A Quasi-Distributed Fiber-Optic Temperature Sensor With a Resolution of 0.07 $^{\circ}$ C Based on Fresnel Reflection

A quasi-distributed fiber-optic temperature sensor for monitoring ambient temperature with a measured temperature resolution of approximately 0.07degC is presented. The sensor operates based on temperature-dependent Fresnel reflection from each interface between a distributed fiber tip and a thermooptic medium, and on the parallel demultiplexing of an arrayed waveguide grating. Thin-film filters are utilized to achieve wavelength-division multiplexing-distributed sensing. Good long-term stability and negligible channel crosstalk between two adjacent sensing heads with a wavelength spacing of 0.8 nm are experimentally achieved. Such a sensor would have biomedical and industrial applications where accurate measurements of temperatures and their locations are essential.