Integrated Reflective Lyot Filter and FBG Structure for Simultaneous Sensing of Temperature and Axial Strain in Fiber Ring Laser
Zhengyu Liu, Haiwei Zhang, Zhihong Chen, Lifang Xue, Pengbo Jiang, Wei Shi, Jianquan Yao
Abstract
An integrated all-fiber reflective Lyot (RL) filter and fiber Bragg gating (FBG) sensor for simultaneous sensing of temperature and axial strain is proposed and demonstrated experimentally based on a dual-wavelength fiber ring laser (FRL) in this article. Because of the gain competition between simultaneous dual-wavelength lasers, a narrow 3-dB bandwidth less than 0.03 nm and an optical signal-to-noise ratio (OSNR) higher than 50 dB are achieved. The laser emission peaks exhibit different wavelength shifts due to their different responses to temperature and axial strain variations; thus, simultaneous measurement of temperature and axial strain can be easily achieved by establishing and demodulating a sensing matrix. The sensing system exhibits the maximum sensitivities of −1.03 nm/°C and 7.33 pm/<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \varepsilon $ </tex-math></inline-formula> for temperature and axial strain, respectively, with a low detection limit (DL) of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$- 1.38\times 10^{-{3}}~^{\circ }$ </tex-math></inline-formula>C and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$0.19~\mu \varepsilon $ </tex-math></inline-formula> as well as a high spectral quality factor (Q) of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$1.77\times 10^{{3}}$ </tex-math></inline-formula> and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$8.95\times 10^{{4}}$ </tex-math></inline-formula>. Through selecting the temperature and axial strain randomly and comparing with data demodulated from the sensing matrix, the corresponding maximum temperature and axial strain errors are measured to be <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$0.172~^{\circ }$ </tex-math></inline-formula>C and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$27~\mu \varepsilon $ </tex-math></inline-formula>, respectively. The proposed sensor is demonstrated to be capable of simultaneous sensing accuracy and potential applications in dual-parameter detection.