Theory of wavelength multiplexing with rectangular transfer functions

We derive the optimum arrangements suitable for efficient multiplexing and demultiplexing in optical networks. By using a planar arrangement of waveguide arrays, nearly ideal rectangular transfer functions are obtained by using two gratings of opposite dispersions. Two different techniques are described. One of these requires several grating. The other is a reflective interferometer that only requires one grating, in which case each signal must pass twice through the same grating.