Highly dispersive photonic crystal fiber for beamforming

Abstract

In this paper, a highly dispersive pure silica photonic crystal fiber is designed and fabricated with maximum chromatic dispersion value of about -600 ps/(nm·km) around 1.55 μm wavelength region. This kind of a photonic crystal fiber structure is suitable for high dispersion application in photonic crystal fiber array based phased array antenna systems. A four-element true-time delay module is constructed using the fabricated highly dispersive photonic crystal fibers. The true time delay value of 10.5m PCF is characterized to provide maximum delay of 31.3ps with 32nm optical wavelength tuning range, which is sufficient to scan from -45° to 45° for a 4-element PAA subarray having 1.3cm spacing. A multiple-beam optical beamformer is designed based on the fabricated highly dispersive photonic crystal fibers. The true-time delay beamformer can be programmed to continuously sweep the antenna aperture independently for multiple RF beams. Since the dispersion of the fabricated photonic crystal fibers is as high as -600 ps/nm•km at 1550 nm, compared to telecom SMF-28 that has a dispersion parameter of 18 ps/nm•km, the length of delay line is reduced by a factor of 33.