Optimization of the sensitivity of a Fabry–Pérot pressure sensor based on a PDMS microlens at the end of a graded-index multimode fiber

In this work, we present the design and optimization of a Fabry–Pérot interferometric (FPI) pressure sensor integrated at the tip of a 62.5/125 µm graded-index multimode fiber (GI-MMF). The fiber is chemically modified using a 20% hydrofluoric acid (HF) solution, enabling the formation of concave micro-cavities. Polydimethylsiloxane (PDMS) is then introduced into these micro-cavities to form microlenses with varying geometries. Pressure and temperature sensitivities are obtained through finite element method (FEM) simulations based on the actual micro-cavity geometries and microlens thicknesses characterized experimentally. The simulated sensor response shows, for the identified optimal configuration, a pressure sensitivity of 92 pm/kPa over a range of 10–154 kPa, as well as a temperature sensitivity of 363 pm/°C over a range of 25°C–61°C. A full experimental validation of these performances is planned in future work.