Characteristics of sapphire fiber connected with ruby sensor head for the fiber-optic thermometer applications

The influences of fiber materials on the performance of the fiber-optic thermometers are evaluated using the thermal probes, in which the sapphire fiber and/or the silica fiber was connected mechanically with the ruby sensor head. The value of photoluminescence (PL) lifetime and its temperature coefficients for the ruby sensor head with sapphire fiber (τ = 3.9 ms and -9.9 μs/K) were slightly different from those using the silica fiber (τ = 4.2 ms and -10.9 μs/K), due to the background PL from the sapphire fibers. The influence of the PL from the sapphire fiber on the temperature measurements can be reduced successfully using a modified lifetime calculation based on the curve fitting of the PL decay with double exponential equation.