Bandwidth optimization of optical add/drop multiplexers using cascaded couplers and Mach-Zehnder sections

A synthesis of channel add/drop filters consisting of cascaded directional couplers and equal Mach-Zehnder sections is presented within this paper yielding a Chebyshev transmission characteristic and therefore, the optimum distribution of the coupling coefficients with respect to sidelobe suppression and filter bandwidth. It is shown that the number of selectable channels N/sub c/ grows approximately linear with the number of filter stages N, resulting in an equal number of channels and filter stages for a 20-dB sidelobe suppression.<<ETX>>