Demonstration of analog links using spatial modes in km-scale few mode fiber

Analog links in a 5-km few mode fiber (FMF) are experimentally investigated by exploiting fundamental and high-order linearly polarized (LP) and OAM modes (LP₀₁, LP_11a, LP_11b, OAM₊₁, OAM_-1). We use spurious free dynamic range (SFDR) of the second-order harmonic distortion (SHD) to evaluate the analog transmission performance. The dependence of analog link performance on the mode relative loss (MRL) between the fundamental and high-order LP and OAM modes is studied. The obtained results indicate that the analog signal transmission performance through a 5-km FMF is affected by MRL of different modes. High-order LP and OAM modes with relatively large MRL suffer degradation of analog link performance. In addition, we further assess the impacts of different modes themselves on the analog link performance. The obtained results imply that all the modes (LP₀₁, LP_11a, LP_11b, OAM₊₁ and OAM_-1) show similar analog link performance after transmitting through a 5-km FMF.