This letter presents a miniature, all-fiber fiber optic twist/rotation sensor. The proposed sensor consists of polarization maintaining lead-in fiber (PMF), a short section of standard (fully circularly symmetric) single-mode fiber, which is exposed to twist/axial rotation, an all-fiber quarter-wave wave plate, and a reflective layer. This sensor exploits the inability of a short-section circular symmetric single-mode fiber to change the polarization state or spatial E-field vector orientation of an optical wave when exposed to mechanical twist/rotation. Thus, the twisting of a single-mode fiber in the proposed configuration causes displacement of the lead-in PMF and wave-plate axis. This enables encoding of the twist angle into a power ratio of the lead-in PMF linearly polarized modes that is propagated in a backward direction by the application of a wave plate, which can be straightforwardly measured by a simple interrogation system. The proposed design allows for compact sensor design with sensors’ active lengths below 5 mm. The unambiguous angular measurement range of the proposed sensor is ±45°. An angular resolution better than 0.03° was demonstrated, while the temperature sensitivity proved to be (0.011 °C. To achieve low-temperature sensitivity of the sensing system, a combination of different PMFs was used to eliminate the temperature sensitivity of the PMF-based wave plate, which is the main source of temperature-induced errors in the presented setup.
COBISS.SI-ID: 18417174
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
The monitoring of sub nano-liter pendant liquid droplets, during their evaporation from the cleaved facet of a standard optical fiber, is proposed and demonstrated. The combined reflections of incident light from the two boundaries, between fiber and liquid and between liquid and air, give rise to interference fringes as the fluid evaporates. The analysis of the fringe pattern allows for the reconstruction of the instantaneous size and evaporation rate of the droplets. These, in turn, provide information regarding the properties of the liquid itself, and the surface to which it is applied. The sensor readout is validated against direct video observation of evaporating droplets. Several examples illustrate the potential of the proposed sensor. Evaporation dynamics measurements identify the ethanol contents in binary ethanol-water mixtures with 2% certainty. The evaporation dynamics are modified by the application of a hydrophobic self-assembled monolayer coating to the tip of the fiber. Ten different organic solvents are accurately classified by clustering analysis of their evaporation data, collected using bare and coated fibers. Potential applications of the sensors could include quality control of water, beverages and oils, recognition of flexible fuel blends and fuel dilutions, mobile point-of-care diagnostics, and laboratory analysis of surface treatments.
COBISS.SI-ID: 17736214
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
In this study we examined whether the level of hearing loss is related to the frequency of communication within different situations and performance activities on social networking sites. It was also investigated as to how the frequency of activities were related to the perceived accessibility of these sites. Firstly, the findings revealed that users with lower levels of hearing loss communicated more frequently with hearing persons in the written language than users at higher levels. In contrast, they communicated less frequently with deaf users in sign language than those with higher levels of hearing loss. Secondly, users with lower levels of hearing loss posted videos more frequently than those with higher levels. Thirdly, the more frequently the deaf and hard of hearing users actualized their profiles, posted photos, videos, commented and liked the content, the higher the perceived accessibility of those sites they reported.
COBISS.SI-ID: 17968406