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Knowledge Base

Optical cable is outage caused ONT offline

Publication Date:  2018-01-29  |   Views:  710  |   Downloads:  0  |   Author:  l00486215  |   Document ID:  EKB1001265638


Issue Description

Customer reported an urgent issue that more than 150 ONT are disconnected from one OLT suddenly. All these ONT are located in a hotel, clients can not surf internet and IPTV.




Alarm Information

Handling Process

1:Check alarm list that there are lots of ONT los alarm reported in MA5608T

2:filter with 'signals(LOS)', shows GPON port 1,2,3,4,5,7,8,9,10 had LOS alarm and optical cable are outage or ONT are broken.

3:Because of there were more than 150 ONT are offline at the same time, so exclude ONT side probable issues.

4:Query the optical module sending power, temperature and states, all works in the right range.

MINE-OLT-3(config-if-gpon-0/0)#display  port  state  0
  Port Information
  F/S/P                        0/0/0
  Port state                   Online
  Last down cause              -
  Last up time                 2017-10-04 09:59:10+08:00
  Last down time               -
  Port energy-saving flag      No
  xPON MAC chipset state       Normal
  Signal detect                Normal
  Available bandwidth(Kbps)    1061492
  Illegal rogue ONT            Inexistent
  Optical Module State
  Optical Module status        Online
  Laser state                  Normal
  TX fault                     Normal
  Temperature(C)               30
  TX Bias current(mA)          24
  Supply Voltage(V)            3.22
  TX power(dBm)                3.79

  Vendor name                  HISILICON      
  Vendor rev                   Unspecified
  Vendor OUI                   Unspecified
  Vendor PN                    SSX1T1LTB      
  Vendor SN                    030SRN6TG1753404
  Date Code                    16-01-26
  Vendor specific              00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
                               00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  Optical Module Static Information
  Module type                  GPON
  Module sub-type              CLASS B+
  Used type                    OLT
  Encapsulation Type           SFP
  SFF-8472 Compliance          Includes functionality described in Rev 9.5
  Max Distance(Km)             20
  Max rate(Kbps)               2500000
  Rate Identifier              Unspecified(0x0)
  Wave length(nm)              1490
  Fiber type                   Single Mode
  Identifier                   SFP or SFP Plus

                               interface ID only
  Connector                    SC
  Encoding                     NRZ
  Length(9um)(km)              20.0
  Length(50um)(m)              -
  Length(62.5um)(m)            -
  Length(copper)(m)            -
  Length(50um,OM3)(m)          -
  BR,max                       Unspecified
  BR,min                       Unspecified
  Diagnostic Monitoring Type   Digital diagnostic monitoring
                               Externally Calibrated
                               Power measurement type: Average Power
  Options                      TX_DISABLE,and disables the serial output
                               LOS(signal inverted from standard definition)
  Enhanced Options             Alarm/warning flags
  OTDR capability              Not support
  Cc_base                      0x1d(Correct)
  CC_EXT                       0x49(Correct)
  Optical Module Threshold Parameter

  threshold(dBm)               [-29.2,-8.0]
  Rx power alarm
  threshold(dBm)               [-30.0,-7.0]
  Tx power warning
  threshold(dBm)               [1.0,5.0]
  Tx power alarm
  threshold(dBm)               [0.6,5.6]
  Tx bias warning
  threshold(mA)                [0.000,70.000]
  Tx bias alarm
  threshold(mA)                [0.000,90.000]
  Supply voltage warning
  threshold(V)                 [3.100,3.500]
  Supply voltage alarm
  threshold(V)                 [3.000,3.600]
  threshold(C)                 [-8,75]
  Temperature alarm
  threshold(C)                 [-13,80]

5: Query the gmac statistics of sending and receiving of  specified gpon port 1, there are sending count raising all long, not increase from receiving count, this enlarge the state of optical module works normally, there might be some problems in main optical cable or ont are broken.  

Root Cause

Outage of optical cable.


1:Measure the receiving optical power to dobule confirm if ONT can't receive any optical line.

2:Use OTDR to test whole fibers in the cable and fix further


1:For outage of optical cable this kind of situation, we need to keep calm and anaylyze alarm and statistics first.

2:Pay more attentiion to the alarm reported in U2000, especially for important alarm like LOS which showed that main fiber is broken.

3:If customer didn't know exact offline ont in which gpon port, we need to find the rule and incident time from alarm and remind customer.