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This paper introduces a double-parameter distributed fiber sensing system that utilizes stimulated Brillouin scattering in a specialized fiber, distinguished by two gain peaks in its scattering spectrum with nearly identical intensity levels. Employing this specialty fiber in a Brillouin optical time domain analysis system, we conduct a comprehensive analysis highlighting their efficacy in the simultaneous measurement of strain and temperature. These fibers are characterized by a significant temperature coefficient disparity (~0.2 MHz/°C) between the two peaks, and similar large peak gain amplitudes resulting minimal Brillouin frequency shift uncertainties, thereby substantially reducing strain and temperature measurement errors. We evaluated strain and temperature coefficients of 47 kHz/με, 1.15 MHz/°C for the first peak, and 51 kHz/με, 1.37 MHz/°C for the second one, which were then applied in the simultaneous measurement of strain and temperature under various conditions, including an applied strain of 1220 με at temperatures of 62°C and 72°C. The results indicate a significant enhancement in measurement accuracy, reducing errors to ~17 με and ~ 0.9°C in terms of strain and temperature respectively. Additionally, strain and temperature errors due to the impact of the variance of Brillouin frequency shift uncertainty between two peaks are explored. This study underscores the potential of the proposed double- Brillouin peak fiber in critical applications such as long-distance natural gas pipeline monitoring, where precise and distinct measurements of strain and temperature are paramount.
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