Keep 40G uplinks stable across longer fiber runs with a transceiver built for single-mode environments. The AddOn QSF-503-AO is a 40GBASE-LR4 QSFP+ module designed for enterprise networks that need dependable optical reach between switches, aggregation points, and distribution layers. This module is positioned for teams standardizing on QSFP+ optics while maintaining compatibility with Gigamon Systems QSF-503 environments. For procurement teams, that matters: it provides a practical path to extend 40G connectivity without moving to a more expensive platform or redesigning the fiber plant. LR4 optics are a strong fit when short-reach multimode modules are no longer enough and the network needs longer-distance transport over single-mode fiber. That makes this transceiver well suited to campus backbones, data center interconnects, and other production links where link budget and interoperability are more important than headline speed alone. For infrastructure buyers, the value is straightforward: a standards-based 40G optic that supports longer reach, preserves QSFP+ density, and fits into environments where uptime and compatibility carry real cost.