SFP+ modules can be described as limiting or linear types; this describes the functionality of the inbuilt electronics. Limiting SFP+ modules include a signal amplifier to re-shape the (degraded) received signal whereas linear ones do not.OverviewSmall Form-factor Pluggable (SFP) is a compact, network interface module format used for both and applications. An SFP interface on. SFP transceivers are available with a variety of transmitter and receiver specifications, allowing users to select the appropriate transceiver for each link to provide the required optical or electrical reach over. Quad Small Form-factor Pluggable (QSFP) transceivers are available with a variety of transmitter and receiver types, allowing users to select the appropriate transceiver for each link to provide the required optical reach over.
[pdf] 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] 
