Multichannel frequency-selective switch employing an arrayed-waveguide grating multiplexer with fold-back optical paths

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Abstract
The optimized configuration of an N-channel frequency-selective 2/spl times/2 switch based on an arrayed-waveguide grating (AWG) (2N+1)/spl times/(2N+1) multiplexer is proposed that offers significant crosstalk reduction and loss-imbalance equalization. The optimization is achieved by employing fold-back optical paths instead of loop-back paths. A switch constructed with a silica-based AWG 16/spl times/16 multiplexer demonstrates coherent crosstalk of less than -30 dB in the transmitting frequency-division-multiplexed (FDM) channels; the gain in optimization is more than 15 dB. The largest loss-difference among the seven FDM channels is simultaneously reduced from 4.5 dB to 1.6 dB. These improvements will extend the cascadable number of nodes in all-optical FDM networks.