PVA partly coated SNS fiber optic temperature sensor

The polyvinyl alcohol (PVA) with non-toxic and environmentally friendly properties has good temperature and humidity sensitivity. The refractive index (RI) is affected by both temperature and humidity. However, the high-temperature irreversibility and the moisture loss of PVA limit its application in temperature sensing. How to effectively reduce the temperature measurement errors caused by moisture loss and cross-sensitivity is an effective way to obtain a highly sensitive temperature sensor based on PVA. In this work, a PVA partly coated singlemode multi-mode single-mode (SMS) fiber temperature sensor is demonstrated. The multi-mode interference (MMI) effect in the SMS fiber structure provides measurable characteristic spectra for temperature sensing. The cross-sensitivity between humidity and temperature in PVA can be effectively reduced by using capillary sealing to prevent water loss. At the same time, partially stripped the coating layer of the coreless fiber to avoid high transmission loss caused by high RI coating. This partly coated structure can reduce dependence on measured light intensity. Experimental measurements indicated that the sensitivity of the sensor is 12.9264nm/°C, which is suitable for measuring small temperature changes with an accuracy of about 1.547 × 10⁻³ °C.