Zyxel OLT2412 [300/326] The alm led is on

Zyxel OLT2412 [300/326] The alm led is on
Chapter 45 Troubleshooting
OLT2412 User’s Guide
300
The ALM LED is on.
The ALM LED is on when at least one fan has failed in the fan module. Working fans emit a low buzz
and blow air. If the fans are not working properly, refer to Section 3.1 on page 43 for instructions on
changing the fan module.
The OLT cannot detect an ONU or an ONU cannot connect to the OLT.
Check if the settings and the connection status for the ONT/ONU are correct on the OLT.
Check if any historic alarm occurred related to the ONT/ONU on the OLT .
Check if the transmitting optical power of the GPON port on the OLT is in the normal range (+7~+2
dbm). You may need to change the PON port optical module if it is too low or too high.
Check if the receiving optical power on the ONT/ONU is in the normal range (-8~-24 dbm) by using
the show interface olt pon-<slot>-<port> ddmi command. A low value may be caused by high
signal attenuation and you need to check the optical line. A high value might be caused by the OLT
emitting a high level of optical power or a low splitting ratio. You may try to increase the
attenuation from the GPON port on the OLT or change the ONT’s or ONU’s optical module.
Make sure the distance between the OLT and the ONT/ONU does not exceed 20 km.
Make sure the ONT/ONU can get an IP address if the ONT/ONU is a routing gateway.
Check if the ONT’s or ONU’s settings are correct and match the settings on the OLT. For example,
the VLAN settings should be properly configured on the OLT’s uplink ports, Gigabit Ethernet ports,
GPON port, and ONT/ONU port.
Check if the ONT/ONU is functioning normally. If not, you may replace it with another.
Check if the GPON port on the OLT is functioning ok.
The OLT cannot detect multiple ONTs/ONUs or ONTs/ONUs cannot connect to the OLT.
Check if the GPON port on the OLT is disabled by using the show interface olt pon-<slot>-
<port> status command. Activate it if it is disabled.
Make sure the distance between the OLT and each ONT/ONU does not exceed 20 km or 30 km
depending on whether you use a class B or a class C transceiver.
Check if the transmitting optical power of the GPON ports on the OLT is in the normal range
(+7~+2 dbm). You may need to change the PON port optical modules if they are too low or too
high.
Check or change the main fiber cables, GPON ports, optical splitters.

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