English
Active Device
A device that requires a source of energy for its operation and has an output that is a function of present and past input signals. Examples include controlled power supplies, transistors, LEDs, amplifiers, and transmitters.
Add/Drop Multiplexing
a multiplexing function offered in connection with SONET that allows lower level signals to be added or dropped from a high-speed optical carrier in a wire center. The connection to the add/drop multiplexer is via a channel to a central office port at a specific digital speed (DS3, DS1, etc.)
Amplifier
A device, inserted within a transmission path, that boosts the strength of an electronic or optical signal. Amplifiers may be placed just after the transmitter (power booster), at a distance between the transmitter and the receiver (in-line amplifier), or just before the receiver (preamplifier).
Attenuation
The decrease in signal strength along a fiber optic waveguide caused by absorption and scattering. Attenuation is usually expressed in dB/km.
Avalanche Photodiode (APD)
A photodiode that exhibits internal amplification of photocurrent through avalanche multiplication of carriers in the junction region.
AWG (Arrayed Waveguide Grating)
A device, built with silicon planar lightwave circuits (PLC), that allows multiple wavelengths to be combined and separated in a dense wavelength-division multiplexing (DWDM) system.
Axis
The center of an optical fiber.
Bandwidth
The range of frequencies within which a fiber optic waveguide or terminal device can transmit data or information.
BIDI
Abbreviation for bidirectional transceiver, a device that sends information in one direction and receives information from the opposite direction.
Bidirectional
Operating in both directions. Bidirectional couplers operate the same way regardless of the direction light passes through them. Bidirectional transmission sends signals in both directions, sometimes through the same fiber.
Broadband
A method of communication where the signal is transmitted by being impressed on a high-frequency carrier.
Bypass
The ability of a station to isolate itself optically from a network while maintaining the continuity of the cable plant.
C-Band
The wavelength range between 1530 nm and 1562 nm used in some CWDM and DWDM applications.
Cable
One or more optical fibers enclosed, with strength members, in a protective covering.
CATV
Originally an abbreviation for community antenna television; the term now typically refers to cable television.
Center Wavelength
In a laser, the nominal value central operating wavelength. It is the wavelength defined by a peak mode measurement where the effective optical power resides (see illustration). In an LED, the average of the two wavelengths measured at the half amplitude points of the power spectrum.
Channel
A communications path or the signal sent over that path. Through multiplexing several channels, voice channels can be transmitted over an optical channel.
Circulator
Passive three-port devices that couple light from Port 1 to 2 and Port 2 to 3 and have high isolation in other directions.
CWDM(Coarse Wavelength Division Multiplexing)
A method of transmitting several connections parallel over one fiber optic line.
Transmission works over different wavelengths (colors) on the same fiber, which do not influence each other.
As opposed to [DWDM], a relatively wide channel spacing is used, which leads to a more cost-saving technology, because temperature stabilized components are not needed. CWDM has been specified for use on distances up to 50 km.
The CWDM wavelength plan of the ITU-T Recommendation G.694.2 defines 18 wavelengths with a grid of 20 nm. But two of these are located in the area of the [Water Peak] and therefore are being omitted.
Because of this, CWDM provides 16 usable parallel data channels.
Connector
A mechanical or optical device that provides a demountable connection between two fibers or a fiber and a source or detector.
Converter
Device that is attached between the television set and the cable system that can increase the number of channels available on the TV set, enabling it to accommodate the multiplicity of channels offered by cable TV. Converter boxes are becoming obsolete as old model televisions requiring a converter are replaced by modern televisions, which incorporate a converter into the television directly. Also called a set-top box.
Coupler
An optical device that combines or splits power from optical fibers.
Coupling Ratio/Loss (CR, CL)
The ratio/loss of optical power from one output port to the total output power, expressed as a percent. For a 1 x 2 WDM or coupler with output powers O1 and O2, and Oi representing both output powers:
CR(%) = (Oi/(O1 + O2)) x 100% and CR(%) = -10·Log10 (Oi/(O1 + O2)).
dBm
Abbreviation for decibel relative to milliwatt.dBμ: Abbreviation for decibel relative to microwatt.
Demultiplexer
A module that separates two or more signals previously combined by compatible multiplexing equipment.
Distributed Feedback Laser (DFB)
An injection laser diode which has a Bragg reflection grating in the active region in order to suppress multiple longitudinal modes and enhance a single longitudinal mode.
DWDM(Dense Wavelength Division Multiplexing)
A method of transmitting many connections parallel over one fiber optic line.Transmission works over different wavelengths (colors) on the same fiber, which are very close together on DWDM. Because of this, highly precise and temperature stabilized laser transmitters must be used. On the other hand, when using DWDM a distance of several 100 km can be covered.By now, DWDM is available with up to 128 colors.
EDFA (Erbium-doped Fiber Amplifier)
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.
Ethernet
A standard protocol (IEEE 802.3) for a 10-Mb/s baseband local area network (LAN) bus using carrier sense multiple access with collision detection (CSMA/CD) as the access method. Ethernet is a standard for using various transmission media, such as coaxial cables, unshielded twisted pairs, and optical fibers.
Fiber Optic Communication System
The transfer of modulated or unmodulated optical energy through optical fiber media which terminates in the same or different media.
Fiber-to-the-Curb (FTTC)
Fiber optic service to a node connected by wires to several nearby homes, typically on a block.
Fiber-to-the-Home (FTTH)
Fiber optic service to a node located inside an individual home.
Filter
A device which transmits only part of the incident energy and may thereby change the spectral distribution of energy.
FP (Fabry Perot)
Generally refers to any device, such as a type of laser diode, that uses mirrors in an internal cavity to produce multiple reflections.
Fused Fiber
A bundle of fibers fused together so they maintain a fixed alignment with respect to each other in a rigid rod.
GHz
Abbreviation for gigahertz. One billion Hertz (cycles per second) or 109 Hertz.
IEEE
Abbreviation for Institute of Electrical and Electronic Engineers. A technical professional association that contributes to voluntary standards in technical areas ranging from computer engineering, biomedical technology and telecommunications, to electric power, aerospace and consumer electronics, among others.
Insertion Loss
The loss of power that results from inserting a component, such as a connector, coupler (illustrated), or splice, into a previously continuous path.
International Telecommunications Union (ITU)
A civil international organization, headquartered in Geneva, Switzerland, established to promote standardized telecommunications on a worldwide basis. The ITU-R and the ITU-T are committees under the ITU, which is recognized by the United Nations as the specialized agency for telecommunications.
L-Band
The wavelength range between 1570 nm and 1610 nm used in some CWDM and DWDM applications.
LAN (Local Area Network)
A communication link between two or more points within a small geographic area, such as between buildings. Smaller than a metropolitan area network (MAN) or a wide area network(WAN).
Laser Diode (LD)
A semiconductor that emits coherent light when forward biased.
Light-emitting Diode (LED)
A semiconductor that emits incoherent light when forward biased. Two types of LED’s include edge-emitting LED’s and surface-emitting LED’s (illustrated).
Long-haul Telecommunications
1. In public switched networks, regarding circuits that span long distances, such as the circuits in inter-LANA, interstate, and international communications.
2. In military use, communications among users on a national or worldwide basis. Long-haul communications are characterized by a higher level of users, more rigorous performance requirements, longer distances between users, including world wide distances, higher traffic volumes and densities, larger switches and trunk cross sections, and fixed and recoverable assets. Usually pertains to the U.S. Defense Communications System.
Loose-tube
A type of fiber optic cable construction where the fiber is contained within a loose tube in the cable jacket.
Multimode (MM) Fiber
An optical fiber that has a core large enough to propagate more than one mode of light The typical diameter is 62.5 micrometers.
Multiplexer
A device that combines two or more signals into one output.
Multiplexing
mW
Abbreviation for milliwatt. One thousandth of a Watt or 10-3 Watts.
Network
1) An interconnection of three or more communicating entities and (usually) one or more nodes (illustrated). 2) A combination of passive or active electronic components that serves a given purpose.
Optical Add/Drop Multiplexer (OADM)
A device which adds or drops individual wavelengths from a DWDM system.
Optical Amplifier
A device that amplifies an input optical signal without converting it into electrical form. The best developed are optical fibers doped with the rare earth element, erbium. See also EDFA.
Optical Isolator
A component used to block out reflected and unwanted light. Also called an isolator.
Optical Spectrum Analyzer (OSA)
A device that allows the details of a region of an optical spectrum to be resolved. Commonly used to diagnose DWDM systems.
OTDR (Optical Time Domain Reflectometer)
An instrument that locates faults in optical fibers or infers attenuation by backscattered light measurements.
Passive Device
Any device that does not require a source of energy for its operation. Examples include electrical resistors or capacitors, diodes, optical fiber (photo), cable, wires, glass, lenses, and filters.
Photodiode (PD)
A semiconductor device that converts light to electrical current.
PLC
Abbreviation for planar lightwave circuit. A device which incorporates a planar waveguide.
Polarization Maintaining Fiber
Fiber designed to propagate only one polarization of light that enters it.
PON
Abbreviation for passive optical network. A broadband fiber optic access network that uses a means of sharing fiber to the home without running individual fiber optic lines from an exchange point, telco CO, or a CATV headend and the subscriber’s home.
S-Band
The wavelength region between 1485 nm and 1520 nm used in some CWDM and DWDM applications.
Single-mode (SM) Fiber
A small-core optical fiber through which only one mode will propagate. The typical diameter is 8-9 microns.
SFP (Small Formfactor Plugable)
A standard for optical transceiver modules. The SFP standard allows a flexible choice of fiber optic transceivers for devices with a SFP slot. Depending on the application, an individually selected SFP module containing the required technology and wavelength can be inserted. This way, the component can be fitted e.g. to any color of a [CWDM] backbone.
SMF
Abbreviation for single-mode fiber.
Switch
1) In communications systems, a mechanical, electro-mechanical, or electronic device for making, breaking, or changing the connections in or among circuits.
2) Synonym for central office, switching center. 3) In communications systems, to transfer a connection from one circuit to another.
TDM (Time Division Multiplexing)
A method of multiplexing and sending several data streams over one line, with the help of time.
Using this method, the data streams are being splitted into time slices, which will be transmitted on a rotating basis. As opposed to the [WDM] methods, TDM is applicable on copper as well as on fiber lines. Only on the latter, there is also the possibility of nesting and combining TDM and [WDM].
Transceiver
A device that performs, within one chassis, both telecommunication transmitting and receiving functions.
Transmitter
A device that includes a source and driving electronics. It functions as an electrical-to-optical converter.
Transponder
The part of a satellite that receives and transmits a signal.
VCSEL
See vertical cavity surface-emitting laser.
WDM (Wavelength Division Multiplexing)
A method of transmitting more than one data stream simultaneously over a fiber. This is being achieved by using a different wavelength for each one. The simplest case is multiplexing two data streams by using two wavelengths at 1310 and 1550nm.More channels will be transmitted using [CWDM] or [DWDM].
Wideband
Possessing large bandwidth.