25-Gbaud 4-WDM Free-Space Optical Communication Using High-Speed 2-D Photodetector Array

We present a newly developed two-dimensional photodetector array (2D-PDA) device and its application for short-range free-space optical (FSO) communication using a wavelength-division multiplexed beam. The 2D-PDA enables direct optical coupling to the FSO beam, simplifying the optical alignment process needed for 10-μm single-mode fiber coupling and reducing the need for beam-tracking function. In the wavelength-division multiplexing (WDM) FSO communication demonstration, a four-wavelength 25-Gbaud parallel beam filtered by a 4-WDM filter through free space was successfully received by 4-pixels in the 2D-PDA. This paper discusses the design and fabrication in the 2D-PDA device, as well as the FSO communication demonstration using four combined WDM filters.