Patent ID: 6924138

Claim:
A fiber-optic-coupler biosensor comprising: a fiber-optic coupler incorporating at least one multi-mode and at least one single-mode optical fibers, each fiber having an input and an output; a source of light having multiple modes being coupled to the input to one of the multi-mode fibers; the coupler including a necked-down section around which an evanescent field is generated when the light passes through, the necked-down section being such that a limited number of modes may be carried by the multi-mode fiber as the light emerges from the coupler, and wherein at least one of the single-mode fibers is supported adjacent the multi-mode fiber to receive and carry one of the limited modes; a biomolecule enveloped by the evanescent field, the biomolecule exhibiting a direct or indirect affinity to a binding partner, such that attachment of the binding partner is at least partially responsible for the limited number of modes carried by the multi-mode fiber as the light emerges from the coupler; and instrumentation for: a) receiving the light from the single-mode fiber carrying one of the limited modes, and b) determining a characteristic of the binding partner in accordance with the detected mode.