CANOGA PERKINS 3240S SNMP Managed Fiber Optic Multiplexer - Manual (Page 31)

3240S F I B E R O P T I C M U L T I P L E X E R
3240S Fiber Optic Multiplexer
2.4.3 Backup Fiber Optic Link Monitor Function
The purpose of the Backup Fiber Optic Link Monitor (BULM) is to continuously verify that the fiber optic link that is not in
use, remains functional. It ensures that the fiber optic signal level is above the minimum level for reliable fiber optic transmis-
sion. This function cannot be configured by the user manually or via NMS.
This circuit automatically monitors, or is switched to monitor the fiber optic link that is not, currently active. The Backup
Indicator is provided on the 3240S Front Panel to indicate when the back up link fails. This condition is also reported to the
NMS for display on the System Status Screen. When the BULM indicates a failure, the Fault Relay and ALM Indicators are
illuminated at both ends of the link. These fault indicators remain illuminated until the failed condition is no longer present.
The alarm indication will remain until the multiplexers are reset. This allows the user to identify that an alarm condition is, or
was present.
2.4.4 To Clear an Alarm Condition
Fault Relay activation caused by the Back up Monitor circuit clears automatically when the fault condition is no longer
present. Fault Relay activation caused by an automatic switch over from the Primary Link to the Secondary Link is latched
and must be cleared with a manual action. The AUTO/ Manual Switch is moved from the AUTO position to either Manual PRI
or SEC, and then back to AUTO. This will clear the fault alarm if the failed condition no longer exists. This operation can also
be performed via NMS by operator command.
2.4.5 Fault Relay (Redundant Optics)
The Alarm Relay is the same relay as the Fault Relay. The relay is deemed the 'Alarm Relay' on a 3240S that is not equipped
with redundant optics, and 'Fault Relay' when the 3240S operates with fiber optic redundancy. On models with fiber
redundancy, the relay contact indicates that an automatic switch over has occurred on the redundant optics or that the back
up link is bad. The alarm (ALM) jack provides a set of relay contacts that are activated by:
• An automatic switch over from the Primary to the Secondary Fiber Optic Link.
• Failure of the Back up Fiber Optic Link.
• A power failure.
If the failure occurs on the secondary, or back up link, the receiving 3240S will illuminate the Backup and ALM Indicators. The
transmitting end of the link will illuminate the ALM Indicator. This condition will remain until the alarm fault is cleared as
described in Section 2.4.3.
If a failure occurs on the primary fiber link, the 3240S experiencing the failed Rx input will switch to operation on the
Secondary Fiber Optic Link, activate the Fault Relay, and illuminate the Backup, SEC, and ALM Indicators. The NMS will
activate the Fault Relay and illuminate the ALM Indicator at the opposite end of the link (indicating a remote failure).
When both fiber optic links are inoperative, both multiplexer units, remote and local, switch back and forth between the links
every two seconds until one of the links becomes usable. As the multiplexers search for a good signal on either link, the SEC
Indicator cycles on and off and the Backup and ALM Indicators remain illuminated. This condition will remain until a good
link is established.
The Fault Relay Contacts can be configured via W12/W13 on the main system board of the 3240S as either normally open
(NO) or normally closed (NC). Insert the jumper across W12 to set the relay contacts as NO. Insert the jumper across W13 to
set the relay contacts as NC. The tip and ring terminals of the jack carry the relay contacts. The I/O cards must be removed
from the chassis to access W12/W13 which is located directly behind the MAST/SLV Switch.
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