High-speed silicon-based integrated optical modulators for optical-fiber telecommunications

摘要

A monolithically integrated silicon-based optical modulator is reviewed with respect to design and high-speed performance. The integrated silicon-based optical modulator consists of nested in-phase/quadrature Mach-Zehnder modulator operated in quadrature phase-shift keying formats. Design and performance of high-speed silicon rib-waveguide phase shifters and high-frequency coplanar-waveguide traveling-wave electrode are presented as key modulator elements which allow high-speed zero-chirp operation of the integrated optical modulator in the quadrature phase-shift keying formats. Transmission performance of the integrated optical modulator in differential quadrature phase-shift keying format is characterized in direct-detection constellation-diagram and bit-error-rate measurements towards 44.6-Gbit/s optical-fiber transmission. High-speed quadrature phase-shift keying operation is characterized in coherent-detection constellation-diagram measurements in C and L bands, and QPSK at bit rates up to 64-Gbit/s is presented. A partial-rib-waveguide polarization rotator, which is essential for 128-Gbit/s small-footprint silicon-based optical modulator for digital coherent communication, is described and high-extinction ratio low-loss polarization conversion over C and L bands is evidenced.