Alcatel-Lucent 7330 Product Information Manual page 105

The following conditions on a single ONT may affect 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.
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.
Duplicate serial numbers
An ONT is automatically disabled when:
•
A ranged ONT sends a broadcast PONID within a serial number PLOAM
message. This indicates the ONT may not be aware of its ranged state or that a
second ONT using the same serial number is on the PON.
•
An ONT sends a serial number PLOAM message that does not match its assigned
ID.
•
An ONT sends a serial number PLOAM message but the ONT has not been
assigned a PONID.
•
A deactivate PLOAM message has been sent to the ONT three times and the ONT
has not deactivated. The ONT is then sent a disable PLOAM message.
Receive and transmit errors
There are two ways to identify marginal receive problems:
1 Self correcting CRC check for the time slot; if the time slot allocation fails a CRC
check, the ONU does not transmit in that time slot.
2 Increasing rate of becdown (Bit Error Rate Count Downstream) statistics.
Alcatel-Lucent 7330/7302 ISAM FTTN R04.02.42a
3FE 54199 AAAA TCZZA Edition 01 ONT Product Information Guide
March 2011
1 — ONT and MDU overview
1-21