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Thursday, 18 January 2007 |
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Optical couplers, also known as optocouplers, are a widely used method for interconnecting different circuits. Optocouplers provide electrical isolation between high and low voltage portions of a circuit. An optocoupler comprises an optical signal transmitter, e.g. a light-emitting diode or laser diode, and an optical signal receiver, for example a photodiode or phototransistor. The optical couplers are popularly used in an optical transmission system. Optical fiber technology is used in a variety of applications such as telecommunication, computer, and medical applications. Optical couplers are typically utilized to separate or combine an optic signal, such as an optic signal in a fiber optic cable. Optical radiation is coupled into the end face of an optical fiber by focusing the light onto the core. |
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Friday, 12 January 2007 |
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Optical spectrum analyzers or spectrometers are used for analyzing the output light beams from lasers, light-emitting diodes and other light sources. Optical spectrum analyzers are particularly useful for analyzing light sources in fiber optic systems which are used for high-bandwidth, high-speed voice, video, and data communications. Optical spectrum analyzers typically comprise a tunable filter that bandpass filters an input signal. A detector is used to measure the filtered signal and thereby determine the optical power within the filter's current pass band. Optical spectrum analyzers frequently use a diffraction grating for separating the light beam to be analyzed into its component wavelengths. Spectrum analyzers can be classified into non-real time and real time type spectrum analyzers. |
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Saturday, 06 January 2007 |
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Optical amplifiers are used in the telecommunications industry to amplify modulated light signals transporting information along an optical fiber. A typical optical network includes transceivers, amplifiers, multiplexers and demultiplexers, amplifiers, switches and other components. Optical amplifiers compensate for the attenuation of optical data signals transmitted over long distances, generate optical carriers in optical transceivers and generate optically amplified signals in optical transmission systems. Optical amplifiers are mainly divided into optical fiber amplifiers including erbium doped fiber amplifier and Raman amplifier, and a semiconductor optical amplifier (SOA). EDFAs are used in line amplifiers and other applications requiring high output power, high data rates, and low noise. |
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Monday, 18 December 2006 |
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An optical attenuator is a passive optical component for reducing optical power propagating in an optical fiber, and may perform fixed or variable attenuation. Optical power levels are regulated over wide ranges based on a configuration of an optical telecommunication system. An optical attenuator is used in optical communication networks to reduce an optical power when an optical signal with an excessive power level greater than an allowed power level is received to an optical signal receiver. Variable optical attenuators (VOA) are used to attenuate light beams in optical systems such as fiber optic communication systems. Variable optical attenuators are commonly formed of a blocking structure disposed in a free space region between an input waveguide and an output waveguide. |
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Wednesday, 13 December 2006 |
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Optical modulators are extensively used in optical telecommunication systems to modulate light from a laser source. Optical signals provide high speed, superior signal quality, and minimal interference from outside electromagnetic energy. Optical modulators are one of the key devices for realizing such high-performance optical networks. Indirect modulation involves the use of an optical modulator that responds to the electrical signals that represent the data to be transmitted. The electroabsorption optical modulator is an optical modulator that utilizes the electroabsorption effect that the optical absorption coefficient of a substance varies depending on the electric field applied to it. Mach-Zehnder optical modulator is used as an external modulator in ultra-high-speed communication systems. |
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Wednesday, 06 December 2006 |
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A superluminescent diode (SLD) is a light source with properties intermediate between those of a light-emitting diode (LED) and laser diode. LEDs operating at relatively high powers and having a relatively broad spectral width are called superluminescent light-emitting diodes. Superluminescent diodes are characterized by very much higher power output than LEDs, and by broad band radiation as compared with the narrow spectral frequencies of lasers. SLDs can emit low coherent light at high output power with good directionality. Superluminescent diodes are used in applications such as fiber optic gyroscopes, fiber optic sensors, optical coherence tomography (OCT), and optical communications. SLD is the most suitable light source for the fiber optic rotation sensor. |
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Wednesday, 22 November 2006 |
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An optical power meter measures the light intensity of the input optical signal received by the selected output waveguide. Fiber optics are increasingly being utilized to carry optical energy from a variety of sources such as pulsed modulated signals originating from laser diodes, intensity and wavelength information indicating the sensed substance, and high power laser beams to cut and/or anneal materials. Fiber optic cable has become the predominant transmission media for telecommunications. The proper utilization of fiber optic systems requires precise instruments for measuring optical power and testing the integrity of optical circuits. Fiber optic test instruments are used to characterize the quality of fiber optic links. The optical power levels may be monitored by optical power meters. |
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Wednesday, 15 November 2006 |
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Optical fibers are commonly used for the transmission of all types of data, including telecommunications, video, and computer data. Fiber optic cables have become an alternative to conventional wire transmission. In optic communication networks, optical switches can be used in optical networks to switch light beams from input optical fibers to output optical fibers. Fiber optic switches play very important roles in advanced technologies such as telecommunications, data communications, computer interconnects, optical computing and optical signal processing. Optical switches use various mechanisms to switch light beams from an input to a selected output. Mechanical optic switch realizes switching operation by moving optic fibers or optic elements with mechanical or electromagnetic means. |
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Sunday, 05 November 2006 |
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Organic light emitting diode (OLED) is a semiconductor device capable of converting electrical energy into light energy with a high conversion efficiency. Organic light emitting diodes, also known as organic electroluminescent devices, comprise an anode, a cathode and an electroluminescent medium made up of extremely thin layers separating the anode and the cathode. The organic light emitting diode is a photoelectric device and can convert the electric energy into optical form in high converting efficiency and is usually used in an indicating lamp or a displaying panel. OLED displays have advantages of light emission, high luminous efficiency, wide viewing angle, fast response speed, high reliability, full color, low-voltage drive, low power consumption, and simple fabrication. |
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Wednesday, 25 October 2006 |
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A photodiode is a semiconductor device which converts the photon energy of light into an electrical signal by releasing and accelerating current-conducting carriers within the semiconductor. A photodiode responds to incident electromagnetic radiation by converting the radiation into electrical energy. Avalanche diodes are based on reverse-biased p-n junction diodes operated at voltages above the breakdown voltage. Compared to PIN photodiodes, avalanche photodiodes can measure even lower level light and are used in a wide variety of applications requiring high sensitivity. Photodiodes are widely used in digital imaging devices to convert optical signals into electrical signals. A typical photodiode image sensor comprises at least a reset transistor and a photodiode. |
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Tuesday, 17 October 2006 |
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Optical depolarizers, optical combiners, and optical isolators are commonly used in optical communication systems. Optical isolators are key elements in fiber optic communications systems in which optical signals are produced by lasers. An optical isolator is designed to allow a beam of light to pass through the device in a chosen direction and to prevent the beam of light from passing through the device in the opposite of that chosen direction. An optical isolator comprises a pair of polarizers whose relative optical angle is set at about 45 degrees and a Faraday rotator plate having a Faraday rotation angle of about 45 degrees is inserted between the polarizers. The optical isolator permits passage of light in the forward direction therethrough but inhibits return light in the reverse direction. |
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Saturday, 07 October 2006 |
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A laser is device that produces a monochromatic, coherent light beam through the stimulated emission of photons from atoms, molecules, or ions of an active gain material. A solid-state laser uses a solid-state laser gain medium which converts energy from an optical pump source to a coherent output laser beam. Laser diodes have been recognized as providing an efficient pump source in solid-state laser systems. When employed as a pump source, the laser diode is used to generate light which overlaps the spectral band of the laser medium. Diode-pumped solid-state laser typically includes a rare earth doped solid-state gain medium pumped by optical radiation from a laser diode. Diode pumped lasers involve semiconductor diodes which laser when excited by electrical current. |
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Wednesday, 20 September 2006 |
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Optical fibers are used to transmit light signals from one place to another for a variety of applications. Optical fiber is useful in communication networks to transmit digital and analog information via modulated optical signals. Fiber optic systems provide significantly higher bandwidth and greater performance and reliability than standard copper wire systems. A fiber optic cable comprises an optical fiber concentrically surrounded by a series of protective layers. Optical fiber communication systems comprise a modulated laser source, a length of optical transmission fiber and a receiver. Optical switches are used to selectively couple light from an input fiber to an output fiber. Fiber optic sensors offer many advantages over conventional electronic sensors used to measure temperature, strain, ultrasonic pressure. |
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Tuesday, 12 September 2006 |
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Image sensors are devices capable of converting an image into a digital image. An image sensor captures images by using an energy response characteristic of a semiconductor material to detect the energy. Charge-coupled devices have been the mainstay of conventional imaging circuits for converting images in the form of light energy into electrical signals. Because of the inherent limitations and expense of CCD technology, CMOS imagers have been increasingly used as low cost imaging devices. A complementary metal oxide semiconductor image sensor is a device that converts an optical image to an electrical signal using a CMOS manufacturing technology. The advantages of CMOS imagers over CCD imagers are that CMOS imagers have a low voltage operation and low power consumption. |
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Friday, 01 September 2006 |
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A charge coupled device (CCD) is an active device for transferring, under the control of a clock pulse, a signal charge corresponding to incident light incoming along a predetermined path. Charge coupled devices are used to capture images received in the form of light. In general, a charge coupled device is an image sensor which converts an image signal into an electrical signal. Charge coupled devices are widely used in digital imaging devices such as optical scanners, fax machines, digital copiers, and digital cameras. The signal transfer of a charge coupled device image sensor may be of three types, a frame transfer type, an interline transfer type, and a frame-interline transfer type. Interline transfer-charge coupled device solid state image sensors convert picture information to voltage information. |
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Wednesday, 16 August 2006 |
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Laser diodes are used in a wide range of commercial, medical and military applications, such as in laser printing, optical data storage, long-haul fiber communication, spectroscopy, metrology, barcode scanners, and fiber amplifier pump sources. Laser diodes have been widely using as devices for high speed data transmission or high speed data recording and reading in communications or players in which optical discs are used. Semiconductor lasers or laser diodes generally consist of a planar multi-layered semiconductor structure having one or more active semiconductor layers bounded at their side ends by cleaved surfaces that act as mirrors. A laser diode utilizes current injection, and such a laser is typically fabricated initially from an intrinsic semiconductor heterostructure grown on a substrate. A telecommunication trunk generally uses an optical telecommunication system in which optical fibers carry information traffic in the form of optical signals. |
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Optoelectronics
