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Polarization Scrambling
Polarization scrambling is the process of rapidly varying the polarization of light within a system using a polarization controller so that the average polarization over time is effectively randomized. Polarization scrambling can be used in scientific experiments to cancel out errors caused by polarization effects. Polarization scrambling is also used on long-distance fibre optic transmission systems with optical amplifiers, in order to avoid polarization hole-burning. Polarization scrambling, also for the variation of polarization mode dispersion, is a mandatory test procedure for fiber optic data transmission systems based on polarization-division multiplexing. Polarization scramblers usually vary the normalized Stokes vector of the polarization state over the entire Poincaré sphere. They are commercially available with speeds of 20 Mrad/s on the Poincaré sphere (see external link). Various speed distributions such as peaked and quasi-Rayleigh can be generated. Some ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Polarization (waves)
, or , is a property of transverse waves which specifies the geometrical orientation of the oscillations. In a transverse wave, the direction of the oscillation is perpendicular to the direction of motion of the wave. One example of a polarized transverse wave is vibrations traveling along a taut string, for example, in a musical instrument like a guitar string. Depending on how the string is plucked, the vibrations can be in a vertical direction, horizontal direction, or at any angle perpendicular to the string. In contrast, in longitudinal waves, such as sound waves in a liquid or gas, the displacement of the particles in the oscillation is always in the direction of propagation, so these waves do not exhibit polarization. Transverse waves that exhibit polarization include electromagnetic waves such as light and radio waves, gravitational waves, and transverse sound waves ( shear waves) in solids. An electromagnetic wave such as light consists of a coupled oscillating el ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Polarization Controller
Polarization or polarisation may refer to: Mathematics *Polarization of an Abelian variety, in the mathematics of complex manifolds *Polarization of an algebraic form, a technique for expressing a homogeneous polynomial in a simpler fashion by adjoining more variables *Polarization identity, expresses an inner product in terms of its associated norm * Polarization (Lie algebra) Physical sciences *Polarization (physics), the ability of waves to oscillate in more than one direction; polarization of light allows the glare-reducing effect of polarized sunglasses **Polarization (antenna), the state of polarization (in the above sense) of electromagnetic waves transmitted by or received by a radio antenna *Dielectric polarization, charge separation in insulating materials: **Polarization density, volume dielectric polarization ** Dipolar polarization, orientation of permanent dipoles ** Ionic polarization, displacement of ions in a crystal **Maxwell–Wagner–Sillars polarization, s ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Optical Amplifier
An optical amplifier is a device that amplifies an optical signal directly, without the need to first convert it to an electrical signal. An optical amplifier may be thought of as a laser without an optical cavity, or one in which feedback from the cavity is suppressed. Optical amplifiers are important in optical communication and laser physics. They are used as optical repeaters in the long distance fiber-optic cables which carry much of the world's telecommunication links. There are several different physical mechanisms that can be used to amplify a light signal, which correspond to the major types of optical amplifiers. In doped fiber amplifiers and bulk lasers, stimulated emission in the amplifier's gain medium causes amplification of incoming light. In semiconductor optical amplifiers (SOAs), electron–hole recombination occurs. In Raman amplifiers, Raman scattering of incoming light with phonons in the lattice of the gain medium produces photons coherent with th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Polarization Hole-burning
Polarization or polarisation may refer to: Mathematics *Polarization of an Abelian variety, in the mathematics of complex manifolds *Polarization of an algebraic form, a technique for expressing a homogeneous polynomial in a simpler fashion by adjoining more variables *Polarization identity, expresses an inner product in terms of its associated norm * Polarization (Lie algebra) Physical sciences *Polarization (physics), the ability of waves to oscillate in more than one direction; polarization of light allows the glare-reducing effect of polarized sunglasses **Polarization (antenna), the state of polarization (in the above sense) of electromagnetic waves transmitted by or received by a radio antenna *Dielectric polarization, charge separation in insulating materials: **Polarization density, volume dielectric polarization ** Dipolar polarization, orientation of permanent dipoles ** Ionic polarization, displacement of ions in a crystal **Maxwell–Wagner–Sillars polarization, s ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Polarization Mode Dispersion
Polarization mode dispersion (PMD) is a form of modal dispersion where two different polarizations of light in a waveguide, which normally travel at the same speed, travel at different speeds due to random imperfections and asymmetries, causing random spreading of optical pulses. Unless it is compensated, which is difficult, this ultimately limits the rate at which data can be transmitted over a fiber. Overview In an ideal optical fiber, the core has a perfectly circular cross-section. In this case, the fundamental mode has two orthogonal polarizations (orientations of the electric field) that travel at the same speed. The signal that is transmitted over the fiber is randomly polarized, i.e. a random superposition of these two polarizations, but that would not matter in an ideal fiber because the two polarizations would propagate identically (are degenerate). In a realistic fiber, however, there are random imperfections that break the circular symmetry, causing the two p ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Stokes Vector
The Stokes parameters are a set of values that describe the polarization state of electromagnetic radiation. They were defined by George Gabriel Stokes in 1851, as a mathematically convenient alternative to the more common description of incoherent or partially polarized radiation in terms of its total intensity (''I''), (fractional) degree of polarization (''p''), and the shape parameters of the polarization ellipse. The effect of an optical system on the polarization of light can be determined by constructing the Stokes vector for the input light and applying Mueller calculus, to obtain the Stokes vector of the light leaving the system. They can be determined from directly observable phenomena. The original Stokes paper was discovered independently by Francis Perrin in 1942 and by Subrahamanyan Chandrasekhar in 1947, who named it as the Stokes parameters. Definitions The relationship of the Stokes parameters ''S''0, ''S''1, ''S''2, ''S''3 to intensity and polarization el ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Poincaré Sphere (optics)
Unpolarized light is light with a random, time-varying polarization. Natural light, like most other common sources of visible light, is produced independently by a large number of atoms or molecules whose emissions are uncorrelated. Unpolarized light can be produced from the incoherent combination of vertical and horizontal linearly polarized light, or right- and left-handed circularly polarized light. Conversely, the two constituent linearly polarized states of unpolarized light cannot form an interference pattern, even if rotated into alignment ( Fresnel–Arago 3rd law). A so-called '' depolarizer'' acts on a polarized beam to create one in which the polarization varies so rapidly across the beam that it may be ignored in the intended applications. Conversely, a ''polarizer'' acts on an unpolarized beam or arbitrarily polarized beam to create one which is polarized. Unpolarized light can be described as a mixture of two independent oppositely polarized streams, each wit ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Megaradian
The radian, denoted by the symbol rad, is the unit of angle in the International System of Units (SI) and is the standard unit of angular measure used in many areas of mathematics. It is defined such that one radian is the angle subtended at the centre of a circle by an arc that is equal in length to the radius. The unit was formerly an SI supplementary unit and is currently a dimensionless SI derived unit,: "The CGPM decided to interpret the supplementary units in the SI, namely the radian and the steradian, as dimensionless derived units." defined in the SI as 1 rad = 1 and expressed in terms of the SI base unit metre (m) as . Angles without explicitly specified units are generally assumed to be measured in radians, especially in mathematical writing. Definition One radian is defined as the angle at the center of a circle in a plane that subtends an arc whose length equals the radius of the circle. More generally, the magnitude in radians of a subtended angle is equal t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Exciton-polaritons
In physics, the exciton–polariton is a type of polariton; a hybrid light and matter quasiparticle arising from the strong coupling of the electromagnetic dipolar oscillations of excitons (either in bulk or quantum wells) and photons. Because light excitations are observed classically as photons, which are massless particles, they do not therefore have mass, like a physical particle. This property makes them a quasiparticle. Theory The coupling of the two oscillators, photons modes in the semiconductor optical microcavity and excitons of the quantum wells, results in the energy anticrossing of the bare oscillators, giving rise to the two new normal modes for the system, known as the upper and lower polariton resonances (or branches). The energy shift is proportional to the coupling strength (dependent, e.g., on the field and polarization overlaps). The higher energy or upper mode (UPB, upper polariton branch) is characterized by the photonic and exciton fields oscillating in-phase ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Depolarizer (optics)
A or is an optical device used to scramble the polarization of light. An ideal depolarizer would output randomly polarized light whatever its input, but all practical depolarizers produce pseudo-random output polarization. Optical systems are often sensitive to the polarization of light reaching them (for example grating-based spectrometers). Unwanted polarization of the input to such a system may cause errors in the system's output. Types Cornu depolarizer The Cornu depolarizer was one of the earliest designs, named after its inventor Marie Alfred Cornu. It consists of a pair of 45° prisms of quartz crystal, optically contacted to form a cuboid. The fast axes are 90° apart and 45° from the sides of the depolarizer (see figure). Any ray entering the prism effectively passes through two wave plates. The thickness of these wave plates and therefore their retardance varies across the beam. The phase shift is given by \delta(y) = \frac _2 - n_12y - a). For an inp ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
