ERBIUM-DOPED SILICA FIBERS FOR INTRINSIC FIBEROPTIC TEMPERATURE SENSORS

The variation in the green intensity ratio (H-2(11/2) and S-4(3/2) ene rgy levels to the ground state) of Er ions in silica fibers has been s tudied as a function of temperature. The different processes that are used to determine the population of these levels are investigated, in particular 800-nm excited-state absorption in Er-doped fibers and 980- nm energy transfer, in Yb-Er-codoped fibers. The invariance of the int ensity ratio at a fixed temperature with respect to power, wavelength, and doped fiber length has been investigated and shown to permit the realization of a high-dynamic-range (greater than 600 degrees C), auto calibrated fiber-optic temperature sensor.