A relative humidity(RH) sensor based on tilted fiber Bragg grating(TFBG) is designed by utilizing polyvinyl alcohol(PVA) as the sensitive cladding film.RH increasing in the PVA coating will result in the reduction of refractive index.Due to the TFBG′s sensitivity to ambient refractive index,the spectral properties of PVA coated TFBG are modified under exposure to different ambient humidity levels ranging from 20% RH to 98% RH.The transmission power of TFBG has different linear behaviors for two ...