Development of a Highly Sensitive and Low Hysteresis Temperature Sensing System With PEDOT:PSS Containing Polymer Sensing Membrane

In our study, we have designed and developed a side-polished optical fiber (SPOF) pulsewidth modulation (PWM)-based sensing system that can detect temperatures from 21 °C (room temperature) to 70 °C. According to the proposed SPOF PWM system, the received sensing signal pulsewidth changes if the optical fiber temperature sensing element (TSE) gets heat. The pulsewidth changes due to a change in the refractive index (RI) of the heat-sensitive polymer membrane of the SPOF TSE. We applied poly (3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT: PSS) as the primary temperature-sensitive sensing material to make the heat-sensitive polymer sensing membrane of the designed TSE. To the best of our knowledge, it is the first temperature sensing system/device where the optical sensing element uses PEDOT:PSS containing polymer sensing membrane and the optical PWM technique. The sensitivity and linearity of the designed TSE were approximately 960 ns/°C and 0.997, respectively. A microcontroller ( $\mu \text{C}$ ) and readily available electronic component-based light detection and signal processing unit were designed to process the received sensing signal. The proposed temperature sensing system has different features: low cost, susceptibility, excellent hysteresis response, good reproducibility, highly stable performance, and others. The proposed SPOF TSE offers first response and recovery times of approximately 2.59 and 3.14 s, respectively. Finally, in our study, we compared the sensing performance of the proposed TSE with other temperature sensors in terms of the temperature measurement range, linearity, and response/recovery time. We found that the overall sensing performance of the proposed TSE is better than the other temperature sensors.