Theoretical characteristics research of fiber-Bragg gratings

Fiber Bragg gratings (FBGs) are essential optical components in fiber-optic sensing systems and are widely used in modern fiber-optic communication systems. Most FBGs are side-written, and because the writing light source itself exhibits polarization characteristics, a certain level of birefringence is inevitably introduced during fabrication. This results in polarization-dependent characteristics in the fabricated gratings. With the rapid development of high-speed fiber-optic communication and fiber-optic sensing technologies, both exploiting and suppressing the polarization effects of FBGs have become increasingly important. In this work, we focus on fiber Bragg gratings and analyze their behavior using coupled-mode theory, thereby establishing the theoretical foundation for accurate characterization of their optical properties.