OWL DZB-SM-1100 - Single-Mode Deadzone Box

Reflections caused by connector interfaces “blind” OTDRs for a short period of time. The period of time it takes for an OTDR to recover from this “blindness” is commonly referred to as a “dead-zone”. During this dead-zone period, OTDRs are unable to distinguish one anomaly (e.g. breaks, shatters, bends, or even another connector) from another.

Without a sufficiently long launch cable, the reflection from the near-end patch panel will be undetectable because it is within the dead-zone caused by the OTDR port. Likewise, at the far-end, lack of a dead-zone box will prevent the OTDR from measuring the relative loss through the far-end patch panel.

In most cases, launch cables that are slightly longer than one kilometer are sufficient to account for dead-zones on nearly all fiber links. However, longer launch cables may be needed for long-haul fiber optic links.