Which instrument is used to locate faults or splices in fiber-optic cables by sending light pulses and analyzing reflections?

Which instrument is used to locate faults or splices in fiber-optic cables by sending light pulses and analyzing reflections?

• A. Cable tester
• B. Toner and probe
• C. Multimeter
• D. OTDR

Answer: (D)

Sending a light pulse into the fiber and analyzing the reflections is the hallmark of an Optical Time Domain Reflectometer. It fires very short light pulses into the fiber and listens for light that bounces back from any discontinuities, such as splices, connectors, bends, or breaks. The time it takes for reflections to return tells you how far away each event is, because you can convert time to distance using the known speed of light in the fiber. The strength of each reflected signal tells you how much loss occurs at that event, so you can locate the exact point of a fault or splice and assess its impact. Other tools aren’t built for this purpose: a cable tester is more general and often used for copper networks; a toner and probe traces cables in a bundle but doesn’t analyze reflections in fiber; a multimeter measures electrical properties and won’t locate fiber faults.

Sending a light pulse into the fiber and analyzing the reflections is the hallmark of an Optical Time Domain Reflectometer. It fires very short light pulses into the fiber and listens for light that bounces back from any discontinuities, such as splices, connectors, bends, or breaks. The time it takes for reflections to return tells you how far away each event is, because you can convert time to distance using the known speed of light in the fiber. The strength of each reflected signal tells you how much loss occurs at that event, so you can locate the exact point of a fault or splice and assess its impact. Other tools aren’t built for this purpose: a cable tester is more general and often used for copper networks; a toner and probe traces cables in a bundle but doesn’t analyze reflections in fiber; a multimeter measures electrical properties and won’t locate fiber faults.