Simultaneous measurement of temperature and magnetic field based on a long period grating concatenated with multimode fiber

Abstract

A dual-parameter measurement scheme based on a long-period fiber grating (LPFG) concatenated with a multimode fiber (MMF) has been proposed and experimentally demonstrated for simultaneous measurement of magnetic field and temperature. Splicing the LPFG with the etched MMF enables the coupling between the core modes and different cladding modes of the LPFG as well as the interferences between higher-order modes in the MMF. Due to different transmission mechanisms of the LPFG and mode interference, the proposed sensor shows transmission dip wavelength sensitivities of 0.02878 nm/Oe and −0.04048 nm/°C for multi-mode interference (MMI) and −0.0024 nm/Oe and 0.03929 nm/°C for the LPFG, respectively. By monitoring the opposite behaviors of resonance wavelength shift corresponding to the LPFG and MMI, the magnetic field and environmental temperature can be simultaneously measured. The spectral characteristics of the proposed sensor that could be tuned through control of both environmental temperature and applied magnetic field, which would provide a promising candidate for dual-channel filtering applications as well as multi-parameter measurement applications.