Silicon ring resonator based optical phase shifter for higher order modulation formats

In this paper, we demonstrate a silicon-on-insulator (SOI)-based optical phase shifter that combines the through and drop ports of a silicon add-drop microring resonator (MRR) modulator. The measured intensity spectra for different bias voltages show that we achieve a 4.29 dB reduction in maximum intensity variation compared to the maximum intensity variation observed at the through port for a ∼2 π phase shift. We also recovered the phase spectrum by placing the optical phase shifter in one arm of an integrated Mach-Zehnder interferometer (MZI) structure. We achieved a full 2 π phase shift of a continuous wave (CW) optical signal with a maximum of ∼4.38 dB of intensity variation. Finally, we created the constellation map of an 8-ary phase-shift keying (8-PSK) data signal based on the recovered phase and the intensity at different forward bias voltages.