Feb. 11, 2026 ■ What are OM and OS type fiber optic cables?
Fiber optic cables used in telecommunication are broadly categorized into two types – Multimode fiber and Single-mode fiber cables. The multimode fiber cable is prefixed with 'OM' and the Single-mode fiber cable is prefixed with 'OS'.
In ISO/IEC 11801 and EIA/TIA standards five types of Multimode – OM1, OM2, OM3, OM4 & OM5 and two types of Single-mode – OS1 & OS2 fibers are mentioned. In all the standards the OM/OS system applies to cabled optical fiber, and the cabling standards deal with cable and connecting hardware.
ISO/IEC 11801 and 24702 make it clear that the nomenclatures OM1, OM2, OM3, OS1, and OS2 relate to cable transmission performance whereas the BS EN 50173 series makes it even clearer by describing the OM/OS nomenclature as "optical fiber cable categories".
· OM (Optical Multimode): Used for short-distance transmission, larger core (50µm or 62.5µm), supports multiple light paths.
· OS (Optical Singlemode): Used for long-distance transmission, smaller core (~9µm), single light path for higher bandwidth.
| Category | Fiber Type | Core Diameter | Use Case | Light Source | Wavelengths |
| OM | Multimode | 50µm / 62.5µm | Short-distance (<550m) | LED or VCSEL | 850 / 1300 nm |
| OS | Singlemode | ~9µm | Long-distance (km level) | Laser / Laser Diode | 1310 / 1550 nm |
Multimode fiber is a common choice to achieve 10 Gbit/s speed over distances required by LAN enterprise and data center applications. There are several kinds of multimode fiber types available for high-speed network installations, and each with a different reach and data-rate capability. With so many options, it can be tough to select the most suitable multimode fiber. OM1 vs OM2 vs OM3 vs OM4 vs OM5, which to choose? You may get answer in this article.
What Is Multimode Fiber?
Multimode fiber (MMF) is a kind of optical fiber mostly used in communication over short distances, for example, inside a building or for the campus. Multimode fiber optic cable has a larger core, typically 50 or 62.5 microns that enables multiple light modes to be propagated. Because of this, more data can pass through the multimode fiber core at a given time. The maximum transmission distance for MMF cable is around 550m at the speed of 10Git/s. It can transmit farther at lower data rates, such as going about 2km at 100Mb/s.
How Many Types of Multimode Fiber?
Identified by ISO 11801 standard, multimode fiber optic cables can be classified into OM1 fiber, OM2 fiber, OM3 fiber, OM4 fiber and newly released OM5 fiber. The next part will compare these fibers from the side of core size, bandwidth, data rate, distance, color and optical source in details.
Physical Difference
Physical difference mainly lies in diameter, jacket color, optical source and bandwidth, which is described in the following table.
| MMF Cable Type | Diameter | Jacket Color | Optical Source | Bandwidth |
| OM1 | 62.5/125µm | Orange | LED | 200MHz*km |
| OM2 | 50/125µm | Orange | LED | 500MHz*km |
| OM3 | 50/125µm | Aqua | VSCEL | 2000MHz*km |
| OM4 | 50/125µm | Aqua | VSCEL | 4700MHz*km |
| OM5 | 50/125µm | Lime Green | VSCEL | 28000MHz*km |
Practical Difference
Multimode fibers are able to transmit different distance ranges at various data rate. You can choose the most suited one according to your actual application. The max multimode fiber distance comparison at different data rate is specified below.
| MMF Category | 1GbE | 10GbE | 40GbE | 100GbE |
| OM1 | 275m | 33m | / | / |
| OM2 | 550m | 82m | / | / |
| OM3 | / | 300m | 100m | 70m |
| OM4 | / | 550m | 150m | 150m |
| OM5 | / | 550m | 150m | 150m |
Conclusion
Due to its high capacity and reliability, multimode fiber is usually used for backbone applications in buildings. In general, mmf cable continues to be the most cost-effective choice for enterprise and data center applications up to the 500-600 meter range. But it's not to say that we can substitute single mode fiber with multimode fiber cable, as for whether to choose a single mode fiber patch cord or multimode patch cord, it all depends on applications that you need, transmission distance to be covered as well as the overall budget allowed.
