We demonstrate experimentally a previously proposed add-drop multiplexer in a two-moded structure with a symmetric Bragg grating. The strong dispersion in the forward direction outside the reflective region of the grating is used to create a phase change for frequencies between the bandgaps of the supermodes of a twin core fiber. The phase change in transmission inverts the interference pattern at the end of the device. Signals within a narrow wavelength range couple out to one core; all other wavelengths couple out to the opposite core. Preliminary experimental results show a crosstalk ratio of 15 dB.
Mattias åslund, Leon Poladian, John Canning, and C. Martijn de Sterke, "Add-Drop Multiplexing By Dispersion Inverted Interference Coupling," J. Lightwave Technol. 20, 1585- (2002)