Multipath lens for eye-safe optical wireless communications

Abstract

This article considers the design and use of multipath lenses (MPLs) for optical wireless communications (OWC). The MPL increases the maximum permissible exposure (MPE) for eye safety and allows for an increase of transmission power of small-sized emitters like laser diodes (LDs). A prototype of a freeform MPL has been fabricated and characterized. The MPL allows an increase of the optical transmission power by 13 dB, which corresponds to an improvement in the maximum range by a factor of 4.5. The lens transforms the elliptical emission pattern of an edge-emitting LD into a rectangular field-of-view (FOV) with homogenous power distribution. The transmission efficiency through the MPL is 0.905.