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.

OTDR launch cables, or dead-zone boxes, placed at near-end patch panels allow the OTDRs detector port sufficient time to recover from its blindness. Dead zone boxes also enable the OTDR to measure the relative loss through the near-end and far-end patch panels (see diagram below).

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.

  Number Description
C1007 Explains the concept of OTDR dead zones, the effect of dead zones on OTDR measurements, and the use of dead zone boxes to counter the effects of dead zones.
M1004 Introducing the OWL pulse suppressor box

Part # Length Fiber Type Connector Type Price
DZB-SM-1100 1100 meters Singlemode SC/UPC 375.00
DZB-M6-450 450 meters 62.5/125um multimode SC/UPC 335.00
DZB-M5-450 450 meters 50/125um multimode SC/UPC 335.00
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