Design and characterisation of high-speed monolithic silicon modulators for digital coherent communication

Latest computational and experimental studies on high-speed monolithic silicon-based Mach-Zehnder optical modulators are studied in the light of photonic integrated circuits for digital coherent communication at a bit rate as fast as 128 Gb/s per wavelength channel. Lateral PN-junction rib-waveguide phase shifters are elaborated with experimental characteristics of DC phase shifter response in comparison with computational characteristics. High-speed response in refractive-index dynamics including electron and hole transport in the PN junction is simulated to study speed limit of the phase shifters. The performance in quadrature phase-shift keying signal generation is characterized in experimental and computational constellation diagrams. Silicon waveguides for polarization-division multiplexing are designed in common design rules with the rib-waveguide phase shifters. Long-haul transmission in polarization-multiplexed quadrature phase-shift keying in 1000-km single-mode fiber link is confirmed with a monolithic silicon Mach-Zehnder modulator assembled with modulator drivers in a ceramic-based metal package.