Optical signal acquisition using an alignment robust receiver based on a photodetector array

A high-speed receiver module for free-space optical communications with robust alignment, incorporating a previously developed photodetector array (PDA), is presented. The packaged receiver was characterized for the frequency response and transmission performance. By optimizing the PCB on which the array is mounted, a flatter modulation response and higher element bandwidth were achieved. The receiver module exhibited an average 3 dB bandwidth of 2.7 GHz, with an alignment tolerance of 37 µm without mechanical beam tracking. The 3 dB, 6 dB, and 10 dB bandwidth have all significantly improved compared with prior work. In a 25 km SMF transmission demonstration, 10 selected elements operated reliably at 10 Gbps (NRZ). With additional transmitter side equalization, NRZ bit error rates (BERs) below 10^-12 were achieved at up to 10 Gbps.