Glossary of Optical Terms

This glossary comes from the METBU for optical switching documentation team. We document the Cisco Metro 1500 series, MAN DWDM and Manhattan platforms. Visit our Web page at http://wwwin.cisco.com/Mkt/Doc/WAN/metro/index.htm.

Last modified on: 8/18/00
Table 1:: Glossary of Optical Terms

Term Definition

add drop

multiplexer (ADM)

Digital multiplexing equipment that provides interfaces between different signals in a network.

amplified spontaneous emissions (ASE)

Noise that is added to an optical signal when it is amplified. This noise (or ASE) accumulates and builds in optical spans that have multiple optical amplifiers between regenerators.

dark fiber

Unused fiber optic cable. When it is carrying a signal, it is called lit fiber.

data communications network (DCN)

An out-of-band network that provides connectivity between network elements and their respective operations support systems (OSS). Its primary function is enabling surveillance and status of a telco/PTT network, but it also facilitates network operations and management such as provisioning, billing, planning, and service assurance.

dispersion-shifted fiber (DSF)

A type of single-mode fiber designed to have zero dispersion near 1550 nm.

dispersion compensating fiber (DCF)

A fiber that has the opposite dispersion of the fiber being used in a transmission system. It is used to nullify the dispersion caused by that fiber.

dense wavelength

division multiplexing (DWDM)

Optical transmission of multiple signals over closely spaced wavelengths in the 1550 nm region. (Wavelength spacings are usually 100 GHz or 200 GHz, which corresponds to 0.8 nm or 1.6 nm.)

erbium-doped fiber amplifier (EDFA)

Optical fibers doped with the rare earth element erbium, which can amplify light in the 1550 nm region when pumped by an external light source.

fiber connectivity (FICON)

FICON channels provide 100-MBps bi-directional link rates at unrepeated distances of up to 20 km over fiber optic cables (compared with ESCON channels that support 17-MBps link rates at maximum unrepeated distances of up to 3 km.)

fiber optics

A method for the transmission of information (audio, video, data). Light is modulated and transmitted over high purity, hair-thin fibers of glass. The bandwidth capacity of fiber optic cable is much greater than that of conventional cable or copper wire.

fiber plant

Arial or buried fiber optic cable that established connectivity between fiber optic transmission equipment locations.

intermediate reach (IR)

The distance specification for optical systems that operate effectively from 3 to 20 km (1.8 to 12.5 mi).

local exchange carrier (LEC)

A telephone company that provides customer access to the world-wide public switched network through one of its central offices.

low optical power (LOP)

long reach (LR)

The distance specification for optical systems that operate effectively from 20 to 100 km (12.5 to 62 mi).

multimode fiber (MM fiber)

A fiber-optic medium in which light travels in multiple modes.

multiplexer (MUX)

Equipment that enables several data streams to be sent over a single physical line. It is also a function by which one connection from an (ISO) layer is used to support more than one connection to the next higher layer. A device for combining several channels to be carried by one line or fiber.

non zero-dispersion-shifted fiber (NZ-DSF)

A dispersion shifted SM fiber that has the zero dispersion point near the 1550 nm window, but outside the window actually used to transmit signals.

optical add drop multiplexer (OADM)

Optical multiplexing equipment that provides interfaces between different signals in a network.

optical fiber amplifier (OFA)

A device that amplifies an optical signal directly, without the need to convert it to an electrical signal, amplify it electrically, and reconvert is to an optical signal.

polarization mode dispersion (PMD)

An inherent property of all optical media, caused by the difference in the propagation velocities of light in the orthogonal principal polarization states of the transmission medium.

short reach (SR)

The distance specification for optical systems that operate effectively up to 3 km (1.8 mi).

single-mode fiber (SM fiber)

Fiber with a relatively low diameter through which only one mode will propagate.

storage area networking (SAN)

An emerging data communications platform that interconnects servers and storage at Gigabaud speeds. By combining LAN networking models with the core building blocks of server performance and mass storage capacity, SAN eliminates the bandwidth bottlenecks and scalability limitations imposed by previous SCSI bus-based architectures

wavelength

The length of one complete wave of an alternating or vibrating phenomenon, generally measured from crest to crest or from trough to trough of successive waves.

wavelength division multiplexing (WDM)

Two or more colors of light on one fiber.

Term	Definition
add drop multiplexer (ADM)	Digital multiplexing equipment that provides interfaces between different signals in a network.
amplified spontaneous emissions (ASE)	Noise that is added to an optical signal when it is amplified. This noise (or ASE) accumulates and builds in optical spans that have multiple optical amplifiers between regenerators.
dark fiber	Unused fiber optic cable. When it is carrying a signal, it is called lit fiber.
data communications network (DCN)	An out-of-band network that provides connectivity between network elements and their respective operations support systems (OSS). Its primary function is enabling surveillance and status of a telco/PTT network, but it also facilitates network operations and management such as provisioning, billing, planning, and service assurance.
dispersion-shifted fiber (DSF)	A type of single-mode fiber designed to have zero dispersion near 1550 nm.
dispersion compensating fiber (DCF)	A fiber that has the opposite dispersion of the fiber being used in a transmission system. It is used to nullify the dispersion caused by that fiber.
dense wavelength division multiplexing (DWDM)	Optical transmission of multiple signals over closely spaced wavelengths in the 1550 nm region. (Wavelength spacings are usually 100 GHz or 200 GHz, which corresponds to 0.8 nm or 1.6 nm.)
erbium-doped fiber amplifier (EDFA)	Optical fibers doped with the rare earth element erbium, which can amplify light in the 1550 nm region when pumped by an external light source.
fiber connectivity (FICON)	FICON channels provide 100-MBps bi-directional link rates at unrepeated distances of up to 20 km over fiber optic cables (compared with ESCON channels that support 17-MBps link rates at maximum unrepeated distances of up to 3 km.)
fiber optics	A method for the transmission of information (audio, video, data). Light is modulated and transmitted over high purity, hair-thin fibers of glass. The bandwidth capacity of fiber optic cable is much greater than that of conventional cable or copper wire.
fiber plant	Arial or buried fiber optic cable that established connectivity between fiber optic transmission equipment locations.
intermediate reach (IR)	The distance specification for optical systems that operate effectively from 3 to 20 km (1.8 to 12.5 mi).
local exchange carrier (LEC)	A telephone company that provides customer access to the world-wide public switched network through one of its central offices.
low optical power (LOP)
long reach (LR)	The distance specification for optical systems that operate effectively from 20 to 100 km (12.5 to 62 mi).
multimode fiber (MM fiber)	A fiber-optic medium in which light travels in multiple modes.
multiplexer (MUX)	Equipment that enables several data streams to be sent over a single physical line. It is also a function by which one connection from an (ISO) layer is used to support more than one connection to the next higher layer. A device for combining several channels to be carried by one line or fiber.
non zero-dispersion-shifted fiber (NZ-DSF)	A dispersion shifted SM fiber that has the zero dispersion point near the 1550 nm window, but outside the window actually used to transmit signals.
optical add drop multiplexer (OADM)	Optical multiplexing equipment that provides interfaces between different signals in a network.
optical fiber amplifier (OFA)	A device that amplifies an optical signal directly, without the need to convert it to an electrical signal, amplify it electrically, and reconvert is to an optical signal.
polarization mode dispersion (PMD)	An inherent property of all optical media, caused by the difference in the propagation velocities of light in the orthogonal principal polarization states of the transmission medium.
short reach (SR)	The distance specification for optical systems that operate effectively up to 3 km (1.8 mi).
single-mode fiber (SM fiber)	Fiber with a relatively low diameter through which only one mode will propagate.
storage area networking (SAN)	An emerging data communications platform that interconnects servers and storage at Gigabaud speeds. By combining LAN networking models with the core building blocks of server performance and mass storage capacity, SAN eliminates the bandwidth bottlenecks and scalability limitations imposed by previous SCSI bus-based architectures
wavelength	The length of one complete wave of an alternating or vibrating phenomenon, generally measured from crest to crest or from trough to trough of successive waves.
wavelength division multiplexing (WDM)	Two or more colors of light on one fiber.

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