DH+/RIO OPTICAL COMMUNICATION MODULES USERS MANUAL
Copyright © 2003 by Phoenix Digital Corporation, All Rights Reserved.
1.3.3.7 DETECT AND LOCATE IMPENDING NETWORK FAILURES
(850nm AND 1300 nm MULTIMODE MODULES ONLY)
Phoenix Digital’s fiber optic modules provide the unique capability to detect impending optical
communication faults on the fiber optic network before they actually occur. Impending Fault
Monitoring may be Enabled on Standalone, Panelmount OCM Modules through Diagnostic
Select Switch 4 (see Table 9); on 1771 Plug-In OCM Modules through Diagnostic Select Switch 4
(see Table 9) and/or the Diagnostic Control Byte (see Figure 9); on 1746 Plug-In OLC Modules
through the Diagnostic Select Switch 2 (see Table 11) and/or the Diagnostic Control Byte (see Figure
9); and on 1756 Plug-In OCX Modules through Diagnostic Select Switch 2 (see Table 11).
The fiber optic module Impending Fault Initialization procedure is accomplished by first con-
necting the module optical receive inputs to the optical transmit outputs of adjacent fiber
module(s) (adjacent on the fiber optic network), with the actual fiber optic cable to be used in
the final installation. (It is recommended that this initialization be accomplished post-installa-
tion in order to match the fiber module impending fault monitoring circuitry to the final commu-
nication link characteristics.) The adjacent fiber modules (adjacent on the fiber optic network)
must be powered during the initialization process to provide a receive signal reference (commu-
nication data carrier) to the fiber optic module undergoing initialization. The fiber modules
must be powered for at least 15 minutes prior to initialization in order to stabilize all internal
references. (The initialization procedure may also be performed on-line with actual network
data transmissions, and will be totally transparent to network operation.) While visually ob-
serving the ISD/ID indicators on the front of the fiber optic module the ISS (Initial Signal Set)
potentiometers should be turned clockwise if the corresponding ISD/ID indicators are off (or red), or
counterclockwise if they are on green, until the ISD/ID indicators switch state (either turning green to
off or off to green). Then, as the final step, the Initial Signal Set potentiometers should be turned
1/4 turn clockwise, at which point the corresponding ISD/ID indicators should be maintained con-
tinuously on (green). (Note: If the Receive Optical Signal Strength is too high, the optical input may
have to be attenuated before proceeding with the Impending Fault Initialization Procedure. If the
Receive Signal Strength is greater than -20dbm, the input signal should be artificially attenuated to
reduce the signal strength below this threshold, before attempting Impending Fault Detect Initializa-
tion. As an alternative, the user may wish to leave the Impending Fault Detect threshold at the
factory default setting of -28dbm.)
The fiber module initialization procedure normalizes the impending fault monitoring detection thresh-
olds to the attenuation characteristics of the final network installation. (It should be noted that the
ISD/ID indicators may occasionally flash green or off, or turn off entirely over time. This is a normal
operating condition and should be ignored post installation.) After initialization any optical network
impending fault condition which causes the optical network receive power level to drop by more than
3.0 decibel-milliwatts (optical power) relative to the initialization power level will cause the corre-
sponding Impending Fault Detect (IFD/IF) indicator to illuminate red, and will be reported on the
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