Detection of volatile organic compounds with a polymeric sensing film deposited on a long period fiber grating

In the present work, the fabrication and characterization of a volatile organic compounds sensor is reported. The sensor was constructed depositing a sensing film of polydimethylsiloxane (PDMS) on a long period fiber grating. The measurements were performed in a Teflon chamber, where the alcohol samples were injected at different concentrations. The measured samples were methanol, ethanol, propanol and butanol. There was observed a different behavior of the response to methanol, which was attributed to the fact that its refractive index is lower than the one for PDMS, while for the other samples is the opposite. The calibration curves of the sensor response were obtained, which were fitted to a second order polynomial with high correlation coefficients. Furthermore, the relationship between the sensitivity and the molecular weight was determined.