An FTTH connection may appear to be in perfect working order, yet still fail to function correctly at the customer’s premises. For example, a good PON signal level does not necessarily mean that the ONT will register correctly, that an IP connection will be established, or that the subscribed data rate will actually be achieved. A comprehensive test should therefore examine the entire connection chain – from the fibre optic cable via the PON and ONT to the IP connection, the subscribed services and the customer’s WLAN. This makes it possible not only to determine whether the connection is working, but also at which level a fault is occurring.
How do I test the fibre optic cable and the PON optical level?
The test begins at the physical level. First, the fibre end faces and connectors are inspected and cleaned if necessary. Contamination or damage can cause additional attenuation and reflections.
The relevant optical levels of the GPON or XGS-PON connection are then measured. Where PON technologies are operated in parallel, the different wavelengths can be measured and evaluated separately using a selective or filtered power metre.
The PON ID can also be used to verify that the intended PON branch is actually being measured.
How can I measure GPON and XGS-PON simultaneously on a single fibre?
What should I do if the PON level appears abnormal?
If the optical level is too low or the measurement reveals another anomaly, the cause must be localised along the fibre-optic link.
An OFL (Optical Fault Locator) or OTDR (Optical Time Domain Reflectometer) can be used for this purpose. Reflectometric measurement methods can detect events on the fibre and determine their distance from the measuring instrument. This allows the search to be narrowed down, for example, to a connector, a splice, a bend or another abnormal section of the fibre.
How do I find out where a fault lies on an active PON?
How do I check the ONT registration?
If the optical layer appears normal, the next step is to test the PON connection. This involves checking whether the ONT is registering correctly with the OLT.
An ONT simulation can assist with fault-finding by having the tester itself take on the role of an ONT. This allows the registration to be checked independently of the customer’s existing ONT and further narrows down the cause of a fault.
For example, this allows you to investigate whether the problem lies with the customer’s ONT or its configuration, or whether it is on the network side.
How do I test a GPON or XGS-PON connection if the ONT does not register?
How do I check the IP connection?
Successful ONT registration does not automatically mean that a working internet connection is established.
After registration, a check is therefore carried out to see whether an IP connection can be established. Tools such as ping, traceroute or other IP tests can be used here to check the connection at the IP level.
Only once this level is also functioning can the actual performance of the connection be properly tested.
How do I measure the actual speed of an FTTH connection?
A performance or speed test can be used to check the actual data throughput achieved via the FTTH connection.
Depending on the measuring device and equipment, tools such as Ookla Speedtest, iperf, and HTTP/FTP downloads and uploads can be used for this purpose. This allows you to check whether the bandwidth available on the connection matches the expected data rate.
Particularly with fast FTTH connections, it is crucial that both the measuring device and the interface used support the data rate being tested.
How do I test internet, VoIP and IPTV services?
In addition to the raw data rate, the services actually being used can also be checked. Depending on the connection and equipment, these may include, for example:
- Internet access
- VoIP
- IPTV
- Uploads and downloads
This helps to determine whether the basic IP connection is already disrupted or whether only a specific service is not working as expected.
What if the FTTH connection is working but the WLAN is slow?
If the connection up to the router or access point is working perfectly, but the customer is still not achieving the expected speed via WLAN, the local wireless network must also be included in the diagnosis.
A WLAN analysis can, for example, provide information on the wireless environment, the channels in use and potential sources of interference.
This makes it possible to determine whether the cause actually lies with the FTTH connection or arises further down the line, within the customer’s local network.
What does a complete FTTH test involve?
The entire test procedure can be summarised as follows:
Which ARGUS testers are suitable for a comprehensive FTTH test?
The ARGUS F Series combines – depending on the model and configuration – various measurement and diagnostic functions for FTTH connections. These include, amongst others, selective PON level measurements, PON ID, OFL or OTDR, ONT simulation, as well as IP, performance and service tests.
This allows multiple levels of an FTTH connection to be examined in sequence, enabling the cause of a fault to be systematically narrowed down.
The crucial question in a comprehensive FTTH test is therefore not simply: “Is the fibre-optic cable in good working order?”
But rather: “Does the connection work from the fibre-optic cable to the internet – and if not, at which level is the fault?”
