Abstract-0.4 THz Photonic-Wireless Link With 106 Gb/s Single Channel Bitrate

Shi Jia,  Xiaodan Pang, Oskars Ozolins,  Xianbin Yu, Hao Hu,  Jinlong Yu,  Pengyu Guan,  Francesco Da Ros,  Sergei Popov,  Gunnar Jacobsen,  Michael Galili,  Toshio Morioka,  Darko Zibar,  Leif K. Oxenløwe

http://ieeexplore.ieee.org/document/8118078/

To accommodate the demand of exponentially increased global wireless data traffic, the prospective data rates for wireless communication in the market place will soon reach 100 Gb/s and beyond. In the lab environment, wireless transmission throughput has been elevated to the level of over 100 Gb/s attributed to the development of photonic-assisted millimeter wave and terahertz (THz) technologies. However, most of recent demonstrations with over 100 Gb/s data rates are based on spatial or frequency division multiplexing techniques, resulting in increased system's complexity and energy consumption. Here, we experimentally demonstrate a single channel 0.4 THz photonic-wireless link achieving a net data rate of beyond 100 Gb/s by using a single pair of THz emitter and receiver, without employing any spatial/frequency division multiplexing techniques. The high throughput up to 106 Gb/s within a single THz channel is enabled by combining spectrally efficient modulation format, ultrabroadband THz transceiver and advanced digital signal processing routine. Besides that, our demonstration from system-wide implementation viewpoint also features high transmission stability, and hence shows its great potential to not only decrease the system's complexity, but also meet the requirements of prospective data rates for bandwidth-hungry short-range wireless applications.

Abstract-120 Gb/s Multi-Channel THz Wireless Transmission and THz Receiver Performance Analysis

Shi Jia,  Xianbin Yu,   Hao Hu,  Jinlong Yu, Toshio Morioka,  Peter U. Jepsen,  Leif K. Oxenløwe,


http://ieeexplore.ieee.org/document/7803602/

A photonic multi-channel terahertz (THz) wireless transmission system in the 350-475 GHz band is experimentally demonstrated. The employment of six THz carriers modulated with 10 Gbaud Nyquist quadrature phase-shift keying baseband signal per carrier results in an overall capacity of up to 120 Gb/s. The THz carriers with high-frequency stability and low phase noise are generated based on photonic photomixing of 25-GHz spaced six optical tones and a single optical local oscillator derived from a same optical frequency comb in an ultrabroadband uni-travelling carrier photodiode. The bit-error-rate performance below the hard decision forward error correction threshold of 3.8×10-3 for all the channels is successfully achieved after wireless delivery. Furthermore, we also investigate the influence of the harmonic spurs in a THz receiver on the performance of transmission system, and the experimental results suggest more than 30 dB spur suppression ratio in downconverted intermediate frequency signals for obtaining less than 1 dB interference.

System Combines Optical and Terahertz Signals at 400 GHz

Jack Browne | Microwaves and RF

http://mwrf.com/systems/system-combines-optical-and-terahertz-signals-400-ghz

Data-hungry applications are steadily consuming wireless bandwidth, to the point where network managers are eying available bandwidth at millimeter-wave and even terahertz frequencies. To that end, researchers based in Lyngby, Denmark and Cambridge, England have surveyed efforts at developing terahertz wireless-communications systems and evaluated various methods of designing  terahertz-frequency communications links for high-data-rate applications.

The team learned that links can be assembled completely from electrical components using electromagnetic (EM) energy or from a combination of electrical and optoelectronic technologies. Since higher data rates have been achieved with the latter approach, the researchers propose an optoelectronics terahertz wireless communications system operating in the 400-GHz band; it uses optical signals in a 12.5-GHz ultradense wavelength division multiplexing (UD-WDM) grid.

The research and system development were performed by Xianbin Yu from Zhejiang University (Hangzhou, China) and DTU Fotonik (Department of Photonics Engineering, Technical University of Denmark), along with Rameez Asif of the University of Cambridge  and a team consisting of Molly Piels, Darko Zibar, Michael Galili, Toshio Morioka, Peter Jepsen, and Leif Oxenlowe (also from DTU Fotonik). The terahertz carriers are generated by heterodyne photomixing of free-running optical sources—in this case, a 100-kHz continuous-wave (CW) laser array with frequency stability of ±12.5 GHz and power stability of ±0.003 over 24 h.

This generation of millimeter-wave and terahertz signals is transparent to modulation sources already being used in WDM optical communications systems. The researchers demonstrated the compatibility of their system with optical networks by using spectrally efficient optical Nyquist channels with a quadrature-phase-shift-keying (QPSK) modulation format, as used for commercial 100 Gigabit Ethernet applications.

For testing, a wireless propagation distance was fixed at 50 cm, with path loss of less than 2 dB achieved under optimum conditions. Downconversion was to intermediate-frequency (IF) channels in the 20-GHz band. The researchers achieved aggregated data rates to 60 Gb/s with their system, and showed the potential for a terahertz-frequency communications link that combines optical and EM signals. Current limits in photodiode responsivity and terahertz-frequency amplifiers and antennas limit the practical application of such a system. However, as engineering efforts lead to more components at terahertz frequencies, this is an attractive communications system for short-distance, high-data-rate applications.

See: “400-GHz Wireless Transmission of 60-Gb/s Nyquist-QPSK Signals Using UTC-PD and Heterodyne Mixer,” IEEE Transactions on Terahertz Science and Technology, Vol. 6, No. 6, November 2016, p. 765.