Integrated Microfibre Device for Refractive Index and Temperature Sensing

Abstract

A microfibre device integrating a microfibre knot resonator in a Sagnac loop reflector is proposed for refractive index and temperature sensing. The reflective configuration of this optical structure offers the advantages of simple fabrication and ease of sensing. To achieve a balance between responsiveness and robustness, the entire microfibre structure is embedded in low index Teflon, except for the 0.5–2 mm diameter microfibre knot resonator sensing region. The proposed sensor has exhibited a linear spectral response with temperature and refractive index. A small change in free spectral range is observed when the microfibre device experiences a large refractive index change in the surrounding medium. The change is found to be in agreement with calculated results based on dispersion relationships.

Cladless few mode fiber grating sensor for simultaneous refractive index and temperature measurement

“…Since last few decades, optical fiber sensors such as fiber Bragg gratings (FBGs), long period gratings (LPGs), interferometers, surface profile scanners, leakage light based sensors etc., have proven their pivotal role as industrial sensors in physical, chemical and biological applications [1][2][3][4][5][6][7][8]. It is due to their tremendous advantages such as compact structures, single sensing element, linear response, good robustness, immune to electromagnetic (EM) interference and capability of simultaneous detection of more than one measurands such as chemical concentration of the solution based on refractive index, temperature and etc.…”

Recent Developments in Micro-Structured Fiber Optic Sensors

“…In order to avoid the evanescent energy leaking into the substrate with higher RI, the microfiber knot was partially embedded in the polymer layer. RI of surrounding solutions has also been measured by the microfiber knot in several works [151][152][153]. layer.…”

“…Experimental results show that different peaks have distinct temperature sensitivities with values up to −0.542 rad/°C as layer. RI of surrounding solutions has also been measured by the microfiber knot in several works [151][152][153]. Recently, our group proposed a novel phase-shift detection scheme in a FFT-based spectrum analysis technique for temperature sensing using the microfiber knot [154].…”

Salinity sensing based on microfiber knot resonator

“…Compared to the above approaches, optical sensors based on microfibers have attracted more and more attention due to their advantages of smaller size, higher sensitivity, faster response, lower cost and simpler fabrication, which have been widely used in physical [11][12][13][14] and biochemical sensing fields [15,16]. As a typical structure of microfiber sensor, microfiber knot resonator (MKR) has been proved sensitive to the surroundings and been successfully used in refractive index (RI) [17][18][19], humidity [20,21], temperature [22,23], magnetic field [24], electric current [25] and UV [26] sensing. Recently, seawater salinity sensing based on microfiber loop resonator has been proposed and modeling on the performance of the salinity sensor has been reported, which proved to be a new optical method to measure seawater salinity with high sensitivity, low detection limit and miniaturized sizes [27].…”