Friday, June 4, 2010

Glossary of Common Fiber Optic Terms: R - Z


Common Fiber Terms A-E


Common Fiber Terms F-L


Common Fiber Terms M-P


Common Fiber Terms: R-Z

R:

Rack Panels
Framework or boxes to hold patch panels and other cable management devices.

Rayleigh Scattering
Scattering by refractive index fluctuations (inhomogeneities in material density or composition) that are small with respect to wavelength. Referred to as backscatter.

Receiver
A device which detects an optical signal, converts into an electronic form, then processes it further so it can be used by electronic equipment. From the standpoints of components, it can be viewed as a combination of detector and single processing electronics.

Receiver I.C.
Consists of photodiode which converts the signal to an elec­tronic one which feeds into an amplifier bringing the signal back to a level.


Receiver Sensitivity (expressed in dBm)
This tells how much optical power the photo-detector must receive to achieve a specified base band per­formance, such as a specified bit-error rate of signal-to-noise ratio.

Reflection
The abrupt change in direction of a light beam at an interface between two dissimilar media so that the light beam returns into the media from which it originated.

Refraction
The bending of a beam of light at an interface between two dissimilar media or in a medium whose refractive index is a continuous function of position (graded index medium).

Repeater (fiber optic)
A device which detects a weak signal in a fiber optic communication system, amplifies it, cleans it up, and retransmits it in optical form. Also known as a regenerator.

Return Loss
Expressed in negative value (-dB), this refers to the amount of back reflection. The lower the dB value, the better the connector and polish finish on the connector ferrule.

RF (Radio Frequency)
The frequency spectrum from 15kHz to 100GHz.

RFI (Radio Frequency Interference)
Electromagnetic radiation in the radio frequency spectrum fiom 15kHz to 100GHz. The best shielding material against RFI is copper and aluminum alloys. The term "EMI" should not be used in place of RFI since shielding materials for the entire electromagnetic frequency spectrum are not available.

Riser
Pathways for indoor cables that pass between floors. It is normally a vertical shaft or space. Also a fire-code rating for indoor cable.
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S:

Scattering
A property of glass that causes light to deflect from the fiber and contributes to optical attenuation.

Scribe Tool
Also called a cutting tool or breaking tool, consisting of cut­ting blade usually made from tungsten carbide or a diamond. Application is to break/scribe fiber @90? without lips or hackles or angular irregularities.

Selco Lenses
Segments of optical fibers specially designed to function as lenses.

Semi-Graded Index
An optical fiber with refractive index profile interme­diate between step-index and graded index. Strictly speaking, this might be considered a type of graded-index fiber with refractive index profile some­what steeper than normal.

Signal-to-Noise Ratio
The ratio of the power of the signal to that of background noise, usually measured in decibels. This is a common measure of the quality of analog electronics or transmission systems.

Simplex Cable
A single cable structure with a single fiber.

Singlemode
One type of low-loss optical waveguide with a very small Core (2-9 microns). It requires a laser source for input signals becauuse of the very small entrance aperture. The core diameter of a single-mode is designed to accept a one mode(wavelength) from the light source .

Skew Rate
A ray somethimes refered to as a dominant ray, that never intersects the axis of fiber while being internally reflected (in contrast with a meridional ray).

Splice
A permanent junction between two optical-fiber ends.

Splice Housing (Fiber Optics)
A housing designed to protect a splice in an optical fiber from damage by the environment, such as from the applica­tion of stress on the fiber. It also can seal the splice fiom environmental agents such as water which could cause it to deteriorate.

Star Coupler (fiber optics)
A coupler in which many fibers are brought together to a single optical element in which their signals are mixed. The mixed signals are then transmitted back through all the fibers. The name comes from the geometric arrangement

Step-Index
An optical fiber in which there is a discontinuous (step-function) change in refractive index at the boundary between fiber core and cladding. Such fibers have a large numerical aperture (light accepting angle), and are simple to connect. but have lower bandwidth than other types of optical fibers.

Stripper
Mechanical tool used to remove buffer coatings from fibers.

STTL
Standard TTL (see TTL)

Swage
To displace metal by pressure.

Switch (fiber optics)
A device for rerouting signals from one optical fiber into others.
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T:

Tap (fiber optic)
A coupler in which part of the light carried by one fiber is split off and inserted into another fiber, essentially the same as a Tee coupler.

Tee Coupler (fiber optic)
A fiber optic coupler in which three fiber ends are joined together, and a signal transmitted from one fiber is split between the other two. A conceptual drawing looks like the letter T, which accounts for the name.

Telecommunications Closet (TC)
An enclosed space for housing telecommunications equipment, cable terminations, and cross-connects. The closet is the recognized cross-connect between the backbone and horizontal cabling.

Termination tools
Tools used in preparing optical fibers for spliciug and/or installation of connectors.

Tight Buffered Cable
a protective coating extruded tightly over fiber for mechanical and environmental protection. The coating material is either nylon or PVC. This buffering offers excellent physical and flexing properties, but higher micro-bending sensitivity.

Time-Division multiplexing
A digital technique for combining two or more signals into a single stream of data by interleaving bits from each signal. Bit one might be from signal one, bit two from signal two, etc.

Total Internal Reflection
The total reflection that occurs when light strikes an interface at angles of incidence greater than the critical angle.

Transmitter (fiber optics)
A light source (LED or diode laser) which is combined with electronic circuitry to drive it. A transmitter operates directly from the signal generated by other electronic equipment to produce the drive current needed for LED or diode laser.
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W:

Wavelength-Division Multiplexing
Combination of two or more signals so they can be transmitted over a common optical path, usually over a single fiber; by a technique in which the signals are generated by light sources having different wavelengths. For example, one signal might be transmitted at 850 nanometers and a second at 1300 nanometers.

WDM
Wave Division Multiplexing. Multiplexing is done by combining different wavelengths over one optical fiber simultaneously. Each wavelength is capable of carrying a certain amount of information.

White Light
A mixture of colors of visible light that appears white to the eye. In theory, a mixture of three colors is sufficient to product white light.
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Z:

Zero-Dispersion Wavelength
Wavelength at which the chromatic dispersion of an optical fiber is zero. Occurs when waveguide dispersion cancels out material dispersion.