To determine if your SFP (Small Form-factor Pluggable) module is single mode or multimode, you can look for specific markings or labels on the module itself. Typically, single mode SFP modules are labeled as "SM" or "single mode," while multimode modules may be labeled as "MM" or "multimode. They might look almost identical from the outside, but knowing the difference is important. The distinction is important as it affects network performance, distance, and overall cost. They cost less and are easier to set up. Here are some methods you can use: Single-mode (SM): Typically has a smaller core diameter, usually around 9 microns.