A systematic approach for designing zero-DGD coupled multi-core optical   fibers
  An analytical method is presented for designing N-coupled multi-core fibers with zero differential group delay. This approach effectively reduces the problem to a system of N-1 algebraic equations involving the associated coupling coefficients and propagation constants as obtained from coupled mode theory. Once the parameters of one of the cores are specified, the roots of the resulting N-1 equations can then be used to determine the characteristics of the remaining waveguide elements. Using this technique, a number of pertinent geometrical configurations are investigated in order to minimize intermodal dispersion. 
Midya Parto, Mohammad Amin Eftekhar, Mohammad-Ali Miri, Rodrigo   Amezcua-Correa, Guifang Li, Demetrios N. Christodoulides
physics.optics