10km optical module maximum transmission distance

In 10G SFP+ modules, “LR” stands for Long Reach and specifically refers to a standardized transmission distance of up to 10km over single-mode fiber. It follows the SFP+ Multi-Source Agreement (MSA) and is widely used to build stable medium-distance 10G links between switches, routers, and servers. Single-fiber bidirectional (BIDI) optical modules must be used in pairs. It utilizes four EML lasers with CWDM wavelengths (5nm wavelength spacing, requiring a TEC cooler to control temperature) and achieves a single-wave rate of 106. 25Gbps based on PAM4 modulation. The fiber optic length, connector quality, cleanliness, and proper handling often determine whether a connection is stable or problematic. [pdf]