This study investigates the detection of internal crack in a material using reinforced optic fiber bundle. There are many external crack detection techniques available but when we look upon internal crack there are only few techniques available which is complex and expensive. So, to overcome this problem we adopted this internal crack detection technique which is compact and cheap using the grid system. The scope of our study is to solve the general problem which occurs during manufacturing of a product which exposes the final material under stress. Four samples were made which had Glass Fiber Mat and the Optic Fiber induced into the samples in X and Y axis. Then the sample was subjected to Drop Impact Test and Flexural Test through which the damage was induced. The light was passed through the optic fiber bundle in uniform way at the entrance. The intensity of light was measured using the lux meter and the change in intensity of light before and after testing was depicted in the graph. It was found that the variation in the optic fiber damage where the crack was induced were able to be detected at the exit fibers arranged in the linear way. Thus the grid points were noted down and the point of damage was able to be narrowed down using this technique The exact effect of this study can be employed in the construction site which are located in the earthquake prone zones so that we can identify the internal cracks in the building and protect them before major accident occurs in the future.