Few-Mode Fiber-Based Free-Space Optical Communication With Nonzero Boresight Pointing Errors

Bit-error rate (BER) performance of free-space optical communication (FSO) systems is compromised by pointing errors. Few-mode fiber (FMF) based receiver emerges as a promising solution for FSO, because FMF can obtain high coupling efficiency in the presence of pointing errors. The high coupling efficiency allows FMF based system to achieve improved BER performance. In this letter, based on a simplified mode demultiplexer model, we propose a method to use the coupling efficiencies of each mode of FMF to characterize the BER of the FMF based FSO system having nonzero boresight pointing errors. We find that the boresight displacement can significantly deteriorate the BER performance, and the jitter variance can reduce the impact of boresight within a suitable range.