METHOD OF RADIAL MODE SELECTION IN AN OPTICAL FIBER USING A THIN ABSORBING CLADDING
V. S. Terentyev, V. A. Simonov
Institute of Automation and Electrometry, Siberian Branch, Russian Academy of Sciences, Novosibirsk, Russia
Keywords: multicladding optical fiber, thin absorbing cladding, mode selection
Abstract
A new method of transverse mode selection in a cylindrical optical fiber using a thin absorbing cladding is proposed. The results of simulations in the COMSOL ® Multiphysics demonstrate the possibility of selecting the HE12 mode based on the losses in a multimode fiber at a wavelength of 1550 nm, when the thin absorbing cladding (with a thickness of 2.5-10 nm) is located in the vicinity of the minima of the field’s components |Er,φ|. The cladding radius is optimized by the minimum of the linear loss α for a given mode; its value is relatively small and varies from -0.02 to -0.06 dB / cm depending on the cladding parameters, while these values for other modes are greater by a factor of tens. An estimated equation for the linear losses is derived for the analytical description. The optimal radii of the absorbing cladding from the viewpoint of minimizing the losses of the selected mode for various absorption coefficients and cladding thicknesses are investigated. It is shown that the spectral dependence of the linear loss coefficient for a given cladding thickness and absorption coefficient is weak.
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