Fibre optical jargon

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Optical Fibre: Thin strands of highly transparent glass or sometimes plastic that guide light.

Core: The center of the fibre where the light is transmitted.

Cladding: The outside optical layer of the fibre that traps the light in the core and guides it along - even through curves.

Buffer coating or primary coating: A hard plastic coating on the outside of the fibre that protects the glass from moisture or physical damage.

Mode: A single electromagnetic field pattern (think of a ray of light) that travels in fibre.

Multi-mode fibre: has a bigger core (almost always 62.5 microns - a micron is one millionth of a meter - but sometimes 50 microns) and is used with LED sources at wavelengths of 850 and 1300 nm for short distance, lower speed networks like LANs.

Single-mode fibre: has a much smaller core, only about 9 microns, and is used for telephony and CATV with laser sources at 1300 and 1550 nm. It can go very long distances at very high speeds.

Both multi-mode and single-mode fibres have an outside diameter of 125 microns - about 5 thousandths of an inch - just slightly larger than a human hair.

terms that describe fibre optic cable

Cable: Fibre needs protection to survive all the places it gets installed and it is the cable that provides it. Cables may have from one to hundreds of fibres inside.

Jacket: The tough outer covering on the cable. Cables installed inside buildings must meet fire codes by using special jacketing materials.

Strength members: Aramid fibres (Kevlar is the duPont trade name) used to pull the cable. The term is also used for the fibreglass rod in some cables used to reinforce it and prevent kinking.

Armor: Discourages rodents from chewing through it.

termination

Connector: A non-permanent device for connecting two fibres or fibres to equipment where they are expected to be occasionally disconnected for testing or rerouting. It also provides protection of both fibres. (Parts for an ST connector are shown)

Ferrule: A tube which holds a fibre for alignment, usually part of a connector.

Splice: a permanent joint between two fibres.

Mechanical Splice: A splice where the fibres are aligned created by mechanical means.

Fusion Splice: A splice created by welding or fusing two fibres together.

Fusion Splicer: An instrument that splices fibres by fusing or welding them, typically by electrical arc.

Hardware: Terminations and splices require hardware for protection and management: patch panels, splice closures, etc.

terms you use for measurements

Attenuation: The reduction in optical power as it passes along a fibre, usually expressed in decibels (dB). See optical loss.

Bandwidth: The range of signal frequencies or bit rate within which a fibre optic component, link or network will operate.

Decibels (dB): A unit of measurement of optical power which indicates relative power. A -10 dB means a reduction in power by 10 times, -20 dB means another 10 times or 10 times overall, -30 means another 10 times or 1000 times overall and so on.

dB: Optical power referenced an arbitrary zero level.

dBm: Optical power referenced to 1 milliwatt.

Micron (m): A unit of measure used to measure wavelength of light.

Nanometer (nm): A unit of measure used to measure the wavelength of light (meaning one one-billionth of a meter).

Optical Loss: The amount of optical power lost as light is transmitted through fibre, splices, couplers, etc, expressed in dB.

Optical Power: is measured in "dBm", or decibels referenced to one miliwatt of power. While loss is a relative reading, optical power is an absolute measurement, referenced to standards. You measure absolute power to test transmitters or receivers and relative power to test loss.

Scattering: The change of direction of light after striking small particles that causes loss in optical fibres and is used to make measurements by an OTDR.

Wavelength: A term for the colour of light, usually expressed in nanometers (nm) or microns (m). Fibre is mostly used in the infrared region where the light is invisible to the human eye.

terms that describe the tools you will need for installation and termination

Jacket Slitter or Stripper: A cutter for removing the heavy outside jacket of cables.

Fibre Stripper: A precise stripper used to remove the buffer coating of the fibre itself for termination. There are three types in common use, called by their trade names: "Miller Stripper", "No-Nik" and "Micro Strip."

Cleaver: A tool that "breaks" the fibre precisely to produce a flat end for polishing or splicing.

Crimper: A tool that crimps the connector to the aramid fibres in the cable to add mechanical strength.

terms that describe testing equipment you will need

Optical Power Meter: An instrument that measures optical power from the end of a fibre.

Test Source: an instrument that uses a laser or LED to send an optical signal into fibre for testing loss of the fibre.

Optical Loss Test Set (OLTS): A measurement instrument for optical loss that includes both a meter and source.

Reference Test Cables: short, single fibre cables with connectors on both ends, used to test unknown cables.

Mating Adapter: also called splice bushing or couplers, allows two cables with connectors to mate.

Fibre Tracer: An instrument that allows visual checking of continuity and tracing for correct connections.

Visual Fault Locator: A device that allows visual tracing and testing of continuity.

Microscope: used to inspect the end surface of a connector for flaws or dirt.