Tapered Plastic Optical Fiber Coated With Al-Doped ZnO Nanostructures for Detecting Relative Humidity

High sensitivity humidity sensor based on cladding-etched optical fiber and lossy mode resonances

“…It can be distinguished different ways of measuring relative humidity with an OFHS. The first way would be by amplitude based techniques which consist of measuring changes in the transmitted optical power caused by changes on the optical absorption or on the refractive index of the coating [1,2,3,4]. The other way is named wavelength based techniques, which overcome the limitations of the previous technique, such as external noises or power fluctuations [5].…”

“…Development of adiabatic tapered optical fibered by means of chemical etching has been previously studied [20,21,23] and some theoretical approaches can be seen in [24]. There are also some OFHS that have employed chemical etching, for example, to improve the sensitivity of some interferometric devices [6], or to taper a plastic optical fiber and then, by adding an appropriate coating [3,4], to develop an evanescent wave OFHS, generally based on changes on the optical absorption or the refractive index of the coating which leads to changes on the transmitted optical power. Chemical etching has been also applied to other structures as long period gratings optical fibers in order to improve their sensitivity [25].…”

Humidity Sensor Based on Bragg Gratings Developed on the End Facet of an Optical Fiber by Sputtering of One Single Material

“…First, OFHSs utilized amplitude-based techniques [8,9,10,11,12], which measure changes on the transmitted optical power. This technique has a strong weakness as it depends on the power emitted by the light source, which can be altered by several undesired factors [13,14].…”

Optical Humidity Sensor Based on Tapered Fiber with Multi-walled Carbon Nanotubes Slurry

“…It is by reason of the differences of the effective refractive index of the cladding and allows more lights to be disseminated from the tapered optical fiber. In the previous research, there are a few of nanostructured materials have been used as a coating material, such as agarose gel [5], zinc oxide (ZnO) [6], graphene [7] and hydroxyethyl cellulose/polyvinylidene fluoride (HEC/PVDF) [8], recently.…”

“…Schematic illustration of the tapered fiber coated with nanostructured material coating A number of evanescent wave sensors have been demonstrated by experiment for humidity measurement. The sensing process is based on the desorption and adsorption activity, and the outer layer region culminated from the water vapor to clarify the sensing properties [6], [14]- [16]. Silica optical fiber (SOF) has been established in various applications including sensors and these features make it remarkable in resistance and flexibility to impacts and chemical reaction [17].…”