Plasmonics is one of the most powerful technology for biomedical detection which may realize single molecule detection. The combination of high sensitive plasmonic technology and flexible fiber-optic sensors opens up a multitude of opportunities for cost-effective and relatively simple-to-implement bio-sample detection. The miniaturized size and remote operation ability offer them a multitude of opportunities for single-point sensing in hard-to-reach spaces, even possibly in vivo. We briefly review the principle of fiber grating based plasmonic biosensors, and the key properties to achieve unprecedented sensitivities (10-6-10-8 RIU) and limits of detection (pM-fM). Meanwhile, we also demonstrate such sensors provide very controllable cross-sensitivities, absolute and relative measurements of various parameters, and their self-calibration ability to the environmental cross-talk (especially to the temperature fluctuations). Finally, we briefly review the recent developments of the surface and localized affinity studies of the biomolecules for real life problems, the electrochemical actives of electroactive biofilms for clean energy resources and the ultra-highly sensitive sensing in gas.