Hello everyone!

Today, I will finish this theme about OLANs. Now, I will finish troubleshooting in OLANs.

As I said in the previous article, troubleshooting is very complex and complicated, especially for passive optical LAN. Documentation is very important for maintenance and troubleshooting.

Troubleshooting in OLAN consists:

• Problems with optical connectors,

• Measuring insertion loss,

• Testing active devices, and

• OTDR testing.

In the last article, I explained the problems with optical connectors. Now, I can continue troubleshooting.

Measuring insertion loss

For measuring IL (Insertion Loss), we have to use OLTS (Optical Loss Test Set). OLTS is composed of a test light source, optical power meter and referent cables. Test light sources can emit different wavelengths. When measuring IL, one should always measure the wavelengths used in the system. So the test source should emit those wavelengths. Also, pay attention to the direction of testing.

For FTTD, the test source will emit 850 nm. For FFTO and passive optical LAN, the test source will emit 1310 nm (for FTTO and passive optical LAN) and 1490 nm (for passive optical LAN). Bi-directional testing is recommended.

In one of the next articles, I will detail explain measuring IL.

Testing active devices

We have to test active devices – OLT, EDFA, optical transmitter, MC, ONT. etc. With an optical power meter (OPM), we can measure output optical power on these active devices. We have to know the normal range of output optical powers for these devices. After that, we can measure it.

Too high optical power can lead to saturation, on the other hand, very low optical power is critical for work and gives poor signal-to-noise (SNR) or MER.

Some devices have loopback tests like ONT. For data transfer, we can use specific protocol testers.

OTDR testing

Measurement of optical traces with an OTDR instrument is recommended. For short links, cables with optical connectors, optical splitters, big reflections, etc, using the OTDR instrument is a problem, especially for passive optical LAN. This problem is because of the limitation in distance resolution of OTDR. For troubleshooting in premises networks, we can use VFL (Visual Fault Locator).

For more information about OTDR testing and using VFL, see the next articles:

OTDR trace analysis (1-7)

Troubleshooting with a VFL

This is the end of this theme. I hope I have well explained OLAN and how to solve the problems in these networks. As well as all the advantages of this new technology.

Thank you!