Design and Analysis of Fiber Bragg Grating Employing Novel Apodization Profile

Dwivedi, Krishna Mohan; Trivedi, Gaurav; Khijwania, Sunil K.

doi:10.1109/wrap.2017.8468558

Cited by 3 publications

(3 citation statements)

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“…As previously discussed, to filter out the resonance peak of π-FBG, a suitable apodized FBG filter is required. Recently, we have proposed a new apodization profile f (z) = J 0 (cos (3z/L)) 8 (cos (2z/L − 1)) 4 , where J 0 is the ordinary Bessel function of the 1 st kind of order 0, for the filter and quasi-distributed sensing network [31]. The same apodized grating is applied here for filtering the resonance peak of π-FBG for the illustration.…”

Section: Numerical Results and Discussionmentioning

confidence: 99%

Metrology and Measurement Systems

Dwivedi,

Trivedi,

Khijwania

et al. 2020

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A π-phase-shifted fiber Bragg grating (π-FBG) shows high sensitivity to the ultrasonic (US) wave as compared to the conventional FBG due to the strong slow-light phenomenon at the resonance peak. However, its sensitivity is limited by the interrogation schemes. A combination of π-FBG and unbalanced fiber Mach-Zehnder interferometer (F-MZI) are theoretically analyzed and optimized for the highly sensitive acoustic sensor. The coupled-mode theory (CMT) and transfer matrix method (TMM) are used to establish the numerical modelling of π-FBG. For the optimized grating parameters of π-FBG, the proposed sensing system shows the high strain sensitivity of 1.2 × 10 8 /ε, the highest dynamic strain resolution of 4.1fε/ √ Hz, and the highest wavelength shift resolution of 4.9 × 10 −9 pm. Further, the proposed sensing system strongly supports both time and wavelength division multiplexing techniques. Therefore, the proposed sensing system shows extreme importance in single as well as quasi-distributed US acoustic wave sensing networks.

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Section: Numerical Results and Discussionmentioning

confidence: 99%

Metrology and Measurement Systems

Dwivedi,

Trivedi,

Khijwania

et al. 2020

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“…A b (z) exp iız − /2 are the forward and backward propagating modes having slowly varying amplitudes of A f and A b , respectively; ı = ˇ − ˇB is the detuning from the phase matching condition; Ä = f (z) ın/ is the AC coupling coefficient for fundamental core mode; the apodization profile is f (z) = J 0 cos 3z/L 8 cos 2z/L − 1 4 , where J 0 is the ordinary Bessel function of 1 st kind of order 0 [26]; ˛ stands for the loss coefficient and ˆ = ı + − 1 2 d dz denotes the general DC self-coupling coefficient. For slow-light gratings general DC self-coupling coefficient is defined as:…”

Section: Numerical Model Of the Slow-light -Fbgmentioning

confidence: 99%

“…However, the transmissivity spectrum of -FBG have multiple side-lobes which reduces the maximum dynamic range. Recently, we have proposed a new symmetrical apodization profile for sensing and communication applications [26]. The same apodization profile is used to mitigate the side-lobes of -FBG too.…”

Section: Introductionmentioning

confidence: 99%

High sensitive and large dynamic range quasi-distributed sensing system based on slow-light π-phase-shifted fiber Bragg gratings

Dwivedi¹,

Osuch²,

Trivedi³

2019

Opto-Electronics Review

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In this paper, we theoretically analyze the slow-light -phase-shifted fiber Bragg grating (-FBG) and its applications for single and multipoint/quasi-distributed sensing. Coupled-mode theory (CMT) and transfer matrix method (TMM) are used to establish the numerical modeling of slow-light -FBG. The impact of slow-light FBG parameters, such as grating length (L), index change ( n), and loss coefficient (˛) on the spectral properties of -FBG along with strain and thermal sensitivities are presented. Simulation results show that for the optimum grating parameters L = 50 mm, n = 1.5×10 −4 , and ˛ = 0.10 m -1 , the proposed slow-light -FBG is characterized with a peak transmissivity of 0.424, the maximum delay of 31.95 ns, strain sensitivity of 8.380 -1 , and temperature sensitivity of 91.064 • C -1 . The strain and temperature sensitivity of proposed slow-light -FBG is the highest as compared to the slow-light sensitivity of apodized FBGs reported in the literature. The proposed grating have the overall full-width at half maximum (FWHM) of 0.2245 nm, and the FWHM of the Bragg wavelength peak transmissivity is of 0.0798 pm. The optimized slow-light -FBG is used for quasi-distributed sensing applications. For the five-stage strain quasi-distributed sensing network, a high strain dynamic range of value 1469 is obtained for sensors wavelength spacing as small as 2 nm. In the case of temperature of quasi-distributed sensing network, the obtained dynamic range is of 133 • C. For measurement system with a sufficiently wide spectral range, the -FBGs wavelength grid can be broadened which results in substantial increase of dynamic range of the system.

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