A multiplexed point temperature fibre sensor array using OTDR technique and TDM mechanism

A relatively inexpensive multiplexed point temperature fibre sensor array using Optical Time Domain Reflectometry (OTDR) technique and Time Domain Multiplexing (TDM) mechanism has been designed. The working principle was analyzed using well known Fresnel reflection equations and Lorentz-Lorenz formula. Based on our design, two single point temperature sensors and a multiplexed point temperature sensor array with two sensor heads were fabricated and characterized. The results show that the temperature variation of sensing parameter fit very well into a second order polynomial. About ±1°C accuracy was achieved for the temperature range from 0 to 100°C. The average sensitivity is about 2.2 mV/°C for the single point sensors and 1.2 mV/°C for the multiplexed point sensor array. Using the multiplexed point sensor array, the oil temperature of a Partial Discharge (PD) measurement system was measured from a distance of 430 m with 20 kV applied voltage. The results were compared with the results of a commercially available GaAs based fibre optic thermometer and an excellent agreement was achieved.