EXFO IQS-12002B Calibration System - Manual (Page 81)

Calibration Methods
Calibration System 77
FTB-7000D and FTB-7000B-B OTDR Modules
Dead Zone Calibration
The dead zone depends on the intensity of the reflectance. Compliance to
the specification must be done for a reflectance of –35 dB in multimode
and –45 dB in singlemode.
Note: There is no uncertainty value associated with this calibration.
Attenuation Dead Zone
The attenuation dead zone is the distance between markers A and B
on the OTDR trace presented below.
Marker A is positioned at the rising edge of the reflective event.
Marker B is positioned within the falling edge, 0.5 dB above the
backscatter level.
Attenuation
dead zone