Influence of humidity and temperature on polyimide-coated fiber Bragg gratings

Characterisation of a polymer-coated fibre Bragg grating sensor for relative humidity sensing

“…The use of a FBG together with a moisture sensitive polymer coating as a mean of relative humidity detection was first demonstrated by Giaccari et al [7,8]. This concept has since been discussed by several authors [9][10][11], with intended applications in various areas.…”

Comparison between PMMA and PVAC coated fiber Bragg grating sensors for relative humidity measurements

“…Most studies already reported in literature [6,[9][10][11][12][13] makes use of saturated salt solutions to create discrete reference RH levels against which calibrating the target sensor. Although use of saturated salt solutions provides a simple yet effective method of obtaining known RH levels in the test chamber, it has to be remarked that the nominal humidity value given for the salt solution actually is not traceable to any primary standard.…”

“…Since the output signal is wavelength-dependent in this case, this class of sensors exhibits significant advantages over intensity-based FOS. This concept, which was first demonstrated by Giaccari et al [9][10], has since been discussed by several authors, with intended applications in several areas. Yeo et al [11][12] used polyimide (PI) as coating material because, although its moisture swelling capability is not as high as that compared to other polymers, it exhibits a linear response when exposed to RH changes.…”

“…If the polymer is coated on the side surface of a long-period grating (LPG) [5][6][7][8] or a fiber Bragg grating (FBG) [9][10][11][12][13][14][15], the wavelength shift induced by the polymer volume swelling can be used for humidity sensing. Since the output signal is wavelength-dependent in this case, this class of sensors exhibits significant advantages over intensity-based FOS.…”

Development of optical fibre humidity sensors for assessing the quality of housing insulation materials

“…Experiments have verified that polyimide (PI), as a moisture sensitive material, gives excellent linear relationship between relative humidity and the wavelength shift of FBG sensors [3,4], as its volume expansion and shrinkage poses a strain on the FBG itself. Humidity sensors have been developed with differently designed packages tailored to various industrial applications including the building industry, where many insulation materials are extensively used.…”