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.
High-speed rotary communication links exhibit high complexity and require challenging assembly tolerances. This article investigates the use of optical wireless communications (OWC) for on-axis rotary communication scenarios. First, OWC is compared with other state-of-the-art technologies. Different realization approaches for bidirectional, full-duplex links are discussed. For the most promising approach, a monolithic hybrid transmitter-receiver lens is designed by ray mapping methodology. Ray tracing simulations are used to study the alignment-depended receiver power level and to determine the effect of optical crosstalk. Over a distance of 12.5 m m , the lens achieves an optical power level at the receiver of − 16.2 dBm to − 8.7 dBm even for misalignments up to 3 m m .
This work considers the use of a freeform total internal reflection (TIR) lens for optical concentration and provides for the first time experimental results in the context of optical wireless communications (OWC). The lens is placed on a surface-mounted device (SMD) avalanche photodiode (APD) to minimize position tolerances and simplify assembly. The lens achieves a concentration ratio of go = 44.7 (16.5 dB) within the FOV center and exhibits an acceptance angle of ±5°. The TIR lens approach is validated by comparing eye diagrams and bit error ratios (BER) of a receiver with and without a TIR lens. For the measurements, non-return-to-zero (NRZ) on-off keying (OOK) signals are transmitted with a data rate of 1.289 Gbit/s.
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