Test and Measurements

Fault Detection Technique by using OTDR: Limitations and drawbacks on practical approach of measurement


Practically in all kind of communication system, more or less losses are involved. To make the system more efficient, it is needed to identify and trace the faults & losses so that suitable techniques can be implemented to eliminate or reduce the losses. In optical fiber communication, optical time domain reflectometry (OTDR) is a commonly used technique for characterization and fault location of optical fiber transmission systems. It involves measuring the fraction of a probe pulse that is scattered back (by Rayleigh scattering) from a silica fiber. Because of the very small levels of backscatter in single-mode fiber at long wavelengths, very sensitive optical detection is necessary to achieve adequate range performance. This paper presents a practical approach, to understand the extent of feasibility of optical fiber cable (OFC) fault detection and rectification technique, being used in the India’s largest telecom service providing organization, Bharat Sanchar Nigam Limited (BSNL). BSNL has a 686644 Km OFC network which covers the entire country. The actual place of fault shows variation with the measured value of OTDR. Hence it becomes a tedious work to locate the actual place of fault, which leads to an uneconomical and time taking rectification method. The practically observed values of OTDR show the gradual decrement of accuracy in locating the actual place of fault. To solve the problem an algorithm is proposed. At the end of this paper, the experiment results are shown to verify the algorithm.