In the term mode coupling, as used in physics and electrical engineering, the word "mode" refers to
eigenmode The mode of electromagnetic systems describes the field pattern of the propagating waves.
Some of the classifications of electromagnetic modes include;
* Modes in waveguides and transmission lines. These modes are analogous to the normal modes of ...
s of an idealized, "unperturbed",
linear system
In systems theory, a linear system is a mathematical model of a system based on the use of a linear operator.
Linear systems typically exhibit features and properties that are much simpler than the nonlinear case.
As a mathematical abstractio ...
. The
superposition principle
The superposition principle, also known as superposition property, states that, for all linear systems, the net response caused by two or more stimuli is the sum of the responses that would have been caused by each stimulus individually. So th ...
says that eigenmodes of linear systems are independent of each other: it is possible to excite or to annihilate a specific mode without influencing any other mode; there is no
dissipation
In thermodynamics, dissipation is the result of an irreversible process that affects a thermodynamic system. In a dissipative process, energy ( internal, bulk flow kinetic, or system potential) transforms from an initial form to a final form, wh ...
. In most real systems, however, there is at least ''some''
perturbation that causes energy transfer between different modes. This perturbation, interpreted as an interaction between the modes, is what is called "mode coupling".
Important applications are:
* In
fiber optics
An optical fiber, or optical fibre, is a flexible glass or plastic fiber that can transmit light from one end to the other. Such fibers find wide usage in fiber-optic communications, where they permit transmission over longer distances and at ...
* In
laser
A laser is a device that emits light through a process of optical amplification based on the stimulated emission of electromagnetic radiation. The word ''laser'' originated as an acronym for light amplification by stimulated emission of radi ...
s (compare
mode-locking)
* In
condensed-matter physics,
critical slowing down can be described by a
Coupled mode theory.
[{{Cite book , last=Götze , first=Wolfgang , author-link=Wolfgang Götze , url=https://academic.oup.com/book/10864 , title=Complex Dynamics of Glass-Forming Liquids: A Mode-Coupling Theory , date=2008-12-11 , publisher=Oxford University Press , isbn=978-0-19-171560-0 , language=en , doi=10.1093/acprof:oso/9780199235346.001.0001]
See also
*
Nonlinear optics
Nonlinear optics (NLO) is the branch of optics that describes the behaviour of light in Nonlinearity, nonlinear media, that is, media in which the polarization density P responds non-linearly to the electric field E of the light. The non-linearity ...
*
Nonlinear acoustics
Nonlinear acoustics (NLA) is a branch of physics and acoustics dealing with sound waves of sufficiently large amplitudes. Large amplitudes require using full systems of governing equations of fluid dynamics (for sound waves in liquids and gases) ...
*
Equilibrium mode distribution
The equilibrium mode owerdistribution of light travelling in an optical waveguide or fiber, is the distribution of light that is no longer changing with fibre length or with input modal excitation. This phenomenon requires both mode filtering and ...
References
Condensed matter physics
Nonlinear optics
Fiber-optic communications