Optical Beamforming of Multiple Independent-Simultaneous RF Beams for Secure Communications

Abstract

We propose and demonstrate a novel architecture for processing simultaneous independent RF beams. The proposed optical processor technology employs wavelength division multiplexing (WDM) encoding and technologies that enhances secure communications for a wide bandwidth of operation. In our example of two-channel approach, four adjacent ITU optical WDM channels are used as optical carriers. Each pair of optical carriers directs RF information of one receive/transmit beam. The optical channels feed a 3-bit programmable dispersion matrix (PDM), which performs true-time delay processing. The PDM is based on three optical delay lines, arranged in a binary or ternary configuration. Each delay line consists of four fiber-Bragg gratings (FBG). The separation between FBG increases by multiples of two for each delay line. Beampatterns are characterized in receive and transmit modes for RF signals in 0.5-1.5 GHz range and are obtained for target angles of plusmn70deg. The measurement results demonstrate the simultaneous processing of two RF-beams and the squint free nature of the beamformer. The scaled up version of beamformer to large array size and its simultaneous multiple-beam processing will be presented. We would also describe a potential architecture of an all-optical delta-sigma modulator that can be implemented in a digital transmit/receive beamformer