A passive frequency noise insensitive fiber strain sensor using post processing

Abstract

Laser frequency fluctuations limit the ultimate resolution in interferometric fiber sensors. In this work, we demonstrate an interferometric sensor insensitive to the effects of frequency change in an interrogating laser. A system is characterized showing a minimum of 4.5 orders of magnitude frequency change reduction, and a demonstrated broadband improvement of up to 1.5 orders of magnitude for signals between 100 mHz and 1 Hz. Using this technique a resolution of less than a nanostrain/rtHz was achieved for a broad range of frequencies.