Refractive Index Sensor Based on Graphene Oxide-Coated Long-Period Fiber Grating Inscribed in a Two-Mode Fiber

Abstract

Refractive index (RI) sensing is a promising technique in a variety of different scientific and industrial applications. In this paper, we theoretically and experimentally propose a newly-designed RI sensor. The proposed sensor consists of a particular long-period fiber grating inscribed in a two-mode fiber (LPFG-TMF) coated with tunable graphene oxide (GO), and the special structure allows an extremely high sensitivity in the transition region. The mode coupling between the LP 11 core mode and the sixth-order cladding mode in the LPFG-TMF offers an apparently higher sensitivity feature. And the sensitivity is higher than that of a single-mode fiber-based LPFG (LPFG-SMF), which originates from the coupling between the core mode and the sixth-order cladding mode. Furthermore, the ultrasonic treatment time of GO, which impacts on the properties and performance of RI sensing, is also studied and investigated. Proof-of-concept results demonstrate significantly that comparing with the bare LPFG-TMF (621.66 nm/RIU) and LPFG-SMF coated with GO ultrasonicated 5 hours (323.68nm/RIU), the LPFG-TMF coated with GO ultra-sonicated 5 hours performs optimized sensitivity of 11605.79 nm/RIU when surrounding RI ranges from 1.4558 to 1.4577. With its premium ability to operate highsensitivity measurements, the RI sensing is expected to be useful for broad applications across the chemical fields. INDEX TERMS graphene oxide, long-period fiber grating, refractive index measurement, two-mode fiber.

Fiber Bragg Grating Salinity Sensor Array Based on Fiber Tapering and HF Etching

“…They are known for their low insertion loss, wide bandwidth, ease of fabrication, and integrative properties. LPFGs can be directly utilized for salinity sensing and exhibit high sensitivity to changes in ambient medium salinity over a wide range [17,18]. However, LPFGs have relatively broad transmission dips [19], leading to lower measurement accuracy.…”

Novel optical fiber Vernier immunosensor based on cascading Sagnac loops embedded with excessively tilted fiber grating for specific detection of canine distemper virus

“…Label-free optical fiber biosensors responding to minute changes of surrounding refractive index (RI) have been attracting continuous attention in biomedical/ chemical engineering, environmental monitoring and food safety owing to the unparalleled advantages of compact size, highly electromagnetic immunity, fast response, easy implementation as well as low cost [5][6][7][8]. Various types of optical fiber RI sensors including microfibers [9][10][11], multimode fibers [12,13], photonic crystal fibers [14], fiber gratings [15][16][17][18] have been proposed, among them, excessively tilted fiber gratings (ExTFGs) have been proved to be a promising candidate for monitoring tiny biomolecule solution samples due to the relatively higher RI sensitivity, much lower temperature crosstalk and higher stability as compared with etched fiber Bragg gratings (FBGs) and long period fiber gratings (LPFGs) [19,20]. Luo [21] developed a novel immunosensor to detect Newcastle disease virus (NDV) based on ExTFG coated with gold nanospheres (AuNs).…”

Intensity Modulated Gas RI Sensor Based on Inornate Antiresonant Hollow-Core Fiber With Ultrahigh Sensitivity

“…The refractive index (RI) of a gas is seen as a gauge of information such as its concentration, type, and optical properties, which are of great significance in the petrochemical industry [1], gas lasing systems [2] and environmental monitoring [3]. Numerous fiber-optic sensors have been proposed for RI detection, such as modal interferometer [4], opened-cavity Mach-Zehnder interferometer [5], fiber surface plasmon resonance sensor [6], trench-embedding fiber taper [7], long-period grating [8][9], and tilted fiber Bragg grating [10]. Most RI sensors are designed for an aquatic environment, that the RI measurement region is approximately 1.33.…”