User Documentation
Installation
2053260000/05/2015
139
3.9.2 OTDR measurement
Alongside the attenuation measurement procedure (insertion loss measurement
procedure), the OTDR (Optical Time Domain Reectometer) measurement
procedure can also be used to measure bre-optic cables. This can be used to
determine faulty points in the bre-optic cable.
To do so, the device transmits a signal into the bre-optic cable via a forerun
bre. An overrun bre is also tted downstream of the section. Forerun and
overrun bres appropriate to the measurement cable should be used for OTDR
measurements in order to minimise measurement errors.
Parts of the signal are reected at connection points in the course of the bre-
optic measurement cable or interference points. The device now measures the
strength of the reected part of the signal and the time between the signal being
sent and the reection being received. From the measurement results, you can
tell the location of defect and its inuence.
Figure3.6:PrincipleoftheOTDRmeasurement