High Sensitivity Hollow Fiber Temperature Sensor Based on Surface Plasmon Resonance and Liquid Filling

A high sensitivity hollow fiber temperature sensor based on surface plasmon resonance (SPR) and liquid core is designed and analyzed using a finite element method. Toluene with high refractive index and large thermo-optic coefficient is sealed into the hollow-core of the fiber to guarantee the total internal reflection and works as the sensing medium. One single air hole near the fiber core is coated with gold to generate surface plasmons, and two orthogonal polarization core modes (
${\rm{HE}}_{{\rm{11}}}^{x}$
and
${\rm{HE}}_{{\rm{11}}}^{y}$
) can be supported due to the asymmetrical SPR region. Contrary to the blue-shift of other liquid-filled SPR temperature sensors, the resonance peak of the designed sensor shifts to the longer wavelength with the increase in temperature. A large temperature range from 20 °C to 100 °C is calculated and the extremely high sensitivity 6.51 nm/°C in a good linear relationship is obtained. Moreover, the structure parameters and liquid factors are also discussed to optimize the sensor's performance.