Optical Phase and Amplitude Control for Beamforming with Multiwavelength Gires-Tournois Bragg Grating Cavities

M.M. Sisto, M.E.M. Pasandi, S. Doucet, S. LaRochelle, and L.A. Rusch (Canada)

Keywords

Beamforming, beamsteering, antenna array, wavelength multiplexed radiooverfibre links, GiresTournois cavity.

Abstract

We present a novel optical beamformer based on Gires-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 8 elements 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. The GT-BF is optimized for 802.11a/g/n 5GHz signals with 20 MHz bandwidth, but we explore its performances up to 100 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 and allow for the use of low cost modulators. Finally, this beamformer can compensate for dispersion of the ROF link, 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 Bragg grating coupled cavities. The former method allows for faster adjustment of the array radiation diagram.

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