Output feedback control for a nonlinear optical interferometry system

In an interferometer system, the interferometer's phase stores essential information of an object of interest. Hence, one of the fundamental optical interferometry problems is to estimate such a phase (aka signal of interest). Another critical issue in the interferometry is the interferometer's stabilization. In this work, we propose a nonlinear observer that estimates the interferometer phase signal. Besides, we design a nonlinear control algorithm that globally stabilizes the interferometer to any of the stable equilibrium points. For that aim, we only use the output voltage, a piece of the usually available information in any interferometer. This fact results in an output feedback control scheme. A rigorous stability analysis is presented together with simulations that corroborate the theoretical results.