OM4 (Optical Multimode 4) is a type of multimode optical fiber commonly used for high-speed data transmission in data centers, local area networks (LANs), and other short-reach applications. OM4 fiber is designed to support higher bandwidths compared to its predecessor, OM3 fiber.

The OM4 fiber is optimized for use with vertical-cavity surface-emitting lasers (VCSELs) at a wavelength of 850 nm, which is commonly used for 10 Gigabit Ethernet (10G) transmission. The effective modal bandwidth (EMB) of OM4 fiber at 850 nm is higher than that of OM3 fiber, providing better performance for 10G applications.

In terms of distance, the maximum reach for OM4 fiber with 10G Ethernet is typically 400 meters. However, it's important to note that the actual distance achievable may vary based on factors such as the specific transceivers used, the quality of connectors and splices, and the overall link configuration.

Keep in mind that while OM4 fiber can support 10G Ethernet, it is also capable of supporting higher data rates such as 40G and 100G Ethernet at shorter distances. When considering fiber optic installations, it's always advisable to refer to the specific technical specifications and recommendations provided by the equipment manufacturers and standards organizations.