A novel class of multi-D-shaped optical fiber suited for refractive index measurements is presented. The multi-D-shaped optical fiber was constructed by forming several D-sections in a multimode optical fiber at localized regions with femtosecond laser pulses. The total number of D-shaped zones fabricated could range from three to seven. Each D-shaped zone covered a sensor volume of 100 μm depth, 250 μm width, and 1 mm length. The mean roughness of the core surface obtained by the AFM images was 231.7 nm, which is relatively smooth. Results of the tensile test indicated that the fibers have sufficient mechanical strength to resist damage from further processing. The multi-D-shaped optical fiber as a high sensitive refractive-index sensor to detect changes in the surrounding refractive index was studied. The results for different concentrations of sucrose solution show that a resolution of 1.27 × 10−3–3.13 × 10−4 RIU is achieved for refractive indices in the range of 1.333 to 1.403, suggesting that the multi-D-shaped fibers are attractive for chemical, biological, and biochemical sensing with aqueous solutions.
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机译：提出了适用于折射率测量的新型一类多D形光纤。通过用飞秒激光脉冲在局部区域的多模光纤中形成几个D形截面来构造多D形光纤。所制造的D形区域的总数可以在三个到七个之间。每个D形区域覆盖的传感器体积为深度100μm，宽度250μm和长度1 mm。通过AFM图像获得的芯表面的平均粗糙度为231.7nm，这是相对光滑的。拉伸试验的结果表明纤维具有足够的机械强度以抵抗进一步加工的损害。研究了将多D形光纤用作检测周围折射率变化的高灵敏折射率传感器。对于不同浓度的蔗糖溶液，结果表明，对于折射率范围为1.333至1.333的RIU，分辨率为1.27×10 -3 –3.13×10 −4 RIU 1.403，表明多D形纤维对于水溶液的化学，生物和生化传感具有吸引力。
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