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.
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机译:基于前锥形单模-多模-单模(FT-SMS)光纤结构,在理论上和实验上证明了一种新颖的强度解调折射率(RI)传感器。通过火焰加热拉伸技术将前锥度加工成一段多模光纤。通过束传播方法分析了锥形区域的强度特征,然后根据RI和温度进行了综合测试。实验结果表明,在FT-SMS中,相对灵敏度在1.33〜1.37范围内约为342.815 dB / RIU。相应的分辨率达到2.92×10×5 RIU,比波长解调的分辨率高四倍以上。温度灵敏度为0.307 dB /°C,交叉灵敏度引起的测量误差小于2×10?4。此外,在连续运行2小时内,制成的RI传感器在波长(±0.045 nm)和强度(±0.386 dB)方面具有很高的稳定性。
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