Integrated optical add-drop multiplexer based on a compact parent-sub microring-resonator structure

A compact parent-sub microring-resonator structure for highly integrated optical add-drop multiplexer (OADM) is proposed and demonstrated by numerical simulation. Due to Vernier effect, large FSR can be obtained by cascaded microrings with relatively large diameter. Furthermore, nearly uniform channel spacing is achieved due to employment of multiple resonances of the parent ring. As a representative example, a 4-channel OADM is simulated. Box-like response with flat passband is obtained by optimizing coupling coefficients. Add-drop crosstalk of −15 dB, drop loss of near 0 dB, and adjacent channel crosstalk of −25 dB can be observed from the calculated transmission spectra. The reconfigurability, loss tolerance as well as the relation between bandwidth and crosstalk are also discussed.