Embedded small-diameter fiber Bragg grating sensors and high speed wavelenth detection

Abstract

We have been studying optical sensing technology using embedded fiber Bragg grating (FBG) sensors. The FBG is inscribed in a small-diameter optical fiber with the cladding diameter of 40 μm. This technology is very promising for health monitoring in aviation components, because the diameter of the sensor optical fiber is so small that embedding of the sensor does not deteriorate mechanical properties of the composite materials. For practical use, we have also studied high reliable fused-splicing method between the small-diameter optical fiber and an ordinary optical fiber in order to improve handling. The embedded FBG sensors are useful for vibration or impact detection as well as static strain detection. For the purpose of detecting dynamic phenomena, we have developed a high speed wavelength detection unit for the FBG sensors which uses wavelength division multiplexing (WDM) coupler based on planar lightwave circuit (PLC) technique. WDM coupler converts wavelength of the light reflected from the FBG sensor into output powers. Since there is no mechanical moving part, this type of wavelength detection technique is suitable for high speed detection.