Dispersion compensation of four-channel high-speed IMDD data using slow-light in a silicon nitride chip

Transmission of high-speed optical data over fiber is inherently limited by optical attenuation and chromatic dispersion, with dispersion impairments becoming increasingly critical as data rates scale and symbol durations shorten. One of the practical solutions is to utilize an integrated photonic device that produces dispersion with the same magnitude but opposite sign, so that net zero aggregate dispersion is achieved in the link. In this work, we demonstrate dispersion compensation of 30 Gb/s NRZ data using an integrated silicon nitride (SiN) grating-based device. The SiN Bragg grating operates in transmission and generates dispersion to counteract the anomalous dispersion intrinsic to the optical fiber using the slow light effect. The dual-period sidewall design is engineered to provide tailored differential group delay characteristics across channels 53, 55, 57, and 59 on the ITU coarse wavelength division multiplexing grid using both transverse electric (TE) and transverse magnetic (TM) modes, enabling effective compensation of accumulated fiber dispersion while maintaining low insertion loss. Experiments show clear improvements in the eye diagrams and reductions in the measured bit error rates after dispersion compensation, confirming the effectiveness of the proposed SiN grating for high-speed 1 by 4 wavelength division multiplexed links. Owing to its CMOS-compatible fabrication, low propagation loss, and sufficiently high dispersion magnitudes for compensation of long fiber propagation lengths, the demonstrated approach offers a compact and scalable solution for dispersion management in short-reach and data-center optical communication systems.