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Quasi-distributed temperature sensor based on the 1.2-μm transition in erbium-doped fibers

We propose the principle of a high-dynamic, quasi-distributed temperature sensor. We previously have demonstrated the possibility of realizing a high-dynamic point sensor based on the behavior of the green emission in erbium doped silica fibers. We present here the study of the 1.13 micrometers and 1.24 micrometers emission lines, coming from the same levels. Those lines present the same temperature dynamic as the green ones. As the lower level of these transitions is the 4I11/2 level and not the fundamental one, the signal is absorption free. The signal wavelength also corresponds to a transparence region of the intermediate fibers. These arguments permit developing an efficient quasi-distributed configuration. In addition, the intensity ratio of the emission lines is only temperature dependant, so the measurement is self-calibrated. We also demonstrate that the emitting levels can be excited around 800 nm, by the excited state absorption process, which allow using a standard laser diode as pumping source.