FSO Receiver With High Optical Alignment Robustness Using High-Speed 2D-PDA and Space Diversity Technique

A free-space optical (FSO) receiver with high optical alignment robustness configured by a single optical lens is presented, in addition to a newly developed 2-D photodetector array (2D-PDA). A 6 × 6 square-shaped aligned arrangement matrix structure in the 2D-PDA provides a large active area for photodetection. In a 1.5-m FSO demonstration, the optical alignment tolerance on the receiver's lens is evaluated to be as large as 12 mm. The multiple-output signals from the 2D-PDA are used for the maximum ratio combining method in space diversity. The system design and alignment tolerance without a mechanical beam-tracking system are presented and the bit error rate contributed by space diversity is discussed.