Passive Optical Networks

4.5.2 Fiber OTDR Monitoring

Conventionally, fiber monitoring is performed by OTDR measurements at

the OLT side in an intrusive way [71–75]. OLT OTDR data, however, suffer

from reduced sensitivity due to high splitting losses and from ambiguity due to

the superposition of OTDR traces originating from different fiber branches.

This subsection introduces the OTDR principles and describes a novel embed-

ded OTDR approach [76, 77, 79], which integrates inexpensive fiber monitoring

functionality into an ONU transceiver module.

4.5.2.1 OTDR Operation Principle

As an example, Fig. 4.30 shows an OTDR system in the dotted box in

conjunction with a typical WDM-PON ...