Fibre Cable: OS1 vs OS2 differences explained

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Fibre Cable – Let me explain the difference OS1 vs OS2

Fibre Cable referred to as OS1 had its inception in 2002 and was written around the 2 glasses available at the time, being G652a and G652b.

In 2006, OS2 was born. It was written around the premise that the Low Water Peak Wavelengths around 1383 nanometers was required to have an attenuation of less than 0.4dB over 1 kilometre for use in CWDM.

This was achieved by the origination of G652c and G652d glasses.

These glasses also fell under the OS1 standard.


Fibre Optic Cabling


Fibre Cable – cable standards

Firstly, OS1 and OS2 are cabled standards not glass only standards.

What is meant by cabled standards is that OS1 uses Tight Buffered Cables (anything that has a 900-micron tight-buffered coating effectively)

This is Indoor Fibre Optic Cable, Indoor/Outdoor Fibre Optic Cable, Patch Cables and Pigtails.

OS2 is a Loose Tube Fibre Optic Cable standard which means it is loose inside a tube and is free to move.

Indoor/Outdoor cable is made of a tight-buffered construction.

A tight-buffered constructed cable cannot technically achieve the OS2 specification.


Why can we not achieve OS2 specification in a tight-buffered contstructed fibre cable?

It is due to the additional stresses placed on the glass during the cable manufacturing process. 

This makes it difficult to adhere to the low attenuation budgets of 0.4decibel per kilometre that OS2 requires.

The Loose Tube manufacturing process is “softer” on the glass. Thereby making it more reliable to adhere to the OS2 specification for distances greater than 5,000 meters.


L-Series Loose Tube Fibre Optic Cable

Fibre cable common thoughts.

There is a common thought that just because we have progressed from OM1 to OM3, OM4 and OM5 in the Multimode arena with each being more advanced than the one before it that the same should apply to the Singlemode equivalents.

However this is not the case, OS1 sits over the top of OS2 as it is a subset of the OS1 standard.

As patch leads use the same manufacturing process as Indoor/Outdoor Cable (it is a Tight buffered Cable Construction) they cannot be considered as an OS2 product, but are an OS1 product.



To be honest the confusion could be removed simply by the recommendation that the cable used must contain G652d glass.

Whether it is OS1 or OS2 is then purely semantics.