Next-Generation Hollow-Core Fibers for High-Speed Communications, Quantum Communication and Distributed Sensing

The proposed Ph.D. project aims to develop and demonstrate the next generation of hollow-core photonic crystal fibers (HCPCFs) for ultra-high-speed data transmission, quantum communication, and distributed sensing. Recent breakthroughs have reduced HCPCF losses to 0.1 dB/km [1-2], positioning this technology as a transformative alternative to conventional silica fibers. 

With light propagating in air rather than glass, HCPCFs enable lower latency and negligible optical nonlinearities, addressing key challenges for future data centers, for optical networks for time- sensitive applications, and quantum key distribution (QKD) systems. The project will explore communicating signals over HCPCFs as a disruptive technique to transmit information in a fast and secure way and to explore distributed sensing capability of these fibers. Our ambition is to demonstrate 400 Gbps transmission over a few kilometers of fiber, and investigate the potentials of QKD transmission and distributed acoustic sensing (DAS) over HCPCFs. Such an achievement requires overcoming stringent specifications in single-mode guidance, polarization control, and low bend and coupling losses. 

Two complementary research groups will co-supervise the work: 

• GPPMM/XLIM/UNILIM-CNRS, internationally recognized for HCPCF design and fabrication [3-5], will supervise the development of novel hybrid-lattice HCPCFs and the implementation of advanced fabrication methods to minimize surface scattering losses.
• GTO/LTCI/Télécom Paris/IMT, a leader in high-speed optical communication systems, will focus on integrating and testing the new fibers within state-of-the-art coherent transmission, quantum communication and DAS platforms. The existence of the expertise on the three topics [6-8] and the three platforms in one academic lab gives GTO a unique position on the national level. 

The synergy between the two teams is essential: iterative feedback between fabrication and system- level testing will ensure that the fiber properties meet operational transmission and sensing requirements. An industrial collaboration with GLOphotonics will complement academic efforts, providing expertise on connectorization and scaling toward deployable fiber lengths. 

Methodologically, the project combines numerical modeling, fabrication, characterization and  experimental validation across the C-band. Digital signal processing for polarization and phase  tracking developed at LTCI will be used to assess and optimize the transmission performance of  HCPCFs. Beyond the immediate targets, this work will pioneer new applications of air-guided fibers  for hybrid classical–quantum networks and distributed sensing infrastructures.  

By merging cutting-edge fiber technology with advanced communication system research, this  thesis will lay the foundations for a new generation of ultrafast, low-latency, and quantum-ready  optical links. Its success depends critically on the unique and complementary expertise of the two  supervisory teams, whose expertise and collaboration make this ambitious and disruptive goal  realistically achievable.