Hello, everyone!
Today, I will explain to you a special optical instrument for measure and test PON optical networks.
Traditional OTDR instruments cannot measure live fibers (they do not have filtered 1650 nm) or measure routes with optical splitters (this is the end of the route). In the next figure, we can see a problem with traditional OTDR measuring. We have some events, OTDR shows it as the end of the optical trace. The question is: what is it? Misconnected connector at splitter? Fiber break? Or simply hitting the optical splitter and going in the noise floor?
Figure 1. Problem with traditional OTDR
These special PON instruments can be new separate optical instruments or part of OTDR. All of these optical instruments are made for special measures and tests in the PON last-mile. They can work on live (filtered wavelength 1650 nm) or dark optical fibers (standard wavelengths 1310 nm and 1550 nm, and/or special wavelength 1490 nm). These instruments can measure/test optical traces like standard OTDR, but they can recognize and draw all reflection and non-reflection events and optical splitters. And we can see the whole link with all fusion splices, connector pairs, optical splitters, etc. This is a very useful option. We can test last-mile very easily. Less documentation is needed as opposed to OTDR. We can see it in the next two figures.
Figure 2. Testing optical link – problem with connector pair
(connector is damaged, dirty or not well connected)
Figure 3. Testing optical link – there are no problems on the link
Many of this device has power level verification and ONT detection. Some instruments have built-in VFL and an option for the optical microscope.
These instruments can show all relevant information on the display, and they show the location of the problem, as well as possible causes and how to fix them. The following three figures show the use of this instrument for troubleshooting the FTTH PON network.
In the first situation - No optical power on the ONT. The instrument is connected to the ONT, after that, it shows us all information about the link on the display. We can see where is a problem – disconnection at the optical splitter. After that, we can fast fix these problems.
Figure 4. No optical power on the ONT
In the second situation, we have very low optical power on the ONT. The instrument is connected to the ONT, after that, it shows us all information about the link on the display. We can see problems with a dirty connector and bad splices. After that, we can fast fix these problems.
Figure 5. Very low optical power on the ONT
In the last situation, ONT does not have input optical power. We have to connect the instrument in the optical splitter, on the output optical ports (as we can see in figure 6 – a situation 1.). We are measured optical power, the problem is between optical splitter and ONT. After that, we have to connect the instrument to the drop cable (as we can see in figure 6 – situation 2.). We can see problems with drop optical cables – broken splice. Then, we can fast fix these problems.
Figure 6. No optical power on the ONT – broken splice
Finally, let me repeat, this is a very useful tool for troubleshooting PON networks. We can detect and fix problems very quickly. The only drawback is the high price.
Thank you!
