Abstract

Three functional materials were coated on tilted fiber Bragg grating (TFBG) sensors, and through the analysis of the characteristics of TBFG sensors’ amplitudes in the core and cladding modes, their abilities to sense humidity were compared. The mechanisms by which physical moisture absorption sensing was achieved through the three materials were investigated. The degree of sensitivity in terms of resonance wavelength in the cladding mode for the three coating materials was PAHP4 > PEDOT:PSS > GO. The sensitivity in the cladding modes of the tested sensor showed that the best resonance wavelength was as high as 0.0112 nm/% RH and was achieved for the TFBG coated with PAHP4 due to the hydrophilic groups around the material, which are good at forming hydrogen bond interactions with H2O.

Highlights

  • Functional materials have attracted considerable attention recently, with the use of such materials in various types of sensors being especially notable

  • Miao et al.11 proposed an Relative humidity (RH) sensor based on the tilted fiber Bragg grating (TFBG) that was fabricated by utilizing polyvinyl alcohol (PVA) as the sensitive cladding film, as the RH increase in the PVA coating would result in the reduction of the refractive index of the fiber

  • Wang12 introduced a sensor coated with a graphene oxide (GO) film to find out the amplitudes of the cladding mode resonances of the TFBG as they varied with the water sorption and desorption processes

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Summary

INTRODUCTION

Functional materials have attracted considerable attention recently, with the use of such materials in various types of sensors being especially notable. There is considerable potential for the further development of their application in optical fiber sensors for strain monitoring, magnetic field and refractive index (RI) sensing, humidity sensing, biochemical sensing, gas sensing, and the sensing of glucose concentrations in vitro.. Fiber sensors used for physical detection have been developed using fiber Bragg grating (FBG) structures fabricated on optic fibers. Fiber optic sensors with tilted fiber Bragg grating (TFBG) structures have been further developed for application in various physical phenomena, and RI detection sensors were used to enhance signal sensitivity with controllable cross-sensitivities.. To combine the advantages of the tilted optical fiber grating and a polymer coated as a smart material, a sulfated polyaromatic hydrocarbon derivative termed PAHP4 was designed through chemical engineering that configures the SO3− functional group and polyaromatic group into a simple polymer configuration that offers high sensitivity, high stability, and a repeatable sensing range for humidity sensing. A TFBG sensor coated with PAHP4 could be utilized in real-time RH monitoring and for evaluation in normal or extremely humid environments

WORKING PRINCIPLE OF THE TFBG
RESULTS AND DISCUSSION
TFBG coated with GO as a humidity sensing material
TFBG coated with PEDOT:PSS as a humidity sensing material
TFBG coated with PAHP4 as a humidity sensing material
CONCLUSION
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