Flexible Fiber-Optic Sensor Based on Upconversion Fluorescence in Tellurite Glass for Dual Parametric Monitoring of Temperature and Pressure

In this article, a flexible single-point sensor integrated into a fiber-optic path, capable of simultaneously detecting temperature and pressure with inherent crosstalk immunity, is presented through the development of a hybrid tellurite glass/polydimethylsiloxane (PDMS) composite probe. Temperature measurement is achieved through the fluorescence intensity ratio (FIR) technique utilizing the thermally coupled levels (2H11/2 and 4S3/2) of Er3+ ions. Meanwhile, pressure sensing is realized by exploiting the temperature-insensitive characteristic of 2H11/2 emission within a limited temperature range, combined with the PDMS-induced optical transmission loss under elastic deformation. To the best of our knowledge, this represents the first implementation of simultaneous temperature and pressure sensing based on upconversion fluorescence in Er3+-doped tellurite glass. Compared with conventional dual-parameter fiber-optic sensors (FOSs), our design eliminates the requirement for complex dual-sensing configurations or sophisticated signal decoupling algorithms, accomplishing dual-parameter detection using a single sensing element. The developed sensor exhibits outstanding features, including compact structure, low-cost fabrication, simple signal interrogation, and excellent flexibility for wearable applications, showing great potential in healthcare monitoring, human–machine interfaces, and motion recognition systems.