JCE_V4_N2_RP2 K. Samrajyam Sobha Bathalapalli Gunneswara Rao T.D. R.L.N. Sai Prasad Journal on Civil Engineering 2249 - 0779 4 2 13 19 Concrete, Crack Mouth Opening Displacement (CMOD), Three Point Bend Test, Plastic Optical Fiber, Phase Difference, LAB View, LVDT Crack detection and measurement of crack width in concrete are important for structural health monitoring of structures. In this paper, we report on a technique for estimation of crack mouth opening displacement ((CMOD) in concrete specimens of M20 composition. It is based on the principle of using Plastic Optical Fiber(POF) based strain displacement sensor employing phase difference measurement technique. The motivation for the method has been to improve on the sensitivity of detection of crack width measurement and propagation by looking at the phase changes rather than amplitude changes as attempted earlier by the authors. March - May 2014 Copyright © 2014 i-manager publications. All rights reserved. i-manager Publications http://www.imanagerpublications.com/Article.aspx?ArticleId=2985