Sub-nano resolution fiber-optic static strain sensor using a sideband interrogation technique.

We propose a novel sideband interrogation technique with multiplex radio frequency intensity and phase modulation to measure the resonance frequency difference between two optical resonators. Based on this new technique, an ultrahighly sensitive fiber-optic static strain sensor system consisting of a pair of identical fiber Fabry-Perot interferometers is built by incorporating a cross-correlation data processing algorithm. A static strain resolution down to 0.8 nε is demonstrated experimentally, which makes the sensor system a useful tool for geophysical research applications.