Experimental analysis and demonstration of a low cost fibre optic temperature sensor system for engineering applications

An epoxy packaged surface mountable fibre temperature sensor for engineering applications is presented in this paper. The temperature sensor is based on a macro-bend single-mode fibre loop employed in a ratiometric power measurement scheme and has a linear characteristic with temperature at a fixed wavelength and bend radius. The sensor head consists of a single turn of a bare bend sensitive single-mode fibre with an applied absorption coating. The temperature of the sensor head is varied up to 80 °C and the linearity of the response is studied with different applied absorption coatings. The sensor head is packaged in a low thermal expansion coefficient two-part epoxy for stability. Such a packaged sensor head can be directly attached to any structure for temperature measurements. The packaged sensor system shows a temperature resolution better than 0.5 °C. The impact of stress and strain on the fabricated sensor is investigated by applying an external load to the sensor and an estimation of magnitude of the stress- and strain-induced error in the temperature measurement of the system has been obtained. It is found that the impact of stress and strain is low and can be compensated, if necessary. A portable prototype of the sensor head and the interrogation system is also demonstrated in this paper. The demonstrated temperature sensing system could be used for a wide range of engineering applications.