LCDG IMPACT
: Loss of frame (LOF) in the system and the ONT goes offline.
Possible LCDG Causes
: Optical fiber is faulty or ONT is faulty.
9.2.4 BIP
Each GPON Transmission Convergence (GTC) upstream frame must contain physical layer overhead data (PLOu) which includes
the physical layer overhead and three fields of data: Preamble and delimiter, BIP, ONU ID and real time ONU status report to OLT.
Looking at the Upstream Frame Structures above (see
Figure 51: GPON upstream frame structure
), BIP - SONET/SDH-style Bit
Interleaved Parity of all bytes since last BIP (1 Byte) is visible.
BIP Impact:
BIP provides an approximate method for monitoring link quality at the bit error level.
9.2.5 RDI
Each ONU upstream frame includes Remote defect status indication (RDI) (1 = Defect, 0 = OK).
9.2.6 REI
Remote error indication.
9.2.7 Corr FEC
FEC is usually disabled for 20km SFP networks but enabled for Class C+ 60km SFP networks. When
FEC is enabled, the unit reports each correctable FEC error detected in the upstream burst.
Possible Corr FEC Causes:
The quality of the optical path is deteriorated. The port of the ONT/ONU is faulty.
Troubleshooting Corr FEC Error:
1. Confirm that the optical fiber is connected properly by gently pulling on cable. Then, check if the alarm is cleared
2. Inspect the optical connectors for contamination or damage by using a FiberScope. Clean connector if dirty and if
scratches/dents/pits detected, replace connector. Then, check if the alarm is cleared.
3. Check if optical fiber is work, bent or broken. Replace the optical fiber if needed. Then, check if the alarm is cleared.
4. Run the
display port state
command to check whether the ports are normal. If not, reset or replace the ONT/ONU, then
check whether the clear alarm is generated.
9.2.8 Uncor FEC
Uncorrectable Forward Error Correction. When FEC is enabled, the unit reports each uncorrectable
FEC error detected in the upstream burst.
MTTplus-420_User_Manual_RevC00
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