Intrinsic Sol−Gel Clad Fiber-Optic Sensors with Time-Resolved Detection

Sol−gel clad fiber-optic waveguides are investigated as intrinsic distributed fiber-optic chemical sensors. The porous sol−gel cladding allows diffusion of analytes into the evanescent field region close to the fiber-optic core. Pulsed optical excitation (0.5 ns) and time-resolved emission detection can be used to simultaneously monitor several multiplexed sensor clad regions along a single optical fiber. Time-resolved detection is also demonstrated as a means of resolving both the spatial location and the fluorescence kinetics of intrinsic sensor chromophores along the fiber-optic waveguide. Narrow band excitation and spectrally resolved emission provide additional experimental means for discriminating between specific sensor clad regions. A fluorescein-doped silica xerogel clad pH sensor and an undoped aluminosilica xerogel clad quinone sensor are demonstrated as intrinsic sol−gel clad fiber-optic sensors.