RECENT TRENDS IN OPTICAL TIME DOMAIN REFLECTOMETRY.

The technique of Optical Time Domain Reflectometry (OTDR) has emerged in recent years as a major diagnostic as well as a research tool in the field of optical communication. The OTDR, whose working principle is similar to that of a radar, can locate faults/breaks along the length of the fiber non-destructively besides being able to measure the attenuation coefficient accurately. With increasing use of monomode fibers in optical communication links and with the opening up of new wavelength window for optical communication at 1. 3 mu m and 1. 5 mu m the OTDR technique has undergone radical changes in recent years. The state-of-the-art of OTDR techniques is discussed using both semiconductor lasers and Nd:YAG lasers as the sources.