Submillimeter crack detection using fiber-based heterodyne interferometer

Abstract

We present a fiber-optic sensor for crack detection using quadrature detection and fiber-based optical interferometry with the wavelength modulation of DFB laser. For crack detection, a compact disk (CD) with a scratch is arranged and scanned over the crack. By observing the variation in phase of the interfered signal, crack interval can be measured. This approach provides a possibility of measuring the crack more accurately than that measuring the intensity of the signal. From the experimental result, we confirmed that the crack width of 0.88mm could be measured with the scan speed of 20m/s.