Fibre optic cable selection guide

This fibre optic cable selection guide explains the differences between the different types and the commonly available construction options. Optical fibres are described by the diameter of both core and cladding, for example multi-mode 62.5/125µm = core diameter of 62.5 micrometres (µm) & cladding diameter of 125µm.

Fibre optic cables are made from a transparent core that carries light, surrounded by glass cladding that (due to its lower refractive index) reflects “escaping” light back into the core, resulting in the light being guided along the fibre. The optical fibre elements are typically individually coated with plastic layers, usually colour coded for identification. 4, 8, 12, 16 or 24 core versions available as standard. Advantages over copper cables include: no electromagnetic interference, lower weight and higher data transmission rates over longer distances.


Single-mode or Multimode
Single-mode fibres have much smaller core diameters than multi-mode fibres so the light does not reflect as often, reducing losses to a minimum and guaranteeing an enormous range.  They are often utilized where low attenuation rates are required over long distances. In multi-mode fibres the light is reflected in a zigzag pattern down the larger core, resulting in higher attenuation rates (losses) than single-mode. Generally used for backbone applications due to the high capacity and reliability. 50/125µm has lower attenuation than 62/125 µm.
single mode fibre light reflection multi mode fibre light reflection


Single-mode OS1 or OS2
The difference between these cables is largely a matter of construction:
OS1 single-mode (9/125µm) commonly used in tight buffered cables for runs up to 2km
OS2 single-mode (9/125µm) commonly used in loose tube cables for runs up to 5/10km


Multi-mode OM1, OM2, OM3 or OM4
The difference between these cables is the optical fibre performance:
OM1 multi-mode (62.5/125µm) can support 10 Gigabit Ethernet at lengths up to 33m
OM2 multi-mode (50/125µm) can support 10 Gigabit Ethernet at lengths up to 82m
OM3 multi-mode (50/125µm) can support 10 Gigabit Ethernet at lengths up to 300m
OM3 multi-mode (50/125µm) can support 10 Gigabit Ethernet at lengths up to 550m


Loose Tube or Tight Buffered
In loose tube (LT) construction the fibres are enclosed within protective tube/s, usually containing a water resistant gel. Ideal for external use and commonly available with SWA (steel wire armour) or CST (corrugated steel tape) protection. In tight buffered (TB) cables the fibres have an additional tough waterproof layer (usually 900µm) over the normal fibre coating. Ideal for internal use, especially for runs around multiple bends. They are not usually armoured.


A printable PDF version is available here: Fibre optic cable selection guide.


To view individual fibre types return to the Fibre Optic Cables front page.

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.