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Flexible-Grid Wavelength-Selective Switch Based on Silicon Microring Resonators With Interferometric Couplers

In this paper, a kind of integrated flexible-grid wavelength-selective switch composed of reconfigurable add-drop silicon microring resonators with interferometric couplers is described in detail. Owing to tunable interferometric couplers, the proposed device is capable of realizing an increase in adjustable channel spacing for a given field coupling coefficient. By carefully controlling the path phase differences and tunable interferometric couplers, the transmission spectra of adjacent channels can be selectively combined to form adjustable bandwidths as desired. As an example, an integrated flexible-grid 1 × 2 wavelength-selective switch is designed and theoretically analyzed. The channel spacing can increase from 0.1 to 0.8 nm. When the channel spacing is selected to be 0.8 nm, the bandwidth varies from 0.36 to 2.91 nm and a minimum extinction ratio of 14.8 dB is obtained.