MULTICHANNEL FREQUENCY-SELECTIVE SWITCH EMPLOYING AN ARRAYED-WAVE-GUIDE GRATING MULTIPLEXER AND FOLDBACK OPTICAL PATHS

The optimized configuration of an N-channel frequency-selective 2 x 2 switch based on an arrayed-waveguide grating (AWG) (2N + 1) x (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 x 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.