Patent ID: 7394547

Claim:
An assembly for use in detecting an analyte in a sample based on interference, comprising: an optical fiber having a tip; a first optical element adapted for coupling to a light source through a mechanical coupling that engages the first optical element with the fiber and provides an air gap between the first optical element and the fiber; and second optical element attached to the first optical element, the second optical element commensurate in size with the fiber tip and adapted for coupling to the first optical element, said second optical element comprising a transparent material, a first reflecting surface, and a second reflecting surface separated from the first reflecting surface by the transparent material, said first and second reflecting surfaces separated by at least 50 nm, wherein said first reflecting surface comprises a layer of analyte binding molecules, and an interference between light reflected into the fiber from said first and second reflecting surfaces varies as analyte in the sample binds to the analyte binding molecules.