Comparison of the sensing mechanisms and capabilities of three functional materials surface-modified TFBG sensors

Three functional materials were coated on tilted fiber Bragg grating (TFBG) sensors, and through the analysis of the characteristics of TBFG sensors’ amplitudes in the core and cladding modes, their abilities to sense humidity were compared. The mechanisms by which physical moisture absorption sensing was achieved through the three materials were investigated. The degree of sensitivity in terms of resonance wavelength in the cladding mode for the three coating materials was PAHP4 > PEDOT:PSS > GO. The sensitivity in the cladding modes of the tested sensor showed that the best resonance wavelength was as high as 0.0112 nm/% RH and was achieved for the TFBG coated with PAHP4 due to the hydrophilic groups around the material, which are good at forming hydrogen bond interactions with H2O.