LPG-based PVA coated sensor for relative humidity measurement

Abstract

A long period grating (LPG)-based optical fiber sensor, coated with polyvinyl alcohol, has been developed for relative humidity (RH) measurement over the range from 33%RH to 97%RH, for which the grating response has been monitored. The fiber optic sensor using the LPG has been designed to monitor the change in resonance loss which is then related to the humidity measured through calibration of the sensor with a series of materials of known refractive index. Results on the calibration and use of the sensor are reported and considered in this work, in light of other gratingbased methods for humidity measurement.

Long Period Fiber Grating Humidity Sensor With Gelatin/Cobalt Chloride Coating

“…The nonlinearity evident in Fig. 3 can be due to light source fluctuations and dual source techniques can be used to overcome this nonlinearity [2]. Stability test was also carried out with sensor probe kept in the humidity control chamber at 70% RH level for 300 minutes and monitoring its transmission spectrum after every 10 minutes as shown in Fig.…”

“…Various sensing schemes based on fiber optics have been studied to develop all-optical RH sensors [1], [2]. Several LPFG based humidity sensors using different overlay materials and distinct sensitivities have been reported [3]- [6].…”

Zinc oxide nanoparticle-doped nanoporous solgel fiber as a humidity sensor with enhanced sensitivity and large linear dynamic range

“…This reagent undergoes a chemical transformation when exposed to RH perturbations, which leads to either the change of its mechanical properties or to an altogether different chemical species optically active (directly interacts) at these wavelengths, enabling intensity/wavelength modulation. For this reason, wavelength modulation sensors in [13][14][15][16][17] have used polymer coated LPG/ FBG. For LPG based RH sensors, highest dynamic range of 33%-97% RH was observed in [13], but the sensor response was nonlinear throughout.…”

“…For this reason, wavelength modulation sensors in [13][14][15][16][17] have used polymer coated LPG/ FBG. For LPG based RH sensors, highest dynamic range of 33%-97% RH was observed in [13], but the sensor response was nonlinear throughout. For FBG based RH sensors, a maximum overall sensitivity of 0.266 mV/%RH with highest linear dynamic range of 11%-98% RH was observed in [17].…”

“…Both the techniques-extrinsic [2] as well as intrinsic-have been employed to develop these sensors. Especially in intrinsic techniques, intensity modulation through evanescent wave absorption/ scattering/modal power coupling [1,[3][4][5][6][7][8][9][10][11][12], wavelength modulation through long period gratings (LPGs) [13][14][15]/fiber Bragg gratings (FBGs) [16,17]/ hetero-core fiber structure [18], and the phase modulation through an interferometric structure [19,20] have emerged as the most popular techniques to realize optical fiber RH sensor. It is worth mentioning that the optical signal propagating in the fiber at an operating wavelength such as ∼632.8 nm or ∼1550 nm does not directly interact with applied humidity perturbations, and hence cannot lead to a direct intensity/wavelength modulation.…”