A Self-Alignment System for LOS Optical Wireless Communication Links

Abstract

This letter presents a self-alignment system using a continuous and a proportional-to-position-error correction algorithm. The system is designed to address uninterrupted point-to-point high-speed line-of-sight optical wireless links. The alignment correction employs amplitude detection from a mm2-scale CMOS-compatible 4-PD array connected to a 4-channel receiver and followed by digital-processing and feedback toward the receiver lens position. The proposed self-alignment method is validated with a receiver position varying over about 5-cm range and a receiver angle covering around ±10 degree with roughly $\times 4$ field-of-view widening due to the automatic alignment. A 50-Mb/s ON–OFF-keying transmission link is maintained across 4 meters distance using a 650-nm-red light-emitting-diode source with a bit-error-rate below the forward-error-correction limit of $3.8\times 10^{-3}$ .