Distributed Axial Strain Sensitivity in Fibers With Different Germanium Concentrations

We examined the influence of germanium concentration in fiber core on distributed axial strain sensitivity in optical frequency-domain reflectometry based on Rayleigh scattering for single-mode step-index fibers differing in the level of germanium concentration (from 3.6 to 40.6 mol%). We observed a monotonically decreasing dependence of axial strain sensitivity on germanium concentration within a range of 0–3.5 mstrain for uncoated fibers. The lowest axial strain sensitivity of 0.7422 1/strain was obtained for fiber doped with 40.6 mol% GeO2 (UHNA7), compared to 0.7859 1/strain for fiber with 3.6 mol% GeO2 content (SMF-28). We also derived an analytical formula for strain sensitivity in optical frequency-domain reflectometry, explaining the experimental results.