Enhanced refractive index sensing characteristics of optical fibre long period grating coated with titanium dioxide thin films

Coelho, L.; Viegas, Diana; Santos, J. L.; Almeida, José

doi:10.1016/j.snb.2014.06.035

Cited by 96 publications

(53 citation statements)

References 20 publications

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“…This disadvantage can be overlapped by coating the bare LPFG with a material that has a RI higher than the cladding 26 . The response of the LPFGs depends on the RI and thickness of the film 27 , as reported for the case of titanium dioxide (TiO 2 ) thin film coating 28 .…”

Section: Introductionmentioning

confidence: 70%

Monitoring of high refractive index edible oils using coated long period fiber grating sensors

Coelho

Viegas

Santos³

et al. 2015

SPIE Proceedings

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Monitoring the quality of high refractive index edible oils is of great importance for the human health. Uncooked edible oils in general are healthy foodstuff, olive oil in particular, however, they are frequently used for baking and cooking. High quality edible oils are made from seeds, nuts or fruits by mechanical processes. Nevertheless, once the mechanical extraction is complete, up to 15% of the oil remains in oil pomace and in the mill wastewater, which can be extracted using organic solvents, often hexane.Optical fiber sensors based on long period fiber gratings (LPFG) have very low wavelength sensitivity when the surround refractive index is higher than the refractive index of the cladding. Titanium dioxide (TiO 2 ) coated LPFG could lead to the realization of high sensitivity chemical sensor for the food industry.In this work LPFG coated with a TiO 2 thin film were successfully used for to detect small levels of hexane diluted in edible oils and for real time monitoring the thermal deterioration of edible oils.For a TiO 2 coating of 30 nm a wavelength sensitivity of 1361.7 nm/RIU (or 0.97 nm / % V/V) in the 1.4610-1.4670 refractive index range was achieved, corresponding to 0 to 12 % V/V of hexane in olive oil.A sensitivity higher than 638 nm/RIU at 225 ºC was calculated, in the 1.4670-1.4735 refractive index range with a detection limit of thermal deterioration of about 1 minute.

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Section: Introductionmentioning

confidence: 70%

Monitoring of high refractive index edible oils using coated long period fiber grating sensors

Coelho

Viegas

Santos³

et al. 2015

SPIE Proceedings

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“…Optical fiber refractometers have attracted widespread attention in the past decades due to many desirable advantages such as the small size, compact structure, high flexibility, immunity to electromagnetic interference, corrosion resistance, and the capacity for in situ and multiplexed operation. Various optical fiber refractometers have been developed including tapered fiber structures [1], optical fiber surface plasmon resonance (SPR) devices [2][3], fiber Bragg gratings (FBGs) [4][5], titled fiber Bragg gratings (TFBGs) [6], long-period gratings (LPGs) [7][8], optical fiber modal interferometers (MIs) [9][10], and fiber Fabry-Perot interferometers (FPIs) [11][12][13][14][15][16]. Among them, the fiber FPIs have advantages of compact probe structure, large measurement range, linear response, low temperature cross-sensitivity, and convenient reflection mode for detection, which make them particularly attractive for RI measurement.…”

Section: Introductionmentioning

confidence: 99%

HCPCF-based in-line fiber Fabry-Perot refractometer and high sensitivity signal processing method

et al. 2017

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An in-line fiber Fabry-Perot interferometer (FPI) based on the hollow-core photonic crystal fiber (HCPCF) for refractive index (RI) measurement is proposed in this paper. The FPI is formed by splicing both ends of a short section of the HCPCF to single mode fibers (SMFs) and cleaving the SMF pigtail to a proper length. The RI response of the sensor is analyzed theoretically and demonstrated experimentally. The results show that the FPI sensor has linear response to external RI and good repeatability. The sensitivity calculated from the maximum fringe contrast is -136 dB/RIU. A new spectrum differential integration (SDI) method for signal processing is also presented in this study. In this method, the RI is obtained from the integrated intensity of the absolute difference between the interference spectrum and its smoothed spectrum. The results show that the sensitivity obtained from the integrated intensity is about -1.34× 10 5 dB/RIU. Compared with the maximum fringe contrast method, the new SDI method can provide the higher sensitivity, better linearity, improved reliability, and accuracy, and it's also convenient for automatic and fast signal processing in real-time monitoring of RI.

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“…One of the problems faced by LPFG as an RI sensor is due to the relatively small shift in the resonant wavelength and the difficulty in identifying the center wavelength of the LPFG notch due to its large bandwidth. Various research works have been focused on improving the sensitivity of the wavelength shift through structure modification methods such as claddingetched [7][8][9] and surface coating [10][11][12]. On the other hand, some research works on hybrid LPFG-FBG configuration introduced by Patrick et al [13] have utilized the reflected signal from the FBG for RI [14,15], temperature [16], and RI/temperature simultaneous sensing [17].…”

Section: Introductionmentioning

confidence: 99%

Sensitization of hybrid LPFG–FBG refractometer using double-pass configuration

Yong

Lee

Rahman

2015

Optics Communications

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Enhanced refractive index sensing characteristics of optical fibre long period grating coated with titanium dioxide thin films

Cited by 96 publications

References 20 publications

Monitoring of high refractive index edible oils using coated long period fiber grating sensors

Monitoring of high refractive index edible oils using coated long period fiber grating sensors

HCPCF-based in-line fiber Fabry-Perot refractometer and high sensitivity signal processing method

Sensitization of hybrid LPFG–FBG refractometer using double-pass configuration

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