3. When the far end receives the shutdown signal, the far end meets (Cond. 2) and shuts
down its WDM output.
4. Both fibers are no longer illuminated by the WDM, and the safety hazard is avoided.
When the fiber cut is repaired, or when the disconnected fiber is reconnected, the recovery
proceeds as follows:
1. The OSC Loss of Light Receive fault on the near end line port is cleared. The near end
no longer meets (Cond. 1).
2. The near end turns on its WDM output and stops transmitting the APSD shutdown
signal to the far end.
3. Since the far end no longer receives the APSD shutdown signal, the far end no longer
meets (Cond. 2) and reenables the WDM output.
4. Both the near end and the far end restore traffic onto the span.
Laser Safety: Automatic Power Reduction
To guard against accidental exposure to high power lasers, some ports support automatic
power reduction (APR). APR reduces the output of the laser when a fiber cut is detected.
WARNING: APR is performed in software on the service module and is
disabled whenever the service module undergoes a warm or cold reload. In
a cold reload, the lasers are turned off and are in a safe state. In a warm
reload, however, the lasers remain on while APR is disabled.
Without being limited to the foregoing, a service module might undergo a
warm reload in the following situations:
•
The user issues an operator command that warm reloads the service
module.
•
The user issues an operator command that cold or warm reloads the Chassis
Management Module (CMM) in a single CMM system.
•
The user performs a software upgrade of the chassis.
•
The user restores a configuration database to the chassis.
•
The user replaces the CMM in the chassis. See Chassis Management Module
Replacement.
•
Any situation where a CMM fails in a single CMM system or where both
CMMs fail in a dual CMM system. See Chassis Management Module Failure
or Removal.
•
APR on 96-Channel Amplifier Modules on page 25
Copyright © 2019, Juniper Networks, Inc.24
BTI7800 Series Hardware Overview and Installation Guide
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