TOKUSHIMA — Scientists at Tokushima University transmitted data at 112 gigabits per second (Gbps) using a compact terahertz wireless communication system operating in the 560 gigahertz (GHz) spectrum band. The achievement, detailed in a study published May 16 in the journal Communications Engineering, marks the first time such high-speed data transmission has been demonstrated above 420 GHz.

The researchers developed a terahertz wireless communication system based on microcombs—photonic devices integrated onto microchips that generate precise optical frequencies. They directly bonded an optical fiber to a silicon nitride microresonator to create a compact microcomb system that eliminates the need for precise optical alignment, a common requirement in conventional photonic setups. The resulting transmitter measures just 5 millimeters (0.2 inches) in size, smaller than traditional microcomb systems, which can span 450 millimeters (17.7 inches).

To achieve high data rates, the team employed high-order modulation techniques, using quadrature phase-shift keying (QPSK) to reach 84 Gbps and 16-quadrature amplitude modulation (16QAM) to attain 112 Gbps. The microresonator also features a temperature control function to stabilize optical resonance despite environmental fluctuations. Researchers converted optical signals into 560 GHz terahertz waves through photomixing for wireless transmission.

Conventional photonic systems often rely on bulky laser arrangements and remain vulnerable to phase noise, which degrades signal quality at ultrahigh frequencies. Optical microcombs offer improved stability by generating evenly spaced lines of light, minimizing phase noise. Previous microcomb systems had not simultaneously achieved stable signal generation and high-order modulation suitable for high-speed data transmission.

"This result represents a major step toward practical 6G wireless systems and ultra-high-speed mobile backhaul," said Takeshi Yasui, a professor in Tokushima University's Institute of Post-LED Photonics and co-author of the study. The researchers plan to further reduce phase noise and increase output power to enable even faster data-transfer speeds.

Terahertz waves for future 6G networks are expected to operate above 350 GHz, as lower bands are already congested with 5G signals. Commercial 6G deployment is anticipated by 2030 or later, with theoretical peak speeds reaching 1 terabit per second—over 3,000 times faster than average U.S. 5G speeds of approximately 300 megabits per second.