MEMS-based wavelength-selective switches

This Ph.D. dissertation focuses on our component and system development for various MEMS wavelength-selective switches (WSS) based on free-space optics. The research includes two major categories: (1) low-voltage-driven 1 x N WSS, and (2) high-port-count 1 x N2 WSS.; The low-voltage-driven 1 x N WSS consists of a grating spectrometer, a linear fiber collimator array, and a low-voltage one-axis analog micromirror array. The one-axis MEMS mirror array is the key component for the 1 x N WSS. We have accomplished a one-axis analog micromirror array driven by hidden vertical comb-drive actuators. It possesses: (1) low actuation voltage---8.5V, more than 10x lower than other competing devices; (2) large mechanical scan angle---+/-6°; (3) excellent angular stability (+/-0.00085°) and repeatability (+/-0.0013°); (4) high mechanical resonant frequency---3.4 kHz; (5) high fill factor--->96%. A 1 x 4 WSS was built using the one-axis scanner array. It exhibits: (1) 5-dB optical insertion loss; (2) excellent stability (+/-0.0035 dB) and repeatability (+/-0.0026 dB); (3) 200-GHz channel spacing; (4) <380-sec switching time.; The high-port-count 1 x N2 WSS increases the port count from N to N 2 by replacing the linear collimator array with a two-dimensional collimator array. Individual wavelength routing is accomplished by cascading two cross-scanning one-axis analog micromirror arrays in a 4-f optical system, or by using a monolithic two-axis micromirror array. The approach of using two cross-scanning one-axis analog micromirror arrays arranged in a 4-f optical configuration leads to a 1 x 5 WSS, scalable to 1 x 14. This WSS demonstrates: (1) 6-dB optical insertion loss; (2) 200-GHz channel spacing; (3) <700-musec switching time. Another approach of using a monolithic two-axis scanner array implements a 1 x 32 WSS, while other researchers reported their WSS's with port counts limited to 4 (1 x 4) by optical diffraction. To our knowledge, this 1 x 32 WSS is the largest-port-count WSS ever reported. The two-axis micromirror array is driven by leverage mechanism. It exhibits: (1) large mechanical scan angles---+/-6.7° at 75V for rotation about both axes; (2) large piston motion---11.7 mum; (3) high mechanical resonant frequency---5.9 kHz; (4) high fill factor---98%. The 1 x 32 WSS demonstrates: (1) 3.72-dB optical insertion loss; (2) 100-GHz channel spacing; (3) <500-musec switching time.