Moving Beyond 5G: Transmitting Uncompressed 4K Video Over Photonics-Based Terahertz Network
Using a directly modulated distributed feedback laser and negative frequency detuning method opens doors toward high-quality video transmission
Photonics-based terahertz (THz) bands, having large bandwidths, are promising candidates for next-generation wireless communication systems. They can transmit data at rates high enough to live-stream uncompressed 4K videos. However, existing THz communication systems are complex and expensive. Now, researchers from Korea have developed a simple and cost-effective photonics-based THz wireless communication system. Utilizing a directly modulated distributed feedback laser and negative frequency detuning method, it successfully transmits 4K video signals over 2.3 meters.
5G, the latest mobile network technology, provides large bandwidths which enable wireless transmission of large amounts of data at high rates for Internet of Things and gaming applications. However, some wireless services, such as live streaming of 4K and 8K videos, require even faster data transmission. In this regard, terahertz (THz) bands, which are much wider than the currently used network bands, are promising. They can transmit over 100 gigabits of data per second — a rate beyond 5G capabilities.
Existing THz-based wireless networks utilize photonic devices, such as external optical modulators, harmonic mixers with local oscillators, and coherent detectors, to generate, transmit, and detect THz band waves, respectively. This makes them expensive to implement. Addressing this issue, a group of researchers led by Dr. Eon-Sang Kim, a postdoctoral researcher at the Optical Network Research Section at the Electronics and Telecommunications Research Institute, has recently developed a simple and cost-effective photonics-based THz wireless communication system for live streaming uncompressed 4K videos. Their work was published online in the ETRI Journal on 25 October 2022.
The present system utilizes a distributed feedback laser diode (DFB-LD) as a light source, which gets directly modulated using a non-return-to-zero on-off keying signal with a data rate of 5.94 gigabits per second — a 6G standard for 4K videos. It results in a modulated DFB-LD output wave which passes through an optical band-pass filter. It negatively detunes the wave frequency to manage adiabatic chirp (the decrease in wave frequency), which helps maintain high signal quality. “Following the frequency detuning, the DFB-LD output is combined with the output of a tunable laser and injected into a uni-traveling-carrier photodiode, which generates a THz wave. It is transmitted using horn antennas and detected by a Schottky barrier diode,” explains Dr. Kim.
The researchers varied the wavelength difference between the DFB-LD and tunable laser outputs to obtain the optimum frequency of the THz wave as 0.29 THz, which provided maximum output power. Additionally, optimized adiabatic chirp management in the THz system increased the extinction ratio — the ratio of maximum and minimum power levels — from 6 to 12 decibels, enhanced the quality of the output THz signal, and maintained the bit error rate below 10–12 over longer transmission distances.
As a result, the developed THz wireless system could successfully transmit uncompressed 4K video signals over 2.3 meters without producing any black frames in the output video. “The present system will enable commercial services requiring high-rate data transmission, including live uncompressed 4K and 8K video streams, holoportation, tactile internet, three-dimensional virtual and augmented reality applications, and real-time telesurgery,” adds Dr. Kim.
We are looking forward to the widespread application of this system!
Reference
Title of original paper: Experimental demonstration of uncompressed 4K video transmission over directly modulated distributed feedback laser-based terahertz wireless link
Name of authors: Eon-Sang Kim1, Sang-Rok Moon1, Minkyu Sung1, Joon Ki Lee1, and Seung-Hyun Cho1
Affiliations: 1Optical Network Research Section, Electronics and Telecommunications Research Institute, Republic of Korea
About Dr. Eon-Sang Kim
Eon-Sang Kim is a postdoctoral researcher at the Optical Network Research Section at the Electronics and Telecommunications Research Institute since 2019. He received a PhD degree in Information and Communication Engineering from the University of Science and Technology in Korea in 2019. His research interests include next-generation optical access networks, mobile fronthaul, indoor distributed antenna systems, radio-over-fiber, and THz wireless transmission system. His group is currently developing THz short distance transmission technology based on photonic devices.
