Performance characterization of non-Lambertian beams for 6G visible-light inter-satellite links

Visible-light inter-satellite communication is a promising physical-layer option for secure and interference-resilient 6G satellite networking. However, most analytical studies still assume Lambertian emission, which limits insight into emitters with asymmetric or multi-lobe radiation patterns. This paper presents a controlled analytical framework for Lambertian, Z-Power, and non-symmetric power-weighted (NSPW) beams using consistent transmitter-receiver modeling, channel-gain, receiver-noise, signal-to-noise ratio (SNR), and bit error rate (BER) formulations, including solar-background effects under Fraunhofer-line operation. The analysis considers six design dimensions: link distance, irradiance angle, transmitted optical power, receiver-bandwidth scaling, optical-filter background leakage, and beam azimuth rotation. The results show a clear operating-regime transition: Lambertian emission is competitive for near-aligned links, whereas non-Lambertian beams offer markedly higher robustness at wide irradiance angles. In a representative proximity-case stress point (0.5 km, [Formula: see text] irradiance angle), Z-Power and NSPW links achieve about 4.7 dB and [Formula: see text] dB, respectively, while the Lambertian baseline remains near [Formula: see text] dB, corresponding to gains of approximately 60 dB and 45.7 dB. The bandwidth, distance-scaling, and link-budget discussions clarify that these values are beam-profile sensitivity margins rather than a flight-qualified payload budget. Overall, the findings provide a practical roadmap for beam selection, link-margin interpretation, and attitude-aware adaptation in robust 6G visible-light inter-satellite communication systems.