Tuning Of Fiber Bragg Grating Technology And Applied Research In The Phased Array Radar

Optical fiber grating are one kind of the passive photonic device formed by ultraviolet light into the core of a photosensitive fiber. With the advantages of low insertion loss, resistance to electromagnetic interference and easy system integration, the fiber gratings have been widely applied in optical fiber communication, fiber sensing, information processing and other fields. Especially, in phased array radar beam-forming network, fiber gratings, instead of the traditional phased array radar microwave phase shifters, can resolve the problem of signal instantaneous bandwidth limited by the aperture diameter and the transit time. The beampointing angles can be controlled continuously by tuning the fiber gratings.In relation to the tuning of fiber grating and its application in phased array radar, the main contents in this thesis are as following:Firstly, starting with the grating equation of the fiber grating, we study the impact of stress, temperature and magnetic field on the fiber grating, and deduce the corresponding wavelength-tunable equations.Secondly, we analyze the tuning principles of fiber grating which is based on simple beam, piezoelectric ceramic and magnetostrictive devices. We prove that the spectral width and center wavelength of fiber gratings can be tuned by making use of simple beam, piezoelectric ceramic and magnetostrictive devices. When simple beam is used, the spectral width of fiber grating broadens with the increasing of the simple beam deflection. When piezoelectric ceramic device is used, fiber gratings stretched uniformly, the center wavelength will shift to the long wavelength with the increasing of the piezoelectric ceramic actuator voltage, while the spectral width maintains. When the fiber gratings are stretched non-uniformly, the spectral width broadens with the increasing of the piezoelectric ceramic actuator voltage. When magnetostrictive device is driven by a homogeneous magnetic field, the center wavelength will shift to the long wavelength with the increasing of the coil-driven currents.Finally, through experimental studies and simulations, we prove that the delay characteristics of fiber gratings can be tuned by simple beam, piezoelectric ceramic and magnetostrictive devices. When fiber gratings are tuned by simple beam, the slope of time delay curve decreases with the increasing of the simple beam deflection. When fiber gratings are stretched uniformly by piezoelectric ceramic device, the time delay of fixed wavelength optical carrier increases with the increasing of the piezoelectric actuator voltage. When a fiber grating is stretched non-uniformly by a number of piezoelectric ceramic devices, the slope of time delay curve decreases with the increasing of the voltage difference of adjacent piezoelectric ceramic device. When magnetostrictive device is used to tune, driven by a homogeneous magnetic field, the time delay curve will shift, while its slope maintains.