Fiber Optic Glossary : L


  • L Band
    Wavelengths of about 1570 to 1625nm where some erbium-doped fiber amplifiers operate. Separate from C Band.
  • Lambertian
    A uniform radiance distribution.
  • Lambertian Emitter
    An emitter that radiates according to Lambert’s cosine law, which states that the radiance of certain idealized surfaces depends on...
  • Lambertian Radiator
    An optical source which has radiance uniform in all directions, proportional to the cosine of the angle from the normal.
  • Lamp Pumped Lasers
    Solid state lasers (not including semiconductor lasers) are in nearly all cases optically pumped, and the pump source is usually...
  • LAN
    Local Area Network. This is a geographically limited data communications network. It is often referred to as premises data communications network....
  • Lanyard
    A sturdy wire attached to plugs of certain connectors which allows unmating and separation of plug and receptacle by a...
  • Large Core Fiber
    Optical fiber with a large core, often a step-index fiber; large is at times defined as greater than 85...
  • Large Effective Area Fiber LEAF
    An optical fiber, developed by Corning, designed to have a large area in the core, which carries the light.
  • Large Mode Area Fibers
    Optical fibers with relatively large mode areas and a single transverse mode or only a few modes.
  • Laser
    An acronym of light amplification by stimulated emission of radiation. A laser is a cavity, with plane or spherical mirrors...
  • Laser Beam
    Light beams propagating dominantly in one direction.
  • Laser Chirp
    A phenomenon in lasers where the wavelength of the emitted light changes during modulation.
  • Laser Cooling
    A variety of techniques for reducing the temperature (i.e., the random motion) of small particles.
  • Laser Crystals
    Transparent crystals with laser-active dopants, used as laser gain media.
  • Laser Diode
    A semiconductor that emits coherent light when forward biased.
  • Laser Diode ILD
    A semiconductor device that emits high powered, coherent light when stimulated by an electrical current. Used in transmitters for singlemode...
  • Laser Diode Wavelengths
    Usual standard wavelengths for laser diodes are 1550 nm and 1310 nm. For WDM applications, laser diodes may be specified at...
  • Laser Light
    Amplification by Stimulated Emission of Radiation. A device which produces coherent light with a narrow range of wavelengths.
  • Laser Modulation
    Turning the laser on and off.
  • Laser Oscillation
    The buildup of the coherent wave between laser cavity end mirrors. In CW mode, the wave bounding back and forth between...
  • Laser Resonator
    A laser requires a laser resonator (or laser cavity), in which the laser radiation can circulate and pass a gain medium which...
  • Laser vs LED
    LEDs, or Light Emitting Diodes, are low cost, slower speed, easy to use, multimode-only, and have a higher output...
  • Lasing Threshold
    The lowest excitation level at which a laser's output is dominated by stimulated emission rather than spontaneous emission.
  • Latency
    The time interval between when a network station seeks access to a transmission channel and when access is granted or received....
  • Lateral Displacement Loss
    The loss of power that results from lateral displacement from optimum alignment between two fibers or between a fiber and an...
  • Lateral Offset Loss
    In fiber optics, a loss of optical power at a splice or connector, caused by a lateral, i.e. , transverse,...
  • Launch Angle
    The angle between the light input propagation vector and the optical axis of an optical fiber or fiber bundle.
  • Launch Cable
    A known good fiber optic jumper cable attached to a source and calibrated for output power used as a reference...
  • Launch Fiber
    1. An optical fiber used to couple and condition light from an optical source into an optical fiber. Often the launch...
  • Launch Numerical Aperture
    The numerical aperture of an optical sustem used to couple (launch) power into an optical waveguide.
  • Launching Fiber
    An optical fiber used in conjunction with a source to excite the modes of another fiber in a particular fashion....
  • Law of Reflection
    Angle of incidence = Angle of reflection.
  • Lay Length
    In communications cables, including fiber optic cables, having the transmission media wrapped helically around a central member, the longitudinal distance...
  • Layer
    In the OSI model, processing-functions that together compose one layer of a hierarchy of computing functions. Each layer performs a number...
  • LC Connector
    LC stands for Lucent Connector. The LC is a small form-factor fiber optic connector.
  • Leaky Mode
    In an optical fiber, a mode having a field that decays monotonically for a finite distance in the transverse direction...
  • Leaky Ray
    In an optical fiber, a ray for which geometric optics would predict total internal reflection at the boundary between the...
  • LEC Local Exchange Carrier
    A local telephone company, i.e., a communications common carrier that provides ordinary local voice-grade telecommunications service under regulation within a...
  • LED
    An abbreviation for light-emitting diode.
  • Lens
    A curved piece of optically transparent material which depending on its shape is used to either converge or diverge light.
  • LEOS
    An acronym for Lasers & Electro-Optics Society (of IEEE).
  • LEX
    Abbreviation for local exchange. Synonym for central office.
  • LI Curve
    The plot of optical output (L) as a function of current (I) which characterizes an electrical to optical converter.
  • Lifetime
    (1) The length of time an electron can be expected to remain in a given energy level. (2) The length of...
  • Light
    1. In a strict sense, the visible spectrum nominally covering the wavelength range of 400 nm to 750 nm. 2. In...
  • Light ARMOR Cable
    A fiber optic cable assembly with ruggedized plastic jacketing providing fiber protection for semi-harsh environment, commercial, or industrial applications.
  • Light Diffusion
    The scattering of light by reflection or transmission. Diffuse reflection results when light strikes an irregular surface such as frosted window...
  • Light Dispersion
    The process whereby white light is separated into its component wavelengths. Light beams of different wavelengths are separated from each...
  • Light Emitting Diode LED
    A semiconductor device that emits light when stimulated by an electrical current. Used in transmitters for multimode fiber links.
  • Light Filter
    A homogeneous optical medium or coating that transmits only in particular regions of the spectrum. It is used to change...
  • Light Pipe
    Transparent matter that usually is drawn into a cylindrical, pyramidical or conical shape through which light is channeled from one...
  • Light Piping
    Use of fiber optic cables to illuminate.
  • Light Source
    The generic term applied to all sources of visible radiation from burning matter to ionized vapors and lasers, regardless of...
  • Lightguide
    A fiber optic cable or fiber bundle.
  • Lightguide Cable
    An optical fiber, multiple fiber, or fiber bundle which includes a cable jacket and strength members, fabricated to meet optical, mechanical...
  • Lightwave Data Communication
    Made possible by fiber optic technology. Based on the fact that pulses of light transmitted over fiber will enable computer networks...
  • Lightwaves
    Electromagnetic waves in the region of optical frequencies. The term "light" was originally restricted to radiation visible to the human eye,...
  • Linearity
    The basic measurement of how well analog-to-digital and digital-to-analog conversions are performed. To test for linearity, a mathematically perfect diagonal...
  • Linewidth
    The rang of wavelengths in an optical signal, sometimes called spectral width.
  • Link
    A fiber optic cable with connectors attached to a transmitter (source) and receiver (detector).
  • Lip
    A defect in the cleaved end face of an optical fiber, in the form of a sharp protrusion at the...
  • LLDPE
    Linear Low Density Polyethylene jacketing.
  • Local Area Network LAN
    Data communications network in a clearly defined geographical location, and extending no more than a few miles in length. It...
  • Local Loop
    The part of the telephone network extending from the central (switching) office to the subscriber.
  • Locator
    Positioner or Turret head – a mechanical device attached to a crimp tool with multiple locators to position different size...
  • Logic Gate
    An electronic component that is capable of directing the flow of electricity in a circuit based on signals from the computer...
  • LOMMF Laser Optimized Multimode Fiber
    LOMMF is the highest capacity medium for 10-gig optical transmission. LOMMF was developed for use with VCSEL lasers. With laser...
  • Long Haul LH
    Abbreviation for long-haul. A classification of video performance under RS-250C. Lower performance than medium-haul or short-haul.
  • Long haul Telecommunications
    1. In public switched networks, regarding circuits that span long distances, such as the circuits in inter-LANA, interstate, and international...
  • Long Reach LR
    LR optical interfaces refer to optical sections with system loss budgets from 10 dB up to 28 dB at OC-3, to...
  • Long Wavelength
    A commonly used term for light in the 1300 and 1550 nm ranges.
  • Longitudinal Mode
    An optical waveguide mode with boundary conditions determined along the length of the opticaI cavity.
  • Loopback
    Type of diagnostic test in which the transmitted signal is returned to the sending device after passing through a data communications...
  • Loose Tube
    A protective tube loosely surrounding a fiber optic cable often filled with a water blocking gel.
  • Loose Tube Buffering
    In fiber optic cable, containment of the fiber or fibers within an outer protective tube in which they can move...
  • Loose Tube vs Tight Buffered
    Fiber optic cables are constructed in two ways: loose tube and tight buffered. Both contain a type of strengthening member,...
  • Loss
    Attenuation of optical signal, normally measured in decibels. The amount of a signal’s power, expressed in dB, that is lost...
  • Loss Budget
    The amount of power lost in the link. Often used in terms of the maximum amount of loss that can...
  • Low Loss Fiber
    Optical fiber that transmits a greater percentage of input light than does high-loss step-index fiber. Low-loss fiber requires higher purity...
  • Low NA
    Numerical Aperture around 0.30.
  • LSZH
    Primarily used for indoor applications, Low Smoke Zero Halogen (LSZH) cable is designed to reduce toxic emissions in event of...

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