Single mode
Single mode fibre is designed for the transmission of a single ray or mode of light as a carrier over long-distance signal transmission.

Multimode
Multimode fibre carries multiple light rays or modes concurrently, each at a slightly different reflection angle within the fibre core. Multimode fibre has a larger core than single mode and is typically either 50µ (Micron) or 62.5µ (Micron) in diameter. Multimode fibre transmission is used for relatively short distances because the modes tend to disperse over longer lengths.
Loose Tube (L/T)
This is the protective tube surrounding one or more fibres and is usually found in cables used for outdoor installations.

Tight Buffered
A protective coating (usually 900 µm) that is used to "buffer" the primary coating of fibres. Provides strength, durability, easy handling and termination.

Internal/External (Int/Ext)
Fibre Cable that is suitable for both indoor and outdoor applications. The cable construction usually uses a gel filled loose tube containing the fibres.

Armoured
The inner jacket of the cable is overlaid with a protective armouring. Two main types are Steel Wire Armoured (SWA) and Corrugated Steel Tape armoured (CST or STA). The armouring gives the best resistance against rodent attack or mechanical damage and provides high tensile strength and crush resistance.