Abstract
In this work, a dual refractive index and temperature sensor based on an interferometric system and on the empirical mode decomposition (EMD) algorithm is presented. Here, it is shown that the EMD provides a comprehensive way to analyze and decompose complex reflection spectra produced by an interferometric filter build at the tip of an optical fiber. By applying the EMD algorithm, the spectrum can be decomposed into a set of intrinsic mode functions (IMF) from which the temperature and the refractive index can be easily extracted. Moreover, the proposed methodology provides a detailed insight of the behavior of this type of interferometric sensors and allows widening of the dynamic measurement ranges of both variables. Here, for proof of principle purposes, a filter based on a stack of three layers (two of them were thermo-sensitive) was fabricated. Finally, it is shown that the proposed methodology can decompose the experimental measured spectra and to determine the refractive index and the temperature, supporting the mathematical model.
Highlights
In recent decades, several optical sensor designs for measuring refractive index have been proposed
It can be clearly observed that the overall spectrum R is formed by the superposition of two main spectra. One of these is due to the PL layer and it has a free spectral range FSR2 ≈22.05 nm and the second one is due to the Si layer with a FSR3 ≈4.16 nm
In this filter the IMF1 has a shorter FSR compared with the obtained for the filter F1; this is due to the F2 has a layer 3 considerably thicker than the used in filter F1
Summary
Several optical sensor designs for measuring refractive index have been proposed. The complexity of the overall spectrum of the reflected intensity distribution of the interferometer increases with the number of films, since it is formed by the superposition of several spectra which are due to multiple reflections occurring between the interfaces of the layers In these designs different materials can be deposited allowing us to control the visibility of the spectral fringes. For simultaneous measurement applications it is compulsory to model the behavior of the spectral pattern to validate the dynamic ranges of temperature and refractive index that can be measured by using linear relationships This is important because of the spectral fringes observed in the reflected intensity distribution spectrum can have different behavior depending on the combination of the refractive index and temperature values. A filter with two thermal-sensitive layers was fabricated and a sensor was implemented, later it is shown that the experimental results agree with the theoretical calculations supporting the proposed methodology
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
