This work presents a methodology to measure deflections in the range of microns in thermo-pneumatic silicon micomembranes. This method is based on the fiber optic interferometry, which was used to study the static behavior of a silicon membrane of 10 mm in thickness, 5 mm in side length and 300 mm in bulk, which was glued to a glass slide. Static behavior is defines as the membrane deflection measurement taking into account only its response to the infrared radiation energy that drives them.