1. In fiber optics, a mode that shares energy among one or more other modes, all of which propagate together. [After 2196]
Note: The distribution of energy among the coupled modes changes with propagation distance.
2. In microwave transmission, a condition where energy is transferred from the fundamental mode to higher order modes.
Note: Energy transferred to coupled modes is… (Read More →)

Seedirectional coupler.

The desirable or undesirable transfer of energy from one medium, such as a metallic wire or an optical fiber, to another like medium, including fortuitous transfer.
Note: Examples of coupling include capacitive (electrostatic) coupling, inductive (magnetic) coupling, conducted (resistive or hard-wire) coupling, and fiber-optic coupling.

A number that expresses the degree of electrical coupling that exists between two circuits.
Note: The coupling coefficient is calculated as the ratio of the mutual impedance to the square root of the product of the self-impedances of the coupled circuits, all impedances being expressed in the same units.

In fiber optics, the efficiency of optical power transfer between two optical components. [After 2196]
Note 1: The transfer may take place (a) between an active component, such as an LED, and a passive component, such as an optical fiber, or (b) between two passive components such as two optical fibers.
Note 2: Coupling efficiency is usually expressed as the… (Read More →)

1. The loss that occurs when energy is transferred from one circuit, circuit element, or medium to another.
Note: Coupling loss is usually expressed in the same units--such as watts or dB--as in the originating circuit element or medium.
2. In fiber optics, the power loss that occurs when coupling light from one optical device or medium to another. [After… (Read More →)

The technique of concealing or altering the characteristics of communications patterns for the purpose of denying an unauthorized receiver information that would be of value; a process of modulo two addition of a pseudorandom bit stream generated by a cryptographic device with bits from the control message.

In radio communications, the geographical area within which service from a radio communications facility can be received.

1. A transmission channel that may be used to transfer data in a manner that violates security policy. [2382-pt.8]
2. [An] unintended and/or unauthorized communications path that can be used to transfer information in a manner that violates an information system (IS) security policy. [INFOSEC-99]
3. A channel which allows information to flow in violation of the System Security policy.… (Read More →)

1. [A] covert channel involving the direct or indirect writing to a storage location by one process and the direct or indirect reading of the storage location by another process. Covert storage channels typically involve a finite resource (e.g., sectors on a disk) that is shared by two subjects at different security levels. [INFOSEC-99]
2. A covert channel that involves… (Read More →)