OS1 and OS2 Singlemode fiber - What's going on?

 There's a huge confusion in the Optical industry, and we are here to explain what's going on. We get several questions from our customers about what are the differences between OS1 and OS2. 

To solve this question. We asked the FIA (Fibreoptic Industry Association), and the reply explains very easily what is the current confusion with distributors, customers, consultants and fiber optics installers.

This article explains clarifies the subtle differences between the European specifications of single-mode fibers (OS1/OS2) and their international counterparts in ISO/IEC - and highlights the more fundamental differences between the international and European requirements and those of the US standards, specifically TIA568-C.3 published in 2008.

According to the FIA, the first singlemode fiber for use within extended length LAN, MAN and access network systems were designated with the category B1 in IEC (and EN) 60793-2-50.

In the ISO/IEC 11801 and EN 50173-1, B1 optical fiber was used as the pillar for what is now the called OS1 Fiber. The scope of ISO/IEC 11801 and EN 50173-1:2002 was

1. Office premises with dimensions not exceeding 2000 metres
2. Fiber attenuation Benchmark of 1,0 dB/km (max) at 1310 nm and 1550 nm

The thing is that during the development of a new ISO/IEC 24702, published in 2006 and covering cabling for industrial premises, it was required that premises of larger dimensions had to be considered.

As the singlemode implementations of 1 Gigabit Ethernet (1000BASE-LX) and 10 Gigabit Ethernet (10GBASE-LR/LW) are specified to support transmission channels of 5000 metres and 10000 metres respectively, it was decided to consider these applications and dimensions as benchmarks.

It was obvious that a cable with attenuation of 1,0 dB/km (max) at 1310 nm would not support these applications over their maximum specified distances. So, it was decided to define a new Category of optical fiber, at that time OS2 was born.

So, the difference in performance between OS1 and OS2 is more like a different cable construction rather than an upgrade in optical fiber performance. (Like in the multimode cables OM1 is a better interaction of OM2...)

If you want to check and download the whole whitepaper you could check it out below:

So, in conclusion:

• OS1 and OS2 are cabled optical fibre specifications
• Category OS1 is appropriate to internal tight buffered cable construction.
• Category OS2 is appropriate to a loose tube or blown fibre solution (where the cabling process applies no stress to the optical fibers)
• Make sure that any performance specifications that are quoted are for the cables and not just the optical fibres contained within them.
• Demand that the cables you purchase have either OS1 or OS2 performance but are constructed from B1.3 optical fibre (also known as ITU specification.
• Beyondtech Offers OS1 and OS2 Patch cables and fiber optics for your custom needs. Let us know your requirement and we can help you out.

Thanks a lot for Jane Morrison at the FIA for the cooperation and the willing to spread the word in our Blog.

And the authors of the original Whitepaper: Mike Gilmore, who is the Technical director of the FIA.