Optical Network Unit (ONU)
1. Slow internet access or frequent disconnections on devices connected via Wi-Fi
Cause: Interference in a congested wireless environment causes signal disruption and disconnections.
Solution: 1) Open the router’s configuration page and change the wireless channel, avoiding the default channels 1, 6, and 11.
2) Alternatively, use a Wi-Fi analyzer to find a less congested channel.
2. A 100M broadband connection does not deliver the expected speed
Speed tests using 360 and Tiantian Internet Assistant show only around 50M. The result remains the same when the router is removed and the computer connects directly via dial-up. Optical attenuation is normal, and the account is correctly provisioned for 100M.
Cause: If the hardware and cabling are functioning correctly, the issue is with the account.
Solution: Notify the relevant support team. If the account checks show no abnormalities, ask the customer to visit a service center to request a broadband account number change. Service should return to normal with the new account.
3. A switch or router cannot connect through the cable entering the premises
Cause: The ONU is installed in the low-voltage service shaft, and the developer-installed cable to the premises is of poor quality.
Solution: Run an Ethernet cable from the ONU and use a switch to distribute the connection.
4. Quickly identifying an unlabeled customer fiber
Solution: Use the FTTH fiber-loop identification method.
Connect a PON optical power meter set to 1490nm, or an ONU with optical power monitoring, at the customer end. Ask a colleague or the customer to monitor optical power changes. At the splitter, form a small loop in each customer fiber in turn. Coordinate by phone to identify the fiber whose optical power reading changes when looped. This method does not require disconnecting other customers.
5. The ONU voice port indicator repeatedly flashes instead of remaining steady, and the customer’s landline service is disrupted
Cause: Excessive load on the power supply results in insufficient power to the ONU.
Solution: Connect the ONU to an outlet shared with fewer household appliances.
Technician’s tip: Troubleshooting should cover more than optical attenuation, cabling, and the ONU. Check smaller details such as the power supply as well.
6. Registration times out, and the management system does not show the ONU online
Cause: The technician did not fully tighten the fiber patch connector.
Solution: Access the first-stage distribution box, locate the fiber patch connector, and tighten it.
7. No link and high optical attenuation
Cause: Fiber drop cables are relatively fragile and have lower tensile strength than other network cables or wired connections.
Solution: Route the fiber drop cable through a dedicated conduit wherever possible. Avoid sharing a conduit with other cables, and do not knot or twist the fiber drop cable.
8. The LOS indicator is red
Possible causes: An interrupted optical path, a faulty ONU, a damaged fiber drop cable, a connector fault, a faulty splitter port, a main fiber fault, or an OLT fault.
Solution: First, use an optical power meter to measure optical loss. If loss is excessive or no optical signal is detected, check that the connectors and distribution box connectors are clean and that the fiber pigtail is connected correctly. If these checks reveal no problems, test the main fiber for an optical signal. If a signal is present, try another splitter port. If optical loss is within the specified range, test with another ONU.
9. The PON indicator is off
Possible causes: The ONU’s upstream POS port does not match the POS port configured in the work order, work order data is missing, the ONU Password was entered incorrectly, or the fiber pigtail was connected before the Password was changed.
Solution: For a newly commissioned residential community, first configure the Password again. If this does not resolve the issue, contact the supervisor to verify the Password data in the installation work order and confirm the associated POS port.
10. The PON connection activates only once
Possible causes: An ONU fault, a work order data issue, or an OLT data fault.
Solution: Contact the supervisor to check the OLT. If it is functioning correctly, arrange to replace the ONU and ask the supervisor to update the data. If the issue persists, ask the service center to cancel the existing service record and create a new work order.
11. The PON indicator is steady, but broadband connection returns error 691: incorrect username or password
Possible causes: An incorrect ONU Password, incorrect broadband username or password, a port binding issue, or a customer computer issue.
Solution: First, re-enter the broadband username and password. If the issue persists, check the ONU Password. If it is correct, contact the service coordinator to verify the broadband credentials, review dial-up information, and remove the binding.
12. The PON indicator is steady, but broadband connection returns error 678: the remote computer did not respond
Possible causes: The Ethernet cable is connected to the wrong LAN port, an ONU fault, a customer computer issue, or an upstream backbone network issue.
Solution: On the current four-port ONU, only LAN1 is available for this service. After confirming the port connection, test with your own laptop. If it connects successfully, the issue is with the customer’s computer. Otherwise, contact the supervisor to check the equipment. If no fault is found, arrange to replace the ONU and ask the supervisor to update the data.
13. ONU registration stops below 30% and reports unsuccessful OLT registration
Cause: An equipment room or line card issue.
Solution: Restart the optical port in the equipment room. If this fails, reset the line card. Use caution: resetting the line card disconnects all customers on the affected PON port.
14. ONU registration stops below 50% and reports a platform connection timeout
Cause: An ONU configuration issue.
Solution: Replace the ONU.
15. After 80%, ONU registration reports successful ITMS platform registration but failed service provisioning
Cause: The ONU itself is functioning correctly.
Solution: Contact the equipment room team. If the ONU has a binding, remove it. If it has no binding, reset it.
16. Speed tests do not reach 200M
Possible causes: The Ethernet cable, computer network adapter, or router.
Solution: Check that the Ethernet cable has eight conductors, the computer has a Gigabit Ethernet adapter, and the router supports Gigabit Ethernet.
17. Registering an ONU when the customer has no computer and the technician has no equipment available
Solution:
1) Use the customer’s wireless router. Connect a phone to the customer’s Wi-Fi. On newer routers that use a web address for login and support access across subnets, set the WAN connection to obtain an address dynamically. The router automatically switches its IP range to another subnet. Open 192.168.1.1 to access the ONU configuration page. On older routers that use an IP address for login, set the LAN gateway to 192.168.1.2, on the same subnet as the ONU. Connect the cable from the ONU’s LAN1 port to a LAN port on the router. Then open 192.168.1.1 to register the ONU. After successful registration, move the cable from the router’s LAN1 port back to its WAN port.
2) Many China Telecom 4K set-top boxes run Android. Enable the wireless hotspot in network settings, then connect the set-top box’s Ethernet cable to port 1 on the ONU. Connect a phone to the set-top box’s hotspot, which shares the wired connection, and enter the ONU registration address to register.
3) Use the customer’s internet-connected TV. Connect the ONU’s broadband Ethernet cable to the TV’s Ethernet port, open the TV browser, and enter the ONU address to register.
Set-Top Boxes
1. Standard HD set-top box faults
If loading stops below 30%, check the Ethernet cable. At 50%, check the ONU service configuration. At 85%, check the network access account. If loading reaches 100% and an error appears, check the service account.
2. Android-based 4K set-top boxes
Below 50%, possible causes include the Ethernet cable, network access account, or ONU configuration. Above 50%, check the service account.
3. 4K HD set-top boxes
7%: Local network connection failure. Check that the Ethernet cable is securely connected and that “Wired Connection” is selected in settings.
52%: Internet connection failure. Check whether the connected network can access the Internet.
83%: Platform authentication failure. Check whether the connected network can access the Internet.
Authentication issue: Check that the Wi-Fi password is correct. Passwords are case-sensitive.
4. Frozen or distorted video on live TV, on-demand content, and catch-up TV; audio without video
Solution: 1) Check optical attenuation. 2) Check the account configuration. 3) Check whether total iTV traffic is overloading the connection.
Routers
1. Speeds below 100M
Possible causes: The main fiber, fiber pigtail, Ethernet cable, ONU, or router.
Solution: Inspect the fiber cabling and measure optical attenuation.
2. Speeds below 200M
Possible causes: The main fiber, fiber pigtail, Ethernet cable, ONU, or router.
Solution: Inspect the fiber cabling and check whether the optical attenuation reading meets the requirement (−26 dB). Check that the Ethernet cable is Cat 5e, the ONU supports Gigabit Ethernet, and the router supports Gigabit Ethernet (Huawei Router A1 WS832, Huawei Honor Pro, ASUS AC66U, Tenda AC9, ZTE E8820).
3. Unstable Wi-Fi, slow speeds, or frequent disconnections
Solution: Restart the customer’s router. If the issue persists, test with a single computer connected directly.
4. Wi-Fi signal below −60 dBm
Cause: The router.
Solution: Check the signal with a Wi-Fi analyzer. If it does not reach −60 dBm, replace the router with a recommended model.
5. Poor Wi-Fi signal
Cause: Co-channel Wi-Fi interference.
Solution: Use a Wi-Fi analyzer to check for interference on the customer’s channel. If interference is detected, connect to the router’s Wi-Fi, enter the gateway IP address in a browser, open the basic wireless settings, and select a different channel from the channel drop-down menu.
Common Faults
1. ONU activation failure
1) The PON port to which the ONU is actually connected does not match the port recorded in the residential customer system. Update the unit number or the PON port associated with the splitter.
2) The authentication code is incorrect.
3) The ONU’s previous data has not been deleted.
4) Optical path quality is poor.
2. Error 691
1) First, check whether the customer’s broadband account has overdue charges.
2) Verify the password, re-enter the account credentials, and retry the dial-up connection.
3) Check for a fault in the computer’s dial-up software and recreate the dial-up connection.
4) The account cannot be found in the unbinding system.
Tip: Before shutting down the computer or when broadband is no longer needed, right-click the broadband connection and select “Disconnect” to prevent the account session from becoming stuck.
3. Error 676
1) The system’s built-in PPPoE dial-up connection is already in use. Disconnect the active PPPoE connection or restart the computer.
2) The client disconnected abnormally. Switch off the ONU for 5 minutes, then switch it on again. Login should work once the system automatically releases the account session.
3) The network adapter’s physical address is incorrect. If the above steps do not resolve the issue, check the physical address. This is commonly caused by unauthorized use of the adapter’s physical address.
4. Error 678
1) First, check the ONU indicators. The PON indicator should remain steady, and the LOS indicator should be off.
2) Check the local area connection status. A red X may indicate an ONU fault, a damaged Ethernet cable, or a network adapter fault.
Unplug and reconnect the Ethernet cable between the ONU and computer, disable and re-enable the local area connection, or restart the computer and test again.
5. Error 769
1) If the network adapter is disabled, enable it.
2) If the network adapter driver is missing, install it.
3) If there is a network adapter driver conflict, uninstall the adapter driver marked with an exclamation point, then reinstall the driver.
6. Error 720
1) “Internet Protocol Version 4 (TCP/IPv4)” is not selected on the Networking tab in Broadband Connection Properties.
2) An IP address has been manually configured in Broadband Connection Properties.
3) There is an operating system fault. Create a new broadband connection or reinstall the operating system.
