Optical coherence tomography (OCT) is a non-invasive imaging method, which allows the econstruction of three dimensional depth-resolved images with microscale resolution. Originally developed for biomedical diagnostics, nowadays it also shows a high potential for applications in the field of non-destructive testing (NDT). This work demonstrates how OCT could help to investigate the delamination growth in fiber composites. A customized OCT system was built with a near-infrared light source with center wavelength at 1550 nm. It was used as an inline NDT tool to monitor the crack tips and image the crack surfaces within a glass fiber composite under static loading. For carbon fiber composites, although it is difficult to acquire the internal structures due to their opaque property, OCT can still work as a surface profilometer to reconstruct 3D crack surface profiles, providing substantial information for the study of crack growth in the composites.