Photonics Dictionary

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lip

A defect in the cleaved end face of an optical fiber, in the form of a sharp protrusion at the edge of the fiber.

liquid core optical fiber

Multimode straight fiber capable of transporting linearly polarized light with any incident polarization angle, and in which no form of internal stress can develop that could lead to birefringence.

liquid lightguide

An optical fiber with a hollow core filled with a liquid material that has a higher refractive index than the solid surrounding it.

local injection detection system

A device used to evaluate the quality of fiber optic splices made in the field by injecting light into the cladding of the fiber and measuring the output at the other end of the splice.

logic-to-light device

A fiber optic component or system designed in such a way that it can be operated by people without specialized knowledge of the field.

long-wavelength system

In fiber optic communications systems, generally one that operates between 1000 and 1700 nm.

longitudinal offset loss -> gap loss

The optical power loss caused by a space between axially aligned fibers.

loose-tube buffering

In fiber optic cable, containment of the fiber or fibers within an outer protective tube in which they can move to some extent. The interstices usually are filled with an insulating material. See...

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 materials and a more sophisticated drawing process and...

macrobending

In optical fiber, bends that are larger than microbends (see microbending), being visible. Generally they are caused by bending the cable beyond the specified bend radius. Light escaping at the bends...

mandrel

A shaft, spindle or any object generally passed through a workpiece to hold, support or shape a particular piece during its machining process or its practical use. In fiber optics, optical fibers are...

mandrel wrap test

A means of testing optical fiber for macrobending losses by wrapping the fiber once at very low tension around a mandrel, and then measuring attenuation vs. wavelength.

marhic method

Nondestructive measurement of the delta and alpha of clad optical fibers that involves interferometry with the fiber immersed in an index-matching oil and illuminated perpendicular to the fiber axis.

MEL

many-element laser; maximum excess loss (MEL) — the many element laser is a laser unit that consists of N like elements of active materials for support with the mode selection of the laser output. The mode selection properties of a many element laser have been experimentally exploited with as many as 10 like elements. Maximum excess loss is the maximum power lost within a give system (typically a fiber optic communication system) including scattering, dispersion, absorption and coupling loss.

MEMS fiber optic switch

A MEMS fiber optic switch is a microelectromechanical system (MEMS) device designed to selectively route optical signals between multiple fiber optic channels. These switches utilize miniature...

metropolitan area network

A cable backbone used to interconnect local area networks at various sites (corporate offices and factories, for example) in a given region. Optical fiber is well-suited to the transmission of both...

micro-optics

Micro-optics refers to the design, fabrication, and application of optical components and systems at a microscale level. These components are miniaturized optical elements that manipulate light at a...

microbend-modulated sensor

A type of fiber optic sensor that detects changes in pressure, vibration, sound level or acceleration by monitoring the ejection of light from the fiber core to the cladding caused by microbending...

microbending

In optical fiber, sharp but microscopic curvatures that create local axial displacements of a few microns and spatial wavelength displacements of a few millimeters. One frequent cause is longitudinal...

microbending loss

Transmission loss in optical fibers caused by packaging processes; it is considered a power-coupling effect from the guided modes to the radiation modes.