Hybrid BOFDA/BOCDA system for distributed static and dynamic strain measurements

We present a distributed optical fiber sensor based on a hybrid Brillouin optical frequency/correlation-domain analysis (BOFDA/BOCDA) configuration for both static and dynamic strain measurements. Distributed static strain (or temperature) measurements are realized using the conventional BOFDA method, i.e., acquiring the baseband transfer function of the fiber through a vector network analyzer (VNA). With little modifications, the same setup can perform dynamic, position-selective measurements synthesizing a correlation peak through a frequency modulation of the laser source while operating the VNA at a single modulation frequency. Experimental tests, carried out at a sampling frequency up to 40 Hz and a spatial resolution of ≈5 cm, demonstrate the validity of the proposed approach.