Alcatel-Lucent 7342 - Laser Stuck on; Figure 4-2 Rogue ONT Failure Conditions

4 — ONT software and security features
4-6 July 2008 Alcatel-Lucent 7342 ISAM FTTU ONT R04.05.06
ONT Product Information Manual Edition 01 3FE 51892 AAAA TCZZA
Figure 4-2 Rogue ONT failure conditions
The following conditions on a single ONT may have effects on other ONTs using the
same PON:
• an ONT continuously sends light up the fiber because a laser is stuck on, which
may render the PON unusable
• two ONTs with the same serial number prevents correct ranging of both ONTs
• an ONT misinterprets the bandwidth map, causing the ONT to transmit for the
wrong time slot allocation, disrupting the PON for another ONT that is trying to
use its correctly allocated time slot
• an ONT signal is outside its timing window, affecting the start of another ONT
time slot
• an ONT signal is too low or too high, causing bit rate errors or a ranging failure
The system is designed to automatically identify these ONT fault or error conditions
using alarms, statistics, or automatic action. This tells operators of a problem or
disables the ONT so a single rogue ONT cannot affect the entire PON. See the
7342 ISAM FTTU ONT Troubleshooting Guide for more information.
Laser stuck on
ONTs use watchdog timers to stop errors that cause light to be continuously sent up
the fiber. These watchdog timers are maintained by the software. When a watchdog
timer fails, the hardware triggers a reset. When a reset is triggered, the laser is
disabled. Before the laser retransmits, the ONT software must pass power on and self
tests.
1899
7
7342
LT
serial # 123abc
serial # 123abc
X
X
X
1) Watching timer
to ensure laser i
s
not stuck on or
no laser until
ONT s/w is read
y
3) Bandwidth map
CRC failure
ONT deactivates
ONT
ONT
ONT
Increasing
becdown
counters?
2)
2) If 2 ONTS report
identical serial #s,
both ONTS are disabled
X
PON