Which device should be used to determine if a fiber-optic splice is faulty?

• A. Power meter
• B. OTDR
• C. Multimeter
• D. TDR

Answer: (B)

Using an OTDR lets you locate faults along a fiber link and assess the quality of a splice. It works by sending a short optical pulse into the fiber and recording the light that returns over distance, creating a trace that shows how signal strength changes along the fiber.

A splice that is faulty typically shows up on this trace as an abrupt change at the splice location—either a higher insertion loss at that point or a reflective event if the fusion wasn’t smooth. Because the OTDR can pinpoint where the splice is and quantify how much loss or reflection it causes, you can determine whether the splice is defective and whether it meets specification.

A power meter only measures the overall power at the end of the fiber, so it can tell you there’s loss but not where it occurs or whether a splice is specifically at fault. A multimeter isn’t applicable to testing fiber optics. A TDR is the general technique, but for fiber the instrument is specialized as an OTDR, which is optimized for the fiber environment and provides distance and loss information needed to identify splice faults.