Single-Mode Modified Tapered Fiber Structure Functionalized With GO-PVA Composite Layer for Relative Humidity Sensing

Abstract

A sensitive tapered optical fiber sensor incorporating graphene oxide (GO) and polyvinyl alcohol (PVA) composite film for the rapid measurement of changes in relative humidity was proposed and experimentally demonstrated. The sensing principle was based on the intensity modulation of the transmitted light induced by the refractive index changes of the sensitive coatings. The sensing region was obtained by tapering a section of single-mode optical fiber (SMF) from its original 125 µm diameter down to 9.03 µm. The tapered structure was then modified through deposition of GO/PVA nanocomposites by using the dip-coating technique. The field emission scanning electron microscope (FESEM) and Raman spectroscopy were used to characterize the structure of the composite film. As evidenced by a Fourier transform infrared spectroscopy (FTIR) analysis, the presence of oxygen functional groups (such as-OH and COOH) on the GO structure enabled the attachment of PVA molecules through hydrogen bonding and strong adhesion between GO/PVA layers. The performance of the sensor was tested over a wide range (20% RH to 99.9% RH) of relative humidity. The sensor showed a good response with its signal increasing linearly with the surrounding humidity. The tapered optical fiber sensor with the coating of GO/0.3 g PVA achieved the highest sensitivity [0.5290 RH (%)]. The stability, repeatability, reversibility, as well as response time of the designated sensor were also measured and analyzed.

Relative Humidity Measurement Based on a Tapered, PVA-Coated Fiber Optics Multimode Interference Sensor

“…This behavior fits the trend with other cited high-sensitivity RH sensors with a shortened sensing range [26][27][28]. Moreover, the taper of the sensor presented is significantly thicker and shorter than those required in other works [27,29], which ultimately favors its manageability and robustness in practical applications. In the following, we analyze in more detail the performance of the sensor presented, starting with its dynamic range.…”

Review of Optical Humidity Sensors

“…Aneez Syuhada et al [ 157 ] fabricated a non-adiabatic tapered fiber coated with humidity-sensitive GO/PVA nanocomposite film and monitored the transmitted intensity count as a function of applied RH. A sensitivity of 0.0062 (a.u.…”

Graphene-Fiber Biochemical Sensors: Principles, Implementations, and Advances

“…In this section, we systematically classify the sensing objects of biochemical sensors into gas and liquid categories. Among them, gases include gas molecules, water molecules, and volatile substances, while liquids mainly include carbohydrates, biomacromolecules, aqueous ions, and other clinically relevant analytes [48][49][50][51][52]. In the following content, we will introduce the latest research progress of graphene-fiber sensors, including different sensing structures and sensing targets, and analyze their sensing performances.…”