Three-element fiber-type optical phased array antenna with high-speed two-dimensional optical beam steering

Abstract

A fiber-type optical phased array antenna is proposed as a new configuration of phased array antennas operating in the optical frequency domain. The proposed antenna consists of fibers that connect an optical beamforming network consisting of integrated optical waveguides to an array antenna consisting of microlenses as the element antenna. High-speed two-dimensional optical beam steering can be achieved by reducing the relative phase fluctuation between element antennas and the generation of the grating lobe. In an experiment on the three-element fiber-type optical phased array antenna, three 1 × 2 variable power dividers and four variable phase shifters are integrated on a LiNbO3 substrate as the optical beamforming network, and graded-index-fiber (GIF) lenses are used as the antenna elements. These components are connected through polarization-maintaining fibers (PMF). The 3-dB bandwidth of the integrated variable phase shifter is from dc to 924 MHz, and the optical beam steering range of the three-element array is 0.2°; they are arranged in a triangle. The parameters of the GIF lens are optimized and it is estimated that at the maximum gain coefficient a grating lobe level of –14.5 dB and a gain coefficient of 0.815 can be obtained. © 1999 Scripta Technica, Electron Comm Jpn Pt 1, 82(8): 42–51, 1999