Spatial modedivision multiplexing is emerging as a potential solution to further increasing optical fiber capacity and spectral efficiency. We report a dualmode, dualpolarization transmission method based on modeselec...Spatial modedivision multiplexing is emerging as a potential solution to further increasing optical fiber capacity and spectral efficiency. We report a dualmode, dualpolarization transmission method based on modeselective excitation and detection over a twomode fiber. In particular, we present 107 Gbit/s coherent optical OFDM (COOFDM) transmission over a 4.5 km twomode fiber using LP and LP. modes in which mode separation is performed optically.展开更多
A new method coherent DWDM system has been proposed. Standard method uses 90 wavelengths with channel capacity 100 G, so total capacity amounts to 9 Terabit, optical power is P. New “channel super” (CS) consists of ...A new method coherent DWDM system has been proposed. Standard method uses 90 wavelengths with channel capacity 100 G, so total capacity amounts to 9 Terabit, optical power is P. New “channel super” (CS) consists of 15 wavelengths, number of CS is 6, so total number of wavelengths is 90 too, total capacity is 6 Terabit, but optical power is 4/15P. Over ULH and EULH markets, standard approach will be forced to reduce the total capacity to 2.4 Terabit with optical power 4/15P as in proposed method. But the new can reach 6 Terabit with the same optical power 4/15P.展开更多
Fiber nonlinearity is one of the most important limiters of capacity in coherent optical communications. In this paper, we review two nonlinear compensation methods: digital backward propagation (BP) and nonlinear ...Fiber nonlinearity is one of the most important limiters of capacity in coherent optical communications. In this paper, we review two nonlinear compensation methods: digital backward propagation (BP) and nonlinear electrical equalizer (NLEE) based on the timedomain Volterra series. These compensation algorithms are implemented in a singlechannel 50 Gb/s coherent optical singlecarrier frequency division multiplexed (CO-SCFDM) system transmitting over 10 × 80 km of standard singlemode fiber (SSMF).展开更多
Split-step digital backward propagation (DBP) can be combined with coherent detection to compensate for fiber nonlinear impairments. A large number of DBP steps is usually needed for a long-haul fiber system, and th...Split-step digital backward propagation (DBP) can be combined with coherent detection to compensate for fiber nonlinear impairments. A large number of DBP steps is usually needed for a long-haul fiber system, and this creates a heavy computational load. In a trade-off between complexity and performance, interchannel nonlinearity can be disregarded in order to simplify the DBP algorithm. The number of steps can also be reduced at the expense of performance. In periodic dispersion-managed long-haul transmission systems, optical waveform distortion is dominated by chromatic dispersion. As a result, the nonlinearity of the optical signal repeats in every dispersion period. Because of this periodic behavior, DBP of many fiber spans can be folded into one span. Using this distance-folded DBP method, the required computation for a transoceanic transmission system with full inline dispersion compensation can be reduced by up to two orders of magnitude with negligible penalty. The folded DBP method can be modified to compensate for nonlinearity in fiber links with non-zero residua dispersion per span.展开更多
An optical phase locking method based on direct phase control is proposed.The core of this method is to synchronize the carrier by directly changing the phase of the local beam.The corresponding experimental device an...An optical phase locking method based on direct phase control is proposed.The core of this method is to synchronize the carrier by directly changing the phase of the local beam.The corresponding experimental device and the supporting algorithm were configured to verify the feasibility of this method.Phase locking can be completed without cycle skipping,and the acquisition time is 530 ns.Without an optical preamplifier,a sensitivity of-34.4 d Bm is obtained,and the bit error rate is 10^(-9) for 2.5 Gbit/s binary phase-shift keying modulation.The measured standard deviation of the phase error is 5.2805°.展开更多
Upcoming generations of coherent intra/inter data center interconnects currently lack a clear path toward a reduction of cost and power consumption,which are the driving factors for these data links.In this work,the t...Upcoming generations of coherent intra/inter data center interconnects currently lack a clear path toward a reduction of cost and power consumption,which are the driving factors for these data links.In this work,the tradeoffs associated with a transition from coherent C-band to O-band silicon photonics are addressed and evaluated.The discussion includes the fundamental components of coherent data links,namely the optical components,fiber link and transceivers.As a major component of these links,a monolithic silicon photonic BiCMOS O-band coherent receiver is evaluated for its potential performance and compared to an analogous C-band device.展开更多
An improved zero-interpolation method with signal clipping to improve fiber nonlinearity tolerance in the long-haul coherent optical orthogonal frequency division multiplexing system (CO-OFDM) is presented. The new ...An improved zero-interpolation method with signal clipping to improve fiber nonlinearity tolerance in the long-haul coherent optical orthogonal frequency division multiplexing system (CO-OFDM) is presented. The new technique is implemented by interpolating zero subcarriers and selecting the odd subcarriers to carry data and clipping conventional CO-OFDM signal at zero. With such a scheme,the effect of fiber nonlinearity can be miti-gated,and the wanted signal carried on odd subcarriers is or-thogonal to clipping noise,which falls on even frequencies. Simu-lation shows that the system Q value is improved by more than 2 dB at the length of 960 km展开更多
For joint modulation format identification(MFI)and optical signal-to-noise ratio(OSNR)monitoring,a simple and intelligent optical communication performance monitoring method is proposed,and the feasibility is demonstr...For joint modulation format identification(MFI)and optical signal-to-noise ratio(OSNR)monitoring,a simple and intelligent optical communication performance monitoring method is proposed,and the feasibility is demonstrated by digital coherent optical communication experiments.The experiment results show that for all modulation formats,including 28 GBaud polarization division multiplexing(PDM)QPSK/8-QAM/16-QAM/64-QAM,100%MFI accuracies are achieved even at OSNR values lower than the corresponding theoretical 20%forward error correction limit,as well as the high accuracies for OSNR monitoring.Furthermore,the proposed scheme has a reasonable monitoring level when chromatic dispersion and fiber nonlinear effects are varied.展开更多
In this paper,we report on polarization combining two-dimensional grating couplers(2D GCs)on amorphous Si:H,fabricated in the backend of line of a photonic BiCMOS platform.The 2D GCs can be used as an interface of a h...In this paper,we report on polarization combining two-dimensional grating couplers(2D GCs)on amorphous Si:H,fabricated in the backend of line of a photonic BiCMOS platform.The 2D GCs can be used as an interface of a hybrid silicon photonic coherent transmitter,which can be implemented on bulk Si wafers.The fabricated 2D GCs operate in the telecom C-band and show an experimental coupling efficiency of−5 dB with a wafer variation of±1.2 dB.Possibilities for efficiency enhancement and improved performance stability in future design generations are outlined and extension toward O-band devices is also investigated.展开更多
We propose and experimentally demonstrate a universal and blind polarization-state tracking scheme for M-quadrature amplitude modulation(QAM) signals based on a decision-free radius-directed linear Kalman filter(RD...We propose and experimentally demonstrate a universal and blind polarization-state tracking scheme for M-quadrature amplitude modulation(QAM) signals based on a decision-free radius-directed linear Kalman filter(RD-LKF).The polarization tracking performance is investigated through simulation and experiments for both quadrature phase-shift keying(QPSK) and 16-QAM signals.The influence of the filter parameters on the static polarization demultiplexing performance and dynamic tracking capability are discussed via simulation.The optimization strategy of the filter parameters in modulation-format-independent scenarios is proposed and simulations are carried out to evaluate the polarization demultiplexing penalty for QPSK,16 QAM,and hybrid QPSK/16 QAM signals.Finally,the proposed decision-free RD-LKF is experimentally compared to the respective algorithms of constant modulus algorithm and multimodulus algorithm for QPSK and 16-QAM and the advantage of ultrafast polarization tracking ability is confirmed.展开更多
We analyze a feasible high-sensitivity homodyne coherent optical receiver for demodulating optical quadrature phase-shift keying(QPSK). A fourth-power phase-lock loop based on a digital look-up table is used. Consider...We analyze a feasible high-sensitivity homodyne coherent optical receiver for demodulating optical quadrature phase-shift keying(QPSK). A fourth-power phase-lock loop based on a digital look-up table is used. Considering the non-negligible loop delay, we optimize the loop natural frequency. Without error correction coding, a sensitivity of -37 dBm/-35 dBm is achieved, while the bit error rate is below 10-9 at 2.5 Gbaud/5 Gbaud rate.For the QPSK communication system, the bit rate is twice the baud rate. The loop natural frequency is 0.647 Mrad/s, and the minimized steady-state phase-error standard deviation is 3.83°.展开更多
The dissipative Kerr soliton microcomb provides a promising laser source for wavelength-division multiplexing(WDM)communication systems thanks to its compatibility with chip integration.However,the soliton microcomb c...The dissipative Kerr soliton microcomb provides a promising laser source for wavelength-division multiplexing(WDM)communication systems thanks to its compatibility with chip integration.However,the soliton microcomb commonly suffers from a low-power level due to the intrinsically limited energy conversion efficiency from the continuous-wave pump laser to ultra-short solitary pulses.Here,we exploit laser injection locking to amplify and equalize dissipative Kerr soliton comb lines,superior gain factor larger than 30 dB,and optical-signal-to-noise-ratio(OSNR)as high as 60 dB obtained experimentally,providing a potential pathway to constitute a high-power chip-integrated WDM laser source for optical communications.展开更多
Probabilistically shaped(PS)high-order quadrature amplitude modulation(QAM)signals are attractive to coherent optical communication due to increased spectral efficiency.However,standard digital signal processing algor...Probabilistically shaped(PS)high-order quadrature amplitude modulation(QAM)signals are attractive to coherent optical communication due to increased spectral efficiency.However,standard digital signal processing algorithms are not optimal to demodulate PS high-order QAM signals.Therefore,a compromise equalization is indispensable to compensate the residual distortion.Meanwhile,the performance of conventional blind equalization highly depends on the accurate amplitude radius and distribution of the signals.The PS high-order QAM signals make the issue worsen because of indistinct amplitude distributions.In this work,we proposed an optimized blind equalization by utilizing a peak-density K-means clustering algorithm to accurately track the amplitude radius and distribution.We experimentally demonstrated the proposed method in a PS 256-QAM coherent optical transmission system and achieved approximately 1 dB optical signal-to-noise ratio improvement at the bit error rate of 1×10^(−3).展开更多
文摘Spatial modedivision multiplexing is emerging as a potential solution to further increasing optical fiber capacity and spectral efficiency. We report a dualmode, dualpolarization transmission method based on modeselective excitation and detection over a twomode fiber. In particular, we present 107 Gbit/s coherent optical OFDM (COOFDM) transmission over a 4.5 km twomode fiber using LP and LP. modes in which mode separation is performed optically.
文摘A new method coherent DWDM system has been proposed. Standard method uses 90 wavelengths with channel capacity 100 G, so total capacity amounts to 9 Terabit, optical power is P. New “channel super” (CS) consists of 15 wavelengths, number of CS is 6, so total number of wavelengths is 90 too, total capacity is 6 Terabit, but optical power is 4/15P. Over ULH and EULH markets, standard approach will be forced to reduce the total capacity to 2.4 Terabit with optical power 4/15P as in proposed method. But the new can reach 6 Terabit with the same optical power 4/15P.
基金supported by National Natural Science Foundation of China (No. 61077053, 60932004, and60877045)National Basic Research Program of China(No. 2010CB328201)
文摘Fiber nonlinearity is one of the most important limiters of capacity in coherent optical communications. In this paper, we review two nonlinear compensation methods: digital backward propagation (BP) and nonlinear electrical equalizer (NLEE) based on the timedomain Volterra series. These compensation algorithms are implemented in a singlechannel 50 Gb/s coherent optical singlecarrier frequency division multiplexed (CO-SCFDM) system transmitting over 10 × 80 km of standard singlemode fiber (SSMF).
文摘Split-step digital backward propagation (DBP) can be combined with coherent detection to compensate for fiber nonlinear impairments. A large number of DBP steps is usually needed for a long-haul fiber system, and this creates a heavy computational load. In a trade-off between complexity and performance, interchannel nonlinearity can be disregarded in order to simplify the DBP algorithm. The number of steps can also be reduced at the expense of performance. In periodic dispersion-managed long-haul transmission systems, optical waveform distortion is dominated by chromatic dispersion. As a result, the nonlinearity of the optical signal repeats in every dispersion period. Because of this periodic behavior, DBP of many fiber spans can be folded into one span. Using this distance-folded DBP method, the required computation for a transoceanic transmission system with full inline dispersion compensation can be reduced by up to two orders of magnitude with negligible penalty. The folded DBP method can be modified to compensate for nonlinearity in fiber links with non-zero residua dispersion per span.
基金supported by the National Key R&D Program of China(No.2020YFB0408302)Strategic Priority Research Program of Chinese Academy of Sciences(No.XDB43030400)+1 种基金National Natural Science Foundation of China(No.91938302)Key Project of Chinese Academy of Sciences(No.ZDRWKT-2019-1-01-0302)。
文摘An optical phase locking method based on direct phase control is proposed.The core of this method is to synchronize the carrier by directly changing the phase of the local beam.The corresponding experimental device and the supporting algorithm were configured to verify the feasibility of this method.Phase locking can be completed without cycle skipping,and the acquisition time is 530 ns.Without an optical preamplifier,a sensitivity of-34.4 d Bm is obtained,and the bit error rate is 10^(-9) for 2.5 Gbit/s binary phase-shift keying modulation.The measured standard deviation of the phase error is 5.2805°.
基金the GermanResearch Foundation (DFG) through the projects EPIC-Sense (ZI 1283-6-1)and EPIDAC (ZI 1283-7-1)the Federal Ministry of Education andResearch (BMBF) through project PEARLS (13N14932)the EuropeanCommission through project H2020-SPACE-ORIONAS (822002).
文摘Upcoming generations of coherent intra/inter data center interconnects currently lack a clear path toward a reduction of cost and power consumption,which are the driving factors for these data links.In this work,the tradeoffs associated with a transition from coherent C-band to O-band silicon photonics are addressed and evaluated.The discussion includes the fundamental components of coherent data links,namely the optical components,fiber link and transceivers.As a major component of these links,a monolithic silicon photonic BiCMOS O-band coherent receiver is evaluated for its potential performance and compared to an analogous C-band device.
基金Supported by the National Natural Science Foundation of China (60871075)
文摘An improved zero-interpolation method with signal clipping to improve fiber nonlinearity tolerance in the long-haul coherent optical orthogonal frequency division multiplexing system (CO-OFDM) is presented. The new technique is implemented by interpolating zero subcarriers and selecting the odd subcarriers to carry data and clipping conventional CO-OFDM signal at zero. With such a scheme,the effect of fiber nonlinearity can be miti-gated,and the wanted signal carried on odd subcarriers is or-thogonal to clipping noise,which falls on even frequencies. Simu-lation shows that the system Q value is improved by more than 2 dB at the length of 960 km
基金This work was supported by the National Key Research and Development Program of China(No.2021YFB2206303)Key Research and Development Plan of Shandong Province(No.2023CXPT100)+1 种基金Sichuan Science Fund for Distinguished Young Scholars(No.2023NSFSC1969)National Student Research Training Program of China(No.20230613037).
文摘For joint modulation format identification(MFI)and optical signal-to-noise ratio(OSNR)monitoring,a simple and intelligent optical communication performance monitoring method is proposed,and the feasibility is demonstrated by digital coherent optical communication experiments.The experiment results show that for all modulation formats,including 28 GBaud polarization division multiplexing(PDM)QPSK/8-QAM/16-QAM/64-QAM,100%MFI accuracies are achieved even at OSNR values lower than the corresponding theoretical 20%forward error correction limit,as well as the high accuracies for OSNR monitoring.Furthermore,the proposed scheme has a reasonable monitoring level when chromatic dispersion and fiber nonlinear effects are varied.
基金This work was supported in part by the German Research Foundation(DFG)through the projects EPIC-Sense(ZI 1283-6-1)EPIDAC(ZI 1283-7-1)the Federal Ministry of Education and Research(BMBF)through project PEARLS(13N14932).
文摘In this paper,we report on polarization combining two-dimensional grating couplers(2D GCs)on amorphous Si:H,fabricated in the backend of line of a photonic BiCMOS platform.The 2D GCs can be used as an interface of a hybrid silicon photonic coherent transmitter,which can be implemented on bulk Si wafers.The fabricated 2D GCs operate in the telecom C-band and show an experimental coupling efficiency of−5 dB with a wafer variation of±1.2 dB.Possibilities for efficiency enhancement and improved performance stability in future design generations are outlined and extension toward O-band devices is also investigated.
基金supported by the National Natural Science Foundation of China(Nos.61205046,61401020,and 61575051)the Shenzhen Municipal Science and Technology Plan Project(Nos.JCYJ20150327155705357,KQCX2015032409501296,and JSGG20150529153336124,and JCYJ20150529114045265)the Hong Kong Government General Research Fund(GRF)(No.PolyU152079/14E)
文摘We propose and experimentally demonstrate a universal and blind polarization-state tracking scheme for M-quadrature amplitude modulation(QAM) signals based on a decision-free radius-directed linear Kalman filter(RD-LKF).The polarization tracking performance is investigated through simulation and experiments for both quadrature phase-shift keying(QPSK) and 16-QAM signals.The influence of the filter parameters on the static polarization demultiplexing performance and dynamic tracking capability are discussed via simulation.The optimization strategy of the filter parameters in modulation-format-independent scenarios is proposed and simulations are carried out to evaluate the polarization demultiplexing penalty for QPSK,16 QAM,and hybrid QPSK/16 QAM signals.Finally,the proposed decision-free RD-LKF is experimentally compared to the respective algorithms of constant modulus algorithm and multimodulus algorithm for QPSK and 16-QAM and the advantage of ultrafast polarization tracking ability is confirmed.
文摘We analyze a feasible high-sensitivity homodyne coherent optical receiver for demodulating optical quadrature phase-shift keying(QPSK). A fourth-power phase-lock loop based on a digital look-up table is used. Considering the non-negligible loop delay, we optimize the loop natural frequency. Without error correction coding, a sensitivity of -37 dBm/-35 dBm is achieved, while the bit error rate is below 10-9 at 2.5 Gbaud/5 Gbaud rate.For the QPSK communication system, the bit rate is twice the baud rate. The loop natural frequency is 0.647 Mrad/s, and the minimized steady-state phase-error standard deviation is 3.83°.
基金supported by the National Key R&D Program of China(Nos.2019YFB-2203103 and 2018YFA0307400)the National Natural Science Foundation of China(NSFC)(Nos.62001086 and 61705033)。
文摘The dissipative Kerr soliton microcomb provides a promising laser source for wavelength-division multiplexing(WDM)communication systems thanks to its compatibility with chip integration.However,the soliton microcomb commonly suffers from a low-power level due to the intrinsically limited energy conversion efficiency from the continuous-wave pump laser to ultra-short solitary pulses.Here,we exploit laser injection locking to amplify and equalize dissipative Kerr soliton comb lines,superior gain factor larger than 30 dB,and optical-signal-to-noise-ratio(OSNR)as high as 60 dB obtained experimentally,providing a potential pathway to constitute a high-power chip-integrated WDM laser source for optical communications.
基金This work was supported in part by the National Key R&D Program of China(No.2020YFB1805805)the National Natural Science Foundation of China(No.62075147).
文摘Probabilistically shaped(PS)high-order quadrature amplitude modulation(QAM)signals are attractive to coherent optical communication due to increased spectral efficiency.However,standard digital signal processing algorithms are not optimal to demodulate PS high-order QAM signals.Therefore,a compromise equalization is indispensable to compensate the residual distortion.Meanwhile,the performance of conventional blind equalization highly depends on the accurate amplitude radius and distribution of the signals.The PS high-order QAM signals make the issue worsen because of indistinct amplitude distributions.In this work,we proposed an optimized blind equalization by utilizing a peak-density K-means clustering algorithm to accurately track the amplitude radius and distribution.We experimentally demonstrated the proposed method in a PS 256-QAM coherent optical transmission system and achieved approximately 1 dB optical signal-to-noise ratio improvement at the bit error rate of 1×10^(−3).