Single-mode OS1 or OS2 fibre optic cable (9/125)

Single-mode OS1 or OS2 fibre optic cable has 9/125µm cores and is commonly utilized where low attenuation rates are required over long distances. Loose tube versions are ideal for external use and commonly available with SWA or CST mechanical protection. Tight buffered versions are designed for runs around multiple bends and not usually armoured. 

Single-mode fibres have much smaller core diameters than multi-mode so the light does not reflect as often, reducing losses to a minimum and guaranteeing an enormous range.

The difference between single-mode OS1 and OS2 cables is largely a matter of construction, please see our Fibre Optic Cable Selection Guide for more information.


Construction – Single-mode OS1 or OS2 fibre optic
9/125µm fibres with coloured coating 
fibres are either contained in a loose tube (LT) or tight buffered (TB)
optional steel wire armour (SWA) or corrugated steel tape armour (CST)
generally with low smoke zero halogen (LSZH) sheathing


Technical –  Single-mode OS1 or OS2 fibre optic
fibre diameter:  core 9µm (micrometres), cladding 125µm
number of fibres: 4, 6, 8, 12, 16 or 24 core versions commonly available
loose tube (LT): fibres are enclosed within protective tube(s), usually with a water resistant gel
tight buffered (TB): fibres have an additional tough waterproof layer over the normal coating


A printable PDF specification is available here: Single-mode OS1 or OS2 fibre optic cable (9/125).


For alternative fibre types return to the Fibre Optic Cables front page,
where our “Fibre Selection Guide” is also available.

Note: low smoke zero halogen / halogen free (LSZH, LSOH, LSHF, OHLS) should not be confused with LSF (low smoke and fume), an in-depth explanation is shown on our LSZH Control Flex front page.


All measurements should be considered nominal and images for illustration purposes only. Although Central Cables Ltd has made every reasonable effort to ensure its accuracy, the information contained herein is subject to error or omission and to change without notice. In no event will Central Cables Ltd be liable for any damages whatsoever, arising in connection with the information described.