Few-mode fiber based optical sensors.

Few-mode fibers (FMFs) have found applications in optical communications and sensors with attractive features that standard single mode fiber (SSMF) do not possess. We report our recent progress on FMF based optical sensors, and show the potential of utilizing the spatial dimension for multi-parameter sensing with discrimination capability. We first show a discrete type FMF sensor based on interferometer structure with a short FMF, utilizing the modal interference between either the polarizations (x and y) or the spatial modes (LP(01) and LP(11)). We then show a distributed type FMF sensor by generating the stimulated Brillouin scattering (SBS) in a long FMF. We characterize the Brillouin gain spectrum (BGS) with a pump-probe configuration, and measure the temperature and strain coefficients for LP(01) and LP(11) modes. The proposed FMF based optical sensor can be applied to sensing a wide range of parameters.