The axial (core centerline) alignment of fiber cores. Coaxiality insertion loss occurs when the positioning of the fiber cores is offset (misalignment). Coaxiality is also called radial offset or radial misalignment. The diagram below shows how the coaxiality (axial misalignment) of fiber cores result in insertion loss. This example shows that the some of the light from the fiber cores size will be absorbed by the cladding and not be transferred between the fibers. [Opt09]
Coaxiality Misalignment Diagram courtesy of Optical Dictionary dot com, http://www.opticaldictionary.com/Optical_Dictionary_Connector_Loss_Definition.html
The sharing of a common center point of circular items (such as a fiber core and fiber cladding or a center conductor in a coaxial cable). When a fiber core is not positioned in the center of the fiber (not concentric), this can cause losses as the end of one fiber may not exactly align with the core of the other fiber. To overcome some of the loss due to cocentricity offset, some optical connectors allow for the rotation of the connector to help align the fiber cores so their cocentric offsets are aligned as much as possible. The diagram below shows how cocentric offset can cause optical connector insertion loss. This diagram shows how the fiber core of one fiber has a concentric offset (core not in the center). When the end of one fiber is connected to the end of the other fiber, the fiber cores do not align. This results in some of the light signals from each fiber core not being transferred to the other fiber (blocked by the cladding). [Opt09]
Cocentricity Diagram courtesy of Optical Dictionary dot com, http://www.opticaldictionary.com/Optical_Dictionary_Connector_Loss_Definition.html
One of the primary forms of man-made signal degradation associated with radio, co-channel interference occurs when the same carrier frequency reaches the same receiver from two separate transmitters as a result of spilling over from an adjoining cell.
Code Division Multiple Access (CDMA)
A spread spectrum access technology that assigns a code to each multiple access stream of data bits, transmits the spread data streams, and then, at the receiver, despreads and reassembles the data streams to their original format.
A function or device that performs compression and decompression, typically on voice or video streams.
Codes Exchange (CODEX)
A telecommunications Codex specifies how different binary values sent across the telephone network are translated to and from specific sample voltages. See also Codec.
Coded Orthogonal Frequency Division Modulation; OFDM used in conjunction with channel coding techniques. As the overhead of doing this in an already digital system is low, and the gains substantial, practical OFDM/DMT systems are all actually COFDM. Although highly complex, COFDM has high performance under even very challenging channel conditions. By combining the OFDM technique with error-correcting codes, adaptive equalization and reconfigurable modulation, COFDM has the following properties:
COFDM also generally has a nearly 'white' spectrum, giving it benign electromagnetic interference properties with respect to other signals. Some COFDM systems use some of the sub carriers to carry pilot signals, which are used for frequency synchronizations, as frequency shifts during the transmission using the main modulation/demodulation process transform into bit errors in the decoded data. In wide area broadcasting, receivers can benefit from receiving signals from several spatially dispersed transmitters simultaneously, since transmitters will only destructively interfere with each other on a limited number of subcarriers, whereas in general they will actually reinforce coverage over a wide area. This is very beneficial in many countries, as it permits the operation of national single frequency networks, and avoids the replication of program content on different carrier frequencies which is necessary with FM or other forms of radio broadcasting. Also, because effectively the bit rate is slowed down on each sub-carrier, the effects of "ghosting" are much reduced. Such single frequency networks utilize the available spectrum more effectively than existing analog radio networks. [Wor11]
In fiber optics, a communication system where the output of a local laser oscillator is mixed optically with a received signal and the difference frequency is detected and amplified. [Fib111]
Coherent Communications Diagram courtesy of Fiber Optics Info, http://www.fiber-optics.info/fiber_optic_glossary/c
Ability of multiple satellites to share the same approximate geostationary orbital assignment frequently due to the fact that different frequency bands are used. [Sat07]
The result of two network nodes transmitting on the same channel at the same time. The transmitted data is not usable.
A test signal, typically containing six (6) basic colors: yellow, cyan, green, magenta, red, and blue, which is used to check the chrominance functions of color TV systems. [Cha07]
Color Bar Test Signal
The color bar test signal shown in the associated figure, consists of discrete steps of chroma and luminance levels that produce eight different colors superimposed upon standard synchronizing and blanking signals. [T1.Rpt16-1992] [ATI11]
Color Bar Test Signal courtesy of ATIS Telecom Glossary 2007, http://www.atis.org/glossary/definition.aspx?id=6395
In NTSC color, normally refers to a burst of approximately 9 cycles of 3.6MHz subcarrier on the back porch of the composite video signal. This serves as a color- synchronizing signal to establish a frequency and phase reference for the chrominance signal.
Color Coordinate Transformation