Excitation coefficients of the guided modes of a parabolic-index optical fiber by narrow input Gaussian beams are calculated. The effects of beam offset, tilt, width, and wave-front curvature are examined. A wave-optical procedure for optimizing the input Gaussian beamwidth (to excite as few mode groups as possible) as a function of beam offset is presented and shown to be in agreement with a simple Fourier-optics optimization.

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and C for the uniform line and right-angled bend, respectively, for frequencies, namely, 0.7 and 2.1 GHz.Note that as one moves away from the discontinuity, the L and C values naturally tend to those corresponding to the uniform line parameters. The variations of L and C versus frequency are consistent, as the predicted value of Z 0 ϭ ͌ L/C is 49.3°at both of the frequencies mentioned above, which, in turn, agrees well with the Z 0 plot shown in Figure 3. The glitch in L distribution that appears in the MoM solution [2] is not observed here, because it is believed to be a numerical artifact appearing in that solution. CONCLUSIONA simple, FDTD-based approach for extracting the parameters of interconnect transmission lines has been introduced. The validity of the method has been demonstrated by analyzing the right-angled bend. The method is straightforward and it enables the desired frequency characteristics to be computed in a single run. 1. J. Zhao and Z.F. Li, A time-domain full-wave extraction method of frequency-dependent equivalent circuit parameters of multiconductor interconnection lines

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