PhD Researcher; Electronics Engineering + Engineering Sciences
mm-wave tomography, Laser Physics, FBG Sensing, Opto-electronics, Fiber Optics, Microwave Photonics, OCT/Medical Physics
MATLAB, TINA, Digital Electronics, Analog electronics, Satellite communication, Electromagnetism, Calculus
Ahmad, E. et al. (2016). High temporal and spatial resolution distributed fiber Bragg grating sensors using time-stretch frequency-domain reflectometry. IEEE/OSA Journal of Lightwave Technology [Online] 35:3289-3295. Available at: http://dx.doi.org/10.1109/JLT.2016.2605401.A novel interrogation technique for fully distributed linearly chirped fiber Bragg grating (LCFBG) strain sensors with simultaneous high temporal and spatial resolution based on optical time-stretch frequency-domain reflectometry (OTS-FDR) is proposed and experimentally demonstrated. LCFBGs is a promising candidate for fully distributed sensors thanks to its longer grating length and broader reflection bandwidth compared to normal uniform FBGs. In the proposed system, two identical LCFBGs are employed in a Michelson interferometer setup with one grating serving as the reference grating whereas the other serving as the sensing element. Broadband spectral interferogram is formed and the strain information is encoded into the wavelength-dependent free spectral range (FSR). Ultrafast interrogation is achieved based on dispersion-induced time stretch such that the target spectral interferogram is mapped to a temporal interference waveform that can be captured in real-time using a single-pixel photodector. The distributed strain along the sensing grating can be reconstructed from the instantaneous RF frequency of the captured waveform. High-spatial resolution is also obtained due to high-speed data acquisition. In a proof-of-concept experiment, ultrafast real-time interrogation of fully-distributed grating sensors with various strain distributions is experimentally demonstrated. An ultrarapid measurement speed of 50 MHz with a high spatial resolution of 31.5 µm over a gauge length of 25 mm and a strain resolution of 9.1 µε have been achieved.
Conference or workshop item
Mididoddi, C., Ahmad, E. and Wang, C. (2017). Data-efficient high-throughput fiber Bragg grating sensors using photonic time-stretch compressive sensing. in: European Conferences on Laser and Opto-electronics.. Available at: https://doi.org/10.1109/CLEOE-EQEC.2017.8086896.In this paper, we demonstrate the first application of photonic compressive sensing technique in a data-efficient interrogation system for high-throughput distributed FBG sensors. In particular, reconstruction of a wide bandwidth chirped temporal waveform has been achieved using compressive sensing with optical integration. This enables data-compressed high-throughput interrogation of FBG sensors for dynamic non-uniform strain sensing
Mididoddi, C., Ahmad, E. and Wang, C. (2017). All-optical random sequence generation for compressive sensing detection of RF signals. in: International Topical Meeting on Microwave Photonics (MWP), 2017. IEEE, pp. 1-4. Available at: https://doi.org/10.1109/MWP.2017.8168639.Photonic compressive sensing is a promising data compression method and has been successfully applied in high-speed RF signal detection with greatly reduced requirement for receiver bandwidth. A key challenge is due to the electronic bottleneck in high-speed random sequence generation and mixing. In this work, we propose and experimentally demonstrated for the first time all-optical random sequence generation and mixing for compressive sensing detection of RF signals. The technique is based on photonic time stretch involving cascaded Mach-Zehnder Interferometers (MZIs) for spectral domain random mixing. In a proof-of-concept experiment, successful detection of 1 GHz RF signal with 25% compression ratio using only 50 MHz detection bandwidth has been demonstrated。
Ahmad, E. et al. (2016). Ultrafast Interrogation of Fully Distributed Chirped Fibre Bragg Grating Strain Sensor. in: 2016 IEEE Photonics Conference (IPC).. Available at: http://ieeexplore.ieee.org/document/7831190/.A novel ultrafast and high spatial-resolution interrogation method for fully distributed chirped fibre Bragg grating sensors based on photonic time-stretch frequency-domain reflectometry is presented. Real-time interrogation at measurement speed of 50 MHz with a spatial resolution of 35 µm was experimentally demonstrated.