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. 2021 Mar 3;12(3):258.
doi: 10.3390/mi12030258.

Dual Demodulation of Temperature and Refractive Index Using Ring Core Fiber Based Mach-Zehnder Interferometer

Weihao Yuan  1 , Changyuan Yu  1
Affiliations

Dual Demodulation of Temperature and Refractive Index Using Ring Core Fiber Based Mach-Zehnder Interferometer

Weihao Yuan et al. Micromachines (Basel). .

Abstract

We report the ring core fiber spliced with single mode fiber and no core fiber which is used for temperature and refractive index (RI) sensing. The Mach-Zehnder interferometer (MZI) is formed with this kind of sandwich fiber structure and the maximum extinction ratio of the interference spectra reaches 27 dB with the free spectra range of 12 nm. The MZI fiber sensor is applied for temperature sensing with the sensitivity of 69 pm/°C and 0.051 dB/°C. The RI sensitivity reaches 182.07 dB/RIU and -31.44 nm/RIU with the RI ranging from 1.33 to 1.38. The RI value can be directly demodulated with the interference dip intensity which shows insensitivity to temperature. The demodulation of temperature can be achieved by using the linear equations between dip wavelength shift with the variation of temperature and RI.

Keywords: Mach-Zehnder interferometer; refractive index; ring core fiber; temperature.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
The microscope images of RCF (a) and the RI distribution along the diameter (dash line) (b).
Figure 2
Figure 2
The schematic diagram of the MZI with the SMF-NCF-RCF-SMF structure.
Figure 3
Figure 3
The Rsoft simulation results of SMF-RCF-SMF structure (a) and SMF-NCF-RCF-SMF structure (b).
Figure 4
Figure 4
The interference spectrum of the MZI (inset) and the FFT spectrum.
Figure 5
Figure 5
The MZI interference spectra at different temperatures ranging from 35 °C to 70 °C with the interval of 5 °C (a) and the mathematical statistics of temperature and dip wavelength with procedure of temperature increasing and decreasing (b).
Figure 6
Figure 6
The relationship between interference dip intensity and temperature change at the dip wavelength of around 1508 nm.
Figure 7
Figure 7
The MZI interference spectra with different RIs ranging from 1.33 to 1.38 with the interval of 0.01 (a) and the relationship between RI and the intensity of interference dips (b).
Figure 8
Figure 8
The mathematical statistics of RI and wavelength shift at the dip of around 1505 nm.
See this image and copyright information in PMC

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