Friday, June 4, 2010

Glossary of Common Fiber Optic Terms: F - L

Common Fiber Terms A-E

Common Fiber Terms: F-L


A multi-fiber cable constructed in a tight buffered tube design. At a termination point, cable fibers must be separated from the cable to their separate connection positions.

A component of fiber optic connections that holds a fiber in place and aids in it's alignment. It is the protruding portion of the connector, made of Ceramic, Stainless Steel, or Polymer, and is polished during the connection process to form a smooth finish.

Fiber Buffer
Material used to protect an optical fiber or cable from physical damage. providing mechanical isolation or protection. Fabrication techniques include both tight jacket, or loose tube buffering, as well as multiple buffer layers.

Fiber Optic Cable
A sub-assembly made up of several optical fibers incorporated into an assembly of organic materials arranged for providing the necessary tensile strength, external protection, and handling properties comparable to those of equivalent diameter coaxial cables.

Fiber Optics
The technique of conveying light or images through a particular configuration of glass or plastic fibers. Fiber optics can be categorized roughly into three groups: incoherent, coherent and specialties.

   1. Incoherent fiber optics will transmit light|like a pipe will water|but not an image.
   2. Coherent fiber optics can transmit an image through the perfectly aligned small (12 micron) clad optical fibers (image carrying).
   3. Specialty fiber optics combines some aspects of a and b.

Fiber Sensor
A sensing device in which the active sensing element is in an optical fiber or an element attached directly to an optical fiber. The quantity being measured changes the optical properties of the fiber in way that can be detected and measured. For example, pressure changes induced in a fiber by acoustics can change the amount of light transmitted by a fiber.

Field Installable (fiberoptics)
Nominally, a fiber optic splice or cable is field installable if it can be mounted by technicians working in the field without a lab-full of equipment at hand. Different manufacturers define the term differently.

Refers to the polish results on the end of the ferrule. Better the Finish, the less the back reflectance.

Frequency-Division Multiplexing
The combination of two or more signals at different frequencies so they can be transmitted as one signal. This can be done electronically, or it can be done optically by using two or more light sources of different wavelengths. The optical version is better known as wavelength division multiplexing.

Fresnel Relflection
Reflection losses that are incurred at the input and output faces of the fiber and are due to the difference in refractive index between the core glass and the immersion medium.

“Fiber to the Home" FTTH is where fiber will be brought directly to the side of your home to support your cable TV, telephone service and internet needs. It looks much like the utility box that you currently have on the side of your home, only with fiber jumpers inside.

Furcation Tubing
A protective tubing used to protect exposed fiber. Commonly used in terminating multi-fiber cable or “fan out” situations.

Fusion splicer
A high precision piece of equipment that allows the user to 'melt' or fuse the ends of two optical fibers together to create one continous fiber. There is typically very low loss at this junction. Alignment of fibers can be by manual or automatic manipulation. The fusing takes place by electrical discharge between two electrodes.


Gigahertz (GHz)
A unit of frequency that is equal to one billion cycles per second.

Graded Index Fiber
An optical fiber in which the refractive index changes gradually between the core and cladding, in a way designed to refract light so it stays in the fiber core. Such fibers have lower dispersion and hence broader bandwidth than step-index fibers.


Hard-Clad Silica Fluid
A liquid with refractive index that matches that of the core or cladding of an optical fiber. It is used in coupling light into or out of optical fibers and can help in suppressing reflections at glass surfaces.

Hybrid Cable
A fiber optic cable containing two or more different types of fiber, such as 62.5um multimode and singlemode.


Index Matching Gel
A gel material with an index of refraction close to that of glass that reduces reflections caused by refractive-index differences.

Index of refraction
The ratio of light velocity in a vacuum to its velocity in a given transmission medium.

Those wavelengths that extend beyond 770 nanometers. Infrared is used extensively in the transmission of light through optical waveguides. These light wavelengths are invisible and harmful to the naked eye.

Insertion Loss
Total optical power loss caused by insertion of an optical component such as a connector, splice, or coupler into a previously continuous path.

Interconnect Sleeve
A mechanical media termination device designed to align and join fiber optic connectors, designed to be mounted on a panel. Often referred to as a coupling, bulkhead, or mating sleeve.

Interferometer Test
A test used to determine the quality of the ferrule surface using three measurements.

   1. The angle of the cut or radius on the end of a connector which determines actual back reflection values or characteristics.
   2. The undercut or protrusion of the fiber. This is mea­sured against the ferrule end face determining how well the physical contact will be.
   3. The position of the fiber in relation to cut or curve, called the apex.

Intrinsic Joint Loss
Loss caused by fiber parameter (e.g.: core dimensions, profile parameter) mismatches when two non identical fibers are joined.


A length of cable with connectors at both ends. Also known as patchcords.


Strands of aramid yarn used to provide strain relief in cable assemblies.

Kilometer (km)
One thousand meters, or approximately 3281 feet. The kilometer is a standard unit of length measurement in fiber optics. Conversion is 1 ft. = 0.3048


A Local Area Network. A network which does not utilize outside telco company lines.

Large-Core Fiber
An optical fiber with a comparatively large core, usually a step-index type. Usually, 400 micrometers or more (see Step Index).

An acronym for Light Amplification by the Stimluated Emission of Radiation, applied to a wide range of devices which produce light by that principle. Compared other light sources, laser light covers a narrow range of wavelengths. tends to be coherent, and is emitted in a directional beam.

Launch Fiber
A fiber used in conjunction with a source to excite the modes of another fiber in a particular way. Launching fibers are most often used in test systems to improve the precision of measurements. See “Pulse Suppressor”

LED (Light-Emitting Diode)
A semiconductor device in which light is produced when current carriers combine at a p-n junction. The emission is spontaneous and there are no feedback mirrors, unlike diode lasers. Output is lower in power than from diode lasers, reflecting the use lower operating currents. Generally LEDs are less expensive than diode lasers, and can operate at shorter wavelengths without the rapid degradation that occurs with visible-wavelength diodes.

Loose Buffer Cable
Loose buffered designs Consist of a loose tube surrounding a coated fiber. It also includes a Kevlar? braid as the strength member for improved flexibility.

LSTTL (Low Power Schottky TTL)
Utilizes a diode-clamped transistor to lower power requirememts.

Common Fiber Terms M-P

Common Fiber Terms R-Z