Abstract
We have proposed a novel tapered-single mode-no core-single mode (TSNS) fiber refractometer based on multimode interference. The TSNS structure exhibits a high contrast ratio (>15 dB) and a uniform interference fringe. The influence of different lengths and diameters of the TSNS on the refractive index unit (RIU) sensitivity was investigated. The experimental investigations indicated a maximum sensitivity of 1517.28 nm/RIU for a refractive index of 1.417 and low-temperature sensitivity (<10 pm/°C). The experimental and simulation results are also in good agreement.
Highlights
Optical fiber refractive index sensors have several advantages such as minimization, stability, fast response, and so on
The low-temperature sensitivity is attributed to the no core fiber (NCF) prepared from pure silica because it has a similar thermo-optic coefficient of the pure silica between the LP01 and LP0m [26]
A simulation model based on the 3D-FD-BPM is used to theoretically study the response to the external refractive index
Summary
Optical fiber refractive index sensors have several advantages such as minimization, stability, fast response, and so on. The interference patterns formed by multiple mode coupling deteriorates with the increase in the refractive index so as to reduce the spectrum quality for sensing signal demodulation [15,16]. These problems result in difficulties in selecting reference wavelengths. SNS or SMS structures exhibit stable interference fringes before reducing the diameter of the fiber. They use taper technology just to get a stronger evanescent field. The test results show that multiple experimental samples have similar temperature responses (about 10 pm/◦ C)
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