Discriminative strain and temperature sensing using a ring-hyperbolic tangent fiber sensor
Alaaeddine Rjeb, Amr M. Ragheb, Maged Abdullah Esmail, Habib Fathallah, Saleh A. Alshebeili
Abstract
Brillouin fiber sensors have demonstrated strong capability in discriminative and high-sensitivity multiparameter measurements. In this study, we proposed and numerically investigated novel ring core fiber–based stimulated Brillouin scattering for the simultaneous measurement of temperature and strain. The novel fiber, referred to as ring hyperbolic tangent (R-HTAN) fiber, is characterized by a shape parameter ( α ) that controls the optical refractive index and longitudinal acoustic velocity profiles. Numerical modal simulations indicated that the Brillouin gain spectrum contained multiple widely spaced and high-gain peaks, which were attributed to the strong interaction between the optical linearly polarized mode (i.e., LP 0,1 as a pump wave) and multiple high-order longitudinal acoustic modes. The designed R-HTAN fiber enabled the discriminative sensing of temperature and strain with levels that clearly surpassed values recently reported in the literature. In case of straight R-HTAN fiber ( α = 0), the maximum <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"> <mml:msubsup> <mml:mi>C</mml:mi> <mml:mrow class="MJX-TeXAtom-ORD"> <mml:mo stretchy="false">(</mml:mo> <mml:mi>α</mml:mi> <mml:mo>=</mml:mo> <mml:mn>0</mml:mn> <mml:mo stretchy="false">)</mml:mo> </mml:mrow> <mml:mi>T</mml:mi> </mml:msubsup> </mml:math> and <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"> <mml:msubsup> <mml:mi>C</mml:mi> <mml:mrow class="MJX-TeXAtom-ORD"> <mml:mo stretchy="false">(</mml:mo> <mml:mi>α</mml:mi> <mml:mo>=</mml:mo> <mml:mn>0</mml:mn> <mml:mo stretchy="false">)</mml:mo> </mml:mrow> <mml:mrow class="MJX-TeXAtom-ORD"> <mml:mi>ε</mml:mi> </mml:mrow> </mml:msubsup> </mml:math> are 1.928 MHz/ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"> <mml:msup> <mml:mi/> <mml:mo>∘</mml:mo> </mml:msup> </mml:math> C and 0.087 MHz, respectively. In case of graded R-HTAN fiber ( α = 1), the maximum <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"> <mml:msubsup> <mml:mi>C</mml:mi> <mml:mrow class="MJX-TeXAtom-ORD"> <mml:mo stretchy="false">(</mml:mo> <mml:mi>α</mml:mi> <mml:mo>=</mml:mo> <mml:mn>1</mml:mn> <mml:mo stretchy="false">)</mml:mo> </mml:mrow> <mml:mi>T</mml:mi> </mml:msubsup> </mml:math> and <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"> <mml:msubsup> <mml:mi>C</mml:mi> <mml:mrow class="MJX-TeXAtom-ORD"> <mml:mo stretchy="false">(</mml:mo> <mml:mi>α</mml:mi> <mml:mo>=</mml:mo> <mml:mn>1</mml:mn> <mml:mo stretchy="false">)</mml:mo> </mml:mrow> <mml:mrow class="MJX-TeXAtom-ORD"> <mml:mi>ε</mml:mi> </mml:mrow> </mml:msubsup> </mml:math> are 1.872 MHz/ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"> <mml:msup> <mml:mi/> <mml:mo>∘</mml:mo> </mml:msup> </mml:math> C and 0.0842 MHz/ μ ɛ, respectively. The errors associated with temperature measurements (maximum δT ( α =0) = 0.0846 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"> <mml:msup> <mml:mi/> <mml:mo>∘</mml:mo> </mml:msup> </mml:math> C and maximum δT ( α =1) = 7.4184 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"> <mml:msup> <mml:mi/> <mml:mo>∘</mml:mo> </mml:msup> </mml:math> C) and strain measurements (maximum δ ɛ ( α =0) = 0.7250 μ ɛ and maximum δ ɛ ( α =1) = 7.4184 μ ɛ) demonstrated that the proposed fiber could be a promising candidate for next-generation Brillouin sensing systems for enabling temperature and strain discrimination.