Patent ID: 7187816
Filing Date: 2007-03-06
Classification: B82Y,G01B,G01D,G01J,G01N,G01Q,G02B

Abstract:
1. A sensing method using an optical fiber sensor, the method comprising: providing a probe including an optical fiber having an inner core region, an outer cladding region, and a long period fiber grating (LPFG) embedded at selected distances from a distal end of the optical fiber; forming a reflective surface over the cladding region at the distal end of the optical fiber; positioning the distal end of the optical fiber adjacent a sample; supplying light to the core of the optical fiber so that upon encountering the LPFG, a first portion of the light wave travels through the core of the optical fiber toward a distal end and a second portion of the light wave is coupled into the cladding region and travels through the cladding region toward distal end; emitting the first portion of the light wave moving through core from the distal end of the optical fiber, the first portion of the light wave striking a surface of the sample and being reflected back into the core, the sample reflective wave moving through the core in a direction away from the distal end; reflecting the second portion of the light wave off the reflective surface so that a cladding reflective wave moves back through the cladding region in a direction away from the distal end, a portion of the cladding reflective wave being coupled back to core at the LPFG; and determining a distance between the distal end of the optical fiber and the surface of the sample based on a phase shift between the cladding reflective wave and the sample reflective wave.