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Optical Circulators
An optical circulator is a three- or four-port optical device designed such that light entering any port exits from the next. This means that if light enters port 1 it is emitted from port 2, but if some of the emitted light is reflected back to the circulator, it does not come out of port 1 but instead exits from port 3. This is analogous to the operation of an electronic circulator. Fiber-optic circulators are used to separate optical signals that travel in opposite directions in an optical fiber, for example to achieve bi-directional transmission over a single fiber. Because of their high isolation of the input and reflected optical powers and their low insertion loss, optical circulators are widely used in advanced communication systems and fiber-optic sensor applications. Optical circulators are ''non-reciprocal'' optics, which means that changes in the properties of light passing through the device are not reversed when the light passes through in the opposite direction. Thi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Optical Device
Optics is the branch of physics that studies the behaviour and properties of light, including its interactions with matter and the construction of instruments that use or detect it. Optics usually describes the behaviour of visible, ultraviolet, and infrared light. Because light is an electromagnetic wave, other forms of electromagnetic radiation such as X-rays, microwaves, and radio waves exhibit similar properties. Most optical phenomena can be accounted for by using the classical electromagnetic description of light. Complete electromagnetic descriptions of light are, however, often difficult to apply in practice. Practical optics is usually done using simplified models. The most common of these, geometric optics, treats light as a collection of rays that travel in straight lines and bend when they pass through or reflect from surfaces. Physical optics is a more comprehensive model of light, which includes wave effects such as diffraction and interference that cannot be ac ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Light
Light or visible light is electromagnetic radiation that can be perceived by the human eye. Visible light is usually defined as having wavelengths in the range of 400–700 nanometres (nm), corresponding to frequencies of 750–420 terahertz, between the infrared (with longer wavelengths) and the ultraviolet (with shorter wavelengths). In physics, the term "light" may refer more broadly to electromagnetic radiation of any wavelength, whether visible or not. In this sense, gamma rays, X-rays, microwaves and radio waves are also light. The primary properties of light are intensity, propagation direction, frequency or wavelength spectrum and polarization. Its speed in a vacuum, 299 792 458 metres a second (m/s), is one of the fundamental constants of nature. Like all types of electromagnetic radiation, visible light propagates by massless elementary particles called photons that represents the quanta of electromagnetic field, and can be analyzed as both waves and par ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Circulator
A circulator is a passive, non-reciprocal three- or four-port device that only allows a microwave or radio-frequency signal to exit through the port directly after the one it entered. Optical circulators have similar behavior. Ports are where an external waveguide or transmission line, such as a microstrip line or a coaxial cable, connects to the device. For a three-port circulator, a signal applied to port 1 only comes out of port 2; a signal applied to port 2 only comes out of port 3; a signal applied to port 3 only comes out of port 1, and so on. An ideal three-port circulator has the following scattering matrix: :S = \begin 0 & 0 & 1\\ 1 & 0 & 0 \\ 0 & 1 & 0 \end Types Depending on the materials involved, circulators fall into two main categories: ferrite circulators and nonferrite circulators. Ferrite Ferrite circulators are radio-frequency circulators which employ magnetized microwave ferrite materials. They fall into two main classes: differential phase shift circ ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Optical Fiber
An optical fiber, or optical fibre in Commonwealth English, is a flexible, transparent fiber made by drawing glass (silica) or plastic to a diameter slightly thicker than that of a human hair. Optical fibers are used most often as a means to transmit light between the two ends of the fiber and find wide usage in fiber-optic communications, where they permit transmission over longer distances and at higher bandwidths (data transfer rates) than electrical cables. Fibers are used instead of metal wires because signals travel along them with less loss; in addition, fibers are immune to electromagnetic interference, a problem from which metal wires suffer. Fibers are also used for illumination and imaging, and are often wrapped in bundles so they may be used to carry light into, or images out of confined spaces, as in the case of a fiberscope. Specially designed fibers are also used for a variety of other applications, some of them being fiber optic sensors and fiber lasers. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Optical Isolator
An optical isolator, or optical diode, is an optical component which allows the transmission of light in only one direction. It is typically used to prevent unwanted feedback into an optical oscillator, such as a laser cavity. The operation of ome ofthe devices depends on the Faraday effect (which in turn is produced by magneto-optic effect), which is used in the main component, the Faraday rotator. Theory The main component of the optical isolator is the Faraday rotator. The magnetic field, B, applied to the Faraday rotator causes a rotation in the polarization of the light due to the Faraday effect. The angle of rotation, \beta, is given by, :\beta=\nu B d\,, where, \nu is the Verdet constant of the material (amorphous or crystalline solid, or liquid, or crystalline liquid, or vaprous, or gaseous) of which the rotator is made, and d is the length of the rotator. This is shown in Figure 2. Specifically for an optical isolator, the values are chosen to give a rotation of 45Â ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Insertion Loss
In telecommunications, insertion loss is the loss of signal power resulting from the insertion of a device in a transmission line or optical fiber and is usually expressed in decibels (dB). If the power transmitted to the load before insertion is ''P''T and the power received by the load after insertion is ''P''R, then the insertion loss in decibels is given by, :IL(\mathrm) = 10 \log_ Electronic filters Insertion loss is a figure of merit for an electronic filter and this data is generally specified with a filter. Insertion loss is defined as a ratio of the signal level in a test configuration without the filter installed (\left\vert V_1 \right\vert) to the signal level with the filter installed (\left\vert V_2 \right\vert). This ratio is described in decibels by the following equation: :\mbox = 10 \log_ = 20 \log_ For passive filters, \left\vert V_2 \right\vert will be smaller than \left\vert V_1 \right\vert. In this case, the insertion loss is positive and measures ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fiber Optic Communications
Fiber-optic communication is a method of transmitting information from one place to another by sending pulses of infrared light through an optical fiber. The light is a form of carrier wave that is modulated to carry information. Fiber is preferred over electrical cabling when high bandwidth, long distance, or immunity to electromagnetic interference is required. This type of communication can transmit voice, video, and telemetry through local area networks or across long distances. Optical fiber is used by many telecommunications companies to transmit telephone signals, internet communication, and cable television signals. Researchers at Bell Labs have reached a record bandwidth–distance product of over kilometers per second using fiber-optic communication. Background First developed in the 1970s, fiber-optics have revolutionized the telecommunications industry and have played a major role in the advent of the Information Age. Because of its advantages over electric ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fiber-optic Sensor
A fiber-optic sensor is a sensor that uses optical fiber either as the sensing element ("intrinsic sensors"), or as a means of relaying signals from a remote sensor to the electronics that process the signals ("extrinsic sensors"). Fibers have many uses in remote sensing. Depending on the application, fiber may be used because of its small size, or because no electrical power is needed at the remote location, or because many sensors can be multiplexed along the length of a fiber by using light wavelength shift for each sensor, or by sensing the time delay as light passes along the fiber through each sensor. Time delay can be determined using a device such as an optical time-domain reflectometer and wavelength shift can be calculated using an instrument implementing optical frequency domain reflectometry. Fiber-optic sensors are also immune to electromagnetic interference, and do not conduct electricity so they can be used in places where there is high voltage electricity or flam ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Magnetic Field
A magnetic field is a vector field that describes the magnetic influence on moving electric charges, electric currents, and magnetic materials. A moving charge in a magnetic field experiences a force perpendicular to its own velocity and to the magnetic field. A permanent magnet's magnetic field pulls on ferromagnetic materials such as iron, and attracts or repels other magnets. In addition, a nonuniform magnetic field exerts minuscule forces on "nonmagnetic" materials by three other magnetic effects: paramagnetism, diamagnetism, and antiferromagnetism, although these forces are usually so small they can only be detected by laboratory equipment. Magnetic fields surround magnetized materials, and are created by electric currents such as those used in electromagnets, and by electric fields varying in time. Since both strength and direction of a magnetic field may vary with location, it is described mathematically by a function assigning a vector to each point of space, cal ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Faraday Rotator
A Faraday rotator is a polarization rotator based on the Faraday effect, a magneto-optic effect involving transmission of light through a material when a longitudinal static magnetic field is present. The state of polarization (such as the axis of linear polarization or the orientation of elliptical polarization) is rotated as the wave traverses the device, which is explained by a slight difference in the phase velocity between the left and right circular polarizations. Thus it is an example of ''circular birefringence'', as is optical activity, but involves a material only having this property in the presence of a magnetic field. Circular birefringence, involving a difference in propagation between opposite ''circular'' polarizations, is distinct from ''linear birefringence'' (or simply birefringence, when the term is not further specified) which also transforms a wave's polarization but not through a simple rotation. The polarization state is rotated in proportion to the applied ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Optical Isolator
An optical isolator, or optical diode, is an optical component which allows the transmission of light in only one direction. It is typically used to prevent unwanted feedback into an optical oscillator, such as a laser cavity. The operation of ome ofthe devices depends on the Faraday effect (which in turn is produced by magneto-optic effect), which is used in the main component, the Faraday rotator. Theory The main component of the optical isolator is the Faraday rotator. The magnetic field, B, applied to the Faraday rotator causes a rotation in the polarization of the light due to the Faraday effect. The angle of rotation, \beta, is given by, :\beta=\nu B d\,, where, \nu is the Verdet constant of the material (amorphous or crystalline solid, or liquid, or crystalline liquid, or vaprous, or gaseous) of which the rotator is made, and d is the length of the rotator. This is shown in Figure 2. Specifically for an optical isolator, the values are chosen to give a rotation of 45Â ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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