These are fiber optic cable designations that originated in the international ISO/IEC 11801 standard. The designations indicate a particular level of performance. OS levels are for singlemode fiber and OM levels are for multimode fiber. OM1 is for is for standard 62.5 micron multimode glass. OM2 is for standard 50 micron glass. OM3 is for enhanced 50 micron glass (capable of 10 gigabit Ethernet out to 300m). OM4 is a new designation, currently used by TIA, but not yet adopted by ISO, that identifies enhanced 50 micron glass capable of 10 gigabit Ethernet out to 550 meters. OS1 applies to standard singlemode glass while OS2 refers to a higher performing, low-water peak singlemode glass. There are additional differences between the designations as well.

optical specifications

Fiber Type Explanation

OS = Singlemode Fiber

  • Sends data over long distances
  • Used in telecom and large networks

OM = Multimode Fiber

  • Ideal for shorter distances
  • Often used in buildings and data centers
     

Type

What It Is

Max Speed Example

OM1

Older fiber, 62.5 micron core

Good for short distances, lower speeds

OM2

Standard 50 micron core

Better performance than OM1

OM3

Enhanced 50 micron core

Supports 10 Gb Ethernet up to 300m

OM4

Advanced OM3 (not ISO standard yet)

Supports 10 Gb Ethernet up to 550m

OS1

Basic singlemode fiber

Used for long-distance connections

OS2

High-quality singlemode fiber

Better signal quality for very long runs