We proposed and experimentally demonstrated a high temperature fiber sensor using a hetero-structured cladding solid-core photonic bandgap fiber (HCSC-PBGF) for the first time to our knowledge. A hetero-structured cladding solid-core photonic bandgap fiber is designed and fabricated that supports vibrant core mode and cladding mode transmission. Then, an all fiber M-Z interference sensor is constructed by splicing single mode fiber at both ends of HCSC-PBGF without any other micromachining. The transmission characteristics of HCSC-PBGF are analyzed with a full-vector beam propagation method and a full-vector finite element method, and the simulation results are consistent with experiment results. The sensitivity of this fiber sensor is as high as 0.09 nm/°C when operating from room temperature to 1000 °C, and the fringe contrast keeps stable and clear. It is obvious that this all fiber sensor will have great application prospects in fiber sensing with the advantages of a compact structure, high sensitivity, and cost-effectiveness.

A heterostructured cladding solid-core photonic bandgap fiber (HCSC-PBGF) is designed and fabricated which supports strong core mode and cladding mode transmission in a wide bandgap. An in-line Mach-Zehnder interferometer (MZI) curvature sensor is constructed by splicing single mode fibers at both ends of a HCSC-PBGF. Theoretical analysis of this heterostructured cladding design has been implemented, and the simulation results are consistent with experiment results. Benefiting from the heterostructured cladding design, an enhanced curvature sensing sensitivity of 24.3 nm/m in the range of 0-1.75 m and a high quality interference spectrum with 20 dB fringe visibility are achieved. In order to eliminate the interference of longitudinal strain and transverse torsion on the result of the curvature sensing experiment, we measure the longitudinal strain and transverse torsion sensing properties of HCSC-PBGF, and the results show that the impact is negligible. It is obvious that this high-sensitivity and cost-effective all fiber sensor with a compact structure will have a promising application in fiber sensing.

Tm-doped fiber laser or amplifier can be applied in varied adverse environments. In this work, we demonstrate the pump bleaching of Tm-doped silica fiber with 793nm pump source under gamma-ray irradiation in the range 50Gy-675Gy. The recovery time, the fiber slope efficiency and the fiber cladding absorption spectra after irradiation and bleaching have been measured. It is found that the recovery time and radiation induce absorption are positively associated with doses, however, the fiber slope efficiency of irradiated TDF and bleached TDF are both negatively correlated with doses. Based on the simulation of the fiber core temperature, the probable mechanism of pump bleaching is also discussed.

We demonstrate a high power four-core Yb-doped fiber amplifier both theoretically and experimentally. An all-fiber MOPA structure without mode selection components was utilized to amplify the 12 m long four-core fiber. An in-phase supermode laser operation was realized in this fiber. The laser slope efficiency is greater than 56.7% with a maximum output power of 11.47 W. The measured M 2 factor of the amplified beam is 1.58, showing the high potential of the fiber.