The Resilience of Hermite– and Laguerre–Gaussian Modes in Turbulence

Vast geographical distances in Africa are a leading cause for the so-called digital divide due to the high cost of installing fiber. Free-space optical (FSO) communications offer a convenient and higher bandwidth alternative to point-to-point radio microwave links, with the possibility of repurposing existing infrastructure. Unfortunately, the range of high-bandwidth FSO remains limited. While there has been extensive research into an optimal mode set for FSO to achieve maximum data throughput by mode division multiplexing, there has been relatively little work investigating optical modes to improve the resilience of FSO links. Here, we experimentally show that a carefully chosen subset of Hermite–Gaussian modes is more resilient to atmospheric turbulence than similar Laguerre–Gauss beams, with a predicted upper bound increase in propagation distance of 167% at a mode-dependent loss of 50%.

[1]  J. Shapiro,et al.  Photon Information Efficient Communication Through Atmospheric Turbulence–Part I: Channel Model and Propagation Statistics , 2014, Journal of Lightwave Technology.

[2]  Wen Cheng,et al.  Propagation of scalar and vector vortex beams through turbulent atmosphere , 2009, LASE.

[3]  R. Noll.  Zernike polynomials and atmospheric turbulence , 1976 .

[4]  A. Zeilinger,et al.  Twisted light transmission over 143 km , 2016, Proceedings of the National Academy of Sciences.

[5]  Gerd Leuchs,et al.  Free-space propagation of high-dimensional structured optical fields in an urban environment , 2017, Science Advances.

[6]  M. Padgett,et al.  Comparing the information capacity of Laguerre-Gaussian and Hermite-Gaussian modal sets in a finite-aperture system. , 2016, Optics express.

[7]  A. Zeilinger,et al.  Communication with spatially modulated light through turbulent air across Vienna , 2014, 1402.2602.

[8]  A. Kolmogorov,et al.  The local structure of turbulence in incompressible viscous fluid for very large Reynolds numbers , 1991, Proceedings of the Royal Society of London. Series A: Mathematical and Physical Sciences.

[9]  Joseph M. Kahn,et al.  Capacity limits of spatially multiplexed free-space communication , 2015 .

[10]  Bernhard Schmauss,et al.  Free space optical communication with spatial diversity based on orbital angular momentum of light , 2015, 2015 4th International Workshop on Optical Wireless Communications (IWOW).

[11]  Thomas Kaiser,et al.  Complete modal decomposition for optical fibers using CGH-based correlation filters. , 2009, Optics express.

[12]  Mojtaba Mansour Abadi,et al.  Tackling Africa’s digital divide , 2018 .

[13]  L. Andrews,et al.  Laser Beam Propagation Through Random Media , 1998 .

[14]  Andrew Forbes,et al.  On the resilience of scalar and vector vortex modes in turbulence. , 2016, Optics express.

[15]  O. Korotkova,et al.  Scintillation of nonuniformly polarized beams in atmospheric turbulence. , 2009, Optics letters.

[16]  A. Willner,et al.  Atmospheric turbulence compensation in orbital angular momentum communications: Advances and perspectives , 2018 .

[17]  A. Forbes,et al.  Orbital-angular-momentum entanglement in turbulence , 2013, 1306.6495.

[18]  Peter J. Winzer,et al.  Making spatial multiplexing a reality , 2014, Nature Photonics.

[19]  Johannes Courtial,et al.  Mode transformations in terms of the constituent Hermite–Gaussian or Laguerre–Gaussian modes and the variable-phase mode converter , 2000 .

[20]  Giovanni Milione,et al.  Comparing mode-crosstalk and mode-dependent loss of laterally displaced orbital angular momentum and Hermite-Gaussian modes for free-space optical communication. , 2017, Optics letters.

[21]  Moshe Tur,et al.  Experimental characterization of a 400 Gbit/s orbital angular momentum multiplexed free-space optical link over 120 m. , 2016, Optics letters.

[22]  Mohsen Kavehrad,et al.  BER Performance of Free-Space Optical Transmission with Spatial Diversity , 2007, IEEE Transactions on Wireless Communications.

[23]  Jian Wang,et al.  Experimental demonstration of 260-meter security free-space optical data transmission using 16-QAM carrying orbital angular momentum (OAM) beams multiplexing , 2016, 2016 Optical Fiber Communications Conference and Exhibition (OFC).

[24]  A. Forbes,et al.  Are Bessel beams resilient to aberrations and turbulence? , 2018, Journal of the Optical Society of America. A, Optics, image science, and vision.

[25]  A. Willner,et al.  Performance metrics and design considerations for a free-space optical orbital-angular-momentum–multiplexed communication link , 2015 .

[26]  Yan Yan,et al.  Recent advances in high-capacity free-space optical and radio-frequency communications using orbital angular momentum multiplexing , 2017, Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences.

[27]  Jeffrey H. Shapiro,et al.  Photon information efficient communication through atmospheric turbulence , 2012, Other Conferences.

[28]  Valerii P. Aksenov,et al.  Orbital angular momentum of a laser beam in a turbulent medium: preservation of the average value and variance of fluctuations , 2016 .

[29]  Mourad Zghal,et al.  Optical communication beyond orbital angular momentum , 2016, Scientific Reports.

[30]  David L. Fried,et al.  Statistics of a Geometric Representation of Wavefront Distortion: Errata , 1965 .

[31]  Majid Safari,et al.  Spatial-Mode Diversity and Multiplexing for FSO Communication With Direct Detection , 2017, IEEE Transactions on Communications.

[32]  Kishan Dholakia,et al.  Is there an optimal basis to maximise optical information transfer? , 2016, Scientific Reports.

[33]  Moshe Tur,et al.  400-Gbit/s QPSK free-space optical communicationlink based on four-fold multiplexing of Hermite-Gaussian or Laguerre-Gaussian modes by varying both modal indices. , 2018, Optics letters.