Fiber Bragg Gratings for Microwave Photonics Applications
Microwave photonics is a field that studies the interaction between microwave and optical waves for the generation, distribution, control, and processing of microwave signals in the optical domain. Various photonic components are needed in microwave photonic systems, such as optical sources, optical amplifiers, dispersive elements, modulators, optical filters, and photodetectors to implement these functions. This chapter provides an introduction to fiber Bragg grating (FBG), including the operation principle, the design, and fabrication. It reviews the applications of FBGs in microwave photonic systems to achieve true-time delay beam forming for phased-array antennas, microwave filtering, and high-quality microwave signal and arbitrary microwave waveform generation. The relationship between the spectral characteristics of an FBG and the corresponding grating refractive index modulation profile can be analyzed by using the coupled-mode theory (CMT). CMT is a straightforward, intuitive, and powerful tool for obtaining quantitative information on the spectral properties for an FBG with a given structure.