Nonlinear dual-core photonic crystal fiber couplers
  We study nonlinear modes of dual-core photonic crystal fiber couplers made of a material with the focusing Kerr nonlinearity. We find numerically the profiles of symmetric, antisymmetric, and asymmetric nonlinear modes, and analyze all-optical switching based on instability of the symmetric mode. We also describe elliptic spatial solitons controlled by the waveguide boundaries. 
Jose R. Salgueiro and Yuri S. Kivshar