Dynamical strain sensing via discrete reflectors interrogated by optical frequency domain reflectometry

Dynamical sensing of strain via discrete reflectors interrogated by optical frequency domain reflectometry is described and demonstrated experimentally. The benefits of using discrete reflectors rather than Rayleigh back-scattering for dynamical measurements are elaborated. The method is tested in a sensor arm made from four discrete fiber segments of different lengths and in a fiber with an array of ten fiber Bragg gratings with the same center wavelength and ~0.5% reflection. Dynamical sensing of oscillatory strain at 100 Hz, with absolute stretching amplitude <100nm, at ~1km is demonstrated.