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Joint scheme for symbol,sampling clock,and carrier frequency synchronization in PDM-CO-OFDM system beyond 100 Gb/s

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Chinese Optics Letters 2014年第10期12卷 20-26页

作者：闫峥刘耀超陈雪 State Key Laboratory of Information Photonics and Optical Communications Beijing University of Posts and Telecommunications

We propose a joint scheme for symbol, sampling clock, and carrier frequency synchronization in a polarization division multiplexing coherent optical orthogonal frequency division multiplexing （PDM-CO-OFDM） system. Unlike other existing algorithms designed for specific impairment, the scheme can estimate and compensate for the interactional synchronization errors effectively without extra training overhead by building a comprehensive error model. The simulation shows that symbol synchronization error and sample timing error can be corrected by channel equalizer, and the estimation ranges of sampling frequency offset and normalized carrier frequency offset are about （-2000, 2000） ppm, and （-0.04 （-3.5）, 0.04 （3.5）） Ghz, respectively.

关键词： Clocks frequency allocation frequency estimation Local area networks Signal encoding Synchronization

A novel OFDM-CPM modulation scheme and its application in WDM-PON

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Chinese Optics Letters 2010年第9期8卷 894-898页

作者：邵宇丰张俊文方武良邹书敏李欣颖黄博迟楠余思远 Department of Communication Science and Engineering and State Key Lab of ASIC & System Fudan University

A novel scheme to generate, transmit, and receive an optical orthogonal frequency division multiplexing （OFDM） continuous phase modulation （CPM） signal, which is combining minimum shift keying （MSK） coding with OFDM optical modulation, for downlink application in a 4×2.5-Gb/s wavelength division multiplexing （WDM） passive optical access network, is proposed and experimentally validated. We also realize wavelength remodulation for carrying upstream on-off keying （OOK） data to reduce the cost budget at the optical network unit. The experimental results show that the power penalties for the downlink and the uplink data after transmission over 25-km SMF-28 fiber are 0.1 dB and smaller than 0.4 dB, respectively.

关键词： Electrostatic discharge Fiber optic networks frequency allocation Multiplexing equipment Optical communication Orthogonal frequency division multiplexing Orthogonal functions Phase modulation Wavelength division multiplexing

Coherent optical OFDM scheme with inter-carrier interference self-cancellation and common phase error compensation

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Chinese Optics Letters 2010年第7期8卷 634-638页

作者：吴毅凌李巨浩赵春旭赵玉萍张帆陈章渊 State Key Laboratory of Advanced Optical Communication Systems & Networks Peking University

Schemes integrating inter-carrier interference （ICI） self-cancellation and common phase error （CPE） com- pensation for coherent optical orthogonal frequency division multiplexing （CO-OFDM） systems are investi- gated. The purpose of our research is to counteract the impacts of laser phase noise and fiber nonlinearity. We propose two ICI self-cancellation-based CO-OFDM schemes, and adopt a pilot-aided decision feedback （DFB） loop for CPE compensation. The proposed schemes are compared with conventional CO-OFDM schemes at the same spectral efficiency. Simulations show that our schemes can not only enhance laser linewidth tolerance of the CO-OFDM system, but also present strong robustness against fiber nonlinearity.

关键词： Error compensation frequency allocation Orthogonal functions Spectrum analyzers Telecommunication systems

Phase pre-emphasis for PAPR reduction in optical OFDM systems based on OIDFT or time lens

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Chinese Optics Letters 2010年第9期8卷 875-880页

作者：邵晶李蔚梁晓军 Wuhan National Lab for Optoelectronics Huazhong University of Science and Technology

Phase pre-emphasis is theoretically studied and introduced to reduce peak-to-average power ratio （PAPR） in optical orthogonal frequency division multiplexing （OFDM） systems. In intensity modulated （IM） systems, simulations show noticeable PAPR reductions： 4.14 dB （N = 16） and 15.48 dB （N = 512） in time lens-based OFDM, N is the number of subcarriers. An equation is developed to calculate phase values and is proved to be effective. Optical implementing methods are proposed and analyzed. In a time lens-based OFDM system, phase pre-emphasis reduces fiber nonlinearity and results in a 5.2-dB increase of launch power at the bit error rate （BER） of 10 ？6 . Simulations also show similar PAPR reduction and fiber nonlinearity mitigation in optical inverse discrete Fourier transformer （OIDFT） based OFDM systems.

关键词： Bit error rate frequency allocation Lenses Optical instruments Orthogonal functions Telecommunication systems

Joint estimation of frequency offset and chromatic dispersion based on the training sequences in M-ary QAM coherent optical transmission system

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Chinese Optics Letters 2014年第10期12卷 27-30页

作者：孙艺萍席丽霞唐先锋赵东鹤乔耀军张霞张晓光 State Key Laboratory of Information Photonics and Optical Communications Beijing University of Posts and Telecommunications The Key Laboratory of Optical Communications Science & Technology in Shandong Province Liaocheng University

A data-aided method of joint frequency offset and chromatic dispersion estimation based on the Chu training sequences is shown in 112 Gb/s polarization-multiplexed （PM） quadrature phase-shift keying and 224 Gb/s PM-16-quadrature amplitude modulation with different pulse-shaping filters, respectively. The proposed method achieves a good accuracy and is verified to be robust to polarization mode dispersion.

关键词： Amplitude modulation Chromatic dispersion Dispersions frequency allocation frequency estimation Optical systems Phase shift Phase shifters Polarization Polarization mode dispersion Pulse shaping Quadrature amplitude modulation Quadrature phase shift keying Signal encoding

Electronic compensator for 100-Gb/s PDM-CO-OFDM long-haul transmission systems

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Chinese Optics Letters 2011年第3期9卷 12-16页

作者：刘学君乔耀军纪越峰 Key Laboratory of Information Photonics and Optical Communications the Ministry of EducationBeijing University of Posts and Telecommunications College of Information Science and Engineering Yanshan University

We study an electronic compensator （EC） as a receiver for a 100-Gb/s polarization division multiplexing coherent optical orthogonal frequency division multiplexing （PDM-CO-OFDM） system without optical dispersion ***,including electrical dispersion compensation （EDC）,least squares channel estimation and compensation （LSCEC）,and phase compensation （PC）,is used to compensate for chromatic dispersion （CD）,phase noise,polarization mode dispersion （PMD）,and channel impairments,*** show that EC is highly effective in compensating for those impairments and that the performance is close to the theoretical limitation of optical signal-to-noise rate （OSNR）,CD,and *** robustness against those transmission impairments and fiber nonlinearity are also systematically studied.

关键词： Channel estimation Dispersion compensation Dispersions Electromagnetic dispersion frequency allocation Multiplexing Optical signal processing Orthogonal functions Polarization

Novel 64×2.5 Gb/s all-optical OFDM symbol generator based on triangle waveform driving-LiNbO_3 modulators

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Chinese Optics Letters 2010年第5期8卷 449-453页

作者：李源李蔚梁晓军杨克成乔耀军 Wuhan National Laboratory for Optoelectronics Huazhong University of Science and Technology Department of Computer Science and Technology Central China Normal University Key Laboratory of Information Photonics and Optical Communications Ministry of EducationBeijing University of Posts and Telecommunications

We propose a novel and simple all-optical 160-Gb/s orthogonal frequency division multiplexing（OFDM） symbol generator which is based on discrete triangle waveform driving-LiNbO_3 modulators to realize large-range linear optical *** entire system needs 64 discrete modulators：at the transmitter,a 2.5-Gb/s optical duobinary（ODB） modulator for data modulation and a 2.5-Gb/s triangle waveform driving-LiNbO_3 phase modulator for phase shift to generate each subcarrier;and at the receiver,a 2.5-GHz optical band pass filter（OBPF） using Faraday anomalous dispersion optical effect to separate *** bit error rate（BER） is observed after 1060 km of transmission without any dispersion compensation.

关键词： Bandpass filters Bit error rate Error compensation frequency allocation Orthogonal frequency division multiplexing Orthogonal functions

All-optical sampling OFDM system performance analysis

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Chinese Optics Letters 2011年第1期9卷 32-35页

作者：叶航陈宏伟唐超陈明华谢世钟 State Key Laboratory on Integrated Optoelectronics Tsinghua National Laboratory for Information Science and Technology (TNList) Department of Electronic Engineering Tsinghua University Beijing 100084 China

The performance of a novel all-optical sampling orthogonal frequency division multiplexing （OFDM） system is proposed and analyzed. Time delays and phase shifters are used to realize all optical forward/inverse discrete Fourier transform （DFT/IDFT）. Different system configurations are tested and analyzed to op- timize the performance, including the system capacity, modulation formats, DFT/IDFT constructions, and the width of the sample pulse. The 50- and 100-Gb/s real-time all-optical sampling （AOS） OFDM systems ave investigated. All results are analyzed, and useful suggestions are offered for future high-speed

关键词： Discrete Fourier transforms frequency allocation Orthogonal functions Real time systems Telecommunication systems

Decreasing the uncertainty of atomic clocks via real-time noise distinguish

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Chinese Optics Letters 2017年第5期15卷 1-5页

作者：董日昌林锦达魏荣王文丽邹凡杜远博陈婷婷王育竹 Key Laboratory of Quantum Optics Shanghai Institute of Optics and Fine Mechanics Chinese Academy of Sciences Shanghai 201800 China University of Chinese Academy of Sciences Beifing 100049 China

The environmental perturbation on atoms is a key factor restricting the performance of atomic frequency standards, especially in the long-term scale. In this Letter, we perform a real-time noise distinguish（RTND） to an atomic clock to decrease the uncertainty of the atomic clock beyond the level that is attained by the current controlling method. In RTND, the related parameters of the clock are monitored in real time by using the calibrated sensors, and their effects on the clock frequency are calculated. By subtracting the effects from the error signal, the local oscillator is treated as equivalently locked to the unperturbed atomic levels. In order to perform quantitative tests, we engineer time-varying noise much larger than the intrinsic noise in our fountain atomic clock. By using RTND, the influences of the added noises are detected and subtracted precisely from the error signals before feeding back to the reference oscillator. The result shows that the statistical uncertainty of our fountain clock is improved by an order of magnitude to 2 × 10^（-15）. Besides, the frequency offset introduced by the noise is also corrected, while the systematic uncertainty is unaffected.

关键词： Fountains frequency allocation frequency standards