OM3, OM4, and OM5 are types of multi-mode optical fibres commonly used in data centres and enterprise environments to support various network speeds and transmission distances, including 10 gigabit Ethernet (10G), 40 gigabit Ethernet (40G), 100 gigabit Ethernet. OM3, OM4, and OM5 are types of multi-mode optical fibres commonly used in data centres and enterprise environments to support various network speeds and transmission distances, including 10 gigabit Ethernet (10G), 40 gigabit Ethernet (40G), 100 gigabit Ethernet. Copper cables are more affordable but limited to shorter distances for 40G transmission. For a 100 GbE network, fiber optic cables are commonly used, except for same-rack connections, where direct-attach copper cables may be used. Single-mode fiber cables support both 40G and 100G transmission up to. Multimode fiber enables the utilization of vertical-cavity, surface-emitting lasers (VCSELs) to provide synergistic, low-cost optical connectivity and electronic solutions. This larger core allows easier light injection and lower-cost optical sources (LEDs and VCSELs), making multimode fiber the cost-effective choice for. QSFP 40G SR4 is a short-reach 40Gbps optical transceiver designed for high-density data center interconnects using multimode fiber and parallel optics. It operates at 850nm, transmits data over four parallel 10Gbps lanes, and typically supports distances up to 100m on OM3 and 150m on OM4 fiber.