fibre bragg gratings
Recently Published Documents


TOTAL DOCUMENTS

516
(FIVE YEARS 35)

H-INDEX

38
(FIVE YEARS 2)

Author(s):  
Moura Mehravar ◽  
Hanrui Yang ◽  
David J Webb ◽  
Wei Zhang ◽  
Sina Fadaie Sestelani ◽  
...  

Measuring soil water content is crucially important and can affect soil strength which is a key parameter in analysis, design and monitoring of geo-structures. In this study, an optical fibre Bragg grating (FBG) sensor inscribed in Polymer Optical Fibre (POF) was developed and for the first time its ability to measure soil water content was investigated. The sensitivity of the sensor to different values of gravimetric soil water content under different compaction conditions of loose and normal compaction was tested. The effect of soil temperature on the sensor’s performance was considered. To assess the sensor’s implementation, accuracy and reliability, a commercial soil water content probe (SM150), which measures volumetric soil water content was employed. The results indicate that the developed sensor when calibrated correctly, is able to provide detailed data on any minor variation of soil water content (e.g. 0.5%) with high precision. The outcomes of this study define an additional capability of the POFBG sensors which is significantly important for long-term performance monitoring of geo-structures.


Sensors ◽  
2021 ◽  
Vol 21 (24) ◽  
pp. 8379
Author(s):  
Antreas Theodosiou ◽  
Arnaldo Leal-Junior ◽  
Carlos Marques ◽  
Anselmo Frizera ◽  
Antonio J. S. Fernandes ◽  
...  

This work presents an extensive, comparative study of the gamma and electron radiation effects on the behaviour of femtosecond laser-inscribed fibre Bragg gratings (FBGs) using the point-by-point and plane-by-plane inscription methods. The FBGs were inscribed in standard telecommunication single mode silica fibre (SMF28) and exposed to a total accumulated radiation dose of 15 kGy for both gamma and electron radiation. The gratings’ spectra were measured and analysed before and after the exposure to radiation, with complementary material characterisation using Fourier transform infrared (FTIR) spectroscopy. Changes in the response of the FBGs’ temperature coefficients were analysed on exposure to the different types of radiation, and we consider which of the two inscription methods result in gratings that are more robust in such harsh environments. Moreover, we used the FTIR spectroscopy to locate which chemical bonds are responsible for the changes on temperature coefficients and which are related with the optical characteristics of the FBGs.


Géotechnique ◽  
2021 ◽  
pp. 1-34
Author(s):  
Zhong-Sen Li ◽  
Matthieu Blanc ◽  
Luc Thorel

Two model piles with outer diameter D = 50 mm are loaded laterally at 100×g in a large-beam geotechnical centrifuge. The normal strains on both the tensile and compressive sides are measured using fibre Bragg gratings. An incremental method is introduced to define the pivot point. The testing and analytical program enables the effect of the embedding depth and load eccentricity to be quantified. The key findings are as follows. 1) The piles generate asymmetric tensile and compressive strains during bending, and the tension-compression asymmetry becomes more pronounced at the pile toe and for shorter piles. 2) The piles transition from flexure to rotation as the embedding depth is decreased from 9D to 3D, where the uniqueness of the ground-level rotation and deflection (θg–yg) relationship disappears. 3) The reaction and deflection (P–y) relationship flattens with increasing embedding depth but seems independent of the load eccentricity.


2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Keivan Mahmoud Aghdami ◽  
Abdullah Rahnama ◽  
Erden Ertorer ◽  
Peter R. Herman

AbstractEmbedding strong photonic stopbands into traditional optical fibre that can directly access and sense the outside environment is challenging, relying on tedious nano-processing steps that result in fragile thinned fibre. Ultrashort-pulsed laser filaments have recently provided a non-contact means of opening high-aspect ratio nano-holes inside of bulk transparent glasses. This method has been extended here to optical fibre, resulting in high density arrays of laser filamented holes penetrating transversely through the silica cladding and guiding core to provide high refractive index contrast Bragg gratings in the telecommunication band. The point‐by‐point fabrication was combined with post-chemical etching to engineer strong photonic stopbands directly inside of the compact and flexible fibre. Fibre Bragg gratings with sharply resolved π-shifts are presented for high resolution refractive index sensing from $${n}_{{{{{{\rm{H}}}}}}}$$ n H  = 1 to 1.67 as the nano-holes were readily wetted and filled with various solvents and oils through an intact fibre cladding.


Author(s):  
V.K Kulkarni ◽  
A.S. Lalasangi ◽  
S.B. Patil ◽  
S.R. Mannopantar ◽  
M.S. Jadhav ◽  
...  

- Lead is a soft, ductile, malleable and naturally present in earth’s crust. Lead is highly toxic element affects living organism even at lower concentration. Lead is used in many industries and its disposable is very difficult. Therefore, it may lead to various environmental hazardous problems. World Health Organization (WHO) and other organisation specify the presence of lead in drinking water not greater than 20 ppb. In the present work, a simple, affordable and precise way to detect the concentration of lead in water using Fibre Bragg gratings (FBG) is presented. FBG are formed using Phase mask technique and the cladding part over the grating region is etched with 40% Hydrofluoric acid (HF) solution. The sensor so developed is sensitive enough to find the presence of lead in water in the range 5-25 ppb.


Author(s):  
Ismael Chiamenti ◽  
Tino Elsmann ◽  
Aaron Reupert ◽  
Oguzhan Kara ◽  
Martin Becker ◽  
...  

Sensors ◽  
2021 ◽  
Vol 21 (10) ◽  
pp. 3348
Author(s):  
Rosaria D’Amato ◽  
Andrea Polimadei ◽  
Gaetano Terranova ◽  
Michele Arturo Caponero

In this work, we report novel relative humidity sensors realized by functionalising fibre Bragg gratings with chitosan, a moisture-sensitive biopolymer never used before for this kind of fibre optic sensor. The swelling capacity of chitosan is fundamental to the sensing mechanism. Different samples were fabricated, testing the influence of coating design and deposition procedure on sensor performance. The sensitivity of the sensors was measured in an airtight humidity-controlled chamber using saturated chemical salt solutions. The best result in terms of sensitivity was obtained for a sensor produced on filter paper substrate. Tests for each design were performed in the environment, lasted several days, and all designs were independently re-tested at different seasons of the year. The produced sensors closely followed the ambient humidity variation common to the 24-h circadian cycle.


2021 ◽  
Author(s):  
S. L. Jantzen ◽  
D. H. Smith ◽  
R. H. S. Bannerman ◽  
L. J. Boyd ◽  
J. C. Gates ◽  
...  

Sign in / Sign up

Export Citation Format

Share Document