OS1 and OS2 are cabled optical fibre specifications.
The difference in performance between OS1 and OS2 is largely a matter of different cable construction rather than in optical fibre performance.

Cable Construction

  • 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 fibres).
  • Loose tube cable made from B1.3 Optical Fibre gives the best installed performance of 0.4db per km.

What’s does that Mean?

  • Category OS1 cable is designed for use in internal situations where the maximum distance is 2,000 metres. This cable type over the distance will allow speeds of 1 to 10 gigabit Ethernet.
  • Category OS2 cable is designed for use all uses where the maximum distance is upwards of 5,000 to 10,000 metres. This cable type over the distance will allow 1 to 10 gigabit Ethernet depending on the switch module you install.

Points to note:

  • Ensure that the cable you have installed is constructed from B1.3 Optical Fibre (also known as ITU specification G652c or G652d
  • The maximum attenuation allowed per km of installed cable is 1.0db for OS1 for 1310nm and 1550nm
  • The maximum attenuation allowed per km of installed cable is 0.4db for OS2 for 1310nm and 1550nm
  • Under 2kms there is no benefit to be gained in using OS2 cable. It is best for distance over 2kms
  • Joining OS1 SM fibre cable and OS2 SM fibre cable  by either splicing or patching does cause a slight interoperability

Summary
So the difference between OS1 & OS2 is therefore largely a matter of different cable construction rather than a technical leap in performance.

Written June 1st, 2013

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