Integrated Polarization Beam Splitter for 100/400 GE Polarization Multiplexed Coherent Optical Communications

Monolithically integrated polarization management is a key objective for the next generation of high speed optical coherent receivers, and will enable transmission rates up to 400 Gbps. In this work we present a polarization beam splitter (PBS) based on an asymmetrical Mach-Zehnder interferometer (MZI) monolithically integrated with a coherent receiver. Thermal tuning is incorporated on the MZI arms to partially compensate fabrication errors. We propose a complete model that predicts that thermal tuning can furthermore be used to adjust the wavelength response of the PBS. Measurements on a fully integrated receiver validate this model. We show full tunability of the PBS response within the C-band, with a polarization extinction ratio in excess of 16 dB for devices with an estimated width error up to 75 nm.