Fabrication, Characterization, and Sensing Applications of a High-Birefringence Suspended-Core Fiber

In this paper, we report on the fabrication, characterization, and sensing applications of a high-birefringence suspended-core fiber (HB-SCF) using the stack-and-draw technique. Capillaries in two sizes were used for stacking, forming an elliptical core, giving rise to geometric modal birefringence of the HB-SCF. Through a finite-element method, the theoretical values of the phase and group modal birefringence of the HB-SCF were found to be 2.59 ×10^-4 and 4.75 ×10^-4, respectively. Based on a Sagnac interferometer (SI), the group modal birefringence of the HB-SCF was measured to be 4.84 ×10^-4 , which agrees well with the theoretical result. The sensing characteristics of the HB-SCF SI for pressure, strain, and torsion measurements were analyzed theoretically and investigated experimentally. It exhibits sensitivities of 2.82 nm/MPa for hydrostatic pressure, 0.43 pm/με for strain, and 0.0157/° for torsion measurements. The HB-SCF is made entirely of pure silica without stress-applying parts, thus its modal birefringence is thermally insensitive, resulting in a low temperature sensitivity of ~1 pm/°C.