Turbulence-Resistant All Optical Relaying Based on Few-Mode EDFA in Free-Space Optical Systems

We investigate the communication performance of a few-mode EDFA based all-optical relaying system for atmospheric channels in this paper. A dual-hop free space optical communication model based on the relay with two-mode EDFA is derived. The bit error rate (BER) performance is numerically calculated. Compared with all-optical relaying system with single-mode EDFA, the power budget is increased by 4 dB, 7.5 dB, and 11.5 dB at BER = 1 × 10
^-4
under the refractive index structure constant C
_n
²
= 2 × 10
^-14
, 5 × 10
^-14
, and 1 × 10
^-13
, respectively, when a few mode fiber supporting four modes is utilized as the receiving fiber at the destination. The optimal relay location is slightly backward from the middle of the link. The BER performance is the best when mode-dependent gain of FM-EDFA is zero.