Glossary of Fiber Optics Terms- Fiber Optics

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90° Boot: Indicates whether or not the part is available as a 90°, or right angle, connector.

900µm Fiber: Indicates whether or not the connector is available with a cable size of 900µm.

ANSI: American National Standards Institute.

APC: Angled Physical Contact.

ATM: Asynchronous Transfer Mode (ATM) A high-speed data transmission protocal. ATM uses 53-byte cells to divide data into packets for ultra fast switching through a high performance communications network.

Attenuation: The decrease in magnitude of power of a signal in transmission between points. A term used for expressing the total loses on a optical fiber consisting of the ration of light output to light input. Attenuation is usually measured in decibels per kilometer (dB/km) at a specific wavelength. The lower the number, the better the fiber. Typical multimode wavelengths are 850 and 1300 nanometers (nm); single mode, at 1300 and 1550 nm. When specifying attenuation, it is important to note if it is nominal or average, room temperature, value or maximum over operating range.

Attenuator: A device inserted into the electrical or optical path to lessen or weaken the signal.

Bandwidth: Measure of the information carrying capacity of an optical fiber, normalize to an unit of MHz-km. (This term is used to specify capacity of multimode fibers only. For singer mode fibers, use dispersion).

Bend Loss: A form of increased attenuation caused by either having the fiber curved around a restrictive radius of curvature, or microbends caused by minute distortions in the fiber imposed by externally induced perturbations. Excessive bend loss may result from poor drawing or cable manufacturing techniques.

Bend Radius: Radius a fiber can bend before the risk of breakage or increase in attenuatin.

Bidirectional: The movement of optical signals in opposite directions through a common fiber cable.

BER: Bit Error Rate. The probability of error per bit in a digital communications system.

Broadband: In general, covering a wide range of frequencies. The broadband label is sometimes used for a network that carries many different services or for video transmission.

Buffer: A protective material extruded directly on the fiber coating to protect it from the environment.

Cable Assembly: Fiber optic cable that has connectors installed on one or both ends. General use of these cable assemblies include the interconnection of multimode and single mode fiber optic cable assemblies. If connectors are attached to only one end of the cable, it is known as a pigtail. If connectors are attached to both ends, it is known as a jumper.

Central Office: A telephone company facility for switching signals among local telephone circuits; connects to subscriber telephones. Also called a switching office.

Cladding: A low refractive index that surrounds the core and provides optical insulation and protection of the core.

Connector: A mechanical device used to align and join two fibers together to provide a means for attaching and decoupling it to a transmitter, receiver or another fiber. Commonly used connectors include ST, STII, FC, SC, FDDI, ESCON, and SMA.

Core: The central region of an optical fiber through which light is transmitted.

Coupling: Transfer of light into or out of an optical fiber. (Note that coupling does not require a coupler.)

Coupler: A device that connects three or more fiber ends, dividing one input between two or more outputs or combining two or more inputs into one output.

Cross-Connect: A method of connecting copper or fiber transmission plant to achieve desired configurations using two interface points.

Decibel (dB): The standard unit used to express gain or loss of optical power.

Dispersion: The cause of bandwidth limitations in a fiber. Dispersion causes a broadening of input pulses along the length of the fiber. Two major types are a)mode dispersion caused by differential optical path lengths in a multimode fiber, and b)material dispersion caused by a differential delay of various wavelengths of light in a waveguide material.

Drop Cable: The coaxial cable that connects the feeder portion of the distribution system to the subscriber's premises.

Duplex: A duplex cable contains two fibers; a duplex connector links two pairs of fibers.

ESCON: Enterprise Systems Connection - developed for high speed communication between mainframes and storage devices, peripheral control units, cluster controllers and other networks. ESCON is a registered trademark of International Business Machines Corporation

Ferrule: A mechanical fixture, generally a rigid tube, used to confine and align the stripped end of a fiber.

Fiber Optics: Light transmission through optical fibers for communication or signaling.

Fiber Channel: A data transfer architecture designed for mass storage devices and other peripheral devices that require very high bandwidth

FITL: Fiber In The Loop.

FOTP: Fiber Optic Test Procedures.

Frequency: The number of cycles per unit of time, denoted by Hertz (Hz). Thus 1 Hz=1 cycle per second.

FTTC: Fiber To The Curb.

Fusing: The actual operation of joining fibers together by fusion or melting.

Gigabit-Per-Second (Gb/s): One billion bits per second.

Graded-Index Fiber: Fiber design in which the refractive index of the core is lower toward the outside of the fiber core and increases toward the center of the core; thus, it bends the rays inward and allows them to travel faster in the lower index of refraction region. This type of fiber provides high bandwidth capabilities.

Hole Size "D": Refers to the dimension labeled "D" on the Mechanical Dimensions drawing.

Light Emitting Diode (LED): A device used in a transmitter to convert information from electric to optical form. It typically has a large spectral width.

Local Area Network (LAN): A geographically limited communications network intended for the local transport of data, video, and voice.

Local Loop: The part of the telephone network extending from the central (switching) office to the subscriber.

Loose Tube: A protective tube loosely surrounding a cabled fiber, often filled with gel.

Mechanical Splicing: Joining two fibers together by mechanical means to enable a continuous signal.

Megabit-Per Second (Mb/s): One million bits per second.

Microbending: In an optical waveguide, sharp curvatures involving local axial displacements of a few micrometers and spatial wavelengths of a few millimeters. Such bends may result from waveguide coating, cabling, packaging, installation, etc.

Micron: (µm) Millionth of a meter.

Modulation: Coding of information onto the carrier frequency. This includes aplitude, frequency or phase and modulation techniques.

Multifiber Cable: An optical cable that contains two or more fibers, each of which provides a separate information channel.

Multimode: Transmits or emits multiple modes of light.

Multimode Fiber: An optical waveguide in which light travels in multiple modes. Typical core/cladding sizes (measured in microns) are 50/125, 62.5/125 and 100/140.

NOD: Non-Optical Disconnect, feature prevents ferrules from separating when force is applied to the cable.

Node: For networks, a branching or exchange point.

Numerical Aperture: The number that expresses the light gathering power of a fiber.

Pigtail: Fiber optic cable that has connectors installed on one end. See also cable assembly.

Plenum Cable: Cable made of fire-retardant material that meets electrical code requirements (UL910) for low smoke generation and installation in air spaces.

Positive Emitter Coupled Logic (PECL): A technology for building logic gates very similar in characteristics to ECL with the exception that the power supply voltage is positive with respect to the ground reference

Return Loss: The ratio of input power to reflect power, measured in decibel (dB).

Riser Cable: Used in applications for indoor cables that pass between floors. It is normally used in a vertical shaft or space.

Single Mode Fiber: An optical waveguide (or fiber) in which the signal travels in one "mode." The fiber has a small core diameter.

Splice: A mechanical or fusion joint connecting two fiber cables together.

Splice Closure: A container used to organize and protect splice trays.

Splitter: Another name for couple (see coupler).

Splitting Ratio: The ratio of power emerging from two output ports of a coupler.

STM-N: Nth level synchronous transport module frame structure in the Synchronous Digital Hierarchy (SDH)