We have proposed and demonstrated a fiber optic magnetic field sensor using a FBG (fiber bragg grating) attached on a Terfenol-D bar. The volume of Terfenol-D is changed by the applied magnetic field due to the magnetostriction effect, as a result, the grating period of FBG varies with the intensity of the magnetic field and the Bragg wavelength of FBG is shifted. The temperature sensitivity of the sensor was measured with and without the magnetic field. The temperature sensitivity of the sensor was measured to be 0.02 nm/℃. We observed that the sensitivity of the fabricated device to magnetic field intensity was decreased with the environment temperature.

We have proposed and demonstrated a fiber optic RH (relative humidity) sensor based on fiber Bragg grating covered with a polyimide film. As the polyimide film absolves the moisture in the air, its volume expands. As a result, the grating period of the FBG (fiber Bragg grating) covered with a polyimide film becomes wide and the Bragg wavelength is shifted. The sensor is implemented by fixing a 30 ㎛ thickness polyimide film on the surface of an optical fiber grating using an adhesive, and the characteristics of the device according to humidity are analyzed. The fabricated FBG RH sensor showed a high sensitivity of 0.0186 nm/RH% and a wide measurement range from 30% to 90%. The influence of environmental temperature on the characteristics of the RH sensor was also measured and analyzed. The feasibility of commercialization is presented.

We proposed and demonstrated a simultaneous measurement method to detect the refractive index and temperature of a medium using a side-polished fiber involving FBG (fiber Bragg grating). The temperature of a medium was obtained by using the Bragg wavelength shift of FBG, while the refractive index of medium were calculated by using the transmission loss. The Bragg wavelength is independent on the refractive index of the covering medium placed on surface of side-polished fiber, while the transmission loss at off-Bragg wavelength highly depends on the environmental temperature because of thermo-optic effect of the medium.