There have been many advancements in fiber optical components and standard multimode fiber over the years. The ISO 11801 standard provides the following system of classification for multimode fibers. The system is based on the bandwidth of various fibers and classifies them as either OM1, OM2, OM3 or OM4.
62.5 um fiber introduced. This fiber had a larger core than the 50 um fiber that it replaced, enabling more of the light from an LED to be injected into the fiber’s core. 62.5 multimode fiber was able transmit over 2 km campuses at 10 Mb/s. Also, the new fiber was easier to install due to its higher numerical aperture.
As data rates increased, 62.5 fiber could not keep pace due to its lower bandwidth at the 850 nm wavelength. In 1995 the new 100 Mb/s Fast Ethernet standard advocated the use of LEDs operating at 1300 nm wavelength which resulted in less attenuation. As a result, 50 um fiber was reintroduced, providing up to ten times the bandwidth of 62.5 um fiber. The newer 1 Gb/s and 10Gb/s transmitters used smaller spot-size lasers, which eliminated the issue relating to LED power coupling losses that was previously associated with 50um fiber.
Laser optimized 50μm fiber was introduced as a cost-effective solution for short-range applications that had to support 1Gb/s or multi-gigabit speeds. OM 3 fiber also offered significant cost savings in terms of electronics when upgrading networks to higher speeds. OM3 became the preferred multimode fiber for LANs, SANs, as well as data center interconnects and access applications.
This is 50μm fiber similar to OM 3 but operating a higher bandwidth. OM 4 is cost effective in that savings can be achieved by using 850 nm VCSELs with long building backbones and medium size campus backbones. Supports 10 Gb/s Ethernet, Fibre Channel, and OIF applications over distances up to 550 meters.