“…Due to small dimensions (few "m  "m), ring resonator based devices can be densely integrated onto optoelectronic chips [10]- [13]. Therefore, the third kind of EO switch reported by our group is based on microring resonator (MRR) structure [14], [15], such as the MRR switch using two-group 2N þ 1 vertical-turning serial-coupled microrings and the grid-type routing switch matrix based on two-ring cross-coupling resonators.…”