A general design rule for interleaved arrayed waveguide gratings (IAWGs) is derived. A 1×<i>N</i> WDM switch that is based on a phase shifter array, which is sandwiched between two <i>N</i>-IAWGs, is systematically analyzed. A practical design example of a 1 × 4 nonblocking wavelength division multiplexing (WDM) switch is detailed to illustrate the design steps and the required phase assignment of each phase shifter for various output states. Based on the reciprocity principle, a simplified structure of the 1×<i>N</i> WDM switch is proposed, which requires only one <i>N</i>-IAWG with total reflection implemented at the end of each phase shifter. This type of 1×<i>N</i> WDM switch can be used as a fundamental building block to construct the nonblocking <i>N</i> × <i>N</i> WDM all-optical switch that will be indispensable for future all-optical networks.
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