Vinod Bajaj

Vinod holds a Bachelor of Technology degree in Electronics and Communication Engineering from Government Engineering College Ajmer, India and Master of Technology degree in Electrical Engineering from Indian Institute of Technology Madras, India. His Master of Technology thesis work was on development of digital signal processing algorithms to mitigate impairments in coherent optical communication. His work was mainly focused on algorithms to mitigate polarization impairments and fiber nonlinearity induced phase modulation for high capacity coherent optical communication systems.

Apart from his academic career, he has two years of industrial experience in R&D department of Sterlite Technologies Limited, India, one of the leading optical fiber and telecom products manufacturer. At Sterlite Tech., he worked on characterization of different optical fibers over 100G DWDM long-haul test-bed. Currently, he is a PhD student at the Technical University of Delft (DTU) in the Fiber Optic Nonlinear Technologies (FONTE) project.



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Vinod’s Blog – the home of his blog is here

State-of-play: Update on Vinod’s’s research in FONTE

  • Numerical and experimental validation of the robust modulation formats
    Nonlinear Fourier transform (NFT) based transmission techniques are seen as a way to mitigate the nonlinearity of the optical fiber. These transmission techniques are very different from the conventional linear transmission techniques. Thus, the modulation techniques used in the conventional linear transmission techniques may not be optimal for NFT based systems and a proper investigation is needed.     There are many aspects that need to be considered in order to find suitable modulation for NFT systems such as spectral efficiency (time-bandwidth product), control of pulse-duration, noise sensitivity. Furthermore, attention is needed on the challenges related to practical impairments such as bandwidth limitations and fiber-loss. In a previous report, a modified NFT for the modulation of data in dispersion-decreasing fibers was described that can take fiber loss into account and therefore neutralizes one of the major impairments in standard NFDM systems. In this report, we evaluate this new data modulation technique numerically and quantify the improvements over standard NFDM systems.(from: FONTE Deliverable D2.3)
  • Software implementations of the developed robust NFT algorithms
    The proposal of using nonlinear Fourier transform (NFT) for data transmission through optical fibers has triggered extensive research in the development of algorithms for the fast computation of NFTs for fiber optics. NFT based transmission techniques however are still far from practical implementation due to the major challenges which come from loss and noise. In order to overcome the challenges imposed by fiber loss, we have recently investigated the use of a suitably tapered fiber for NFDM systems.Such fibers are specially designed to overcome the challenge of signal power attenuation and make the NFDM transmission exact. The (I) NFT operations at both transceiver sides need to be adapted for such fibers. Furthermore, specialized code is required in order to simulate transmissions. In this report, we describe our implementations of both the specialized (I) NFT and fiber simulation algorithms. They have both been added to NFDM Lab, which is a publically available open source simulation environment for fiber-optic transmission systems based on NFTs, together with specific simulation code that can recreate the examples presentation in our paper. (from: FONTE Deliverable D2.2)
  • Major impairments in NFT-based transmission
    The rapidly increasing demand of high data rates is pushing the transmission capacity of optical fiber communication system towards its limit. Modern optical fiber communication systems uses coherent receiver along with digital signal processing to compensate the linear impairments. It is widely accepted that the capacity of current systems is mainly limited by the nonlinear effects. Over the past decade, different techniques have been proposed to mitigate the nonlinear impairments in optical and digital domain. In Wavelength Division Multiplexing (WDM) systems, where carriers are multiplexed in linear frequency domain, nonlinear interference among the carriers due to fiber nonlinearity limits the transmission capacity. Recently, Nonlinear Fourier Transform (NFT) based transmission techniques have been proposed as promising approach to overcome the nonlinear behaviour of optical fiber. These transmission methods are consider nonlinear behaviour of optical fiber as essential element in designing communication system as the optical fiber is inherently nonlinear channel. NFT is a mathematical tool that linearizes nonlinear fiber optic channel into set of parallel linear channel. As like, in the ordinary Fourier domain the effect of dispersion is translated into simple phase rotations, the NFT converts the combined effect of nonlinearity and dispersion into trivial phase rotations in nonlinear Fourier domain. Many research groups have demonstrated proof-of-concept experiments using NFT. While NFT based techniques offer attractive solution, originally these techniques are applicable to ideal lossless optical fiber system. In practical systems it face challenges due to loss and amplification noise. In addition to this, there are implementation challenges at transceiver due to component imperfection, quantization noise and algorithmic limitations. In order to make NFT based techniques realizable, signal processing techniques to compensate such impairments and modulation formats which are more robust to such impairments are needed. In D2.1 major impairments in NFT are surveyed as first step towards this goal. (from: FONTE Deliverable D2.1)