| Title |
Study on Temperature Measurement Using Dual-Tapered Double-Clad Fiber Insensitive to Longitudinal Strain and External Refractive Index |
| Authors |
Minchan Bae ; Jaeho Seo ; Yong Wook Lee |
| DOI |
http://doi.org/10.5207/JIEIE.2024.38.2.094 |
| Keywords |
Double-clad fiber; Dual-taper; Refractive index; Strain; Temperature |
| Abstract |
In this study, we have demonstrated temperature measurement using dual-tapered double-clad fiber (DT-DCF), which generates in-fiber Mach-Zehnder interference and is insensitive to longitudinal strain and external refractive index (RI) perturbations. In the transmission spectrum of the fabricated DT-DCF, two interference dips were selected as sensor indicators and designated D1 and D2. The spectral responses of the two sensor indicators were investigated for ambient temperature, longitudinal strain, and surrounding refractive index variations. First, the ambient temperature of the DT-DCF was increased from 30 to 80°C using a hot plate to investigate the wavelength shifts of D1 and D2 with temperature changes. D1 and D2 showed temperature-induced wavelength shifts of ∼3.98 and ∼3.80nm, and the adjusted R 2 values in linear regression results were evaluated as ∼0.99746 and ∼0.99863, respectively. For longitudinal strain variations from 0 to ∼4137.94με, applied to the DT-DCF, D1 and D2 showed strain-induced wavelength changes of -0.48 and 0.08nm, respectively. From this strain response of the DT-DCF, it is expected that an unwanted longitudinal strain of 100με, which can be applied to the DT-DCF during temperature measurement, can cause measurement errors of 0.30% and 0.06% for D1 and D2, respectively, over the entire temperature measurement range (30∼50°C), confirming that the DT-DCF is insensitive to longitudinal strain. Similarly, for the surrounding RI changes of the DT-DCF (from 1.3330 to 1.4201 RIU), D1 and D2 showed RI-induced wavelength shifts of -0.16 and 0.08nm, respectively. From the RI response of the DT-DCF, we can see that the above total RI change can introduce measurement errors of 0.46% and 0.24% for D1 and D2, respectively, during temperature measurement, and that the sensor indicators are insensitive to external RI. |