This blog post is created with single, particular reason in mind: AD-net’s R&D team discovered that in some cases customers are having troubles when installing the Optical fiber applications. Particular confusion is whether Multimode (MM) and Single mode (SM) optical patch cords are interchangeable.
Figure 1. Correct use of Multimode and Singlemode cables.
In order to analyze question better, please refer to Figure 1. As one could see, there are standard installations using standard 1.25G 1310nm 2km MM SFP and the same specifications SM SFP modules. Bot are using cables with matching indexes. The results are expectable, signal is passing through and working as intended.
Figure 2. Incorrect use of MM and SM cables.
In the Figure 2, another scenario is presented. The cables are interchanged, and now MM SFP module is using SM patch cord, while SM SFP module – MM patch cord. One would not expect so dramatic changes, but real field tests state that this simple mistake could cost the whole node to function properly.