10-19
Cisco ONS 15454 DWDM Reference Manual, R8.5
78-18343-02
Chapter 10 Network Reference
10.7.1 Automatic Laser Shutdown
• Manual Restart—ALS is on. The OSC laser transmitter and optical amplifiers automatically shut
down when traffic outages (LOS) occur. However, the laser must be manually restarted when
conditions that caused the outage are resolved.
• Manual Restart for Test—Manually restarts the OSC laser transmitter and optical amplifiers for
testing.
Warning
All ONS 15454 users must be properly trained on laser safety hazards in accordance with IEC 60825-2,
or ANSI Z136.1.
10.7.1 Automatic Laser Shutdown
When ALS is enabled on OPT-BST, OPT-BST-E, OPT-BST-L, OPT-AMP-L, OPT-AMP-C,
OPT-AMP-17-C, OSCM, and OSC-CSM cards, a network safety mechanism will occur in the event of
a system failure. ALS provisioning is also provided on the transponder (TXP) and muxponder (MXP)
cards. However, if a network uses ALS-enabled OPT-BST, OPT-BST-E, OPT-BST-L, OPT-AMP-L,
OPT-AMP-C, OPT-AMP-17-C, OSCM, and OSC-CSM cards, ALS does not need to be enabled on the
TXP cards or MXP cards. ALS is disabled on TXP and MXP cards by default and the network optical
safety is not impacted.
If TXP and MXP cards are connected directly to each other without passing through a DWDM layer,
ALS should be enabled on them. The ALS protocol goes into effect when a fiber is cut, enabling some
degree of network point-to-point bidirectional traffic management between the cards.
If ALS is disabled on the OPT-BST, OPT-BST-E, OPT-BST-L, OPT-AMP-L, OPT-AMP-C,
OPT-AMP-17-C, OSCM, and OSC-CSM cards (the DWDM network), ALS can be enabled on the TXP
and MXP cards to provide laser management in the event of a fiber break in the network between the
cards.
10.7.2 Automatic Power Reduction
Automatic power reduction (APR) is controlled by the software and is not user configurable. During
amplifier restart after a system failure, the amplifier (OPT-BST, for example) operates in pulse mode and
an APR level is activated so that the Hazard Level 1 power limit is not exceeded. This is done to ensure
personnel safety.
When a system failure occurs (cut fiber or equipment failure, for example) and ALS Auto Restart is
enabled, a sequence of events is placed in motion to shut down the amplifier laser power, then
automatically restart the amplifier after the system problem is corrected. As soon as a loss of optical
payload and OSC is detected at the far end, the far-end amplifier shuts down. The near-end amplifier
then shuts down because it detects a loss of payload and OSC due to the far-end amplifier shutdown. At
this point, the near end attempts to establish communication to the far end using the OSC laser
transmitter. To do this, the OSC emits a two-second pulse at very low power (maximum of 0 dBm) and
waits for a similar two-second pulse in response from the far-end OSC laser transmitter. If no response
is received within 100 seconds, the near end tries again. This process continues until the near end
receives a two-second response pulse from the far end, indicating the system failure is corrected and full
continuity in the fiber between the two ends exists.
After the OSC communication is established, the near-end amplifier is configured by the software to
operate in pulse mode at a reduced power level. It emits a nine-second laser pulse with an automatic
power reduction to +8 dBm. This level assures that Hazard Level 1 is not exceeded, for personnel safety,
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