Continuous true-time-delay beamforming employing a tunable multiwavelength fiber ring laser source with equally increased or decreased wavelength spacing

Abstract

The authors propose a true-time-delay system for wideband continuous phased array beamforming using a chirped grating-based true-time-delay beamforming network incorporating a novel multiwavelength tunable fiber ring laser with equally increased or decreased wavelength spacing. The wavelength of each lasing is determined by the fiber Bragg grating in the laser cavity and tuned by compressing or stretching the fiber Bragg grating. For simultaneously achieving N tunable lasings, N fiber Bragg gratings are used. To ensure wavelength tuning with equally increased or decreased wavelength spacing, the N fiber Bragg gratings are mounted on an organic plastic plate with angles between adjacent gratings such that the tuning forces applied to the gratings experience equal increments. Time delays with equally increased or decreased time-delay difference for the equally spaced wavelengths are obtained when the modulated light waves are reflected at different locations of a linearly chirped grating. A four-channel chirped-grating-based true-time-delay system using the proposed light source for continuous beamsteering at microwave frequencies up to 10 GHz has been constructed and demonstrated.