Heterogeneous integrated optical fiber with side nickel core for distributed magnetic field sensing.

A design of a heterogeneous integrated optical fiber with side nickel core (SNCF) has been proposed and demonstrated for distributed fiber-optic magnetic field sensing. Experimental results show that magnetic properties of nickel can be preserved well after the high temperature drawing process. The functionality of the SNCF has been well verified, with the sensitivity for DC magnetic field being up to -2.42 µÎµ/mT (below 8 mT). Besides, the SNCF finally presents magnetostriction saturation under a certain magnetic field, which agrees with the simulation. The proposed direct thermal drawing method to produce metal-heterogeneous integrated optical fiber paves the way for a simple and scalable means of incorporating metallic materials into fibers, as well as providing a promising candidate for long-distance distributed magnetic field sensing.

Towards high-sensitivity and high-accuracy forward Brillouin scattering-based optomechanical temperature sensing in thin-diameter fibers.

We numerically and experimentally demonstrated a high-sensitivity and high-accuracy temperature sensor based on guided acoustic radial modes of forward stimulated Brillouin scattering (FSBS)-based optomechanics in thin-diameter fibers (TDF). The dependence of the FSBS-involved electrostrictive force on the fiber diameter is systematically investigated. As the diameters of the fiber core and cladding decrease, the intrinsic frequency of each activated acoustic mode and corresponding FSBS gain are expected to be accordingly increased, which benefits the significant enhancement of its temperature sensitivity as well as the optimization of the measurement accuracy. In validations, by utilizing TDFs with fiber diameters of 80 µm and 60 µm, the proof-of-concept experiments proved that sensitivities of the TDF-based FSBS temperature sensor with radial modes from R0,4 to R0,15 increased from 35.23 kHz/°C to 130.38 kHz/°C with an interval of 8.74 kHz/°C. The minimum measurement error (i.e., 0.15 °C) of the temperature sensor with the 60 µm-TDF is 2.5 times lower than that of the 125 µm-SSMF (i.e., 0.39 °C). The experimental and simulated results are consistent with theoretical predictions. It is believed that the proposed approach with high sensitivity and accuracy could find potential in a wide range of applications such as environmental monitoring, chemical engineering, and cancer detection in human beings.