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Xinliang Zhang - One of the best experts on this subject based on the ideXlab platform.

  • resolution improvement of the large bandwidth and high speed Electrical Spectrum analyzer based on dual optical frequency combs
    International Topical Meeting on Microwave Photonics, 2017
    Co-Authors: Yuhua Duan, Liao Chen, Xi Zhou, Chi Zhang, Lei Zhang, Xinliang Zhang
    Abstract:

    An all-optical Electrical Spectrum analyzer is demonstrated based on dual optical frequency combs and microwave photonics, and it improves the resolution to be 250 MHz over 10-GHz bandwidth, with the 1-kHz frame rate. The Spectrum is directly obtained in the time domain, using as low as 10-MHz acquisition bandwidth, without any post-processing.

  • ultrafast Electrical Spectrum analyzer based on all optical fourier transform and temporal magnification
    Optics Express, 2017
    Co-Authors: Yuhua Duan, Liao Chen, Haidong Zhou, Xi Zhou, Chi Zhang, Xinliang Zhang
    Abstract:

    Real-time Electrical Spectrum analysis is of great significance for applications involving radio astronomy and electronic warfare, e.g. the dynamic Spectrum monitoring of outer space signal, and the instantaneous capture of frequency from other electronic systems. However, conventional Electrical Spectrum analyzer (ESA) has limited operation speed and observation bandwidth due to the electronic bottleneck. Therefore, a variety of photonics-assisted methods have been extensively explored due to the bandwidth advantage of the optical domain. Alternatively, we proposed and experimentally demonstrated an ultrafast ESA based on all-optical Fourier transform and temporal magnification in this paper. The radio-frequency (RF) signal under test is temporally multiplexed to the Spectrum of an ultrashort pulse, thus the frequency information is converted to the time axis. Moreover, since the bandwidth of this ultrashort pulse is far beyond that of the state-of-the-art photo-detector, a temporal magnification system is applied to stretch the time axis, and capture the RF Spectrum with 1-GHz resolution. The observation bandwidth of this ultrafast ESA is over 20 GHz, limited by that of the electro-optic modulator. Since all the signal processing is in the optical domain, the acquisition frame rate can be as high as 50 MHz. This ultrafast ESA scheme can be further improved with better dispersive engineering, and is promising for some ultrafast spectral information acquisition applications.

  • orbital angular momentum complex Spectrum analyzer for vortex light based on the rotational doppler effect
    Light-Science & Applications, 2017
    Co-Authors: Hailong Zhou, Jianji Dong, Pei Zhang, Dongxu Chen, Xinlun Cai, Xinliang Zhang
    Abstract:

    The ability to measure the orbital angular momentum (OAM) distribution of vortex light is essential for OAM applications. Although there have been many studies on the measurement of OAM modes, it is difficult to quantitatively and instantaneously measure the power distribution among different OAM modes, let alone measure the phase distribution among them. In this work, we propose an OAM complex Spectrum analyzer that enables simultaneous measurements of the power and phase distributions of OAM modes by employing the rotational Doppler effect. The original OAM mode distribution is mapped to an Electrical Spectrum of beat signals using a photodetector. The power and phase distributions of superimposed OAM beams are successfully retrieved by analyzing the Electrical Spectrum. We also extend the measurement technique to other spatial modes, such as linear polarization modes. These results represent a new landmark in spatial mode analysis and show great potential for applications in OAM-based systems and optical communication systems with mode-division multiplexing. An instrument that can map the power and phase distributions of vortex light beams that have orbital angular momentum (OAM) has been built. The ability to measure the OAM distribution of vortex light is essential for OAM applications, but it is challenging to instantaneously measure the power and phase distribution of different OAM modes. The OAM Spectrum analyzer developed by Jianji Dong of Huazhong University of Science and Technology and co-workers characterizes a beam with unknown OAM by sending it and a reference beam to a spinning object, which scatters the light, imparting a rotational Doppler frequency shift in the process. The scattered light is then passed through a mode filter and collected by a photodetector for analysis. The frequency shift of the scattered light reveals information about the OAM content of the unknown beam.

Pengyu Guan - One of the best experts on this subject based on the ideXlab platform.

  • Combined Optical and Electrical Spectrum Shaping for High-Baud-Rate Nyquist-WDM Transceivers
    IEEE Photonics Journal, 2016
    Co-Authors: Edson P. Da Silva, Fabian Schwartau, Simone Gaiarin, Miguel I. Olmedo, Armand Vedadi, Stefan Preußler, Robert Borkowski, Molly Piels, Michael Galili, Pengyu Guan
    Abstract:

    We discuss the benefits and limitations of optical time-division multiplexing (OTDM) techniques based on the optical generation of a periodic train of sinc pulses for wavelength-division multiplexing (WDM) transmission at high baud rates. It is shown how the modulated OTDM Spectrum bandwidth is related to the optical comb parameters and the pulse shaping of the modulating waveforms in the Electrical domain. Such dependence may result in broadening of the modulated spectra, which can degrade the performance of Nyquist-WDM systems due to interchannel crosstalk penalties. However, it is shown and experimentally demonstrated that the same technique of optical pulse train generation can be allied with digital pulse shaping to improve the confinement of the modulated Spectrum toward the Nyquist limit independently of the number of OTDM tributaries used. To investigate the benefits of the proposed approach, we demonstrate the first WDM Nyquist-OTDM signal generation based on the periodic train of sinc pulses and Electrical Spectrum shaping. Straight line transmission of five 112.5-Gbd Nyquist-OTDM dual-polarization quadrature phase-shift keying (QPSK) channels is demonstrated over a dispersion uncompensated link up to 640 km, with full-field coherent detection at the receiver. It is shown that such a design strategy effectively improves the spectral confinement of the modulated OTDM signal, providing a minimum intercarrier crosstalk penalty of 1.5 dB in baud-rate-spaced Nyquist-WDM systems.

  • Combined Optical and Electrical Spectrum Shaping for High-Baud-Rate Nyquist-WDM
    2016
    Co-Authors: Edson P. Da Silva, Fabian Schwartau, Simone Gaiarin, Miguel I. Olmedo, Armand Vedadi, Pengyu Guan, Robert Borkowski, Molly Piels, Michael Galili, Sergei Popov
    Abstract:

    Abstract: We discuss the benefits and limitations of optical time-division multiplexing(OTDM) techniques based on the optical generation of a periodic train of sinc pulses forwavelength-division multiplexing (WDM) transmission at high baud rates. It is shownhow the modulated OTDM Spectrum bandwidth is related to the optical comb parametersand the pulse shaping of the modulating waveforms in the Electrical domain. Such de-pendence may result in broadening of the modulated spectra, which can degrade theperformance of Nyquist-WDM systems due to interchannel crosstalk penalties. However,it is shown and experimentally demonstrated that the same technique of optical pulsetrain generation can be allied with digital pulse shaping to improve the confinement ofthe modulated Spectrum toward the Nyquist limit independently of the number of OTDMtributaries used. To investigate the benefits of the proposed approach, we demonstratethe first WDM Nyquist-OTDM signal generation based on the periodic train of sinc pulsesand Electrical Spectrum shaping. Straight line transmission of five 112.5-Gbd Nyquist-OTDM dual-polarization quadrature phase-shift keying (QPSK) channels is demon-strated over a dispersion uncompensated link up to 640 km, with full-field coherentdetection at the receiver. It is shown that such a design strategy effectively improves thespectral confinement of the modulated OTDM signal, providing a minimum intercarriercrosstalk penalty of 1.5 dB in baud-rate-spaced Nyquist-WDM systems.Index Terms: Coherent communications, Nyquist-OTDM.

Shangjian Zhang - One of the best experts on this subject based on the ideXlab platform.

  • self calibrated Electrical Spectrum measurement of optical frequency comb based on segmental electro optic up conversion
    Semiconductor Lasers and Applications XI, 2021
    Co-Authors: Mengke Wang, Shangjian Zhang, Yali Zhang, Zhao Liu, Zhiyao Zhang, Yong Liu
    Abstract:

    A self-calibrated method is proposed for Electrical Spectrum measurement of optical frequency comb (OFC) based on segmental electro-optic up-conversion. In the method, every N comb teeth of OFC are divided into one segment in the frequency domain, and M segments are investigated with the measuring frequency range of M×N×fr (fr is the repetition frequency of the OFC). Through symmetric frequency modulation, intra-segment measurement and seamless stitching between different segments are performed. Finally, only a low-frequency microwave source is required to achieve the Electrical Spectrum measurement of OFC within ultra-wideband frequency range, and the measuring frequency range can be 2M-fold expanded with respect to the modulation frequency rang. Meanwhile, the frequency responses of MachZehnder modulator and photodetector are fully cancelled out, realizing the self-calibrated Electrical Spectrum measurement of OFC within ultra-wideband frequency range.

  • extinction ratio independent Electrical method for measuring chirp parameters of mach zehnder modulators using frequency shifted heterodyne
    Optics Letters, 2015
    Co-Authors: Shangjian Zhang, Yali Zhang, Heng Wang, Rongguo Lu
    Abstract:

    An extinction-ratio-independent Electrical method is proposed for measuring chirp parameters of Mach–Zehnder electric-optic intensity modulators based on frequency-shifted optical heterodyne. The method utilizes the Electrical Spectrum analysis of the heterodyne products between the intensity modulated optical signal and the frequency-shifted optical carrier, and achieves the intrinsic chirp parameters measurement at microwave region with high-frequency resolution and wide-frequency range for the Mach–Zehnder modulator with a finite extinction ratio. Moreover, the proposed method avoids calibrating the responsivity fluctuation of the photodiode in spite of the involved photodetection. Chirp parameters as a function of modulation frequency are experimentally measured and compared to those with the conventional optical Spectrum analysis method. Our method enables an extinction-ratio-independent and calibration-free Electrical measurement of Mach–Zehnder intensity modulators by using the high-resolution frequency-shifted heterodyne technique.

  • self calibrating measurement of high speed electro optic phase modulators based on two tone modulation
    Optics Letters, 2014
    Co-Authors: Shangjian Zhang, Yali Zhang, Heng Wang, Xinhai Zou, Yong Liu
    Abstract:

    We propose a self-calibrating method for high-frequency response measurement of electro-optic phase modulators based on two-tone modulation. The method utilizes the Electrical domain measurement of heterodyning Spectrum between the two-tone modulation optical signal and the frequency-shifted optical carrier, and eliminates the need to correct the responsivity fluctuation in the photodetection. High-frequency modulation depth and half-wave voltages are measured and compared to those with the traditional optical Spectrum analysis method in the experimental demonstration. The proposed method enables calibration-free and accurate frequency response measurement of electro-optic phase modulators by using high-resolution Electrical Spectrum analysis.

  • Calibration-Free Electrical Spectrum Analysis for Microwave Characterization of Optical Phase Modulators Using Frequency-Shifted Heterodyning
    IEEE Photonics Journal, 2014
    Co-Authors: Shangjian Zhang, Yali Zhang, Heng Wang, Rongguo Lu
    Abstract:

    A novel calibration-free Electrical Spectrum analysis method for microwave characterization of electrooptic phase modulators is proposed and experimentally demonstrated based on frequency-shifted optical heterodyning. The method achieves the Electrical domain measurement of the modulation efficiency of phase modulators without the need for correcting the responsivity fluctuation in the photodetection. Moreover, it extends double the measuring frequency range through setting a specific frequency relationship between the driving microwave signals. Modulation depth and half-wave voltage of phase modulators are experimentally extracted from the heterodyning Spectrum of two phase-modulated signals with and without frequency shifting, and the measured results are compared to those obtained with the traditional optical Spectrum analysis method to check the consistency. The proposed method provides calibration-free and accurate measurement for high-speed optical phase modulators with the high-resolution Electrical Spectrum analysis.

William Shieh - One of the best experts on this subject based on the ideXlab platform.

  • advanced modulation formats for high performance short reach optical interconnects
    Optics Express, 2015
    Co-Authors: Di Che, Yifei Wang, William Shieh
    Abstract:

    The explosive growth of the traffic between data centers has led to an urgent demand for high-performance short-reach optical interconnects with data rate beyond 100G per wavelength and transmission distance over hundreds of kilometers. Since direct detection (DD) provides a cost-efficient solution for short-reach interconnects, various advanced modulation formats have been intensively studied to improve the performance of DD for high-performance short-reach optical interconnects. In this paper, we report the recent progress on the advanced DD modulation formats that provide superior Electrical spectral efficiency (SE) and transmission reach beyond that of simple direct modulation (DM) based direct detection (DM/DD). We first provide a review of the current advanced modulation formats for high-performance short-reach optical interconnects. Among these formats, Stokes vector direct detection (SV-DD) achieves the highest Electrical Spectrum efficiency, presenting itself as a promising candidate for future short-reach networks. We then expound some novel algorithms to achieve high-performance SV-DD systems under severe impairments of either polarization mode dispersion (PMD) or polarization dependent loss (PDL).

  • stokes vector direct detection for short reach optical communication
    Optics Letters, 2014
    Co-Authors: Di Che, Xi Chen, Yifei Wang, William Shieh
    Abstract:

    We propose the Stokes vector direct detection (SV-DD) scheme which simultaneously achieves receiver phase diversity and the cancellation of photodetection nonlinearity. An 80  Gb/s single-polarization modulated SV-DD signal is successfully received after 160 km SSMF transmission with 11.64  bit/s/Hz Electrical Spectrum efficiency.

  • 160 gb s stokes vector direct detection for short reach optical communication
    Optics InfoBase Conference Papers, 2014
    Co-Authors: Di Che, Xi Chen, Yifei Wang, William Shieh
    Abstract:

    We propose the Stokes vector direct detection (SV-DD) algorithm to achieve photo-detection nonlinearity cancellation and phase diversity. A 160-Gb/s single-polarization modulated SV-DD signal is successfully received after 160-km SSMF transmission with 7.76-bit/s/Hz Electrical Spectrum efficiency. © 2014 OSA.

Kentaro Nakamura - One of the best experts on this subject based on the ideXlab platform.

  • fiber optic interferometry using narrowband light source and Electrical Spectrum analyzer influence on brillouin measurement
    Journal of Lightwave Technology, 2014
    Co-Authors: Yosuke Mizuno, Neisei Hayashi, Kentaro Nakamura
    Abstract:

    We observe an interference pattern using a simple fiber-optic interferometer consisting of an Electrical Spectrum analyzer and a narrowband light source, which is commonly employed for observing the Brillouin gain Spectrum. This interference pattern expands well beyond the frequency range corresponding to the Brillouin frequency shift in silica fibers (∼11 GHz at 1.55 μm). Using both silica single-mode and polymer optical sensing fibers, we then experimentally prove that the distinctive noise in a self-heterodyne-based Brillouin measurement with an unoptimized polarization state originates from the interference between the reference light and the Fresnel-reflected light. This noise can be almost completely suppressed by employing a delay line that is longer than the coherence length of the light source and by artificially applying a high loss near the open end of the sensing fiber.

  • fiber optic interferometry using narrowband light source and Electrical Spectrum analyzer influence on brillouin measurement
    arXiv: Optics, 2014
    Co-Authors: Yosuke Mizuno, Neisei Hayashi, Kentaro Nakamura
    Abstract:

    We observe an interference pattern using a simple fiber-optic interferometer consisting of an Electrical Spectrum analyzer and a narrowband light source, which is commonly employed for observing the Brillouin gain Spectrum. This interference pattern expands well beyond the frequency range corresponding to the Brillouin frequency shift in silica fibers (approximately 11 GHz at 1550 nm). Using both silica single-mode and polymer optical sensing fibers, we then experimentally prove that the distinctive noise in a self-heterodyne-based Brillouin measurement with an unoptimized polarization state originates from the interference between the reference light and the Fresnel-reflected light. This noise can be almost completely suppressed by employing a delay line that is longer than the coherence length of the light source and by artificially applying a high loss near the open end of the sensing fiber.