Strictly non-blocking 4×4 silicon electro–optic switch matrix
Zhou Pei-Ji, Xing Jie-Jiang, Li Xian-Yao, Li Zhi-Yong, Yu Jin-Zhong, Yu Yu-De†
       
(a) Schematic view of a commonly used 2×2 Mach–Zehnder interferometer (MZI) switch. (b) Cross section view of an implemented p–i–n phase shifter. (c) The principle of electro–optic switch matrix.