Temperature-compensated high-sensitivity refractive index, liquid level and PH sensing realization enabled by a small-period microfiber long period grating cascaded with microfiber Bragg grating

• Published in: Sensors and actuators. A. Physical. Vol. 372; p. 115402
• Main Authors: Li, Hongtao, Wang, Weisheng, Sun, Huojiao, Wu, Hao, Wang, Xu, Zheng, Aiyun, Liang, Lili, Lu, Liang, Zhu, Jun, Yu, Qi, Lv, Jialiang, Yu, Benli
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.07.2024
• Subjects: Dual physicochemical parameters sensing; High sensitivity; Small-period microfiber long period grating; Temperature compensation; Small-period microfiber long period grating; Dual physicochemical parameters sensing; Temperature compensation; High sensitivity
• ISSN: 0924-4247; 1873-3069
• DOI: 10.1016/j.sna.2024.115402

Conventional reported optical fiber sensors could not have both good temperature-compensated characteristic and high PH sensing sensitivity. In this study, we proposed and fabricated a small-period microfiber long period grating (SP-mFLPG) cascaded with a line-by-line microfiber Bragg grating (mFBG) by using femtosecond (fs) laser directly writing technique for high-sensitivity temperature-compensated sensing refractive index(RI), liquid level(LL), PH value. To be the different from traditional LPG devices, the temperature sensitivities of SP-mFLPG was measured as −8.61 pm/℃ owing to the strong coupling occurred between the fundamental mode of TE11 mode and the higher-order mode of TE111, which could be compensated with the mFBG device with a temperature sensitivity of 7.85 pm/℃. On the basis of this temperature-insensitive sensing strategy, our proposed SP-mFLPG sensor can sense RI, LL and pH with high sensitivities of 866.343 nm/RIU, 7.224 nm/mm, −5.70 nm/PH, respectively. Our obtained PH sensitivity is much higher than numerous reported state-of-the-art optical fiber PH sensors. Thus, our proposed optical microfiber device can be found potential applications in real-time measuring some important biochemical reaction procedures. [Display omitted] •Temperature-compensated sensing by a SP-mFLPG cascaded with a mFBG sensor.•Temperature-insensitive sensing applications of LL, RI, and PH.•High RI, LL, and PH sensing sensitivities for the sensor.