Fault-Locating Accuracy with an OTDR: Reflective Versus Nonreflective Faults

When using an OTDR, fault-locating accuracy can be improved if the nature of the fiber discontinuity can be taken into account in estimating the true distance to the fault. Basically, two types of faults can be encountered: reflective and nonreflective faults. Recognizing that the slope of the rising part of the back-reflected pulse is a function of the optical reflectivity at the fault, a scheme has been devised for correcting the measured distance on the OTDR to derive the exact location of the fault to within ±1 m.