Materials science

Optical time-domain reflectometer

Optical fiber

Demodulation

Telecommunications

Vibration

Computer science

Fiber optic sensor

Acoustics

Wavelength

Structural health monitoring

Physics

Optics

Rayleigh scattering

Interferometry

Composite material

Time domain

Polarization-maintaining optical fiber

Channel (broadcasting)

Distributed acoustic sensing

Reflectometry

Fiber Bragg grating

Dynamic range

Computer vision

Optics Express

Distributed vibration sensing in optical fibers opened entirely new opportunities and penetrated various sectors from security to seismic monitoring. Here, we demonstrate a most simple and robust approach for dynamic strain measurement using wavelength-scanning coherent optical time domain reflectometry (C-OTDR). Our method is based on laser current modulation and Rayleigh backscatter shift correlation. As opposed to common single-wavelength phase demodulation techniques, also the algebraic sign of the strain change is retrieved. This is crucial for the intended applications in structural health monitoring and modal analysis. A linear strain response down to 47.5 pε and strain noise of 100 pε/√Hz is demonstrated for repetition rates in the kHz range. A field application of a vibrating bridge is presented. Our approach provides a cost-effective high-resolution method for structural vibration analysis and geophysical applications.

Wavelength-scanning coherent OTDR for dynamic high strain resolution sensing