Abstract
A refractive index sensor based on a multi-core micro/nano fiber is proposed for low refractive index solutions. At first, the mode field distribution of the tapered multi-core fiber is analyzed with the finite element model (FEM). After that, the relationship between the refractive index sensitivity and the diameter of the multi-core micro/nano fiber is calculated. At last, four sensors with different sizes are explored, and when the taper length is 16.20 mm, the refractive index sensitivity of the sensor can reach 5815.50 nm/RIU, which agrees with the theoretical analysis. The refractive index measurement error is less than 0.5‰, which has a high practical application value. The longer the taper length is, the smaller the fiber diameter is. According to the theoretical analysis, when the fiber diameter is less than 4.864 µm, the structure sensor’s refractive index sensitivity is higher than 10000 nm/RIU. At the same time, when the sensor’s taper length is 15.99 mm, its temperature sensitivity is −0.1084 nm/°C. Compared with single-mode fiber, the sensor proposed here has the advantages of stability, compact structure, and high sensitivity, which has a potential in the field of seawater salinity measurement.
Highlights
The measurement of refractive index plays an important role in the fields of biological, chemical, and water environmental monitoring [1]
Both ends of the three-core fiber (TCF) are fused with two sections of multi-mode fiber (MMF) of 1 mm length, the other ends of the two MMFs are fused with two single mode fiber (SMF), separately
A multi-core micro/nano fiber sensor is developed for the requirements of high-precision measurement of refractive index
Summary
The measurement of refractive index plays an important role in the fields of biological, chemical, and water environmental monitoring [1]. The minimum deflection angle method [2] and the Abbe refractometer instrument [3] are two main techniques in the measurement of liquid refractive index. These technologies are low in sensitivity and require a lot of manual operations, which are not suitable for practical industrial applications. A Fabry-Perot interferometer is formed by the RIMD and fiber end face. This sensor has an ultra-high sensitivity of. At the end of the paper, the temperature sensing experiments are carried out by this multi-core micro/nano fiber interferometric sensor. When the taper length is 15.99 mm, the temperature sensitivity of 0.1084 nm/ °C is obtained
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