Abstract
This review is focused on microstructured optical fiber sensors developed in recent years for liquid RI sensing. The review is divided into three parts: the first section introduces a general view of the most relevant refractometric sensors that have been reported over the last thirty years. Section 2 discusses several microstructured optical fiber designs, namely, suspended-core fiber, photonic crystal fiber, large-core air-clad photonic crystal fiber, and others. This part is also divided into two main groups: the interferometric-based and resonance-based configurations. The sensing methods rely either on full/selective filling of the microstructured fiber air holes with a liquid analyte or by simply immersing the sensing fiber into the liquid analyte. The sensitivities and resolutions are tabled at the end of this section followed by a brief discussion of the obtained results. The last section concludes with some remarks about the microstructured fiber-based configurations developed for RI sensing and their potential for future applications.
Highlights
The great importance of measuring the refractive index (RI) in order to characterize the optical properties of fluids has led, over the past decades, to the development of RI sensors for applications in several areas such as the measurement of salinity of water [1], fuel quality analysis [2], or biotechnology processes [3]
This review focuses on microstructured optical fibers (MOFs) sensors developed in recent years for liquid RI sensing
In 2012, Lu et al [47] investigated numerically an surface plasmon resonance (SPR) sensor based on a grapefruit photonic crystal fiber (PCF) filled with different numbers of silver nanowires for RI sensing in aqueous environments
Summary
The great importance of measuring the refractive index (RI) in order to characterize the optical properties of fluids has led, over the past decades, to the development of RI sensors for applications in several areas such as the measurement of salinity of water [1], fuel quality analysis [2], or biotechnology processes [3]. Asseh et al [15] developed in 1998 an evanescent field RI sensor based on a fiber Bragg grating (FBG) with etched cladding, interrogated by a tunable DBR laser. This type of RI sensor relied on the evanescent tail of the core modes under fiber etching conditions. The appearance of new fiber geometries and drawing techniques allowed the fabrication of microstructured optical fibers (MOFs) These fibers have shown to be highly promising for sensing applications, due to its unique guiding properties, having greatly contributed to the expansion of RI sensing-area of research.
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