Shiying Xiao

An Optical Liquid-Level Sensor Based on D-Shape Fiber Modal Interferometer

A novel coreless-D-shape-coreless (CDC) fiber structure for liquid-level sensing is proposed and experimentally investigated. The D-shape fiber with cladding partially etched is sensitive to the ambient refractive index change and the CDC structure transmission dip wavelength shifts related to the length of D-shape fiber immersed in the liquid, so liquid level is measured by monitoring the dip wavelength. The sensitivities for three different liquids with the RIs of 1.333, 1.355, and 1.377 are 191.89, 208.11, and 213.80 pm/mm, respectively. The temperature influence is also studied. The sensor exhibits a low-temperature cross-sensitivity of −0.128 mm/°C. The proposed modal interferometer based on the D-shape fiber with high sensitivity, low cost, and easy fabrication is suitable to liquid-level sensing applications.

Generation of the Tunable Second-Order Optical Vortex Beams in Narrow Linewidth Fiber Laser

We experimentally demonstrate a narrow linewidth single-longitudinal-mode erbium-doped fiber ring laser with an output of tunable second-order optical vortex beams (OVB). The laser is based on a mode selective all-fiber fused coupler, which is composed of a single-mode fiber (SMF) and a few-mode fiber (FMF). The fused SMF–FMF coupler inserted in the cavity of the laser acts as a mode converter, which converts LP01 mode to LP21 mode group. The tunable OVB is produced by combing two even LP21 modes with orthogonal polarization directions. The tunability of second order OVB in the fiber laser is experimentally realized by adjusting a polarizer at the output end of the fiber. The 20 dB linewidth of the fiber laser is approximate 7.2 kHz.

SMFs With a Ge/F Co-Doped Inner Core for SBS-Based Discriminative Sensing of Temperature and Strain

Three-layered single mode fibers with a GeO2 and F co-doped inner core are proposed. Stimulated Brillouin scattering properties in the fibers are investigated for the discriminative sensing of strain and temperature. The optical properties of the proposed fibers are designed to be well compatible with those of the widely used standard single mode fibers. The acoustic properties, including effective acoustic velocity, Brillouin frequency shifts, and peak Brillouin gain efficiencies of the first three acoustic modes, are numerically calculated and elaborately analyzed under different structural and doping parameters. The co-doped fibers with three different structural and doping parameters are chosen for simultaneous sensing of temperature and strain because of their capability of supporting two comparable peaks, which can be easily identified and distinguished in the Brillouin gain spectrum. The sensing properties of the fibers are estimated and discussed. The temperature and strain sensitivities as well as the temperature and strain errors are calculated to be comparable to those of the few mode fibers and multimode fibers.