Many SFP modules come with clear markings or labels that provide information about their specifications, including whether they are single-mode or multimode. Look for keywords or abbreviations such. 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. A 1-core module uses a single fiber core for data transmission, while a 2-core module uses two cores. Precise verification prevents "Ghost Links" and Mode Field Diameter (MFD) mismatches that degrade 800G AI fabric performance. To determine whether the SFP module in your hand is single-mode or multi-mode, the most straightforward method is to check the color of the pull ring, for example, blue pull rings and red pull rings are single mode, and black pull rings are multimode. Single-Mode vs Multimode: How to Check Your SFP. SFP modules are transceivers used to connect network devices to various fiber optic or copper cables. Fiber Type: Single-mode fiber uses one mode of light to propagate through the fiber.