fig5
Figure 5. Schematic diagram of the working principle of the MMI-MZI type TOSs: (A) “bar” status; (B) “cross” status. The arrow indicates the direction of light propagation in the yellow-highlighted waveguide. Deep red sections represent the heating electrodes with voltage applied, while light red ones indicate electrodes with no applied voltage. MMI: Multimode interference; MZI: Mach-Zehnder interferometer; TOSs: thermo-optic switches.
