This paper presents a highly-sensitive, miniature, all-silica, dual parameter fiber-optic Fabry-Perot sensor, which is suitable for independent measurement of the refractive index and the temperature of the fluid surrounding the sensor. The experimental sensor was produced by a micromachining process based on the selective etching of doped silica glass and a simple assembly procedure that included fiber cleaving, splicing and etching of optical fibers. The presented sensor also allows for direct compensation of the temperature’s effect on the fluid’s refractive index change and consequently provides opportunities for the detection of very small changes in the surrounding fluid’s composition. A measurement resolution of 2x10-7 RIU was demonstrated experimentally for a component of the refractive index that is related purely to the fluid’s composition. This resolution was achieved under non-stabilized temperature conditions. The temperature resolution of the sensor proved to be about 10-3 °C. These high resolution measurements were obtained by phase-tracking of characteristic components in a Fourier transform of sensor’s optical spectrum.
COBISS.SI-ID: 17928982
This letter presents a fiber-optic sensor created at the tip of an optical fiber for simultaneous measurements of pressure and refractive index. The sensor diameter does not exceed the standard fiber diameter and is shorter than 300 µm. Measurement resolutions of 0.2 mBar and 2x10^-5 RIU were demonstrated experimentally by using spectral interrogation and Furrier transform-based measurement algorithms (interrogation system bandwidth corresponded to 1 Hz). A micromachining process based on the selective chemical etching of specially designed phosphorus-doped fibers and a sequence of splice and cleave steps were used to fabricate the sensor.
COBISS.SI-ID: 18181910
Focused ion beam technology is combined with chemical etching of specifically designed fibers to create Fabry-Perot interferometers. Hydrofluoric acid is used to etch special fibers and create microwires with diameters of 15 nm. These microwires are then milled with a focused ion beam to create two different structures: an indented Fabry-Perot structure and a cantilever Fabry-Perot structure that are characterized in terms of temperature. The cantilever structure is also sensitive to vibrations and is capable of measuring frequencies in the range 1 Hz - 40 kHz.
COBISS.SI-ID: 17851670