Demodulation Method for GaAs Fiber-Optic Temperature Sensing Based on Reference Filter

This article presents a demodulation method for GaAs fiber-optic temperature sensing utilizing reference filters. The method employs a long-pass filter (LPF) waveform as the baseline reference waveform in the wavelength demodulation algorithm, effectively mitigating crosstalk from environmental parameters through the use of passive devices, thereby achieving superior noise resistance in GaAs fiber temperature sensing demodulation. Within the temperature measurement range from <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$- 30~^{\circ }$ </tex-math></inline-formula>C to <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$250~^{\circ }$ </tex-math></inline-formula>C, the theoretical wavelength demodulation error of this method can attain the picometer level. The average temperature demodulation error using the cross correlation algorithm with the LPF waveform as the reference baseline waveform is <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\pm 0.388~^{\circ }$ </tex-math></inline-formula>C. Compared with existing normalized optical intensity demodulation methods, the refined demodulation algorithm achieves a noise performance enhancement of up to 6.22 times. Moreover, compared to cross-correlation operations without using LPF reference waveform, improvements of up to 2.76 times are achieved.