Temperature dependence of the Brillouin shift in a commercially available dispersion-shifted fiber has been experimentally investigated in the range of 20 to 820~ °C . When the as-fabricated fiber underwent a temperature cycle in the entire temperature rage, the Brillouin shift exhibited a noticeable hysteresis having the maximum frequency discrepancy of 48 MHz or larger between heating and cooling processes. After the fiber was annealed for 9 h at 850~ °C , however, the hysteresis almost disappeared and, among repeated temperature cycles in the ranges of 20-820~ °C and of 500-800~ °C , the maximum frequency discrepancy was reduced to ±12.5 MHz or less. It is thus demonstrated that a suitably annealed fiber is reliable for the Brillouin shift-based distributed sensing over the wide temperature range.
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