Polydimethylsiloxane Fabry-Perot interferometer and its sensing application

A preparation of polydimethylsiloxane (PDMS) interferometer located at the end of a single-mode optical fiber is presented. For preparation of Fabry-Perot interferometer (FPI) we used the PDMS Sylgard 184 (Dow Corning). During fabrication process of FPI the length of micro-cavity in PDMS can be set to required size. After the setting the length of microcavity was fixed by encapsulating of another layer of PDMS. By measuring the transmission characteristic under the constant conditions of environments we observe a periodic change of signal depending on the wavelength – interference pattern. When the measurand is applied on FPI, PDMS changes its volume and also its refractive index resulting in a change in length of microcavity. The change of length of FPI modifies the interference pattern. For evaluation of influence of measurands change, we chose one maximum (wavelength of the maximum) as a reference wavelength at the reflected spectra. Then we changed the amount of measurand and we observed wavelength shift of the maximum and compared it with the wavelength of reference maximum of reflected spectra. We investigated the sensitivity of PDMS FPI on temperature and pressure. The dependencies to temperature and pressure have linear character. The temperature sensitivity of fabricated PDMS FPI is 5.76 nm/°C. In free spectral range of FPI it is possible to determine the difference of temperature 2.7 °C. After that 2π jump in reflected spectra occurs. The pressure sensitivity is -0.64 nm/kPa and free spectral range of FPI corresponds to 11 kPa.