Multiplexed interferometric displacement sensing below the laser frequency noise limit

Abstract

The resolution of fiber optic interferometry sensors is often limited by frequency noise in the laser. For this reason, prestabilization techniques have been used to reduce laser frequency fluctuations and improve signal resolution. However, for multi-element systems this becomes cumbersome and difficult to implement. In this paper, we demonstrate the use of digitally-enhanced interferometry for the interrogation of a multi-element sensing system. Over 50 dB of cross-talk rejection was found, with displacement resolutions of ∼ 100 pm. Furthermore, using this technique, sub-frequency noise displacement resolution was obtained without the need for high performance sensors.