- Отрасли: Telecommunications
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In optical systems, the ratio of emitted optical power of a source to the input electrical power.
Industry:Telecommunications
In optical systems, a ray that is close to and nearly parallel with the optical axis.
Industry:Telecommunications
In optical systems, a field-intensity pattern produced by the mutual interference of partially coherent beams that are subject to minute temporal and spatial fluctuations. Note: In a multimode fiber, a speckle pattern results from a superposition of mode field patterns. If the relative modal group velocities change with time, the speckle pattern will also change with time. If differential mode attenuation occurs, modal noise results.
Industry:Telecommunications
In optical fibers, the absorption of electromagnetic waves, including the near-infrared, due to the presence of trapped hydroxyl ions remaining from water as a contaminant. Note: The hydroxyl (OH-) ion can penetrate glass during or after product fabrication, resulting in significant attenuation of discrete optical wavelengths, e.g., approximately 1. 3 m, used for communications via optical fibers.
Industry:Telecommunications
In optical fiber technology, a method of measuring the transmission loss by (a) using a stable optical source, at the wavelength of interest, to drive a mode scrambler, the output of which overfills (drives) a 1-meter to 2-meter reference fiber having physical and optical characteristics matching those of the fiber under test, (b) measuring the power level at the output of the reference fiber, (c) repeating the procedure, substituting the fiber under test for the reference fiber, and (d) subtracting the power level obtained at the output of the fiber under test from the power level obtained at the output of the reference fiber, to get the transmission loss of the fiber under test. Note 1: The substitution method has certain shortcomings with regard to its accuracy, but its simplicity makes it a popular field test method. It is conservative, in that if it were used to measure the individual losses of several long fibers, and the long fibers were concatenated, the total loss obtained (excluding splice losses) would be expected to be lower than the sum of the individual fiber losses. Note 2: Some modern optical power meters have the capability to set to zero the reference level measured at the output of the reference fiber, so that the transmission loss of the fiber under test may be read out directly.
Industry:Telecommunications
In optical fiber communications, any technique by which two or more optical signals having different wavelengths may be simultaneously transmitted in the same direction over one fiber, and then be separated by wavelength at the distant end.
Industry:Telecommunications
In optical communications, a two-fiber cable consisting essentially of two single-fiber cables having their jackets conjoined by a strip of jacket material. Note 1: This name is borrowed from electrical terminology referring to lamp cord. As with lamp cord, optical zip-cord may be easily furcated by slitting or tearing the two jackets apart, permitting the installation of optical connectors. Note 2: Zip-cord cables include both loose-buffer and tight-buffer designs.
Industry:Telecommunications
In optical communications, a form of modulation in which the optical power output of a source is varied in accordance with some characteristic of the modulating signal. Note: In intensity modulation, there are no discrete upper and lower sidebands in the usually understood sense of these terms, because present optical sources lack sufficient coherence to produce them. The envelope of the modulated optical signal is an analog of the modulating signal in the sense that the instantaneous power of the envelope is an analog of the characteristic of interest in the modulating signal. Recovery of the modulating signal is by direct detection, not heterodyning.
Industry:Telecommunications
In optical communications, a device used to reduce the power level of an optical signal. Note 1: Optical attenuators used in fiber optic communications systems may use a variety of principles for their functioning. Those using the gap-loss principle are sensitive to the modal distribution ahead of the attenuator, and should be used at or near the transmitting end, or they may introduce less loss than intended. Optical attenuators using absorptive or reflective techniques avoid this problem. Note 2: The basic types of optical attenuators are fixed, step-wise variable, and continuously variable.
Industry:Telecommunications
In optical communications, a device that converts an electrical signal into an optical signal. Note: The two most commonly used optical sources are light-emitting diodes (LEDs) and laser diodes. 2. Test equipment that generates a stable optical signal for the purpose of making optical transmission loss measurements.
Industry:Telecommunications
