Characteristics of fiber Bragg gratings in spun fibers

Abstract

The long-span and high-speed optical transmission networks require high-quality optical cables and components to reduce the detrimental effects of polarization-mode dispersion (PMD) and polarization-dependent loss (PDL) on system performance. In addition, many high-accuracy fiber-optic sensing networks also require low polarization-dependent components. As a result, polarization-insensitive transmission fibers and components have been pursued recently. A well-established technique to produce low-PMD and PDL fibers is to spin the fiber during the fiber drawing process, known as spun fibers. As key optical components, fiber Bragg gratings (FBGs) play important roles in optical fiber communications and fiber sensors. However, FBGs written into traditional single-mode fibers exhibit relatively high polarization dependence due to the birefringence introduced by side UV exposure in FBG fabrication process. In this paper, we report for the first time the characteristics of FBGs written into spun fibers that were formed by spinning fibers with certain intrinsic birefringence. Distinct properties of FBGs in spun fibers are found in the experiments, compared to those in traditional single-mode fibers. Based on Jones matrix method, the FBG spectra are simulated and compared with the measured ones. Preliminary experimental results indicate that the spun fiber gratings suffer lower PMD under the same fabrication conditions. Moreover, our theoretical analysis shows that the PMD and PDL characteristics of spun fiber gratings can be further improved by optimizing the structures of spun fibers.