Faculty Publications

Permanent URI for this communityhttps://idr.nitk.ac.in/handle/123456789/18736

Publications by NITK Faculty

Browse

Subject: search.filters.subject.Fiber Bragg gratings

Search Results

Now showing 1 - 6 of 6
  • No Thumbnail Available
    Item
    A comparative study on the effectiveness of system parameters in monitoring pre-load loss in bolted joints
    (Springer Verlag service@springer.de, 2018) Anginthaya, K.; Kuchibhatla, S.A.R.; Gangadharan, K.V.; Kishan, A.
    This article presents the monitoring of bolt loosening in a single bolted lap joint between two steel beams. The bolt loosening is initially studied using system modal parameters for various boundary conditions. Natural frequency and modal damping ratio in lower modes were not found to be reliable. Transmissibility function was seen to have a more reliable trend to identify the state of the joint. An in-house setup was developed to produce loosening in the bolted joint. Testing configuration was optimized by structural analysis. Strain measurements were carried out using Fiber Bragg-grating sensors while sinusoidal load was applied on the test structure. The results have been used to discuss a viable approach to identify the health of, or recognize a loosening trend, in a bolted joint. © 2018, The Brazilian Society of Mechanical Sciences and Engineering.
  • No Thumbnail Available
    Item
    Highly steerable microwave beamforming system near Ku band based on the application of linearly CFBG
    (Institution of Engineering and Technology jbristow@theiet.org, 2020) Raghuwanshi, S.K.; Srivastava, N.K.; Singh, M.
    In this study, the authors present theoretical and experimental results of wideband beamforming networks steered by a single linear chirped fibre Bragg grating (CFBG). The standard single-sideband modulation technique is followed to validate the wideband (at 18 GHz) operation of the proposed system. CFBG has been fabricated by phase mask technology for the desired specification to be compatible with the antenna array. To the authors knowledge, the effect of dispersion slope feature of fabricated FBG on the performance of beam-steering capability of the antenna is reported for the first time in this study. Theoretically preceded by experimental testing, it was found that the scanning angle increased with the rise in the number of antenna elements and the frequency of modulating microwave signal. © 2019 The Institution of Engineering and Technology.
  • No Thumbnail Available
    Item
    Analysis and optimization of uniform FBG structure for sensing and communication applications
    (Springer, 2020) Divya Shree, M.; Sangeetha, A.; Krishnan, P.
    A uniform fiber Bragg grating sensor is sketched and inspected by the finite-difference time-domain method in furtherance of obtaining ultimate transmission and reflection spectra by optimizing the FBG parameters like refractive index, grating height, grating width, wafer width, wafer length. The maximum transmission power spectrum is achieved as ? 7 dB for the refractive index of 3.005, and the maximum reflection spectra are obtained as 6 dB for the grating height of 1 ?m which is enhanced nine times than the precedent work. The proposed FBG is a simple, light-weight, low-cost uniform structure, and it offers high reflectivity and ease of handling. Therefore, it is highly useful in sensing and communication applications. © 2020, Springer Science+Business Media, LLC, part of Springer Nature.
  • No Thumbnail Available
    Item
    High-Resolution Fiber Optic Sensor based on Coated Linearly Chirped Bragg Grating
    (Elsevier GmbH, 2020) Singh, M.; Raghuwanshi, S.K.; Prakash, O.; Kumar, P.K.
    a fiber optic strain sensor is proposed and experimentally demonstrated using fiber Bragg grating (FBG) based interrogation scheme. Due to fast response time and better sensitivity of graphene oxide (GO) material, coated linearly chirped fiber Bragg grating (LCFBG) is used in this work. Interrogation scheme is used for the efficient strain sensing by placing LCFBG within the Sagnac loop (wavelength dependent receiver). The GO deposition is confirmed by ultraviolet–visible spectroscopy, atomic force microscopy (AFM), and field emission scanning electron micrograph (FESEM). Our proposed fiber optic strain sensor possesses better resolution, stable operation in the infra-red region. In addition, sensor demonstrates 5.25 ?? static strain and 0.645 ??/?Hz dynamic strain resolutions, respectively. © 2020 Elsevier GmbH
  • No Thumbnail Available
    Item
    High sensitivity detection of chemicals based on sinusoidally apodized structured grating assisted liquid filled directional coupler
    (Springer, 2021) Raghuwanshi, S.K.; Singh, Y.; Singh, M.; Chack, D.; Kumar, R.; Prakash, O.
    The grating has a significant role in sensing applications. Similarly, the grating-assisted coupler has excellent potential in chemical sensing applications. The power coupling between two closely coupled waveguide couplers can be significantly tuned by incorporating grating between them. The grating has been taken of silica material with sinusoidal shape in variation. The grating layer is assumed to be embedded within the sensing layer while considering a changeable effective refractive index depending on the sensing layer substances. In the present paper, grating assisted directional coupler has been numerically analysed using its own developed MATLAB-based algorithm of finite difference method (FDM) scheme. FDM method has been applied to solve the Eigenvalue equation to obtain allowed Eigenvalues and corresponding Eigen vectors (TE and TM cases). In FDM, the analysis domain has been fine discretized into the mesh of 1-D equal spacing for reasonable accurate computation results. In experimental validation, Fibre Bragg grating (FBG) has been suspended between two high refractive index coupler regions, which act as a power coupling zone. Also, the coupling length has been changed from 5 to 20 ? m for tuning purposes and then optimized for grating parameters viz. length, period, etc. The whole structure is 2-Dimensional (x and y directions) with invariant in the y-direction. © 2021, The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.
  • No Thumbnail Available
    Item
    Phase Noise Reduction in Optoelectronic Oscillator With Quadratic Fiber Bragg Grating Dispersion Engineering
    (Institute of Electrical and Electronics Engineers Inc., 2025) Renuka, B.; Singh, M.
    This article presents the design, implementation, and performance analysis of an optoelectronic oscillator (OEO) incorporating a quadratic fiber Bragg grating (Q-FBG). Integrating Q-FBG in OEO architecture introduces enhanced filtering capabilities and precise frequency control, which are critical for applications requiring high stability and low phase noise. It provides a tailored reflection spectrum, enabling improved mode selection and reduced spurious tones. Experiments confirm oscillator’s superior performance metrics, including phase noise reduction and frequency stability. Theoretical modeling and simulation corroborate the experimental results, confirming the Q-FBG’s effectiveness in optimizing OEO performance. An error vector magnitude (EVM) of 2.5% is obtained for the generated signal, indicating high quality and improved modulation accuracy of the microwave signal. The uncertainty of measurement, particularly the standard deviation in EVM values, is analyzed to assess system reliability. The potential applications of the proposed OEO include telecommunications, radar systems, and precision measurement instruments. The study underscores the significant advantages of incorporating Q-FBG in OEOs and paves the way for further advancements in microwave photonics technology. © 1963-2012 IEEE.