A New Liquid-Crystal-Based Fiber-Optic Temperature Sensor

A new fiber-optic temperature sensor has been developed, based upon selective reflection from a cholesteric liquid crystal. The change of reflected-light intensity can be 40 times larger than background over a temperature range of only 0.4°C. For the demonstrated system, the temperature at which maximum reflection occurred was at 14.578°C, with a standard deviation of 0.026°C. The relative standard deviation of the peak reflected-light intensity was 7.1%. The dependence of the magnitude of reflection and that of peak temperature on the heating rate were studied. The response time of the present sensor is about 2 s, but it could be shortened with slight design modifications. Each sensor of the new type should be applicable to temperature sensing or control over a temperature range of about 1°C.