Multiple-Beam Fiber-Optic Beamformer With Binary Array of Delay Lines

A multibeam optical beamformer capable of controlling a phased-array antenna in receive/transmit mode is proposed. The processor can be programmed to sweep the antenna aperture following an independent angular sequence for each radio-frequency (RF) beam. A two-beam two-channel 3-bit version of the beamformer has been experimentally demonstrated. The optical beamformer processes two independent RF beams, for eight different angular directions, and it is based on a binary array of three delay lines. Each delay line is composed of four fiber Bragg gratings whose center wavelengths are channels 30 to 33 of the International Telecommunications Union (ITU) grid. Measurements are performed for both receive and transmit modes and for RF values between 0.5 and 1.5 GHz. We present beam-pattern results showing the squint-free performance of the beamformer within this frequency range. In the transmit mode, two RF beams are steered and characterized for a broadside target position. In the receive mode, the beamformer performance is characterized by detecting two simultaneous RF beams.