Nortel Networks OPTera Metro 3500 - Manual (Page 93)

Operation, administration, and maintenance (OAM) features 2-55
Planning and Ordering Guide—Part 1 of 2 NTRN10AN Rel 12.1 Standard Iss 1 Apr 2004
Figure 2-29
Electrical Loopback types
Optical loopback
Optical facility loopbacks
Optical loopback functionality provides maintenance personnel the capability
to test portions of optical circuits for signal continuity by having the OC-n
circuit packs loopback test signals that are sent to them on either the terminal
or facility side of the connection. Sectioning of a SONET path facilitates
remote fault isolation.
Note: Site Manager supports provisioning of optical loopbacks.
Figure 2-30 illustrates an optical facility loopback.
Facility Loopback
DS1
Facility Loopback
DS3
STS equipped
with DS3 AIS
VT equipped with DS1 AIS
for async mapping or VT AIS
for byte synch mapping
Terminal Loopback
DS1
DS1 AIS
DS3
DS3 AIS
Terminal Loopback
Facility Loopback
EC1
AIS
Terminal Loopback
EC1
Copy of signal on optics