Humidity and Temperature Sensing Using an Optical Fiber and a Corner Cube Prism

An optical sensing method for the measurement of humidity and temperature, which uses a sensor head composed of a cholesteric liquid crystal (LC) cell and a corner cube prism coated with a cobalt chloride (CoCl 2 ) film is proposed. The CoCl 2 film is used as a color reaction reagent for measuring the humidity. The temperature is measured by the shift of the selective reflection band of the cholesteric LC cell. In addition, an OTDR method is applied to measure the humidity and temperature, and the location of the sensor head is also determined.