Generalized modeling and turbulence resistance evaluation for higher-order Laguerre-Gaussian beam.

In current free-space optical (FSO) communication systems, the fundamental Gaussian beam is typically used as the signal carrier. However, its simple spatial structure makes it highly susceptible to atmospheric turbulence, significantly degrading system performance. This study addresses the issue by employing higher-order Laguerre-Gaussian (LG) beams as signal carriers. A universal transmission model based on the modified von Kármán turbulence spectrum is developed using confluent hypergeometric functions. The model reproduces Huygens-Fresnel diffraction integration within 0.9% power error and accelerates computation by more than tenfold. Combined simulations and a 40 Gbps QPSK FSO experiment show that higher-order LG beams exhibit reduced beam spreading, lower power loss, and mitigated scintillation compared to the fundamental Gaussian mode. For a target BER of 1 × 10^-4, the LG₀₁ mode beam reduces the transmitted power budget by 1-1.5 dB, while LG₁₀ and LG₀₂ beams reduce it by 2-4 dB compared to fundamental Gaussian beam. Incorporating the experimentally measured mixing efficiency penalty into the predictions leaves the mode ranking and performance trends unchanged, further validating the reliability and practical applicability of the proposed intensity model.