Fiber optic volatile organic compounds sensor based on polymer coated FBG refractometer

Mid-IR evanescent-field fiber sensor with enhanced sensitivity for volatile organic compounds

“…Functionalized coatings have been used to adsorb and concentrate VOCs from gas-phase to enable better detection for monitoring refractive index changes. [22][23][24][25] Although sensitive measurement of refractive index changes was successfully achieved by some of these methods, they do not allow molecular specicity. Nano-porous materials, such as porous silicon (pSi), have been shown to be highly useful in adsorbing and condensing VOCs due to capillary action in the nanopores of the pSi.…”

Hydrogel-coated fiber Bragg grating sensor for pH monitoring

“…Long period gratings (LPGs) have a distinct advantage in this context, as they allow coupling of light between core and cladding modes. [26][27][28][29][30][31] The estimation of pH is an obvious factor in environmental monitoring such as waste water monitoring, seawater analysis, food processing industry, river and industry water quality monitoring, blood analysis, and in various chemical and biomedical fields. [8][9][10][11][12][13][14] However, LPG sensing suffers from some disadvantages such as incapability for multipoint sensing, broad transmission resonance, and appearance of multiple peaks, which lowers the accuracy due to the presence of leaky modes.…”