Accurate compensation and prediction of the temperature cross-sensitivity of tilted FBG cladding mode resonances

Abstract

The temperature dependence of core mode resonance has been thoroughly studied in fiber Bragg gratings (FBGs), but it is not the case for cladding mode resonances in multi-resonance gratings such as tilted FBGs (TFBGs). In this work, the temperature sensitivity of ultraviolet written TFBGs in SMF-28 fibers is assessed, demonstrating in the first, to the best of our knowledge, place that a single gauge factor K T = 6.25 ⋅ 10 − 6 ± 0.02 ⋅ 10 − 6 ∘ C − 1 can be employed to characterize the response to temperature of the resonances over the full spectrum in the 10°–50°C range. Then, a simulation model is obtained, enabling to predict TFBG spectra in the 10°–50°C range with high accuracy. This requires a calibration of the core index and dispersion of the TFBG measured in air at 25°C, and determination of the glass refractive index thermo-optic coefficient ( d n / d T = 8.46 ⋅ 10 − 6 ± 0.1 ⋅ 10 − 6 ∘ C − 1 , common to both core and cladding glasses), leading to a mean error on the wavelength position of resonances between 1 and 3 pm. This mean error can be further reduced (less than 1 pm) by considering a linear dependence with temperature of d n / d T . Therefore, this model will enable to completely remove the temperature-induced shifts of all resonances in TFBG sensing applications and measure with great accuracy the variables of interest by using the scaled averages of groups of resonances instead of (less accurate) individual shifts.

Dual-Mode Comb Plasmonic Optical Fiber Sensing

“…The “multiresonant” approach, naturally resulting from the hybrid nature of the spectral content featuring well-resolved S and P cladding mode resonance families, is ideally suited to the development of more advanced data extraction algorithms to extract target measurements from the simultaneous values of multiple parameters of the spectra, − using least-squares optimization techniques or machine learning tools. − It is hoped that these simplified fiber SPR probes, along with less complex interrogation instrumentation, will stimulate new efforts into developing lab-on-fiber tools for field applications.…”

Simplification of data extraction and measurements from tilted FBG surface plasmon resonance sensors

“…A differential sensitivity of almost two orders of magnitude was measured between the amplitude shifts different resonances in the same spectrum, allowing for unambiguous surrounding refractive index change measurements from relative power level change measurements (thus eliminating the impact of broadband power level fluctuations from the source or the light path. This is yet another step in the move towards "multiresonant" fiber grating sensors that are exploiting mode sensitivity differences to improve fiber sensor modalities and accuracy [11][12] . Further calibration and exploration of the accuracy and limits of detection available with this configuration are in progress and will be reported at the meeting.…”

Design of real time monitoring and intelligent analysis system for fiber optic sensor networks driven by big data

“…Among various types of fiber optic sensors, Fiber Bragg grating (FBG) is the most commonly used and widely used type of grating, and coupled mode theory is the sensing foundation of FBG[6-7]. The coupled mode theory mainly studies the general laws of coupling between different electromagnetic wave modes [8][9]. Within the same cavity, coupling can occur between different electromagnetic wave modes.…”