Multi-Beam Access Point Design for 6G Laser-Based Optical Wireless Networks: Eye Safety-Coverage Tradeoff

We propose a multi-beam access point (AP) design comprising a vertical cavity surface emitting laser (VCSEL) array followed by a plano-convex lens as a cost-effective and scalable angle diversity transmitter (ADT) solution to realize multi-Gb/s downlink data rates in sixth generation (6G) optical wireless networks. The AP structure is elaborated using the VCSEL array and lens parameters including inter-element spacing in the array, the array-to-lens distance, and the diameter, thickness and radius of curvature of the lens. The design parameters are properly configured to ensure that the beam spots are sufficiently separated from one another on the receiver plane. To address the eye safety for infrared (IR) laser emission, we conduct a thorough eye safety analysis of a VCSEL array when combined with a lens to compute the maximum permissible transmit power (MPTP) for each transmitter element. The coverage performance of the AP is evaluated as a function of the array-to-lens distance based on a non-imaging angle diversity receiver (ADR), identifying a tradeoff between the MPTP value and the coverage performance. Simulation results demonstrate downlink data rates >= 11 Gb/s while achieving a 100% coverage over an area of 1x1 m(2) on the receiver plane at 3 m under the AP based on a 2 GHz bandwidth and coordinated multi-beam joint transmission (CoMB-JT).