Abstract
A novel intensity demodulated refractive index (RI) sensor is theoretically and experimentally demonstrated based on the front-tapered single-mode-multimode-single-mode (FT-SMS) fiber structure. The front taper is fabricated in a section of multimode fiber by flame-heated drawing technique. The intensity feature in the taper area is analyzed through the beam propagation method and the comprehensive tests are then conducted in terms of RI and temperature. The experimental results show that, in FT-SMS, the relative sensitivity is −342.815 dB/RIU in the range of 1.33~1.37. The corresponding resolution reaches 2.92 × 10−5 RIU, which is more than four times higher than that in wavelength demodulation. The temperature sensitivity is 0.307 dB/°C and the measurement error from cross-sensitivity is less than 2 × 10−4. In addition, fabricated RI sensor presents high stability in terms of wavelength (±0.045 nm) and intensity (±0.386 dB) within 2 h of continuous operation.
Highlights
Fiber refractive index (RI) sensors play a significant role in the fields of biology, chemistry, and medicine [1]
The tapered-multi-core and multi-taper-based schemes have been respectively proposed, and the over-200-nm/RIU sensitivity was obtained in References [16,17]
An intensity demodulated RI sensor is proposed to gain higher measured precision based on the front-taper SMS (FT-SMS) fiber structure, in which a taper is fabricated in the front of a based on the front-taper SMS (FT-SMS) fiber structure, in which a taper is fabricated in the front section of multimode fiber (MMF) by flame-heated drawing
Summary
Fiber refractive index (RI) sensors play a significant role in the fields of biology, chemistry, and medicine [1]. An intensity demodulated RI sensor is proposed to gain higher measured precision based on the front-taper SMS (FT-SMS) fiber structure, in which a taper is fabricated in the front of a based on the front-taper SMS (FT-SMS) fiber structure, in which a taper is fabricated in the front section of MMF by flame-heated drawing. The composite modal interference is formed, intensity feature in taper area is analyzed through the beam propagation method. With the increased external RI, and the relative sensitivity reaches −342.815 dB/RIU in the range of Compared to wavelength demodulation, four times enhancement in detecting resolution is obtained. The measured error from cross-sensitivity is limited within 2 × 10−4 , owing temperature sensitivity This fabricated RI sensor, presents high stability in terms of wavelength to low-temperature sensitivity.
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