In a fiber optic cable, a buffer is one type of component used to encapsulate one or more optical fibers for the purpose of providing such functions as mechanical isolation, protection from physical damage and fiber identification.

Bare glass fibers are composed of core and cladding and both are based on silica or other glass materials.

The buffer may take the form of a miniature conduit, contained within the cable and called a "loose buffer(Loose Tube)", or "Tight Buffer”. A loose or tight buffer may contain more than one fiber, and sometimes contains a lubricating (thixotropic) gel. A "tight buffer" consists of a polymer coating in intimate contact with the primary coating applied to the fiber during production

Loose Tube: Loose tube fibers are designed for harsh environmental conditions in the outdoors. In loose tube cables, the coated fiber “floats” within a rugged, abrasion resistant, oversized tube which is filled with optical gel.

Tight Buffer: Tight buffered cables, in contrast, are optimized for indoor applications. In the tight buffer construction, instead of using the gel layer loose tube cable has, it uses a two-layer coating.

A strength Member is an added component to a jacketed Cable to help protect and strengthen the cable construction. Most of the time it is Aramid Yarn and Glass Yarn, but can also be a flexible, but stiff fiberglass rod that runs the length of the cable. That part of a Fiber Optic Cable composed of aramid yarn, steel strands, or fiberglass filaments that increase the Tensile Strength of the cable.

Structural and strength members can be solid or stranded steel wire, Aramid Yarn or fiber glass. They must have a high Young’s modulus, high strain capability, flexibility and low weight per unit length.

The fiber optic cable cab be surrounded by an outer jacket for reducing the abrasion and the first line of defense against the surrounding environment. This layer of the cable is usually made of plastic based products and called fiber cable jacket or fiber cable sheath. It resists water entry while remaining inert to gases and liquids that the cable may be exposed to during its service life

The fiber cable jacket contains the cable core and has various complexity from one simple extruded plastic jacket to a multilayer structure consisting of two or more jackets and with intermediate armoring.

Types

PE - Polyethylene (MDPE - medium density PE / HDPE - high density PE)

•Primary outside jacket material.
•Good resistance to UV (sun light) due to carbon black.
•Good flexibility over wide range of temperatures.
•Good abrasion and crack resistance.

PVC -Polyvinyl chloride

•Provides good mechanical protection.
•Flexible at normal installation temperatures.
•Flame retardant.(typical riser material)
•Used for many indoor applications.
•Can be protected against sunlight with various UV inhibitors.

LSZH - Low smoke, zero halogen

•Flame Retardant with low smoke and no halogenated materials
•For use in unventilated areas exposed to public, e.g., subways and tunnels.
•Good mechanical performance.

Fibre optic cables are usually installed in non-watertight piping and cable ducts. The fibres need to be effectively protected from humidity and water flooding in order to make sure the operational reliability of the fiber optic cables.

And the plastic sheath material tends to give very limited protection against the penetration of water into the cable.

General water barriers for regular cables are axially laid aluminum foil/polyethylene laminated film immediately inside the polyurethane or polyethylene plastic sheaths; and/or the use of moisture resistant compounds such as Swallable Glass Yarn around the fibers.