Patent ID: 6882429
Filing Date: 2005-04-19
Classification: A61B,B82Y,G01K,G02B,G11B

Abstract:
1. A device, comprising: a reference fiber having a first terminal and a second terminal; a signal fiber having a first terminal and a second terminal, and a tapered section between said first and second terminals which has a reduced dimension to allow a desired portion of a guided optical beam at a signal frequency to exist outside said signal fiber in form of an evanescent field; a first optical coupler to divide a signal laser beam at said signal frequency into a first signals beam and a second signal beam of an equal intensity and to couple said first and said second signal beams into said first terminals of said signal and said reference fibers, respectively; a second optical coupler coupled to said second terminals of said signal and said reference fibers to combine said first and said second signal beams into an output signal beam in which said first and said second signal beams are 180 degrees out of phase relative to each other; a measurand surface disposed adjacent to said tapered section of said signal fiber to absorb optical energy in said evanescent field; and a signal photodetector to receive said output signal beam from said second optical coupler to produce a detector output indicating a spacing between said measurand surface and said signal fiber at said tapered section.