Theoretical Analysis of Slow-light in π-phase-shifted fiber Bragg grating for sensing applications

Dwivedi, Krishna Mohan; Trivedi, Gaurav; Osuch, Tomasz; Juryca, Karel; Pidanič, Jan

doi:10.1109/comite.2019.8733540

Cited by 4 publications

(3 citation statements)

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“…We also assume that the grating is lossless. The lossy grating has a low transmissivity peak and wide FWHM at the Bragg wavelength [18,19]. The wider FWHM, the lower the OPD value, and thus the sensitivity of the sensing system is reduced as stated in (17).…”

Section: Numerical Results and Discussionmentioning

confidence: 99%

“…It shows better sensitivity and is capable of detecting the megahertz frequency range of ultrasonic signals [16,17]. Due to strong resonance, a slow-light phenomenon is observed in π-FBG at Bragg wavelength which increases the optical path length and, thus, enhanced sensitivity is achieved [18,19]. Further, light is confined in the phase-shifted area, which reduces the effective length of the grating and enables the π-FBG to detect megahertz frequencies.…”

Section: Introductionmentioning

confidence: 99%

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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%

Section: Introductionmentioning

confidence: 99%

Metrology and Measurement Systems

Dwivedi,

Trivedi,

Khijwania

et al. 2020

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“…Since the sensitivity of a phase sensor to external perturbations is inversely proportional to a group velocity in the slow-light region, the sensitivity of a π-PSFBG is significantly enhanced over the sensitivity of traditional FBG sensors operated around the Bragg wavelength [ 6 ]. The influence of slow-light grating parameters, on the spectral and sensing characteristics of the π-FBG were studied in detail in [ 11 ] where for the maximum slow-light sensitivity the optimal grating parameters were obtained. In [ 12 ], a review of the current state-of-the-art interrogation principles of πFBG sensors, including a detailed overview of available experimental configurations and their working principles, is presented.…”

Section: Introductionmentioning

confidence: 99%

Design, Optimization, and Experimental Evaluation of Slow Light Generated by π-Phase-Shifted Fiber Bragg Grating for Use in Sensing Applications

Vaňko,

Glesk,

Müllerová

et al. 2024

Sensors

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This paper describes design, theoretical analysis, and experimental evaluation of a π-Phase-Shifted Fiber Bragg Grating (π-PSFBG) inscribed in the standard telecom fiber for slow light generation. At first, the grating was designed for its use in the reflection mode with a central wavelength of 1552 nm and a pass band width of less than 100 pm. The impact of fabrication imperfections was experimentally investigated and compared to model predictions. The optical spectra obtained experimentally show that the spectral region used for slow light generation is narrower (less than 10 pm), thus allowing for too-low levels of slow light optical-output power. In the next step, the optimization of the grating design was conducted to account for fabrication errors, to improve the grating’s spectral behavior and its temporal performance, and to widen the spectral interval for slow light generation in the grating’s transmission mode. The targeted central wavelength was 1553 nm. The π-PSFBG was then commercially fabricated, and the achieved parameters were experimentally investigated. For the region of (1551–1554) nm, a 15-fold increase in the grating’s pass band width was achieved. We have shown that a pair of retarded optical pulses were generated. The measured group delay was found to be ~10.5 ps (compared to 19 ps predicted by the model). The π-PSFBG operating in its transmission mode has the potential to operate as tunable delay line for applications in RF photonics, ultra-fast signal processing, and optical communications, where tunable high precision delay lines are highly desirable. The π-PSFBG can be designed and used for the generation of variable group delays from tens to hundreds of ps, depending on application needs.

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