Free-Space Optical Communication System Using Non-mode-Selective Photonic Lantern Based Receiver With Different Number of Single-Mode Fiber Cores

Abstract

The optical receiver based on non-mode-selective photonic lantern (NMS-PL) can be used to improve the communication performance of free-space optical communication (FSOC) systems, because the NMS-PL receiver can take advantages of the high coupling efficiency of multimode fiber (MMF) receivers and the high mixing efficiency of single-mode fiber (SMF) receivers. However, previous studies on the NMS-PL receiver did not consider the impact of the number of SMF cores of the NMS-PL on the bit-error rate (BER) performance under different power distributions of the NMS- PL. In this paper, we study the BER of the NMS-PL receiver using equal-gain combining (EGC) for FSOC systems under a log-normal turbulent fading channel with pointing errors. We derive both a lower bound and an approximated upper bound of the BER of the NMS-PL receiver using EGC. Numerical results show that the BER of NMS-PL receiver attains its minimum value when the number of SMF cores equals the number of guided modes of NMS-PL. Besides, numerical results also show that the power distribution of the NMS-PL has only limited influence on the BER of NMS-PL receiver using EGC when either strong turbulence or large pointing error is considered.