METRObility Optical Systems RADIANCE 10/100MBPS ACCESS OPTICAL NETWORK UNIT - Manual (Page 18)

18 User Guide
Link Loss Return (LLR)
The fiber optic port of the Access ONU has been designed with Link Loss
Return functionality
* for troubleshooting a remote connection.
When LLR is enabled, the fiber port’s transmitter shuts down if its receiver fails
to detect a valid receive link. LLR should only be enabled on one end of the link
and is typically enabled on either the unmanaged or remote device.
The diagram below shows a typical network configuration with a good link
status using a Radiance Access Line Card and an Access ONU for remote
connectivity.
*The unit is shipped with LLR disabled (OFF).
If one of the optical conductors is bad (as shown in the diagram box below), the
unit with LLR enabled will return a no link condition to its link partner. This
aids the network administrator in determining the source of the loss.
Important: LLR must not be active on both ends of a configuration. If it is, the
link can never be established.
PC
Switch/Hub
w/SNMP
Customer
Site
Access
Line Card
Fiber
Cable
LED lit = established link LED unlit = no link
LLR is OFF LLR is ON
Access
ONU
PC
Switch/Hub
w/SNMP
Customer
Site
Link Loss Returned
LED lit = established link LED unlit = no link
Broken
Fiber
Conductor
LLR is OFF LLR is ON
Access
Line Card
Access
ONU