Quantitative measurement of dynamic nanostrain based on a phase-sensitive optical time domain reflectometer

A sensing system is proposed for quantitative measurement of large-range dynamic nanostrain based on a phase-sensitive optical time domain reflectometer, where the coherent detection and I/Q demodulation methods are employed to demodulate both the phase and the amplitude of the Rayleigh scattering light in real time. A nanopositioning translation stage is utilized to apply precise nanostrain to fiber. By measuring phase differences between two adjacent sections, the quantitative nanostrain with a large measurement range is demonstrated; this is also a method to measure the strain parameter of refractive index. For the Panda polarization-maintaining fiber under test in the experiment, the strain parameter of phase difference is measured to be 8.714 mrad/(n epsilon.m), while the strain parameter of refractive index is measured to be -0.3751 epsilon(-1). As a proof of the concept, the dynamic strain sensing with a range of 10-1000 n epsilon is experimentally demonstrated, and the strain resolution is 1 or 2 n epsilon, corresponding to 5 or 2.5 m spatial resolution, respectively. The experimental measurement also shows a triangular wave with a 12-Hz vibrating frequency and a 100-n. strain amplitude as well as a 188-Hz resonant signal of the tensile section. (C) 2016 Optical Society of America