPTICAL PHASE AND AMPLITUDE CONTROL FOR BEAMFORMING WITHMULTIWAVELENGTH GIRES-TOURNOIS BRAGG GRATING CAVITIES

摘要

We present a novel optical beamformer based onGires-Tournois fibre Bragg grating coupled cavities(GT-BF). This beamformer allows for independent con-trol of both amplitude and phase of each antenna in an 8elements array. It is designed to be used in radio-over-fibre (ROF) dense wavelength division multiplexed an-tenna remoting links with 25 GHz wavelength spacing,and allows for remote centralized array control. TheGT-BF is optimized for 802.11a/g/n 5GHz signals with20 MHz bandwidth, but we explore its performances up to100 Mhz bandwidth. This is not a true time delay beam-former so the bandwidth is limited by the "beam squint"effect. The GT-BF is designed for the double sideband(DSB) optical modulation format, which is simple andallow for the use of low cost modulators. Finally, thisbeamformer can compensate for dispersion of the ROFlink, which otherwise would cause DSB signal attenua-tion. The GT-BF is controlled by stretching or by adjust-ing the temperature of the Gires-Tournois fibre Bragggrating coupled cavities. The former method allows forfaster adjustment of the array radiation diagram.