Fiber optic cable can be divided into several types. Usually, we see single-mode and multimode fiber types available on the market. Multimode fibers are described by their core and cladding diameters. The diameter of the multi-mode fiber is either 50/125 µm or 62.5/125 µm. At present, there are four commonly used OM (multimode) fibers: OM1, OM2, OM3, and OM4. Each type of them has different characteristics.
The picture above shows the development of OM multimode fibers. The Lime Green OM5 fibers are newly released and sure to be the mainstream transmission media in the near future.
OM Multimode Fiber Standard
Each “OM” has a minimum Modal Bandwidth (MBW) requirement. OM1, OM2, and OM3 are determined by the ISO 11801 standard, which is based on the modal bandwidth of the multi-mode fiber. In August of 2009, TIA/EIA approved and released 492AAAD, which defines the performance criteria for OM4. While they developed the original “OM” designations, IEC has not yet released an approved equivalent standard that will eventually be documented as fiber type A1a.3 in IEC 60793-2-10.
According to the above table,
- OM1 cable typically comes with an orange jacket and has a core size of 62.5 micrometers (µm). It can support 10 Gigabit Ethernet at lengths up 33 meters. It is most commonly used for 100 Megabit Ethernet applications
- OM2 also has a suggested jacket color of orange. Its core size is 50µm instead of 62.5µm. It supports 10 Gigabit Ethernet at lengths up to 82 meters but is more commonly used for 1 Gigabit Ethernet applications.
- OM3 has a suggested jacket color of aqua. Like OM2, its core size is 50µm. OM3 supports 10 Gigabit Ethernet at lengths up to 300 meters. Besides OM3 is able to support 40 Gigabit and 100 Gigabit Ethernet up to 100 meters. 10 Gigabit Ethernet is its most common use.
- OM4 also has a suggested jacket color of aqua. It is a further improvement to OM3. It also uses a 50µm core but it supports 10 Gigabit Ethernet at lengths up 550 meters and it supports 100 Gigabit Ethernet at lengths up to 150 meters.
OM1 Vs. OM2 Vs. OM3 Vs. OM4 Fiber
There are several differences between the four kinds of multi-mode fiber, and we can see them clearly from the table below:
- Diameter: The core diameter of OM1 is 62.5 µm, however, the core diameter of the OM2, OM3, and OM4 is 50 µm.
- Jacket Color: OM1 and OM2 MMF are generally defined by an orange jacket. OM3 and OM4 are usually defined with an aqua jacket.
- Optical Source: OM1 and OM2 commonly use an LED light source. However, OM3 and OM4 usually use 850 nm VCSELs.
- Bandwidth: At 850 nm the minimal modal bandwidth of OM1 is 200MHz*km, of OM2, is 500MHz*km, of OM3, is 2000MHz*km, of OM4, is 4700MHz*km.
Why Are OM3 & OM4 Fiber Superior to OM1 & OM2?
OM4 fiber is optimized for laser (eg. VCSEL) based equipment that uses fewer modes of light. LEDs cannot be turned on/off fast enough to support higher bandwidth applications, while VCSELs are capable of modulation over 10 Gbit/s and are used in many high-speed networks. For this reason, OM3 and OM4 are the multimode fibers included in the 40G and 100G Ethernet standard. Now OM1 and OM2 are usually used for 1G which are not suitable for today’s higher-speed networks. OM3 and OM4 are used for 10G mostly at present. But in the future, since OM3 and OM4 can support the 40G and 100G, which may make them the tendency.
Overview of Commonly Used Multimode Fibers