Minimum distance on the OTDR’s trace, where two separate events can still be distinguished.

• For a reflective event, the EDZ definition is the distance between the two opposite points which are 1.5 dB (or FWHM) down from the peak. The reflectance of the event shall be specified (as an example Bellcore gives a reflectance of -30 dB).
• For a non-reflective event, the event dead zone definition is the distance between the points where the beginning and ending levels at a splice or a given value (≤1 dB) are within ±0.1 dB of their initial and final values. Usually this dead zone is a fixed value and depends only on the pulse-width and the fiber.