On-chip OSNR monitoring system based on power-balanced Mach-Zehnder interferometers

Abstract Optical signal-to-noise ratio (OSNR) monitor is a key unit in the modern optical networks, serving as an indicator of the transmission link quality. With the demand for cost efficiency, commercial systems require OSNR monitors with compact footprint, low cost, and less power consumption. In this paper, we demonstrate a fully integrated in-band optical signal-to-noise ratio (OSNR) monitor based on silicon-on-insulator (SOI) platform. Assembling the variable optical attenuators (VOAs) and photodetectors (PDs) together with power-balanced Mach-Zehnder interferometers (MZIs), the device has a compact footprint of 3 mm ×1 mm, and is fabricated through a commercial Multi-Project Wafer (MPW) run. 28 Gbaud NRZ-QPSK signal is used to characterize the device performance, and experimental results show errors within ± 0.5 dB for OSNR range from 7.8 dB to 24.5 dB can be successfully achieved. Furthermore, the robustness of the tested device to signal power and chromatic dispersion is also proved. This monitor has potential to be deployed in the intermediation nodes of transmission links in a cost-effective way.