Ultra-Wideband Free-Space Optical Phase Stabilization

Free-space optical (FSO) communications have the potential to revolutionize wireless communications due to the advantages of greater inherent security, high-directionality, high available bandwidth and small physical footprint. The effects of atmospheric turbulence currently limit the performance of FSO communications. In this letter, we demonstrate a system capable of indiscriminately suppressing the atmospheric phase noise encountered by independent optical signals spread over a range of 7.2 THz (encompassing the full optical C-Band), by actively phase stabilizing a primary optical signal at 193.1 THz (1553 nm). We show ~30 dB of indiscriminate phase stabilization over the full range, down to average phase noise at 10 Hz of −39.6 dBc Hz−1 when using an acousto-optic modulator (AOM) as a Doppler actuator, and −39.9 dBc Hz−1 when using a fiber-stretcher as group-delay actuator to provide the phase-stabilization system’s feedback. We demonstrate that this suppression is limited by the noise of the independent optical signals, and that the expected achievable suppression is over 40 dB greater, reaching around −90 dB Hz−1 at 10 Hz. We conclude that 40 Tbps ground-to-space FSO transmission would be made possible with the combination of our stabilization system and other demonstrated technologies.

[1]  Paul L. Csonka,et al.  Demonstration of free-space optical communication for long-range data links between balloons on Project Loon , 2017, LASE.

[2]  Annika Dochhan,et al.  13.16 Tbit/s Free-space Optical Transmission over 10.45 km for Geostationary Satellite Feeder-links , 2020, 2006.05349.

[3]  R. Fante.  Electromagnetic beam propagation in turbulent media , 1975, Proceedings of the IEEE.

[4]  Guido Aben,et al.  High-precision optical-frequency dissemination on branching optical-fiber networks. , 2013, Optics letters.

[5]  Ramon Mata Calvo,et al.  Demonstration of 1.72 Tbit/s Optical Data Transmission Under Worst-Case Turbulence Conditions for Ground-to-Geostationary Satellite Communications , 2018, IEEE Communications Letters.

[6]  Fritz Riehle,et al.  Optical clock networks , 2017, Nature Photonics.

[8]  J. Conan,et al.  Single-Mode Fiber Coupling with Adaptive Optics for Free-Space Optical Communication under Strong Scintillation , 2019, 2019 IEEE International Conference on Space Optical Systems and Applications (ICSOS).

[9]  Chen Qiang,et al.  Sub-picosecond timing fluctuation suppression in laser-based atmospheric transfer of microwave signal using electronic phase compensation , 2017 .

[10]  Roberto Rojas-Cessa,et al.  A Survey on Acquisition, Tracking, and Pointing Mechanisms for Mobile Free-Space Optical Communications , 2018, IEEE Communications Surveys & Tutorials.

[11]  Roberto Morandotti,et al.  Ultra-dense optical data transmission over standard fibre with a single chip source , 2020, Nature Communications.

[12]  Davide Calonico,et al.  Geodesy and metrology with a transportable optical clock , 2018 .

[13]  Jun Ye,et al.  Remote transfer of ultrastable frequency references via fiber networks. , 2007, The Review of scientific instruments.

[14]  C. Guerlin,et al.  Determination of a high spatial resolution geopotential model using atomic clock comparisons , 2016, Journal of Geodesy.

[15]  K. Djerroud,et al.  A coherent optical link through the turbulent atmosphere , 2010, EFTF-2010 24th European Frequency and Time Forum.

[16]  Jean-Marc Conan,et al.  Impact of turbulence on high-precision ground-satellite frequency transfer with two-way coherent optical links , 2016 .

[17]  Z. Sodnik,et al.  First Experimental Demonstration of Adaptive Optics Pre-Compensation for GEO Feeder Links in a Relevant Environment , 2019, 2019 IEEE International Conference on Space Optical Systems and Applications (ICSOS).

[18]  H. Shinkai,et al.  Test of general relativity by a pair of transportable optical lattice clocks , 2020 .

[19]  M. Lewis,et al.  Demonstration of a bidirectional coherent air-to-ground optical link , 2018, LASE.

[20]  Young‐Jin Kim,et al.  Free-space transfer of comb-rooted optical frequencies over an 18 km open-air link , 2019, Nature Communications.

[21]  L S Ma,et al.  Delivering the same optical frequency at two places: accurate cancellation of phase noise introduced by an optical fiber or other time-varying path. , 1994, Optics letters.

[22]  Sascha Schediwy,et al.  Stabilized Free-Space Optical Frequency Transfer , 2018, Physical Review Applied.

[23]  S. Meimon,et al.  Adaptive optics pre-compensation for GEO feeder links: the FEEDELIO experiment , 2019, International Conference on Space Optics.

[24]  N. Newbury,et al.  Low-loss reciprocal optical terminals for two-way time-frequency transfer. , 2017, Applied optics.

[25]  Annika Dochhan,et al.  Optical technologies for very high throughput satellite communications , 2019, LASE.