Programmable On-chip Electro-optic Frequency Comb Generation for DWDM Applications

Project: Research

View graph of relations


The global internet traffic is expected to reach 4.8 trillion gigabytes (4.8 ZB) in 2022, which approximately corresponds to 1 hour of YouTube streaming every day for everyone in the world. As a result, the existing optical fiber links that support the underlining telecommunication networks and datacenters will soon become obsolete, urgently demanding more compact, lower cost, higher speed and more energy efficient optical interconnect solutions. Photonic integrated circuits hold great promise to address this demand by miniaturizing and integrating various optical components on the same microchip. One prominent example is a chip-based electro-optic frequency comb (EO comb) source that produces a series of equally spaced frequency lines, potentially replacing the many individual lasers in a dense wavelength-division multiplexing (DWDM) optical communication systems. A major challenge for current on-chip EO combs to be used in DWDM applications is thetrade-offbetween the comb span and the power flatness. To address this challenge, we propose to precisely program the comb profile by creating mode splitting at selected resonant modes, which abruptly cuts off the sideband generation process and limits the EO comb power within the designed wavelength range. The selective mode splitting will be achieved by engineering the width profile along the circumference of a lithium niobate (LiNbO3, LN) microresonator. PI has previously demonstrated a number of LN-based frequency comb generation devices, including resonant EO comb with more than 900 comb lines spanning > 80 nm bandwidth, as well as soliton mode-locked Kerr frequency combs, which lay important foundation for the current project. Our preliminary simulation results suggest that the proposed scheme can effectively generate an EO comb with DWDM-compatible channel spacing, wavelength span and spectral flatness. Importantly, the proposed EO comb does not require exotic resonator quality factors and is achievable using the nanofabrication facilities at City University of Hong Kong, as indicated by our preliminary fabrication and testing results. The successful accomplishment of this project will deliver a chip-based resonant EO comb that is compact, energy-efficient and most importantly DWDM compatible. The system can be further integrated with other LN photonic components to realize a fully on-chip DWDM optical transmitter system with ultrahigh bandwidths and low power consumption, ideally suited for future datacenter communication networks. The excellent programmability of the proposed EO comb spectrum could also enable a wide range of applications including spectroscopy, remote sensing and precision metrology. 


Project number9043159
Grant typeGRF
Effective start/end date1/01/22 → …