Glossary of Terms for Fiber Optics

Adapter – A mechanical termination device designed to align and join fiber optic connections.

Attenuation - A term indicating a decrease in power from one point to another. In optical fibers, it is measured in decibels per kilometer at a specified wavelength.

Backbone Cabling – The portion of the cabling that provides connections between communication closets, equipment rooms and entrance facilities.

Bundle – Many individual fibers contained within a single jacket or buffered tubes.

Cable – Designed to provide mechanical and environmental protection to the fibers.

CATV – Cable television systems.

Connector - A mechanical device used to provide a means for aligning, attaching and achieving continuity between fibers.

Core – The center of the fiber optic cable through which light is transmitted.

dB (Decibel) - In fiber optics, a logarithmic unit for the ratio of the power that was received over the power that was originally sent. (dB = 10 log, so 10 dB is 10 times more power than 0 dB, 20dB is 100 times more power than 0dB, etc.)

dBm - Optical power referenced to 1 milliwatt. (0dBm = 1 milliwatt, 10dBm = 10 milliwatts, 20dBm = 100 miliwatts, etc.)

dBµ - Decibel referenced to 1 microwatt.

Detector - An electronic transducer used in fiber optics for converting optical power to electric current. In fiber optics, usually a photodiode.

Entrance Facility – Entrance facilities are the pathways where outside services, such as telephone and cable TV enter the building.

Equipment Room - A centralized space for telecommunications equipment that serves the occupants of the building.

Frequency - The number of cycles per second of a periodic waveform, usually expressed in Hertz.

Horizontal Cross-Connect - A cross-connect of horizontal cabling to other cabling, e.g., horizontal to backbone cabling.

IC (Intermediate Cross-Connect) - A cross-connect between the main cross-connect and the horizontal cross- connect in backbone cabling.

Interconnection - A connection scheme that provides for the direct connection of a cable to another cable or to an equipment cable without a patch cord or jumper.

Insertion Loss - The loss of power that results from inserting a component, such as a connector or splice, into a previously continuous path.

Laser - A light source that is almost perfectly coherent and monochromatic. Lasers in fiber optics are used with single mode fiber cable for long distance applications, such as cable TV and telephone. The Fiber OWL Model EO610 is designed to directly measure the high output power of a laser transmitter.

LCD - Acronym for Liquid Crystal Display. Liquid crystals form patterns when polarized. The orientation of the molecules in the liquid are arranged by the meter to form the display.

LED (Light-Emitting Diode) - A semiconductor device that emits light when current is applied. LEDs are commonly used with multimode fiber cables for LAN and premise cabling. Generally, they are not as powerful as a Laser, but are less costly.

Main Cross-Connect - The cross-connect in the main equipment room for connecting entrance cables, backbone cables, and equipment cables.

Mode - A possible path followed by light rays.

Multimode Fiber - A type of optical fiber that supports more than one propagating mode. Multimode fiber cables are typically used up to 2000 meters in LAN and premise cabling. The fibers core diameters are normally 62.5m m and 50m m.

OTDR (Optical Time Domain Reflectometer) - A meter that evaluates optical fibers based on detecting reflected light. It’s used to measure fiber attenuation, evaluate splice and connector joints, and locate faults.

Patch Panel – A collection of connector panels located in a common housing.

Photo detector - An optoelectronic transducer, such as a PIN photodiode or avalanche photodiode.

Photodiode - A semiconductor diode that produces current in response to incident optical power and used as a detector in fiber optics.

Receiver – A device that converts optical signals to an electrical signals.

Single Mode Fiber - An optical fiber that supports only one propagation mode. It has much less loss than multimode fiber and is used by telephone and cable TV companies for long distance applications. The core diameter is typically 9m m.

Source - The light emitter, either an LED or laser diode, in a fiber optic link.

Spectral Width - For a light source, the width of wavelengths contained in the output at one half of the wavelength of peak power. Typical spectral widths are 20 to 60 nm for an LED and 2 to 5 nm for a laser diode.

Splice - An interconnection method for joining the ends of two optical fibers in a permanent or semi-permanent fashion.

TC (Telecommunications Closet) - An enclosed space for housing telecommunications equipment, cable terminations, and cross-connects. The closet is the recognized cross-connect between the backbone cable and horizontal cabling.

TIA – Telecommunication Industry Association. TIA/EIA-568-A is equivalent to ISO/IEC 11801 in Europe.

Transmitter - An electronic device, which converts an electrical signal to an optical signal.

WA (Work Area) - A building space where the occupants interact with telecommunications terminal equipment such as PCs, telephones, and other office equipment.

Wavelength - The distance between the same two points on adjacent waves; the length required for a wave to complete a single cycle.

Interconnection - A connection scheme that provides for the direct connection of a cable to another cable or to an equipment cable without a patch cord or jumper.

Insertion Loss - The loss of power that results from inserting a component, such as a connector or splice, into a previously continuous path.

LCD - Acronym for Liquid Crystal Display commonly used in portable test meters.

Main Cross-Connect - The cross-connect in the main equipment room for connecting entrance cables, backbone cables, and equipment cables.

Mode - A possible path followed by light rays.

OTDR (Optical Time Domain Reflectometer) - A meter that evaluates optical fibers based on detecting reflected light. It is used to measure fiber attenuation, evaluate splice and connector joints, and locate faults.

Patch Panel - A collection of connector panels located in a common housing.