In this paper,we review our joint timing and frequency synchronization algorithms in coherent optical orthogonal frequency division multiplexing(CO-OFDM)systems.We first present a timing estimation method by designing...In this paper,we review our joint timing and frequency synchronization algorithms in coherent optical orthogonal frequency division multiplexing(CO-OFDM)systems.We first present a timing estimation method by designing the pattern of the training symbol,whose timing metric has a sharp and clear peak,to ensure accurate timing offset(TO)estimation performance.Then we provide both data-aided(DA)and blind(BL)approaches to estimate the carrier frequency offset(CFO).For the DA algorithm,we utilize the same training symbol structure as the timing estimation does,while for the BL algorithm,we utilize the zero-subcarrier power(ZSP)to achieve full-range CFO estimation.Note that our joint timing and frequency synchronization approaches require only one OFDM symbol,which ensure not only the data transmission efficiency,but also the TO and CFO estimation performance.A modified BL ZSP algorithm is proposed to further improve the CFO estimation performance by taking the power average over a series of OFDM symbols.The effectiveness of the TO estimation algorithm,and both the DA and BL CFO estimation algorithms are verified and demonstrated in both simulations and experiments.展开更多
介绍了光纤射频传输(Radio over Fiber,RoF)系统中相干正交频分复用(CO-OFDM)的原理和发展现状,并对主流的基于直接调制结构和上下变频结构的CO-OFDM方案进行了论述,分析比较了不同方案的优缺点。此外还对一些基于相干解调的改进方案进...介绍了光纤射频传输(Radio over Fiber,RoF)系统中相干正交频分复用(CO-OFDM)的原理和发展现状,并对主流的基于直接调制结构和上下变频结构的CO-OFDM方案进行了论述,分析比较了不同方案的优缺点。此外还对一些基于相干解调的改进方案进行了研究,包括相位噪声补偿和自载波提取,从而有效地改善了系统性能,降低了系统成本。展开更多
Aiming at the problem of the peak to average power ratio(PAPR)in coherent optical orthogonal frequency division multiplexing(CO-OFDM),a hybrid PAPR reduction technique of the CO-OFDM system by combining iterative part...Aiming at the problem of the peak to average power ratio(PAPR)in coherent optical orthogonal frequency division multiplexing(CO-OFDM),a hybrid PAPR reduction technique of the CO-OFDM system by combining iterative partial transmit sequence(IPTS)scheme with modified clipping and filtering(MCF)is proposed.The simulation results show that at the complementary cumulative distribution function(CCDF)of 10^(-4),the PAPR of proposed scheme is optimized by 1.86 d B and 2.13 d B compared with those of IPTS and CF schemes,respectively.Meanwhile,when the bit error rate(BER)is 10^(-3),the optical signal to noise ratio(OSNR)are optimized by 1.57 dB and 0.66 d B compared with those of CF and IPTS-CF schemes,respectively.展开更多
This paper investigates the architecture of Tbits/s Wavelength Division Multiplexing (WDM) system by using a Coherent Optical Orthogonal Frequency Division Multiplexing (CO-OFDM) with 4-QAM for long haul transmissions...This paper investigates the architecture of Tbits/s Wavelength Division Multiplexing (WDM) system by using a Coherent Optical Orthogonal Frequency Division Multiplexing (CO-OFDM) with 4-QAM for long haul transmissions of 1800 Km SM. A simulation of 20 WDM channels spaced at 50 GHz, and 20 OFDM signals each with 50 Gbits/s bitrate to produce data rate of 1 Tbits/s is built. The system performance is studied by observing the constellation diagram of the signal and the relationship of BER and OSNR with regard to transmission distance. The results show that the BER increases as the transmission distance increases. Also, as the transmission distance increases, the OSNR needs to be increased to maintain BER in less than 10-3.展开更多
The 5G cellular network aims at providing three major services:Massive machine-type communication(mMTC),ultra-reliable low-latency communications(URLLC),and enhanced-mobile-broadband(eMBB).Among these services,the URL...The 5G cellular network aims at providing three major services:Massive machine-type communication(mMTC),ultra-reliable low-latency communications(URLLC),and enhanced-mobile-broadband(eMBB).Among these services,the URLLC and eMBB require strict end-to-end latency of 1 ms while maintaining 99.999%reliability,and availability of extremely high data rates for the users,respectively.One of the critical challenges in meeting these requirements is to upgrade the existing optical fiber backhaul network interconnecting the base stations with a multigigabit capacity,low latency and very high reliability system.To address this issue,we have numerically analyzed 100 Gbit/s coherent optical orthogonal frequency division multiplexing(CO-OFDM)transmission performance over 400 km single-mode fiber(SMF)and 100 km of multi-mode fiber(MMF)links.The system is simulated over optically repeated and non-repeated SMF and MMF links.Coherent transmission is used,and the system is analyzed in a linear and non-linear regime.The system performance is quantified by bit error ratio(BER).Spectrally efficient and optimal transmission performance is achieved for 400 km SMF and 100 km MMF link.The results designate thatMMF links can be employed beyond short reach applications by using them in the existing SMF infrastructure for long haul transmission.In particular,the proposed CO-OFDM system can be efficiently employed in 5G backhaul network.The multi-gigabit capacity and lower BER of the proposed system makes it a suitable candidate especially for the eMBB and URLLC requirements for 5G backhaul network.展开更多
The compensation effects of fiber nonlinearity in 112 Gb/s polarization division multiplexing（PDM） coherent optical systems by mid-span optical phase conjugation（OPC） based on four wave mixing（FWM） effect are st...The compensation effects of fiber nonlinearity in 112 Gb/s polarization division multiplexing（PDM） coherent optical systems by mid-span optical phase conjugation（OPC） based on four wave mixing（FWM） effect are studied. Comparisons of the compensation results between PDM coherent optical-orthogonal frequency division multiplexing（CO-OFDM）system and the single carrier（SC） PDM quadrature phase shift keying（QPSK） system are provided as well. The results demonstrate that nonlinear compensation effect with mid-span OPC in PDM CO-OFDM system is much more obvious than that in SC PDM QPSK system.展开更多
文摘In this paper,we review our joint timing and frequency synchronization algorithms in coherent optical orthogonal frequency division multiplexing(CO-OFDM)systems.We first present a timing estimation method by designing the pattern of the training symbol,whose timing metric has a sharp and clear peak,to ensure accurate timing offset(TO)estimation performance.Then we provide both data-aided(DA)and blind(BL)approaches to estimate the carrier frequency offset(CFO).For the DA algorithm,we utilize the same training symbol structure as the timing estimation does,while for the BL algorithm,we utilize the zero-subcarrier power(ZSP)to achieve full-range CFO estimation.Note that our joint timing and frequency synchronization approaches require only one OFDM symbol,which ensure not only the data transmission efficiency,but also the TO and CFO estimation performance.A modified BL ZSP algorithm is proposed to further improve the CFO estimation performance by taking the power average over a series of OFDM symbols.The effectiveness of the TO estimation algorithm,and both the DA and BL CFO estimation algorithms are verified and demonstrated in both simulations and experiments.
文摘介绍了光纤射频传输(Radio over Fiber,RoF)系统中相干正交频分复用(CO-OFDM)的原理和发展现状,并对主流的基于直接调制结构和上下变频结构的CO-OFDM方案进行了论述,分析比较了不同方案的优缺点。此外还对一些基于相干解调的改进方案进行了研究,包括相位噪声补偿和自载波提取,从而有效地改善了系统性能,降低了系统成本。
基金supported by the National Natural Science Foundation of China(No.61475118)the State Key Laboratory on Integrated Optoelectronics of China(No.IOSKL2015KF06)the National High-Tech Research and Development Program of China(No.2013AA014201)
文摘Aiming at the problem of the peak to average power ratio(PAPR)in coherent optical orthogonal frequency division multiplexing(CO-OFDM),a hybrid PAPR reduction technique of the CO-OFDM system by combining iterative partial transmit sequence(IPTS)scheme with modified clipping and filtering(MCF)is proposed.The simulation results show that at the complementary cumulative distribution function(CCDF)of 10^(-4),the PAPR of proposed scheme is optimized by 1.86 d B and 2.13 d B compared with those of IPTS and CF schemes,respectively.Meanwhile,when the bit error rate(BER)is 10^(-3),the optical signal to noise ratio(OSNR)are optimized by 1.57 dB and 0.66 d B compared with those of CF and IPTS-CF schemes,respectively.
文摘This paper investigates the architecture of Tbits/s Wavelength Division Multiplexing (WDM) system by using a Coherent Optical Orthogonal Frequency Division Multiplexing (CO-OFDM) with 4-QAM for long haul transmissions of 1800 Km SM. A simulation of 20 WDM channels spaced at 50 GHz, and 20 OFDM signals each with 50 Gbits/s bitrate to produce data rate of 1 Tbits/s is built. The system performance is studied by observing the constellation diagram of the signal and the relationship of BER and OSNR with regard to transmission distance. The results show that the BER increases as the transmission distance increases. Also, as the transmission distance increases, the OSNR needs to be increased to maintain BER in less than 10-3.
基金supported by the National Research Foundation of Korea(NRF)grant funded by the Korean government(MSIT)(Nos.2019R1A4A1023746,2019R1F1A1060799)the Strengthening R&D Capability Program of Sejong University。
文摘The 5G cellular network aims at providing three major services:Massive machine-type communication(mMTC),ultra-reliable low-latency communications(URLLC),and enhanced-mobile-broadband(eMBB).Among these services,the URLLC and eMBB require strict end-to-end latency of 1 ms while maintaining 99.999%reliability,and availability of extremely high data rates for the users,respectively.One of the critical challenges in meeting these requirements is to upgrade the existing optical fiber backhaul network interconnecting the base stations with a multigigabit capacity,low latency and very high reliability system.To address this issue,we have numerically analyzed 100 Gbit/s coherent optical orthogonal frequency division multiplexing(CO-OFDM)transmission performance over 400 km single-mode fiber(SMF)and 100 km of multi-mode fiber(MMF)links.The system is simulated over optically repeated and non-repeated SMF and MMF links.Coherent transmission is used,and the system is analyzed in a linear and non-linear regime.The system performance is quantified by bit error ratio(BER).Spectrally efficient and optimal transmission performance is achieved for 400 km SMF and 100 km MMF link.The results designate thatMMF links can be employed beyond short reach applications by using them in the existing SMF infrastructure for long haul transmission.In particular,the proposed CO-OFDM system can be efficiently employed in 5G backhaul network.The multi-gigabit capacity and lower BER of the proposed system makes it a suitable candidate especially for the eMBB and URLLC requirements for 5G backhaul network.
基金supported by the National Natural Science Foundation of China(Grant Nos.61271192,61427813,and 61331010)the National Basic Research Program of China(Grant No.2013AA013401)
文摘The compensation effects of fiber nonlinearity in 112 Gb/s polarization division multiplexing（PDM） coherent optical systems by mid-span optical phase conjugation（OPC） based on four wave mixing（FWM） effect are studied. Comparisons of the compensation results between PDM coherent optical-orthogonal frequency division multiplexing（CO-OFDM）system and the single carrier（SC） PDM quadrature phase shift keying（QPSK） system are provided as well. The results demonstrate that nonlinear compensation effect with mid-span OPC in PDM CO-OFDM system is much more obvious than that in SC PDM QPSK system.
