A novel prism coupled device as an Fabry-Perot oscillating field sensor has been developed. In the proposed configuration, liquid or gaseous sample to be probed supports oscillating field in Fabry-Perot cavity, rather than evanescent field as in the conventional SPR sensors or the waveguide mode sensors. Because most energy of incident light is coupled in oscillating field, the sensor′s detection sensitivity is very high. Prototype sensor based on this approach has been successfully fabricated and tested. The detection limity for glucose solution is 10 -5 (mass fraction) in the experiments with the system.