Senzorji temperature
All-fiber quasi-distributed polarimetric temperature sensor

This paper presents an all-fiber design of a quasi-distributed polarimetric temperature sensor array that utilizes commercially available single polarization and high birefringence fibers. The modulation depth of temperature induced loss and the operational temperature range of individual sensors in the network are set by the rotational alignment of fibers before fusion splicing and through fine adjustment of the sensing fiber lengths. A practical sensor network was built with sensors that operated in the temperature range from 0 to 100 C. Individual sensors in the network generated temperature dependent loss that changed proportionally from 0.9 to 1.8 dB. With current standard telecommunication OTDRs, more than 20 prototype sensors could be interrogated.

All-fiber, low-cost single-point and quasi-distributed evanescent field temperature sensors with extended temperature measurement range, based on standard telecommunication graded index fibers

Fiber-optic single-point and quasi-distributed evanescent temperature sensors recoated with a blend of poly(methyl methacrylate) and poly(vinylidene fluoride) are proposed. Solid cladding enables the construction of small-size, low-cost, relatively wide-range and fast-response temperature sensors. The diameter of the sensor does not exceed the dimensions of the original optical fiber, while the response time of the sensor is 7:4ms. Different mass ratios of polymers in the blend enable fine tuning of the applied claddings refractive index. This allows the construction of sensors for different temperature ranges, while the application of all-silica graded-index multimode fibers enables the construction of quasidistributed sensor systems with considerably reduced cross talk.

High resolution, all-fiber, micro-machined sensor for simultaneous measurement of refractive index and temperature

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 temperatures effect on the fluids refractive index change and consequently provides opportunities for the detection of very small changes in the surrounding fluids composition. A measurement resolution of 2x10-7 RIU was demonstrated experimentally for a component of the refractive index that is related purely to the fluids 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 sensors optical spectrum.

Polarimetric temperature sensor: extinction ratio and sensing length examination

We theoretically and experimentally investigated the influences of the sensing and lead fiber length, the extinction ratio of the input polarizer, and the coherence properties of the light source on polarimetric temperature measurements. We have shown that there is a possibility to construct a simple and inexpensive fiber optic polarimetric thermometer for absolute temperature measurements by using a low extinction-ratio polarizer and a low-coherence source. An experimentaltemperature sensor for absolute temperature measurement that works in the range from 20 to 60C has been produced.

Miniature all-fiber FabryPerot sensor for simultaneous measurement of pressure and temperature

This article presents a miniature, high-sensitivity, all-silica FabryPerot fiber-optic sensor suitable for simultaneous measurements of pressure and temperature. The proposed sensor diameter does not exceed 125 ?m and consists of two low-finesse FabryPerot resonators created at the tip of an optical fiber. The first resonator is embodied in the form of a short air cavity positioned at the tip of the fiber. This resonator utilizes a thin silica diaphragm to achieve the sensors pressure response. The second resonator exploits the refractive index dependence of silica fiber in order to provide the proposed sensors temperature measurement function. Both resonators have substantially different lengths that permit straightforward spectrally resolved signal processing and unambiguous determination of the applied pressure and temperature.

Low-loss semi-reflective in-fiber mirrors

This paper presents a method for the efficient production of all-fiber semi reflective mirrors suitable for fiber sensors and other all-fiber device applications. The mirrors are obtained by the short duration etching of a standard single mode fiber in hydrofluoric acid, followed by an on-line feedback-assisted fusion splicing process. Fiber mirror reflectance up to 9.5% with excess losses below 0.25 dB were produced in practice, which is in good agreement with provided theoretical and modeling analyses. Control over the etching time and fusion splicing process allows for balancing between reflectance and transmittance, while maintaining low excess loss of experimentally produced mirrors.

Miniature all-silica fiber-optic sensor for simultaneous measurement of relative humidity and temperature

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 FabryPerot interferometers, the first configured as a relative humidity sensing element made from silica micro-wire coated with thin porous SiO2SiO2 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 a sensitivity of 0.48 deg/%RH and 3.7 deg/C.