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Multimode Distortion
Modal dispersion is a distortion mechanism occurring in multimode fibers and other waveguides, in which the signal is spread in time because the Wave propagation, propagation velocity of the optical signal is not the same for all normal mode, modes. Other names for this phenomenon include multimode distortion, multimode dispersion, modal distortion, intermodal distortion, intermodal dispersion, and intermodal delay distortion. In the ray optics analogy, modal dispersion in a step-index optical fiber may be compared to multipath propagation of a radio, radio signal. Rays of light enter the fiber with different angles to the fiber axis, up to the fiber's Guided ray, acceptance angle. Rays that enter with a shallower angle travel by a more direct path, and arrive sooner than rays that enter at a steeper angle (which reflection (physics), reflect many more times off the boundaries of the core as they travel the length of the fiber). The arrival of different components of the signal at ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Multimode Fiber
Multi-mode optical fiber is a type of optical fiber mostly used for communication over short distances, such as within a building or on a campus. Multi-mode links can be used for data rates up to 800 Gbit/s. Multi-mode fiber has a fairly #Comparison with single-mode fiber, large core diameter that enables multiple light normal mode, modes to be propagated and limits the maximum length of a transmission link because of modal dispersion. The standard G.651.1 defines the most widely used forms of multi-mode optical fiber. Applications The equipment used for communications over multi-mode optical fiber is less expensive than that for single-mode optical fiber. Typical transmission speed and distance limits are 100 Mbit/s for distances up to 2 km (100BASE-FX), 1 Gbit/s up to 1000 m, and 10 Gbit/s up to 550 m. Because of its high capacity and reliability, multi-mode optical fiber generally is used for backbone applications in buildings. An increasin ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fiber Axis
An optical axis is an imaginary line that passes through the geometrical center of an optical system such as a camera lens, microscope or telescopic sight. Lens elements often have rotational symmetry about the axis. The optical axis defines the path along which light propagates through the system, up to first approximation. For a system composed of simple lenses and mirrors, the axis passes through the center of curvature of each surface, and coincides with the axis of rotational symmetry. The optical axis is often coincident with the system's mechanical axis, but not always, as in the case of off-axis optical systems. For an optical fiber, the optical axis is along the center of the fiber core, and is also known as the ''fiber axis''. See also * Ray (optics) * Cardinal point (optics) In Gaussian optics, the cardinal points consist of three pairs of Point (geometry), points located on the optical axis of a Rotational symmetry, rotationally symmetric, focal, optical system. ... [...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] |
Chromatic Dispersion
Dispersion is the phenomenon in which the phase velocity of a wave depends on its frequency. Sometimes the term chromatic dispersion is used to refer to optics specifically, as opposed to wave propagation in general. A medium having this common property may be termed a dispersive medium. Although the term is used in the field of optics to describe light and other electromagnetic waves, dispersion in the same sense can apply to any sort of wave motion such as acoustic dispersion in the case of sound and seismic waves, and in gravity waves (ocean waves). Within optics, dispersion is a property of telecommunication signals along transmission lines (such as microwaves in coaxial cable) or the pulses of light in optical fiber. In optics, one important and familiar consequence of dispersion is the change in the angle of refraction of different colors of light, as seen in the spectrum produced by a dispersive prism and in chromatic aberration of lenses. Design of compound achr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Graded Refractive Index
A graded-index fiber, or gradient-index fiber, is an optical fiber whose core has a refractive index that decreases ''continuously'' with increasing radial distance from the optical axis of the fiber, as opposed to a step-index fiber, which has a uniform index of refraction in the core, and a lower index in the surrounding cladding. Because parts of the core closer to the fiber axis have a higher refractive index than the parts near the cladding, light rays follow sinusoidal paths down the fiber. The most common refractive index profile for a graded-index fiber is very nearly parabolic. The parabolic profile results in continual refocusing of the rays in the core, and minimizes modal dispersion. Multi-mode optical fiber can be built with either a graded-index or a step-index profile. The advantage of graded-index multi-mode fiber compared to step-index fiber is a considerable decrease in modal dispersion. This means that the trip time of photons traversing the fiber is mor ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Micrometre
The micrometre (English in the Commonwealth of Nations, Commonwealth English as used by the International Bureau of Weights and Measures; SI symbol: μm) or micrometer (American English), also commonly known by the non-SI term micron, is a unit of length in the International System of Units (SI) equalling (SI standard prefix "micro-" = ); that is, one millionth of a metre (or one thousandth of a millimetre, , or about ). The nearest smaller common SI Unit, SI unit is the nanometre, equivalent to one thousandth of a micrometre, one millionth of a millimetre or one billionth of a metre (). The micrometre is a common unit of measurement for wavelengths of infrared radiation as well as sizes of biological cell (biology), cells and bacteria, and for grading wool by the diameter of the fibres. The width of a single human hair ranges from approximately 20 to . Examples Between 1 μm and 10 μm: * 1–10 μm – length of a typical bacterium * 3–8 μm – width of str ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bandwidth (signal Processing)
Bandwidth is the difference between the upper and lower Frequency, frequencies in a continuous Frequency band, band of frequencies. It is typically measured in unit of measurement, unit of hertz (symbol Hz). It may refer more specifically to two subcategories: ''Passband bandwidth'' is the difference between the upper and lower cutoff frequencies of, for example, a band-pass filter, a communication channel, or a signal spectrum. ''Baseband bandwidth'' is equal to the upper cutoff frequency of a low-pass filter or baseband signal, which includes a zero frequency. Bandwidth in hertz is a central concept in many fields, including electronics, information theory, digital communications, radio communications, signal processing, and spectroscopy and is one of the determinants of the capacity of a given communication channel. A key characteristic of bandwidth is that any band of a given width can carry the same amount of information, regardless of where that band is located in the f ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Reflection (physics)
Reflection is the change in direction of a wavefront at an interface between two different media so that the wavefront returns into the medium from which it originated. Common examples include the reflection of light, sound and water waves. The ''law of reflection'' says that for specular reflection (for example at a mirror) the angle at which the wave is incident on the surface equals the angle at which it is reflected. In acoustics, reflection causes echoes and is used in sonar. In geology, it is important in the study of seismic waves. Reflection is observed with surface waves in bodies of water. Reflection is observed with many types of electromagnetic wave, besides visible light. Reflection of VHF and higher frequencies is important for radio transmission and for radar. Even hard X-rays and gamma rays can be reflected at shallow angles with special "grazing" mirrors. Reflection of light Reflection of light is either '' specular'' (mirror-like) or '' diffuse'' (retai ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Guided Ray
A guided ray (also bound ray or trapped ray) is a ray of light in a multi-mode optical fiber, which is confined by the core. For step index fiber, light entering the fiber will be guided if it falls within the acceptance cone of the fiber, that is if it makes an angle with the fiber axis that is less than the acceptance angle, :\theta < \arcsin \left( \sqrt \right) , where :''θ'' is the angle the ray makes with the fiber axis, ''before'' entering the fiber, :''n''0 is the along the central axis (core) of the fiber, and :''n''c is the refractive index of the cladding. The quantity is the of the fiber. The quantity |
Radio
Radio is the technology of communicating using radio waves. Radio waves are electromagnetic waves of frequency between 3 hertz (Hz) and 300 gigahertz (GHz). They are generated by an electronic device called a transmitter connected to an antenna which radiates the waves. They can be received by other antennas connected to a radio receiver; this is the fundamental principle of radio communication. In addition to communication, radio is used for radar, radio navigation, remote control, remote sensing, and other applications. In radio communication, used in radio and television broadcasting, cell phones, two-way radios, wireless networking, and satellite communication, among numerous other uses, radio waves are used to carry information across space from a transmitter to a receiver, by modulating the radio signal (impressing an information signal on the radio wave by varying some aspect of the wave) in the transmitter. In radar, used to locate and track ob ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Waveguide
A waveguide is a structure that guides waves by restricting the transmission of energy to one direction. Common types of waveguides include acoustic waveguides which direct sound, optical waveguides which direct light, and radio-frequency waveguides which direct electromagnetic waves other than light like radio waves. Without the physical constraint of a waveguide, waves would expand into three-dimensional space and their intensities would decrease according to the inverse square law. There are different types of waveguides for different types of waves. The original and most common meaning is a hollow conductive metal pipe used to carry high frequency radio waves, particularly microwaves. Dielectric waveguides are used at higher radio frequencies, and transparent dielectric waveguides and optical fibers serve as waveguides for light. In acoustics, air ducts and horns are used as waveguides for sound in musical instruments and loudspeakers, and specially-shaped metal rod ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Multipath Propagation
In radio communication, multipath is the propagation phenomenon that results in radio signals reaching the receiving antenna by two or more paths. Causes of multipath include atmospheric ducting, ionospheric reflection and refraction, and reflection from water bodies and terrestrial objects such as mountains and buildings. When the same signal is received over more than one path, it can create interference and phase shifting of the signal. Destructive interference causes fading; this may cause a radio signal to become too weak in certain areas to be received adequately. For this reason, this effect is also known as multipath interference or multipath distortion. Where the magnitudes of the signals arriving by the various paths have a distribution known as the Rayleigh distribution, this is known as Rayleigh fading. Where one component (often, but not necessarily, a line of sight component) dominates, a Rician distribution provides a more accurate model, and this is k ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
