This paper presents a miniature, all-silica four/multi-parameter sensor for simultaneous measurements of thermal conductivity, pressure, refractive index, and temperature of gases. The sensor is composed of multiple Fabry-Perot interferometers that were created at the tip of a standard optical fiber by a micromachining process based on selective etching and standard fiber manipulation steps. The experimental sensor length was below 3.4 mm, while the diameter did not exceed 125 µm. Interrogation of the sensor utilized acquisition and appropriate signal processing of the back-reflected optical spectrum, which allowed for cross-talk free extraction of individual resonators’ lengths. High repeatability and resolutions were demonstrated for all four sensed parameters. The sensor might be applied to a variety of problems related to gas monitoring or composition analyze as, for example, binary, or even trinary gas mixtures.
COBISS.SI-ID: 20212502
This letter presents a miniature fiber-optic sensor created at the tip of an optical fiber suitable for simultaneous measurement of relative humidity and temperature. The proposed sensor is based on two cascaded Fabry-Perot interferometers, the first configured as a relative humidity sensing element made from silica micro-wire coated with thin porous SiO2 layer, and the second as a temperature sensing element, made from a segment of a standard single mode fiber. The sensor has linear characteristics for both measurement parameters, and sensitivity of 0.48 degree/%RH and 3.7 degree/°C.
COBISS.SI-ID: 19189782
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