Research Overview

My work is centred on high-capacity Terahertz (THz) wireless communications
and their integration into future 6G photonic network infrastructures.
At Fraunhofer HHI I develop advanced digital signal processing techniques
and experimental systems pushing beyond 100 Gbit/s over THz wireless links.
I also serve as a University Lecturer at HTW Berlin and BHT Berlin,
teaching communications engineering at Bachelor’s and Master’s level.

  • THz Wireless
  • DSP
  • Photonic Networks

Affiliations & Memberships

Fraunhofer TU Berlin HTW Berlin BHT Berlin KIT Karlsruhe KAIST Baden-Württemberg Stiftung EnBW Siemens IEEE
Terahertz wireless communications

Terahertz Wireless
Communications

I design and characterise experimental high-speed wireless transmission systems operating in the 300 GHz band (WR-3). My research covers the full signal chain — from photonic upconversion using PIN photodiode and WR3-coupled transmitters through to receiver-side DSP and link characterisation — with demonstrated throughputs exceeding 109 Gbit/s over fiber-integrated point-to-point THz links, and a record 221 Gb/s dual-polarisation transmission over 500 m.

Probabilistic Constellation Shaping

Probabilistic Constellation
Shaping & Rate Adaptation

A central theme of my research is Probabilistic Constellation Shaping (PCS) applied to THz wireless links. PCS enables flexible, rate-adaptive modulation by biasing the symbol distribution toward the Shannon limit. I study time-adaptive PCS for combined optical/THz links, the impact of photodiode nonlinearities on shaped transmissions, and their mitigation via neural-network-based DSP.

Converged optical and THz networks for 6G

Converged Optical & THz
Links for 6G Networks

I investigate the seamless integration of THz wireless segments into fiber-optic backhaul networks targeting future 6G requirements. This includes analysis of weather-related link availability for outdoor THz deployments, high-capacity system design supporting 6G transport, and adaptive baseband techniques for converged optical/THz links — the subject of my PhD dissertation at TU Berlin.

Publications

Complete list of first-author and co-authored publications.
Google Scholar  •  IEEE Xplore

  • IEEE PTL — Submitted

    In-Ho Baek, J. Honecker, M. Bittiehn, R. Elschner, C. Schubert, R. Freund, “Experimental Demonstration of Neural-Network Based Transceiver Nonlinearity Mitigation for Probabilistically Shaped Photonic THz Wireless Transmission,” IEEE Photonics Technology Letters.

  • OECC — Submitted

    In-Ho Baek, O. Stiewe, R. Elschner, M. Rösch, A. Tessmann, M. Nölle, L. Molle, C. Schubert, R. Freund, “Record 221 Gb/s Dual Polarization THz Wireless Transmission Over 500 m Using PCS-64QAM at 300 GHz,” Opto-Electronics and Communications Conference (OECC).

  • J. Lightwave Technol. 2025

    In-Ho Baek, O. Stiewe, J. Gläsel, S. Nellen, G. Schwanke, T. T. Tran, R. Elschner, C. Schubert, R. B. Kohlhaas, P. Runge, M. Schell, R. Freund, “Experimental Characterization of Photodiode Transmitters for Probabilistically Shaped High-Speed THz Wireless Transmission,” Journal of Lightwave Technology, 2025.

  • Microwave Photonics 2024

    IH Baek, O. Stiewe, J. Gläsel, M. F. Ulukan, A. Schindler, F. Ganzer, T. T. Tran, “Experimental Characterization of a WR3-Coupled Photodiode Transmitter for High-Speed Terahertz Wireless Communication,” Int. Topical Meeting on Microwave Photonics, 2024.

  • IET Conference Proceedings 2023

    IH Baek, O. Stiewe, S. Nellen, G. Schwanke, R. Elschner, C. Schubert, “32 GBd, 109 Gbit/s Probabilistically Shaped THz Wireless Transmission using PIN-PD Based Photonic Upconversion,” IET Conf. Proc. CP839, pp. 1302–1305, 2023.

  • ITG Symposium 2022

    IH Baek, F. Bart, R. Elschner, F. Meier, D. Hellmann, A. Maassen, C. Schubert, “Time Adaptive Probabilistic Shaping for Combined Optical/THz Links,” Photonic Networks; 23rd ITG-Symposium, pp. 1–8, 2022.

  • J. Lightwave Technol. 2025 — Co-Author

    R. Elschner, F. Bart, F. Meier, O. Stiewe, IH Baek et al., “Analysis of Weather-Related Link Availabilities for Fiber-Integrated THz-Wireless Transmission Systems,” Journal of Lightwave Technology, 2025.

  • OFC 2025 — Co-Author

    C. Schubert, R. Elschner, O. Stiewe, IH Baek et al., “High-Capacity THz Wireless Transmission Supporting Future 6G Optical Networks,” Optical Fiber Communication Conference (OFC), M3D.1, 2025.

  • ITG Symposium 2022 — Co-Author

    C. Schmidt-Langhorst, J. Pfeiffer, R. Elschner, R. Emmerich, F. Chowanek, IH Baek, R. F. H. Fischer, C. Schubert, “Experimental Investigation of Information Bit Scrambling for Physical-Layer Security in Coherent Fiber-Optic Systems,” Photonic Networks; 23rd ITG-Symposium, pp. 1–6, 2022.

Get in Touch

I welcome discussions on research collaborations, project inquiries,
and opportunities in THz communications and photonic networks.

Fraunhofer Institute for Telecommunications
Heinrich Hertz Institute (HHI)
Department of Photonic Networks and Systems
Berlin, Germany

in-ho.baek@proton.me