Patent ID: 7491491

Claim:
For use in a system including a light source, and a light detector, for determining the presence or concentration of a substance in a medium, a sensor comprising: a) at least one optical fiber; b) a plurality of microspheres, each of the plurality of microspheres being coupled with the optical fiber, and at least one of the microspheres having a surface including receptors for the substance, wherein, when light is applied to the optical fiber, a resonance within each of the microspheres is excited, wherein, if the substance adsorbs to the receptors on a surface of one of the microspheres, a shift in the resonance occurs, wherein a presence or concentration of the substance can be determined based on the shift in resonance, wherein a resonance frequency of each of the plurality of microspheres can be distinguished from resonance frequencies of the other of the plurality of microspheres, and wherein a quality factor of the resonance excited within at least one of the microspheres by the light applied to the optical fiber is at least 10 5 .