High Speed 2-D Photodetector Array for Space and Mode-Division Multiplexing Fiber Communications

We report a high-data-rate two-dimensional photodetector array (2D-PDA) operated over 10 GHz for compact receiver systems in multicore fiber (MCF), few-mode fiber (FMF), and FMF-MCF, which can be directly coupled to multiparallel beams from the MCF and FMF. The 2D-PDA (pixel size of 20-30 μm, pixel number of 32) were designed and characterized for the frequency response and crosstalk. In the on-wafer probing test, the averaged 3-dB bandwidth of 11.2 GHz and 19.8 GHz were measured for 30-μm and 20-μm pixels, respectively. In the MCF direct-coupling demonstration with the 2D-PDA, the selected 16 pixels could work well at 25 Gb/s (nonreturn-to-zero: NRZ). By using triangular-shape-aligned seven-core fiber and the square-shape-aligned seven cores in the 2D-PDA, the coupling efficiency and alignment tolerance were investigated for the universal MCF photoreceiver. In the demonstration of the mode-division multiplexing signal detection with 2D-PDA, the multiplexed three-mode signal with 20-Gbps quadrature phase-shift keying was directly coupled to the 2D-PDA. Through the electrical phase matching system with the multiple-input multiple-output function, the three-mode signal (20 Gbps in each mode) could be successfully detected and separated error-free.