Discrete and Fine Wavelength Tunable Thermo-Optic WSS for Low Power Consumption ${\rm C}{+}{\rm L}$ Band Tunability

Broadband wavelength tunability is demonstrated in a microring resonator (MRR)-based thermo-optic wavelength selective switch (TO-WSS) with low power consumption and low thermal crosstalk. Instead of direct tuning a single MRR spectrum, the discrete and fine wavelength tunability in a Vernier configured TO-WSS has been used to achieve single wavelength selection over a high free spectral range (FSR). With the observed discrete tunability (7.3 mW/FSR) and fine tunability (5 mW/nm) of the WSS, the power requirement for full band tuning can be reduced to 32.7% of that of a single ring tuning.