In this research, we design tunable micro-ring resonators and propose the employment of an integrated control circuit to compensate for the fabrication error, and tune as well as lock the wavelength in a thermal-actuated ring-type optical switch through an amplitude modulation scheme. Additional functionalities can also be added in this circuit by tailoring externally the roundtrip loss or coupling constants of the ring. The design concept can be easily scaled up for a large array optical switch system without much change to the terminal numbers thanks to the three-dimensional hierarchy of the high gray-scale control circuit design, which effectively reduces the terminal numbers to the cubic root of the total control unit numbers. The integrated circuit has been designed, simulated, as well as fabricated, and demonstrated a decent performance with free spectral range (FSR) equal to 1.5 nm at 1532 nm and very accurate wavelength modulation to 0.3 nm within 0.01 nm fluctuation for a thermal actuated ring type optical switch.
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