Differences between OS1 and OS2 fiber

Single mode and Multimode are the two types of optical fiber that exist, but they are classified in several categories. Multimode fiber can be OM1, OM2, OM3 and OM4 and Single mode is categorized as OS1 and OS2 by the ITU-T G.652A/B/C/D and ITU-T G.652C/D standards, respectively.

And what the differences between the two Single mode fiber categories?

Both Single mode fibers are suitable for Gigabit applications and have the same jacket color, which can turn a little confusing, but actually there are obvious differences between them.


Is an old fiber specification that was introduced back in 2002, which mechanical, environmental and optical features comply with ITU-T G.652A or ITU-T G.652B standards. It is a tight buffered cable, suitable for indoor applications, such as data centers or enterprises campuses.

It has an attenuation of 1 dB per kilometer and a top transmission distance of 2 km at 10 Gigabit Ethernet. It works between 1310 nm and 1550 nm.



It was introduced back in 2006 under the ITU-T G.652C and ITU-T G.652D specifications. It is manufactured with a chemical process that reduces the presence of hydroxyl ions in order to decrease loss at the water peak region.

 It is a loose tube fiber recommended to be used in outdoor applications, even in underground conditions. OS2 fiber has an attenuation of 0.4 dB between 1310 nm and 1550 nm, with a top transmission distance of 10 km at 10 Gigabit Ethernet.

So, it doesn’t have to do with which fiber is better, but what are you using them for. It you are working in an outdoor deployment, you’ll need OS2 fiber. If it is indoor, the right chose is OS1 fiber, but you should also consider this kind of fiber if working in an outdoor project that doesn’t require more than 2 km of fiber.

OS1 and OS2 fiber cables can be mated or spliced together without performance being affected. What you need to make sure when mating these cable's categories is, if working with WDM, both of them have the same low water peak fiber in them. 

FIA's OS1 and OS2 are cabled optical fiber specifications:

  • Category OS1 is appropriate to internal tight buffered cable construction.
  • Category OS2 is appropriate to a loose tube or blown fiber solution (where the cabling process applies no stress to the optical fiber).
  • Make sure that any performance specifications that are quoted are for the cables and not just the optical fiber contained within them.
  • Demand that the cables you purchase have either OS1 or OS2 performance but are constructed from B1.3 optical fiber (also known as ITU specification G.652c or G.652d).


We received a contribution from Michael Parry-Jones in this article from a great discussion on LinkedIn. We thank him! 

March 17, 2016 by
Older Post / Newer Post