Xingwen Yi

University of Electronic Science and Technology of China, Hua-yang, Sichuan, China

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Publications (72)96.29 Total impact

  • Xingwen Yi, Bo Xu, Jing Zhang, Yun Lin, Kun Qiu
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    ABSTRACT: Digital coherent superposition (DCS) of optical OFDM subcarrier pairs with Hermitian symmetry can reduce the inter-carrier-interference (ICI) noise resulted from phase noise. In this paper, we show two different implementations of DCS-OFDM that have the same performance in the presence of laser phase noise. We complete the theoretical calculation on ICI reduction by using the model of pure Wiener phase noise. By Taylor expansion of the ICI, we show that the ICI power is cancelled to the second order by DCS. The fourth order term is further derived out and only decided by the ratio of laser linewidth to OFDM subcarrier symbol rate, which can greatly simplify the system design. Finally, we verify our theoretical calculations in simulations and use the analytical results to predict the system performance. DCS-OFDM is expected to be beneficial to certain optical fiber transmissions.
    Optics Express 12/2014; 22(25). · 3.53 Impact Factor
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    ABSTRACT: We have recently demonstrated polarization demultiplexing in Stokes space (SS-PDM), which is susceptible to polarization-dependent loss (PDL). In this paper, we apply the method of PDL monitoring and compensation in Stokes space to enhance SS-PDM. It is applied for each subcarrier in the frequency domain after SS-PDM. Because each subcarrier has a much lower speed and narrower bandwidth, the polarization effects that it experiences can be treated as flat. This method can work for different modulation formats on orthogonal frequency-division multiplexing (OFDM) subcarriers and only needs a small number of samples for convergence. In simulation, when the PDL is less than 3.5 dB, it significantly improves the performance of SS-PDM and is comparable with the conventional channel estimation based on training symbols (TSs). We also conduct the experiments of 66.6-Gb/s coherent optical PDM-OFDM with 4QAM subcarrier modulation over 5440-km SSMF and 133.3-Gb/s coherent optical PDM-OFDM with 16QAM subcarrier modulation over 960-km SSMF, respectively. The experimental results show that this method improves the performance of SS-PDM significantly and can match the performance of channel estimation based on TSs. To the best of our knowledge, this is the first experimental validation of PDL monitoring and compensation in Stokes space.
    Journal of Lightwave Technology 12/2014; 32(23). · 2.86 Impact Factor
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    ABSTRACT: Digital coherent superposition (DCS) provides an approach to combat fiber nonlinearities by trading off the spectrum efficiency. In analogy, we extend the concept of DCS to the optical OFDM subcarrier pairs with Hermitian symmetry to combat the linear and nonlinear phase noise. At the transmitter, we simply use a real-valued OFDM signal to drive a Mach-Zehnder (MZ) intensity modulator biased at the null point and the so-generated OFDM signal is Hermitian in the frequency domain. At receiver, after the conventional OFDM signal processing, we conduct DCS of the optical OFDM subcarrier pairs, which requires only conjugation and summation. We show that the inter-carrier-interference (ICI) due to phase noise can be reduced because of the Hermitain symmetry. In a simulation, this method improves the tolerance to the laser phase noise. In a nonlinear WDM transmission experiment, this method also achieves better performance under the influence of cross phase modulation (XPM).
    Optics Express 06/2014; 22(11):13454-13459. · 3.53 Impact Factor
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    ABSTRACT: We experimentally demonstrate digital coherent superposition of optical OFDM subcarrier pairs with Hermitian symmetry to mitigate phase noise, including laser phase noise and cross-phase modulation in a WDM transmission.
    Optical Fiber Communication Conference; 03/2014
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    ABSTRACT: A novel superchannel transmission scheme is proposed where an optical comb source is used to carry the multiband signal and one subcarrier is reserved for regeneration as a local oscillator at the receiver end. By combining carrier tracking and carrier expanding, a 4 × 2 Tbit/s superchannel wavelength division multiplexed self-coherent transmission over a 320 km standard single mode fibre has been successfully demonstrated.
    Electronics Letters 01/2014; 50(3):195-197. · 1.07 Impact Factor
  • IEEE Photonics Technology Letters 11/2013; 25(22):2174-2177. · 2.18 Impact Factor
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    ABSTRACT: We propose a modified method of constant modulus algorithm (CMA) based on polarization demultiplexing in Stokes space for polarization demultiplexing (SS-PDM) in optical coherent receivers. SS-PDM can tolerate chromatic dispersion (CD) and polarization-dependent loss (PDL), but is sensitive to PMD. On the other hand, the CMA with high-order FIR filters could compensate for polarization-mode-dispersion (PMD) effectively, but suffers from the singularity problem which results from PDL. Therefore, we use the polarization rotation matrix estimated by SS-PDM to set the initial center taps of the CMA. The singularity problem of the CMA is avoided effectively in a much wider range of PDL and its convergence speed is also improved. We demonstrate this modified CMA in a simulation of 100-Gbit/s PDM-QPSK with PDL of 1, 3, and 5 dB, respectively. PDL is emulated by attenuating one polarization tributary before polarization multiplexing and the interaction between PDL and PMD is ignored. The singularity problem disappears as expected. Because the tolerance of PDL is affected by DGD, we further investigate the PDL tolerance under different DGD. Finally, we conduct the simulation of 100-Gbit/s PDM-QPSK with PDL of 3 dB over 3000 km SSMF and 4000 km SSMF separately. The convergence speed accelerates indeed compared with that of the conventional CMA.
    Journal of Lightwave Technology 10/2013; 31(19):3203-3209. · 2.86 Impact Factor
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    ABSTRACT: A technique is proposed to measure the high-resolution and wide-band characterization of amplitude, phase responses, and polarization property of optical components. This technique combines the optical spectrum stitching and optical channel estimation methods. Two kinds of fiber Bragg grating based Fabry-Perot cavities with ultrafine structures have been characterized based on this technique. By using 1024 point fast Fourier transform and a narrow linewidth, wavelength-tunable laser source, a frequency resolution of ∼10 MHz is realized with an optical measurement range beyond 250 GHz.
    Optics Letters 07/2013; 38(13):2314-6. · 3.39 Impact Factor
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    ABSTRACT: In coherent optical communication systems, the transmitter usually employs an optical in-phase and quadrature (IQ) modulator to perform electrical-to-optical up-conversion. However, some environmental factors, such as temperature and mechanical stress, strongly influence the stability. To stabilize the quality of the transmitted signal, auto bias control (ABC) is essential to keep modulator in optimum bias. In this paper, we present a novel method of ABC for the optical orthogonal frequency division multiplexing (O-OFDM) signal. In the proposed scheme, a small cosine/sine wave dither signal is added on to the I/Q baseband signal, respectively. Based on the power monitoring of the 1st and 2nd harmonics of the dither signal, the biases of the optical IQ modulator for O-OFDM system can be adjusted very precisely. The simulation and experimental results show good performance on locating the optimum bias voltages for the IQ modulator with high precision.
    Optics Express 03/2013; 21(5):5833-5841. · 3.53 Impact Factor
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    ABSTRACT: We propose a polarization demultiplexing method for coherent optical PDM-OFDM based on Stokes space, without inserting training symbols. The proposed approach performs well for different modulation formats of OFDM subcarrier, and shows comparable performances with that of conventional methods, but with a fast convergence speed and reduced overhead. The OFDM signal in the time domain cannot satisfy the conditions of SS-PDM accurately. Therefore, we first digitally convert the received OFDM signals to the frequency domain using fast Fourier transform (FFT). Each subcarrier of the OFDM signal has a much lower speed and narrower bandwidth, the polarization effects that it experiences can be treated as flat. Consequently, we can apply the polarization demultiplexing in Stokes space (SS-PDM) on per subcarrier basis. We verify this method in experiment by transmitting 66.6-Gb/s PDM-OFDM signal with 4QAM subcarrier modulation over 5440km SSMF and 133.3-Gb/s PDM-OFDM signal with 16QAM subcarrier modulation over 960km SSMF respectively. We also compare the results with those of training symbols. Finally, we analyze of the convergence speed of this method.
    Optics Express 02/2013; 21(3):3885-3890. · 3.53 Impact Factor
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    ABSTRACT: We propose an approach based on constant envelope modulation to mitigate fiber induced nonlinearities in CO-OFDM systems. The extensive simulation results demonstrate that the proposed scheme not only greatly mitigates the nonlinear sensitivity of CO-OFDM transmissions but also avoids the severe nonlinear tolerance degradation caused by inline dispersion compensation.
    Optical Communications and Networks (ICOCN), 2013 12th International Conference on; 01/2013
  • Xingwen Yi, Qi Yang, Kun Qiu
    Asia Communications and Photonics Conference; 01/2013
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    ABSTRACT: As an alternate to fast Fourier transform-based orthogonal frequency-division multiplexing (OFDM), wavelet packet transform (WPT)-based OFDM (WPT-OFDM) does not require cyclic prefix to avoid inter-symbol-interference. The wavelet has many varieties and therefore, it can provide more freedom for system design to suit different applications. We propose a real-valued WPT-OFDM that uses intensity modulation/direct detection. We also conduct an experiment to verify its performance through a 75-km standard single-mode fiber.
    Optical Engineering 10/2012; · 0.96 Impact Factor
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    ABSTRACT: Multiband discrete Fourier transform spread (DFT-S) is a promising technology to reduce peak-to-average power ratio and mitigate the fiber nonlinearity. We investigate DFT-S coherent optical orthogonal frequency division multiplexing (CO-OFDM) in terms of computational complexity and nonlinearity. With the nonlinearity improvement, 450-Gb/s two-band DFT-S CO-OFDM outperforms conventional CO-OFDM, and is successfully transmitted over a 9280-km fiber link.
    IEEE Photonics Technology Letters 10/2012; 24(19):1704-1707. · 2.18 Impact Factor
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    ABSTRACT: The passive optical components with very fine structures in wavelength domain are very sensitive to the mechanical vibrations or thermal fluctuations. If the measurement speed is lower than the temperature and mechanical fluctuation, we cannot measure the dynamic characteristics of the optical components. In this paper, we propose and demonstrate a novel method with ultra-fast measurement speed and high-resolution based on optical channel estimation using direct-detected orthogonal frequency division multiplexing (DD-OFDM) signal, which can be used to measure the dynamic characteristics and fine structure of the passive optical components. In experiment, by using fast Fourier transform (FFT) and a low-cost electro-absorption modulated laser (EML), we can achieve the transfer function characteristics with 3.9MHz resolution. Compared with the optical channel estimation using coherent OFDM signal reported before, the proposed measurement technique is cost-effective.
    Optics Express 09/2012; 20(20):22079-86. · 3.53 Impact Factor
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    ABSTRACT: We propose and demonstrate a novel OFDM-PON upstream transmission architecture with traffic aggregation by orthogonal band multiplexing. The aggregated data streams that propagate in different fiber lengths from ONUs are collectively received and demodulated using one receiver, when the OFDM signals are in a synchronous state. In simulation, four optical network units (ONUs) transmit upstream data at four different frequency bands, and use orthogonal band multiplexing with a proper configuration. The orthogonal band multiplexed 10-Gb/s OFDM signal is collectively received to validate the feasibility of the architecture. We also conduct a proof-of-concept experiment to verify the orthogonal band multiplexing and collective reception. We also verify that the tolerance to the time mismatch of the orthogonal band multiplexing is twice of the CP length.
    Optics Communications 08/2012; 285(17):3597–3603. · 1.54 Impact Factor
  • Xingwen Yi, Zhaohui Li, Yuan Bao, Kun Qiu
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    ABSTRACT: Passive optical components with fine structures require a characterization method with high-resolution and fast measurement speed. In this letter, we extend the digital signal processing-based optical channel estimation to measure their transfer functions, including the intensity and phase responses. In the experiment, by using 16384-point fast Fourier transform and a narrow line-width laser, we demonstrate sub-MHz resolution with a measurement speed bounded by the theoretical limit.
    IEEE Photonics Technology Letters 03/2012; 24(6):443-445. · 2.18 Impact Factor
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    ABSTRACT: Coherent optical OFDM (CO-OFDM) combined with orthogonal band multiplexing provides a scalable and flexible solution for achieving ultra high-speed rate. Among many CO-OFDM implementations, digital Fourier transform spread (DFT-S) CO-OFDM is proposed to mitigate fiber nonlinearity in long-haul transmission. In this paper, we first illustrate the principle of DFT-S OFDM. We then experimentally evaluate the performance of coherent optical DFT-S OFDM in a band-multiplexed transmission system. Compared with conventional clipping methods, DFT-S OFDM can reduce the OFDM peak-to-average power ratio (PAPR) value without suffering from the interference of the neighboring bands. With the benefit of much reduced PAPR, we successfully demonstrate 1.45 Tb/s DFT-S OFDM over 480 km SSMF transmission.
    Optics Express 01/2012; 20(3):2379-85. · 3.53 Impact Factor
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    ABSTRACT: Fiber nonlinearity limits the use of coherent optical orthogonal frequency division multiplexing (CO-OFDM) to upgrade wavelength-division multiplexing (WDM) systems using legacy non-return-to-zero-on-off-keying (NRZ-OOK) channels. This letter proposes to compensate for the fiber nonlinearity of CO-OFDM with NRZ-OOK neighbors by combining digital signal processing (DSP)-based self-phase modulation (SPM) post-compensation with pilot-tone-based cross-phase modulation (XPM) compensation. The simulation results demonstrate that the optimum low-pass filter bandwidth for pilot-tone-based XPM compensation depends on the pilot-to-signal ratio value and launch optical power. Our method allows a 4-dB increase in the launch power for a 40-Gb/s single polarization CO-OFDM channel placed in the middle of six 10.7-Gb/s NRZ channels in a 50-GHz space and 1 200-km WDM system.
    Chinese Optics Letters 01/2012; 10(11):0602-. · 1.07 Impact Factor
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    ABSTRACT: Asymmetrical transmitter and receiver are proposed and employed in Multi-band-OOFDM system. Compared with the all optical OFDM system, the proposed scheme using less single carrier coherent receivers could obtain the same OSNR tolerance.
    Communications and Photonics Conference (ACP), 2012 Asia; 01/2012

Publication Stats

605 Citations
96.29 Total Impact Points

Institutions

  • 2009–2014
    • University of Electronic Science and Technology of China
      Hua-yang, Sichuan, China
    • Technische Universiteit Eindhoven
      Eindhoven, North Brabant, Netherlands
  • 2010
    • University of California, Davis
      • Department of Electrical and Computer Engineering
      Davis, California, United States
  • 2006–2009
    • University of Melbourne
      • Department of Electrical and Electronic Engineering
      Melbourne, Victoria, Australia
    • National ICT Australia Ltd
      Sydney, New South Wales, Australia