| 单词 | FWM (Four-Wave Mixing) |
| 释义 | FWM (Four-Wave Mixing) A type of noise created in fiber optic transmission systems (FOTS) when wavelengths interact to create additional wavelengths. FWM occurs in optical fibers engineered with a zero dispersion point at or near the wavelengths being transmitted.The number of additional wavelengths that can result is determined by the following formula: FWM = N2 (N – 1)/2 Based on this formula, 2 wavelengths will produce 2 additional wavelengths, 4 wavelengths will produce 24 additional wavelengths, and 8 wavelengths will produce 224 additional wavelengths. FWM can particularly be a problem at 1550 nm in systems using dense wavelength division multiplexing (DWDM), and especially when erbium-doped fiber amplifiers (EDFAs) are employed.The EDFAs amplify the additional wavelengths and superimpose them on the original wavelengths. Non Zero Dispersion-Shifted Fiber (NZDF) addresses this issue by shifting the optimal dispersion point slightly away from the 1550 nm range where DWDM operates. Fiber fabricated to have a zero dispersion point at 1540 nm or 1560 nm, for example, will reduce dispersion significantly and eliminate the issue of four-wave mixing. See also amplification, dispersion, DWDM, EDFA, NZDF, and wavelength. |
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