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.

Placing the DZB-SM-1100 Dead-Zone Box at near-end patch panels allows the OTDRs detector port sufficient time to recover from its blindness. The dead zone box also enables the OTDR to measure the relative loss through the near-end and far-end patch panels.

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.