Patent ID: 7212712

Claim:
A permutation switch for switching wavelength-division multiplexed signals received from one or more optical waveguides, comprising: (a) a substrate having at least one surface; and (b) a single-mode to multi-mode backward coupler, coupled to said surface of said substrate, for receiving single-mode wavelength division multiplexed signals from said one or more optical waveguides, and for backward coupling said signals into a plurality of single-mode signals, each having its own unique mode; wherein said single-mode to multi-mode backward coupler further comprises: (a) a receiving layer, coupled to said substrate surface, for receiving said single-mode wavelength-division multiplexed signals; (b) a separation layer having a first surface and a second surface, said first surface coupled to said receiving layer, for permitting said backward coupling between said single-mode wavelength-division multiplexed signal and said plurality of single-mode signals; and; (c) a multi-mode waveguide, coupled to said second surface of said separation layer, for receiving said backward coupled plurality of single-mode signals.