Glossary

  • Bandwidth (of a signal or a transmission path)

    A measure of the maximum frequency by which a signal be modulated. It is a measure of information-carrying capacity; the greater the bandwidth, the greater the information carrying capacity.

    Bandwidth (of a WDM-channel)

    The range of optical wavelengths which can be transmitted through a component. It is the wavelength range, which defines the spectral width of one WDM channel.

    Center Wavelength

    Wavelength of an optical source (e.g. laser) at peak power.

    Center Wavelength (of a WDM channel)

    Middle position of an optical bandpass.

    Channel

    A communication path or the signal sent over that path. See also: Optical Channel.

    Channel Spacing

    The wavelength separation of the center wavelengths between adjacent WDM channels.

    Coupler

    An optical device containing one or several input and output ports to distribute an optical signal.

    Coupling Ratio

    The ratio of optical power from one output port to the total output power, expressed as a percentage.

    CWDM

    Coarse wavelength division multiplexing. Very cost-effective WDM transmission technology due to larger channel spacing and the possibility of using uncooled laser transmitters.

    dB Decibel

    Standard logarithmic unit for the ratio of two quantities. In optical fibers, the ratio is power and represents loss or gain.

    Demux

    Demultiplexer. The process that separates two or more signals from a single communications line.

    Directivity

    Fraction of optical power transferred from one input port to any other input port.

    DWDM

    Dense Wavelength Division Multiplexing involving high channel counts.

    Excess Loss

    Lost optical power in an optical component i.e. light that does not emerge from any optical output port.

    Fiber Coating

    Material immediately around the optical fiber to preserve the integrity of the fiber.

    Insertion Loss

    Loss of optical power resulting from the insertion of a component or device into the optical path.

    Interference Filter

    Optical element consisting of multiple layers of dielectric thin films coated on a glass substrate transmitting a certain wavelength range and reflecting the residual light.

    Isolation

    Ability to prevent undesired optical energy from appearing in a signal path.

    Isolator

    An optical component used to block out reflected light.

    LAN Local Area Network

    A high speed transmission network (Mb/s) in which all segments of the transmission are situated in an office, building or campus environment. The network is owned by the user organization.

    Laser

    Light Amplification by Stimulated Emission of Radiation. Light source producing coherent light through stimulated emission.

    Link Loss

    Insertion loss for the combined WDM mux and demux components.

    Loose tube

    Thin plastic tube around the optical fiber – providing protection and better handling of the fiber.

    Multiplexing

    The process by which two or more signals are transmitted over a single communications line.

    Mux, Multiplexer

    A device that puts two or more signals into a single channel.

    nm Nanometer

    A unit of measurement equal to one billionth of a meter. Commonly used to define optical wavelengths.

    Optical Bandpass

    See Bandwidth (of a WDM-channel).

    Optical Channel

    An optical wavelength band for WDM optical communications.

    Optical Fiber

    Fiber made of dielectric material and consisting of the core, light- carrying medium, and the cladding, protective layer allowing total internal reflection of the light for propagation purposes.

    PDL, Polarization Dependent Loss

    The difference in dB between the maximum and the minimum values of loss (attenuation) due to the variation of the polarization states of light propagating through a device.

    Pigtail

    Fiber attached to a connector, source, detector, coupler or any other optical component.

    Polarization

    Characteristic of electromagnetic radiation where the electric-field vector of the wave energy is perpendicular to the main direction, or vector, of the electromagnetic beam.

    Port

    Opening for light or fiber to and from a component.

    Return Loss

    Fraction of power transferred from an input port back to the same input port.

    Switch

    Device that switches light between one or multiple input ports to one or multiple output ports on coupler products.

    Tap

    Branching component that removes and/or inserts a small fraction of optical power onto the fiber.

    Uniformity

    The difference between the maximum insertion loss and the minimum insertion loss for each input port and all output ports. For WDM devices this is measured at 23°C .

    WDM Wavelength Division Multiplexing

    Optical transmission technique using two or more optical channels over a common optical fiber. The channels are differentiated by their wavelengths and frequencies.

    WWDM

    Wide WDM – Transmission technology using only two optical channels. WWDM mux/demux components combine/split the optical spectrum into a short wavelength and a long wavelength region.