⮞ Département SP ⮞ Thématiques de recherche⮞ Activités « Communications Optiques »
Free-space optical communication offers advantages over radio-frequency systems, including higher bandwidth and improved security, but requires high beam quality and power to overcome atmospheric disturbances. To tackle nonlinear effects and power scaling limitations, one solution is coherent beam combining (CBC), where signals are split, amplified, and recombined coherently using active phase-locking. The main challenge is the compatibility between CBC techniques and WDM telecom signals, which is essential for future terabit-per-second satellite communication links.
In collaboration with ONERA, we have demonstrated a CBC system designed to enhance free-space optical telecommunications by simultaneously achieving high optical power and high data rates. The system combines eight optical arms seeded by four wavelength-division multiplexed (WDM) channels, each modulated at 10 Gbit/s, spanning a total spectral width of 2.4 THz in the C-band. A key contribution of the work is demonstrating that CBC can efficiently combine multiple WDM channels without degrading data transmission performance.
The system relies on precise optical path difference (OPD) equalization between the arms and phase-locking of a reference (“leader”) channel using the LOCSET technique. Analytical and experimental results show that OPD control is critical: even micrometer-scale mismatches can significantly reduce combining efficiency.
Experiments demonstrate combining efficiencies above 95% for all channels, with no observable penalties in bit error rate (BER) or eye diagrams, confirming reliable data transmission. The study also establishes tolerancing rules linking OPD accuracy to performance, showing that tighter control is required as the number of channels or spectral width increases.
In this work, we have validated the approach on an 8-arm system and highlighted its scalability toward high-power WDM laser sources. This work represents a significant step toward practical high-capacity free-space optical communication systems, particularly for satellite links requiring both high throughput and high optical power.
Collaborations
Projets Financés
1 thèse : Thomas Le Beux 2023-2026
Publications associées
B. Rouzé, P. Pichon, M. Gay, L. Bramerie, L. Lombard, A. Durécu, “Experimental study of the impact of carrying a telecom signal on LOCSET-based coherent beam combining,” Optics Express 31, 26552–26564 (2023). oe-31-16-26552
T. Le Beux, L. Bramerie, T. Chartier, M. Gay, S. Lobo, L. Lombard, P. Pichon, B. Rouzé, “Coherent Beam Combining of Wavelength-Division-Multiplexed channels at 10 Gbit/s,” ECOC 2024. ECOC2024_ONERA_Foton
T. Le Beux, L. Bramerie, T. Chartier, M. Gay, L. Lombard, P. Pichon, B. Rouzé, “Coherent beam combining of wavelength-division multiplexed telecom signals: toward high-power and high-bit-rate free-space optical telecommunications,” Optics Express 33, 5600–5614 (2025), Editors’ Pick