Fabrication Quality Analysis of a Fiber Optic Refractive Index Sensor Created by CO2 Laser Machining

Sensors

Chien-Hsing Chen¹  Bo-Kuan Yeh²  Jaw-Luen Tang¹ 

[1] Department of Physics, National Chung Cheng University, Chiayi 621, Taiwan; E-Mails:;Department of Biomechatronics Engineering, National Pingtung University of Science and Technology, Pingtung 912, Taiwan; E-Mail:

关键词: CO₂ laser machining;    optical fiber sensor;    refractive index sensing;   

DOI  :  10.3390/s130404067

来源: mdpi

【 摘 要 】

This study investigates the CO₂ laser-stripped partial cladding of silica-based optic fibers with a core diameter of 400 μm, which enables them to sense the refractive index of the surrounding environment. However, inappropriate treatments during the machining process can generate a number of defects in the optic fiber sensors. Therefore, the quality of optic fiber sensors fabricated using CO₂ laser machining must be analyzed. The results show that analysis of the fiber core size after machining can provide preliminary defect detection, and qualitative analysis of the optical transmission defects can be used to identify imperfections that are difficult to observe through size analysis. To more precisely and quantitatively detect fabrication defects, we included a tensile test and numerical aperture measurements in this study. After a series of quality inspections, we proposed improvements to the existing CO₂ laser machining parameters, namely, a vertical scanning pathway, 4 W of power, and a feed rate of 9.45 cm/s. Using these improved parameters, we created optical fiber sensors with a core diameter of approximately 400 μm, no obvious optical transmission defects, a numerical aperture of 0.52 ± 0.019, a 0.886 Weibull modulus, and a 1.186 Weibull-shaped parameter. Finally, we used the optical fiber sensor fabricated using the improved parameters to measure the refractive indices of various solutions. The results show that a refractive-index resolution of 1.8 × 10⁻⁴ RIU (linear fitting R² = 0.954) was achieved for sucrose solutions with refractive indices ranging between 1.333 and 1.383. We also adopted the particle plasmon resonance sensing scheme using the fabricated optical fibers. The results provided additional information, specifically, a superior sensor resolution of 5.73 × 10⁻⁵ RIU, and greater linearity at R² = 0.999.

【 授权许可】

CC BY   
© 2013 by the authors; licensee MDPI, Basel, Switzerland.