Hello, everyone!
Today, I will continue to write about testing the IL of optical cables. In the last article, I explained the testing IL of installed optical cable, now, I will explain the single-ended method.
Single-ended method
The single-ended method is a method used with short cables, such as patch cords. This method is used for both MM and SM optical cables. The measured loss is the loss that includes the attenuation of the optical fiber and the attenuation of the connector pair.
For this method, we must have a test source, optical power meter, and launch referent cable. Test source can be used for MM fibers (850 nm and 1300 nm) and for SM fibers (1310 nm and 1550 nm).
Figure 1. Single-ended method
Launch reference cable is tested optical cable, with 0 dB attenuation. It has the same fiber type and size as the short optical cable (e. g. patch cord) for test and has an optical connector compatible with an optical connector of cable for test.
Before every connection, all optical connectors from the test source, optical power meter, and reference cable should be inspected and cleaned. For this procedure, we can use an optical microscope and tools for cleaning optical connectors, like one-click cleaners.
We have to connect the launch reference cable to the test source, and this cable is recommended not to disconnect, otherwise, the measurements will be incorrect.
For setting 0 dB, there is only one option – with one referent optical cable. It is shown in the next figure.
Figure 2. Reference method - setting 0 dB
Only after all of these procedures, we can start to measure. We can see the single-ended method in figure 1.
In case the optical cable to be tested uses optical connectors that do not match the optical connectors on the optical power meter and/or launch referent cable or “plug and jack” type we cannot use the single-ended method. Then a method with two or three reference cables is used. Then the total losses include the attenuation of all connector pairs.
As with the previously described method, documentation is made during and after testing. It must include the following information: date and time, name of the operator, equipment used for testing, type of cable, fibers and optical connectors, test wavelength, loss measured, etc.
This is the end of this article. In the next article, I will continue to write about this topic >> Testing IL of optical cables (3).
Thank you!
