Novel Optical Fiber Sensors For Magnetic Field And Temperature Measurement

The fiber-optic sensors are intrinsically insulated and can play a practical role in magnetic field sensing.In this paper,novel fiber-optic magnetic field sensors with magnetic fluid and temperature sensors based on highly Germania-doped fiber are proposed.1.A magnetic field sensor based on magnetic-fluid-filled phase-shifted fiber Bragg grating is proposed.By filling the resonant cavity with microfluidic magnetic fluid,its phase and loss change with the magnetic field.It results in the variation of wavelength and intensity of the transmission peak.The micron-sized resonator not only reduces the amount of magnetic fluid,but also greatly reduces the length of the probe,which has a prospect in magnetic field distribution detecting.2.A magnetic field sensor based on magnetic-fluid-filled micro-structured fiber Bragg grating is proposed.The grating is written on a six-hole fiber and magnetic fluid is filled into its air holes,so that light wave can closely interact to the magnetic fluid.It does not damage the structure of the fiber and is compact in size for distributed applications.3.A temperature sensor based on Michelson interferometer with highly Germania-doped fiber is proposed,which can be used for temperature compensation.The sensing fiber length is 1 mm,the free spectral range is 18.9 nm and the extinction ratio is increased to 19 dB.A sensitivity of 100 pm/~oC is achieved,which is much high than normal fiber-based sensors.This sensor shows a good potential in the point temperature measurement.4.A high temperature sensor based on highly Germania-doped fiber with a spherical end is proposed.The end face of the fiber is melted into spherical shape by multiple discharges that provides a convex lens-like effect to enhance reflection.The sensor has a sensitivity of 89.5 pm/~oC and is a complement to the above sensor.