Which instrument emits pulses and measures backscatter to locate faults along a fiber?

• A. Optical Time Domain Reflectometer
• B. Optical Loss Test Set
• C. Visual Fault Locator
• D. Tracer

Answer: (A)

Emitting pulses and measuring backscatter to locate faults along a fiber is the job of an Optical Time Domain Reflectometer. It sends short light pulses into the fiber and records the backscattered light as a function of time. Because the time delay of the returned signal corresponds to the distance the light traveled, you can map every event along the fiber—breaks, connectors, or splices—to a specific location. The trace lets you pinpoint exactly where a fault is and also assess the loss at each event. Other tools either measure overall end-to-end loss without showing where along the length it occurred, rely on visual indication without a distance trace, or use a tone to identify a fiber without performing backscatter-based fault localization.