B&B Electronics 860-12100 - Manual - Manual (Page 9)

6
Loss Carry Forward (LCF)
When a fault is detected on the incoming optical line that would severely affect the
quality of the corresponding output optical signal, this signal is turned OFF as
opposed to sending a bad optical signal to the next unit over the optical line. The
Loss Carry Forward function provides a very positive fault indication to the
downstream unit.
If the LCF function is not enabled, the transmitted optical signal is dependent on the
XFP units installed. This fault indication may become very intermittent depending on
the actual optical signal level.
XFP Loopback
XFP Loopback is based on what the XFP module is capable of. There are 2 types of
loopback that an XFP has the potential to do: Lineside Loopback (red) and XFI
Loopback (blue). (If an OEM XFP is not capable of loopback, the SNMP Management
Module will provide notification of this status.)
If an XFP is capable of Lineside Loopback, that is the type of loopback that will be
used. Lineside Loopback should be enabled on XFP1 OR XFP2. However, if both
XFP1 and XFP2 are enabled via the DIP Switches, XFP1 as the primary XFP will
support the task of Lineside Loopback. In addition, if just one port has an XFP
installed in it, and the other remains unoccupied, the loopback is still functional.
XFI Loopback has a different set of requirements. First, both XFP ports must be
installed for it to function. If an end user wants to perform a loopback on XFP1, and
it is not capable of Lineside Loopback, it must verify that XFP2 can do XFI Loopback,
and a message ‘not capable’ will be displayed. By following the receive signal on
XFP1, it goes through the XFP1 to XFP2 where it loops it back to the transmit signal of
XFP1.
If an end user enables loopback on both XFPs that are capable of XFI Loopback,
loopback is allowed on XFP1 and ‘not capable’ on XFP2. The loopback LED on XFP2
will blink to indicate this status.