Digital holographic testing of the optical fiber at welding area

Abstract

Abstract A method to analyse of optical fibers inhomogeneity in welding junction using digital holography is proposed. The method utilizes lens-less Gabor scheme for recording of a digital hologram with numerical reconstruction by angular spectrum approach. Qualitative image analysis applied on the intensity distribution of specimen after hologram reconstruction enables to evaluate the structural defects inside the fiber core and cladding after welding procedure, which are not observable with conventional microscopy. The opportunities of presented method were approved with a wavelength-division multiplexing fibers of known defects introduced by axial misalignment of welded parts. A compact in-line digital holographic recording set-up for express and robust optical fiber analysis was developed through its application to a welding quality testing. It is shown how the value of axial misalignment of welding fibers lead to a variation of artificial intensity distribution around the joint in reconstructed image.