Hello, everyone!
Today I will finish writing about reflectance testing. In this last article, I will write about the OTDR method for measuring reflectance. In the previous two articles, I explained problems and solutions, and the OCWR method for measuring reflectance. Let’s get started.
Another method of measuring reflection is to use OTDR (Optical Time Domain Reflectometer). OTDR is one of the most important and useful instruments for measuring in all optical networks. With this instrument we can measure the length of the fiber, the total attenuation and reflection, the attenuation and reflection of individual events, we can find the place of break cable, etc. For this topic, the ability to measure reflection is important.
OTDR is especially used when it is necessary to measure the reflection on long optical cables. The OTDR sends an optical signal and records all events in the optical fiber. Upon completion of the test, the OTDR displays the optical trace and provides a table of all events. Here we can see details (attenuation and reflection) related to all events. On the display of the OTDR instrument, the connectors will see how the reflections, the mechanical joints can show the peaks of the reflection, and the fusion joints will not show any reflection. OTDR measures the peaks, larger peaks also mean greater reflection.
We can also analyze and measure reflection with markers. You have to be careful here. One marker is placed at the beginning of the event, and the other marker at the top of the reflection – peak.
Figure 1. Calculation of reflectance
Optical Return Loss or short ORL is composed of reflectance and backscatter. It is an important factor in transmission systems. OTDR can calculate it from the optical trace.
I wrote about OTDR in particular in the articles, which you can read at the following link: OTDR trace analysis.
One note for the end. If APC optical connectors are used on the route, this can be a "problem", no reflections or connector connections will be seen. That is why documentation is important.
Thank you!
