Low-power and Wide-Band 1 × 8 Silica Waveguide Optical Switch

A silica waveguide 1 x 8 thermo-optic switch consisting of cascaded three-stage Mach-Zehnder interferometers (MZIs) is demonstrated. The multimode interference (MMI) coupler is adopted in the MMI-MZI 1 x 2 switch unit due to its insensitivity to wavelength and favorable fabrication tolerance. Beam propagation method (BPM) is used in the switch design and optimization. Standard CMOS technologies have been adopted in the preparation of switch fabric. At 1550 nm, the measurement results of 1 x 8 switch show that the fiber-to-fiber insertion loss ranges from 3.4 to 3.6 dB for all routing states. Meanwhile, the extinction ratio is no less than 15.63 dB, and the crosstalk is restrained to be lower than -15.65 dB. Due the adoption of MZI structure, the average driving power for the channel switching is 315.8 mW. Within the wavelength range from 1500 to 1620 nm, the extinction ratio is larger than 15.06 dB, the insertion loss is less than 5.8 dB, and PDL is smaller than 1.18 dB for all routing states. The experimental results fit the simulations well, which proves the proposed switch good potentials in wideband applications.