Two-photon excited fluorescence in rare-earth doped optical fiber for applications in distributed sensing of temperature

Distributed temperature sensing based on time-correlated two-photon excited fluorescence (TPF) in doped optical fiber is described. Counter-propagating laser pulses generate a TPF flash at the position of their overlap which is scanned along the fiber by a variable relative time delay. The flash is transmitted to one end where it is detected and analyzed to yield the temperature from its thermal dependence. To identify suitable dopants, the two-photon excitation spectra of glass doped with various rare-earths were recorded. Preliminary results on TPF in praseodymium doped single-mode fiber are presented