![]() ![]() He holds a B.Tech degree in ceramic technology from Calcutta University, India and M.Tech degree in ceramic technology from IIT-BHU. He joined Sterlite in 1998 as process development engineer in Optical Fiber Plant. Therefore, cut-off wavelengths can not always be precisely determined in experiments.Sudipta Bhaumik is an Associate General Manager – Application Engineering in Sterlite Technologies Limited and located at Sterlite’s Center of Excellence, Aurangabad, India. Therefore, even for moderate bending of the fiber one may obtain sharply increasing propagation losses near the cut-off wavelength. Just below its cut-off wavelength, the bend losses of a mode can become very high due to the increased mode area. In step-index fibers, there is no cut-off for the fundamental (LP 01) mode.įor other fiber designs, in particular for some photonic crystal fibers, there can also be a fundamental cut-off.įibers with not radially symmetric designs (and strongly bent fibers) can have polarization-dependent cut-off wavelengths. The diagram has been produced with the software RP Fiber Power.įor LP lm modes of a fiber, only for l = 0 the fraction of the power guided in the core goes to zero when approaching the cut-off.įor modes with higher l, the mode size stays finite there. The thin vertical lines indicate the calculated cut-off wavelengths of the modes. Figure 1:įraction of the power of various guided modes (where the colors are related to the l indices of those) which is contained in the fiber core as a function of the wavelength. That effect is shown in Figure 1 for a multimode step-index fiber similar behavior occurs for fibers with other transverse refractive index profiles. Typically, the mode radius (and thus the effective mode area) increases sharply near the cut-off, and the fraction of power propagating within the waveguide core decreases accordingly. Just below the cut-off wavelength, the mode properties often vary substantially. When a particular mode ceases to exist beyond a certain wavelength, that wavelength is called its cut-off wavelength.įor an optical fiber, the cut-off wavelength for the LP 11 mode sets a limit to the single-mode regime, as below that wavelength there is at least the LP 01 and the LP 11 mode. The number of guided modes of a waveguide (for example, an optical fiber) depends on the optical wavelength: the shorter the wavelength, the more modes can be guided.įor long wavelengths, there may be only a single guided mode (→ single-mode fibers) or even none at all, whereas multimode behavior is obtained at shorter wavelengths. How to cite the article suggest additional literature Encyclopedia > letter C > cut-off wavelength Cut-off WavelengthĬut-off wavelengths and other properties of guided modes can be calculated with our free fiber optics software RP Fiber Calculator.ĭefinition: a wavelength above which a guided mode of a waveguide ceases to exist ![]()
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