Keep 40 GbE links stable across longer fiber runs with a QSFP+ transceiver designed for 40GBASE-LR4 environments. The JG661A-ST compatible module supports 40 Gbps Ethernet over single-mode fiber and uses an LC duplex connector, making it a fit for backbone uplinks, aggregation switches, and inter-rack connectivity where distance and signal integrity are both critical. This class of optics is chosen when short-reach modules are not enough. LR4 optics are built for longer campus and data center paths, helping teams maintain performance without moving to a more expensive architecture. For procurement teams, that means a targeted upgrade path that preserves existing 40 GbE infrastructure while extending reach to the edge of the network. Use it where predictable throughput, longer distance, and standards-based interoperability matter. The result is a cleaner network design with fewer compromises at the physical layer and a module that aligns with enterprise-grade deployment requirements.