High-speed free-space optical communication systems

Due to the scarce resources of RF spectrum and growing demand for higher capacity, there is an increasing interest in the free-space optical communication (FSOC) systems. For example, Google and Facebook have launched Project Loon and Aquila to extend internet connectivity to anywhere in the world by using FSOC-based balloons and drones, respectively. NASA is also employing this technology for energy-efficient and high-speed deep-space communications between spaceship and earth station. We are currently working on various technologies to improve the reliability of high-speed FSOC systems. We also conducting researches to lower the size, weight, and power of FSOC transceivers.

Photonics-based sub-THz technology for 6G and beyond

Current technological advances in wireless communication tell us that future systems should utilize the sub-THz band to deliver hundreds of gigabit per second data to mobile users for cellular networks. However, it is very challenging to generate and detect such high-bandwidth sub-THz wireless signals if we rely only on the traditional electronics. We are currently working on the photonics technologies for the cost-effective and future-proof transmission of sub-THz wireless signals.

Beyond 100G transmission using a single laser

The simplest and most economical method for implementing an optical transmission system is to utilize a directly modulated laser (DML) and a direct-detection receiver. Thus, such a system is widely used in many short- and intermediate-haul applications. However, the performance of this system can be seriously limited by waveform distortions caused by the limited bandwidth of laser and the interplay between the large frequency chirp of laser and fiber chromatic dispersion. We are pushing the limits of this attractive system to see how fast and how far we can transport data.

Transmission technologies for datacenters

Due to the proliferation of cloud services, Internet of Things, social networking, etc., there are strong demands for connectivity inside datacenters and between datacenters. Datacenter is a house of computer systems with storage, each interconnected with one another. There are >1 million optical transceivers in a large datacenter, delivering tens of gigabit data per second. We are focusing on various cost-effective technologies for datacenter applications. Some examples include Stokes-vector receiver and optical single-side band transmission using Kramer-Kronig direct-detection technique.