Electromagnetic Fields, Field Confinement, and Energy Flow in Dispersionless Single-Mode Lightguides With Graded-Index Profiles

Our earlier work described a method of designing single-mode lightguides with zero total dispersion by varying the index profile in the core. 1 In the range of wavelengths between 1.3 /im and 1.55 /mi, bandwidths in excess of 100 GHz-Km are attainable by balancing material dispersion with waveguide dispersion. 2 ' 3 However, one of the serious difficulties with single-mode fibers is microbending loss. We know that the microbending loss for the case of the step-index, singlemode fiber is proportional to A2/A3.4'5,6 Here, X refers to the operating wavelength and A to the relative index difference which is defined as: A = (iVcore - ^Vclad) / N c o r e · (1)