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International Journal of Antennas and Propagation
Volume 2014, Article ID 938693, 9 pages
http://dx.doi.org/10.1155/2014/938693
Research Article

Optical Coupling Structures of Fiber-Optic Mach-Zehnder Interferometers Using CO2 Laser Irradiation

1Department of Physics, National Chung Cheng University, Chiayi 62102, Taiwan
2Center for Nano Bio-Detection, National Chung Cheng University, Chiayi 62102, Taiwan
3Department of Biomechatronics Engineering, National Pingtung University of Science and Technology, Pingtung 912, Taiwan
4Department of Mechanical Engineering, National Pingtung University of Science and Technology, Pingtung 912, Taiwan
5Department of Construction Engineering, National Yunlin University of Science and Technology, Yunlin 640, Taiwan

Received 3 January 2014; Accepted 3 March 2014; Published 15 June 2014

Academic Editor: Chung-Liang Chang

Copyright © 2014 Chien-Hsing Chen et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

The Mach-Zehnder interferometer (MZI) can be used to test changes in the refractive index of sucrose solutions at different concentrations. However, the popularity of this measurement tool is limited by its substantial size and portability. Therefore, the MZI was integrated with a small fiber-optic waveguide component to develop an interferometer with fiber-optic characteristics, specifically a fiber-optic Mach-Zehnder interferometer (FO-MZI). Optical fiber must be processed to fabricate two optical coupling structures. The two optical coupling structures are a duplicate of the beam splitter, an optical component of the interferometer. Therefore, when the sensor length and the two optical coupling structures vary, the time or path for optical transmission in the sensor changes, thereby influencing the back-end interference signals. The researchers successfully developed an asymmetrical FO-MZI with sensing abilities. The spacing value between the troughs of the sensor length and interference signal exhibited an inverse relationship. In addition, image analysis was employed to examine the size-matching relationship between various sensor lengths and the coupling and decoupling structure. Furthermore, the spectral wavelength shift results measured using a refractive index sensor indicate that FO-MZIs with a sensor length of 38 mm exhibited excellent sensitivity, measuring 59.7 nm/RIU.