EU COST Action on future generation optical wireless communication technologies, 2nd White paper. - Zabih Ghassemlooy; Mohammad Ali Khalighi; Stanislav Zvanovec; A. Shrestha; Beatriz Ortega; Milica I. Petkovic; X. Pang; Carlo Sirtori; Davide Orsucci; Florian Moll; Giulio Cossu; Veronica Spirito; et al. (CoRR, 2023)