If the indicator light is on at one end but off at the other, swap the fiber jumpers at both ends. A single-mode optical module can use only the single-mode optical fiber, similarly, a multi-mode optical module can use only the multi-mode optical fiber. Here's a structured. In this article, we focus on optic transceivers, as they're called, which deliver 1Gbps of data across single-mode or multi-mode fibers. Now, the difference between SFP and SFP+ is an important one when. Based on typical issues encountered with optical modules in daily switch applications, this document summarizes basic troubleshooting steps for resolving common faults: 1.