High speed and high sensitivity fiber Bragg grating interrogator based on the RF phase-shift technique

A high speed and high sensitivity fiber Bragg grating (FBG) interrogator based on RF phase-shift measurement is presented. Using a sinusoidal modulated source and a chromatic dispersion element, Bragg-wavelength shifts are converted directly to RF phase shifts. Interrogation speeds >1 MHz with <10 pm spectral sensitivity, and sensitivity <0.1 pm at 100 Hz speed are demonstrated. An overall sensitivity vs. speed dependence of 3.4 fm/Hz, which is equivalent to 3 nanostrain/Hz, is shown. As it is based on standard telecommunication components and electronic RF processing, without moving parts or reliance on interferometry, this technique is simple, robust and inexpensive, opening new applications that require fast and sensitive sensing.