Sparkling granular pattern that is observed when an object diffusely reflects coincident laser light. Speckle appears as an irregularity in many holographs but has been exploited as a measurement technique. [Pho11] Lashing Wire
Stainless steel wire used for securing coaxial cable to strand or wire rope. [Arr11] Last Mile
Refers to the last “mile” between a central office and a customer in a telephone network or a node and a customer in a cable television network. Last-mile distances generally range from 0 miles to 3 miles. Last Mile Framing
The data encapsulation and transmission protocols used between the consumer premises and the headend. Framing techniques include ATM, MPEG and IP.
LATA Local Access and Transport Area
The time taken for a signal element to pass through a device or system.
Lateral Displacement Loss
The loss of power that results from lateral displacement of optimum alignment between two fibers or between a fiber and an active device. [Fib111]
Lateral Displacement Loss Diagram courtesy of Fiber Optics Info, http://www.fiber-optics.info/fiber_optic_glossary/l
An optical fiber used to couple and condition light from an optical source into an optical fiber. Often the launch fiber is used to create an equilibrium mode distribution in multimode fiber. Also called launching fiber. [Fib111] Layer
In networks, layers refer to software protocol levels comprising the architecture, with each layer performing functions for the layers above it. Or a subdivision of the Open System Interconnection (OSI) architecture, constituted by subsystems of the same rank.
Layer 2 Link layer in Open Systems Interconnection (OSI) framework
Layer 3 Network layer in OSI stack; layer in firewall in which routing is based on IP address L-Band
That portion of the electromagnetic spectrum from 950 to1450 MHz. [Arr11] LC Connector
LC stands for Lucent Connector. The LC is a small form-factor fiber optic connector. [Tim11]
Photo courtesy of http://www.timbercon.com/
LCD Liquid Crystal Display. A low power device used to display alphanumeric characters, graphs and charts. [Arr11] LD
Large Effective Area Fiber Leapfrogging
Cable television operators' practice of skipping over one or more of the nearest TV stations to bring in a further signal for more program diversity. FCC rules establish priority for carrying stations that lie outside the cable systems service area.
The practice by telephone companies of installing and maintaining cable television distribution systems, and leasing the facilities back to separate contractors for operation of the system.
On some systems, a public access channel for which programmers pay a fee for use and are permitted to sell commercial time in their programming. Also known as Leased Channel.
Least Significant Bit
In a binary code, the bit or bit position assigned to the smallest quantity or increment that can be represented by the code. [Fib111] Leakage
The undesirable passage of signal over the surface of or through an insulator. [Arr11] 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 specified service area. [Fib111] LED
Light emitting diode. LEDs are used in various applications ranging from being used as simple display indicators to use in fiber optics as a relatively low cost light source. [Arr11] Level
A measure of the difference between a quantity or value and an established reference. [Arr11] Level Diagram
A graphic diagram indicating the signal level at any point in the system. LEX
Local Exchange; synonym for central office (CO). [Fib111]
Logical Group Identifier; the optical line termination (OLT) assigns new group identifies (LGIDs) for grouping or separating some ports from other port groups. These LGIDs can be related to the virtual local area network (VLAN) group identifiers (VIDs) or multicast address/addresses, and can be applied for link segregation or multicasting. LH
Long-Haul; a classification of video performance under RS-250C. Lower performance than medium-haul or short-haul. [Fib111] L-I Curve
The plot of optical output (L) as a function of current (I) which characterizes an electrical-to-optical converter. A typical L-I curve is shown below. [Fib111]
Graph of L-I Curve courtesy of Fiber Optics Info, http://www.fiber-optics.info/fiber_optic_glossary/l
LIDB Line Information Database Lifetime of an Application
The lifetime of an application characterizes the time from which the application is loaded to the time the application is destroyed.
Light or visible light is the portion of electromagnetic radiation that is visible to the human eye, responsible for the sense of sight. Visible light has a wavelength in a range from about 380 or 400 nanometers to about 760 or 780 nm,  with a frequency range of about 405 THz to 790 THz. In physics, the term light often comprises the adjacent radiation regions of infrared (at lower frequencies) and ultraviolet (at higher), not visible to the human eye.  [Wik11] CIE (1987). International Lighting Vocabulary. Number 17.4. CIE, 4th edition. ISBN 978-3-900734-07-7.
By the International Lighting Vocabulary, the definition of light is: “Any radiation capable of causing a visual sensation directly.”
Gregory Hallock Smith (2006), Camera lenses: from box camera to digital, SPIE Press, p. 4, ISBN 9780819460936, http://books.google.com/?id=6mb0C0cFCEYC&pg=PA4
Narinder Kumar (2008), Comprehensive Physics XII, Laxmi Publications, p. 1416, ISBN 9788170085928
A semiconductor that emits incoherent light when forward biased. Two types of LED’s include edge-emitting LEDs and surface-emitting LEDs (illustrated). [Fib111]
LED Diagram courtesy of Fiber Optics Info, http://www.fiber-optics.info/fiber_optic_glossary/l
Use of optical fibers to illuminate. [Fib111] Light Source
A generic term that includes lasers and LEDs. [Arr11] Lightguide
Synonym for optical fiber. [Fib111] Lightwave
Any electromagnetic radiation having a wavelength in the range from 800 to 1,600 nanometers in the near infrared region. [Arr11] Also, the path of a point on a wavefront. The direction of the lightwave is generally normal (perpendicular) to the wavefront. [Fib111]
Line or Loop
An analog or digital access connection from a user terminal which carries user media content and telephony access signaling (DP, DTMF, BRI, proprietary business set).
The basic measurement of how well analog-to-digital and digital-to-analog conversions are performed. To test for linearity, a mathematically perfect diagonal line is converted and then compared to a copy of itself. The difference between the two lines is calculated to show linearity of the system and is given as a percentage or range of least significant bits. [Fib111] Line Amplifier
An amplifier in a transmission line that boosts the strength of a signal. [Arr11] Line Extender (LE)
Types of amplifiers used in the feeder system. Also known as a Distribution Amplifier. In most HFC networks configured in Node + 1 or higher integer architectures, the LE is the only transmission line amplifier connected to subscribers.
Excerpt from ANSI/SCTE 87-1 2008,
“Graphic Symbols For Cable Systems Part 1: HFC Symbols”
Photograph of Arris C-Cor Model # Flex Max 331 1-GHz LE (Courtesy of TVC Canada web site: http://www.tvccanada.com/broadband-products/broadband-amplifiers/eng/products.aspx)