Which instrument is used to locate faults along a fiber by analyzing reflections?

Which instrument is used to locate faults along a fiber by analyzing reflections?

• A. OTDR
• B. Multimeter
• C. Spectrum Analyzer
• D. Optical Power Meter

Answer: (A)

Locating faults along a fiber by analyzing reflections is done with an Optical Time Domain Reflectometer. It sends a short light pulse into the fiber and watches the backscattered light as a function of time. Each event along the fiber—such as a splice, connector, bend loss, or a break—produces either a reflection or a change in the backscatter that shows up as a feature on the trace. Because light travels at a known speed in the fiber, the time after launch maps to a distance along the cable, so you can pinpoint exactly where the fault is and quantify the associated loss. The other instruments don’t provide this time-domain, location-specific view: a Multimeter checks continuity or resistance but not where along a long fiber a fault lies; a Spectrum Analyzer examines frequency content rather than time-domain reflections; an Optical Power Meter measures power at a point but not how power changes along the fiber or where a fault is located.

Locating faults along a fiber by analyzing reflections is done with an Optical Time Domain Reflectometer. It sends a short light pulse into the fiber and watches the backscattered light as a function of time. Each event along the fiber—such as a splice, connector, bend loss, or a break—produces either a reflection or a change in the backscatter that shows up as a feature on the trace. Because light travels at a known speed in the fiber, the time after launch maps to a distance along the cable, so you can pinpoint exactly where the fault is and quantify the associated loss. The other instruments don’t provide this time-domain, location-specific view: a Multimeter checks continuity or resistance but not where along a long fiber a fault lies; a Spectrum Analyzer examines frequency content rather than time-domain reflections; an Optical Power Meter measures power at a point but not how power changes along the fiber or where a fault is located.