A novel technique in BDG sensors: combination of phase and frequency correlation techniques

Abstract

This paper investigates a novel theoretical model based on Brillouin dynamic grating (BDG) sensors with ultrahigh spatial resolution over long sensing length. So far, frequency correlation or phase correlation technique is singly used to measure properties of the BDG sensors, although each of the techniques has its own drawbacks due to either low spatial resolution and short sensing length or processing complexities. We introduce a straightforward theoretical technique in BDG sensors based on the combination of phase and frequency correlations (CPFC) in a polarization-maintaining fiber. Correlation peak points in the CPFC technique are points where the correlation peaks in the phase correlation technique are matched with the correlation peaks in the frequency correlation technique. The spatial resolution in this novel technique is the same as the spatial resolution of the phase correlation technique. The peaks of the frequency correlation technique have no effect on the final spatial resolution of the CPFC technique and can only increase its sensing length. Long sensing length with no complexity and short calculation process are advantages of the CPFC technique. By simulation of this innovative theoretical technique, a 9 mm spatial resolution over 17.7 km sensing length has achieved, which to the best of our knowledge is the longest sensing length in millimeter range spatial resolution reported so far in BDG sensors.