Which instrument is used to visually locate faults by emitting visible light along the fiber?

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

Answer: (C)

Visual fault location relies on injecting visible light into the fiber and watching for where the light glows or leaks, so you can spot faults, breaks, or loose connections with the eye. The instrument that does this best is the Visual Fault Locator. It sends a low-power visible light (usually red) into the fiber and lets you see the glow along the strand. When you encounter a fault or break, the light behavior changes at that point, making the problem easy to identify quickly without special meters.

Other tools work differently: an Optical Loss Test Set measures how much signal is lost using a calibrated light source and a power meter, not for visual spotting; an Optical Time Domain Reflectometer sends pulses and analyzes reflections to calculate exact fault locations, which requires interpretation of traces rather than direct eye observations; a tracer is used mainly to locate a fiber path, not to visibly pinpoint faults along the fiber.