Analysis of Related Problems after Optical Fiber Patch Cord Testing

(1) Why does the optical fiber test pass but still lose packets when the network is running?

In the standard selection, many users will make some obvious mistakes, such as paying little attention to the 50/125 optical fiber tested during the test μ M (OM2, OM3, OM4) or 62.5/125 μ M (OM1).

The requirements for the maximum loss value of the optical fiber with two apertures are quite different, and the wrong selection of the optical fiber test standard will directly lead to the change of the judgment threshold. For example, if the measured link is 50 μ M optical fiber, and the selected test standard is 62.5 μ m. The application is 100Base FX. If the test result is 10dB, the tester will get the PASS result, but the real situation should be unqualified, because it exceeds the 6.3dB threshold. This answers the previous question. The test passed, but why does the running data still cause packet loss.

(2) After passing the 10G standard, why can't we support 10G rate?

There are such users who upgrade the network backbone. They will upgrade the switch module and server module, and of course, they will also test the loss of optical fiber in the network. It seems that there is no problem in the method. The measured optical fiber meets the requirements of 10 gigabit network, and the loss is less than the standard limit value, but the actual operation effect is still not ideal.

This is mainly because the mode bandwidth of optical cables is not taken into account. The mode bandwidth of different optical cables represents the maximum bandwidth that can be provided within a certain distance. The larger the mode bandwidth is, the higher the transmission rate can be within a certain distance. However, since many optical fibers were laid in earlier years, the mode bandwidth is generally low, less than 160, resulting in a longer distance, the rate will not go up, although the loss is qualified at this time.

(3) The test loss is up to the standard, and there is no problem with the mode bandwidth. Why is there a problem in the actual operation?

There is another error in our test. As long as the loss passes, we think that the optical fiber is OK, but this is not the case. Assume that the standard design requires the link loss to be 2.6dB. However, due to the adapter failure during the test, the loss of an adapter is more than 0.75dB, but the total link loss is still less than 2.6dB. At this time, if you simply test the loss, you may not find the adapter problem, However, in real network use, the transmission error rate will increase greatly due to the adapter problem.