Q: What does OS1, OS2, OM1, OM2, OM3 and OM4 mean?
A: 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.