40G optical module wavelength

40G QSFP+ optical modules achieve 40Gbps transmission by using four parallel wavelengths, each carrying 10Gbps, over single-mode or multimode fiber.Overview40G optical modules, such as 40GBASE-SR4, LR4, and ER4, use four optical lanes to transmit 40Gbps data. Each lane operates at 10Gbps, and the lanes are either multiplexed or transmitted in parallel depending on the module type. These modules are typically implemented in QSFP+ form factors, compatible with standard switch and router ports.Wavelength Schemes40GBASE-SR4: Short-reach multimode fiber module using four 850nm wavelengths over parallel fibers, supporting distances up to 100m on OM3 and 150m on OM4 fiber, connected via MPO/MTP connectors .40GBASE-LR4: Long-reach single-mode fiber module using CWDM wavelengths at 1271nm, 1291nm, 1311nm, and 1331nm, supporting distances up to 10km over duplex LC fiber .40GBASE-ER4: Extended-reach single-mode fiber module also using CWDM wavelengths at 1271nm, 1291nm, 1311nm, and 1331nm, supporting distances up to 40km over duplex LC fiber .Architecture40G modules split the 40Gbps signal into four parallel 10Gbps electrical lanes, which are then converted into optical signals. In LR4 and ER4 modules, these signals are multiplexed using CWDM onto a single duplex fiber pair. At the receiving end, the optical signals are demultiplexed back into four electrical channels, restoring the full 40Gbps data stream .ApplicationsSR4 modules: Ideal for short-distance data center interconnects and high-density switching.LR4 modules: Suitable for metro networks and campus backbones requiring up to 10km reach.ER4 modules: Used in longer metro or extended campus networks where 10km or 20km optics are insufficient but full DWDM systems are unnecessary .ConnectivitySR4: Uses 12-fiber MPO/MTP cables for parallel transmission; four fibers remain unused.LR4/ER4: Uses duplex LC fiber with CWDM multiplexing for long-distance single-mode fiber links . These 40G QSFP+ modules provide flexible deployment options, allowing network engineers to select the appropriate module based on distance, fiber type, and wavelength requirements. They are widely used in data centers, high-speed interconnects, and metro Ethernet networks.