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Wavelength Selective Switching
Wavelength selective switching components are used in WDM optical communications networks to route (switch) signals between optical fibres on a per-wavelength basis. What is a WSS A WSS comprises a switching array that operates on light that has been dispersed in wavelength without the requirement that the dispersed light be physically demultiplexed into separate ports. This is termed a ‘disperse and switch’ configuration. For example, an 88 channel WDM system can be routed from a “common” fiber to any one of N fibers by employing 88 1 x N switches. This represents a significant simplification of a demux and switch and multiplex architecture that would require (in addition to N +1 mux/demux elements) a non-blocking switch for 88 N x N channels which would test severely the manufacturability limits of large-scale optical cross-connects for even moderate fiber counts. A more practical approach, and one adopted by the majority of WSS manufacturers is shown schematically i ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Wavelength-division Multiplexing
In fiber-optic communications, wavelength-division multiplexing (WDM) is a technology which multiplexes a number of optical carrier signals onto a single optical fiber by using different wavelengths (i.e., colors) of laser light. This technique enables bidirectional communications over a single strand of fiber (also called wavelength-division duplexing) as well as multiplication of capacity. The term WDM is commonly applied to an optical carrier, which is typically described by its wavelength, whereas frequency-division multiplexing typically applies to a radio carrier, more often described by frequency. This is purely conventional because wavelength and frequency communicate the same information. Specifically, frequency (in Hertz, which is cycles per second) multiplied by wavelength (the physical length of one cycle) equals velocity of the carrier wave. In a vacuum, this is the speed of light (usually denoted by the lowercase letter, c). In glass fiber, velocity is substan ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Grism
A grism (also called a grating prism) is a combination of a prism and grating arranged so that light at a chosen central wavelength passes straight through. The advantage of this arrangement is that one and the same camera can be used both for imaging (without the grism) and spectroscopy (with the grism) without having to be moved. Grisms are inserted into a camera beam that is already collimated. They then create a dispersed spectrum centered on the object's location in the camera's field of view. The resolution of a grism is proportional to the tangent of the wedge angle of the prism in much the same way as the resolutions of gratings are proportional to the angle between the input and the normal to the grating. The dispersed wavefront sensing system (as part the NIRCam instrument) on the James Webb Space Telescope uses grisms. The system allows coarse optical path length matching between the different mirror segments. See also * Diffraction grating * Echelle grating An e ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
MEMS
MEMS (micro-electromechanical systems) is the technology of microscopic devices incorporating both electronic and moving parts. MEMS are made up of components between 1 and 100 micrometres in size (i.e., 0.001 to 0.1 mm), and MEMS devices generally range in size from 20 micrometres to a millimetre (i.e., 0.02 to 1.0 mm), although components arranged in arrays (e.g., digital micromirror devices) can be more than 1000 mm2. They usually consist of a central unit that processes data (an integrated circuit chip such as microprocessor) and several components that interact with the surroundings (such as microsensors). Because of the large surface area to volume ratio of MEMS, forces produced by ambient electromagnetism (e.g., electrostatic charges and magnetic moments), and fluid dynamics (e.g., surface tension and viscosity) are more important design considerations than with larger scale mechanical devices. MEMS technology is distinguished from molecular nanotechnolo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Loop Performance
Loop performance in control engineering indicates the performance of control loops, such as a regulatory PID loop. Performance refers to the accuracy of a control system's ability to track (output) the desired signals to regulate the plant process variables in the most beneficial and optimised way, without delay or overshoot. Importance Regulatory control loops are critical in automated manufacturing and utility industries like refining, paper and chemicals manufacturing, power generation, among others. They are used to control a particular parameter within a process. The parameter that is being controlled could be temperature, pressure, flow or level of some process. For example, temperature controllers are used in boilers which are used in production of gasoline. Software There are many software applications that help in measuring and analysing the performance of control loops in industrial plants. Benchmarking Benchmarking is the practice of comparing business processes and ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Liquid Crystal On Silicon
Liquid crystal on silicon (LCoS or LCOS) is a miniaturized reflective active-matrix liquid-crystal display or "microdisplay" using a liquid crystal layer on top of a silicon backplane. It is also known as a spatial light modulator. LCoS initially was developed for projection televisions, but has since found additional uses in wavelength selective switching, structured illumination, near-eye displays and optical pulse shaping. LCoS is distinct from other LCD projector technologies which use transmissive LCD, allowing light to pass through the light processing unit (s). LCoS is more similar to Digital Light Processing, DLP micro-mirror displays. Technology The Hughes liquid crystal light valve (LCLV) was designed to modulate a high-intensity light beam using a weaker light source, conceptually similar to how an amplifier increases the amplitude of an electrical signal; LCLV was named after the common name for the triode vacuum tube. A high-resolution, low-intensity light source ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Optical Devices
An optical instrument is a device that processes light waves (or photons), either to enhance an image for viewing or to analyze and determine their characteristic properties. Common examples include periscopes, microscopes, telescopes, and cameras. Image enhancement The first optical instruments were telescopes used for magnification of distant images, and microscopes used for magnifying very tiny images. Since the days of Galileo and Van Leeuwenhoek, these instruments have been greatly improved and extended into other portions of the electromagnetic spectrum. The binocular device is a generally compact instrument for both eyes designed for mobile use. A camera could be considered a type of optical instrument, with the pinhole camera and camera obscura being very simple examples of such devices. Analysis Another class of optical instrument is used to analyze the properties of light or optical materials. They include: *Interferometer for measuring the interference properties of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
