Photoinduced Fresnel reflectors for point-wise and distributed sensing applications

Large, photoinduced refractive index changes on the order 10-2 can now be achieved in hydrogen-loaded, GeO2-doped optical fiber. Much of this work has focused on the research and development of Bragg gratings fabricated by exposing the core of fiber to the intensity pattern of two interfering plane waves. Unlike interferometrically formed Bragg gratings, we have exposed optical fibers to a single focused 244 nm laser beam to obtain two Fresnel reflections from each exposure site. Reflectors formed in this way are broadband and have application as markers in OTDR-based distributed sensing systems and as resonant cavities for localized intrinsic Fabry-Perot interferometric strain and temperature sensors.