What are common OTDR testing mistakes?

The most common OTDR testing mistakes are skipping a launch cable, testing at the wrong wavelength for the fiber type, and misreading dead zones — all of which produce inaccurate or incomplete trace data.

Without a launch cable (typically 100–500 meters of known-good fiber), the OTDR's event dead zone swallows the first connector on the link entirely, and you lose the most fault-prone point in the run. Testing a single-mode plant at 850nm instead of 1310nm or 1550nm returns meaningless loss figures. Confusing the event dead zone with the attenuation dead zone leads technicians to report accurate event locations but wrong loss values — a critical distinction on splice documentation for FTTx builds. The D YEDEMC Mini-Pro OTDR's 3-meter event dead zone and 8-meter attenuation dead zone are short enough for dense FTTH enclosures, but only if the technician knows which number applies to which measurement.

• Mini-Pro OTDR event dead zone: 3 meters — minimum distance to detect a second event after a reflection.
• Mini-Pro OTDR attenuation dead zone: 8 meters — minimum distance to accurately measure loss after a reflection.
• Recommended launch cable length for OTDR testing: 100–500 meters of matched fiber type.
• Single-mode OTDR testing wavelengths: 1310nm and 1550nm — not 850nm, which is multimode-only.
• Splice loss threshold warranting a re-splice: any fusion splice showing greater than 0.2 dB on an OTDR trace.