A hybrid polarization division multiplexed-differential phase shift keying-multipulse pulse position modulation(PDM-DPSK-MPPM) scheme for multi-hop free-space optical(FSO) communication is investigated. The analytical...A hybrid polarization division multiplexed-differential phase shift keying-multipulse pulse position modulation(PDM-DPSK-MPPM) scheme for multi-hop free-space optical(FSO) communication is investigated. The analytical bit error rate(BER) of the proposed system in Gamma-Gamma turbulence channels is derived and verified using computer simulation. The results show that both multi-hop and hybrid modulation schemes are efficient techniques to improve the performance of FSO links. Compared with the traditional binary phase shift keying(BPSK) and MPPM, the hybrid scheme can improve the bandwidth-utilization efficiency and reliability of the system. Compared with the coherent demodulation of PDM-QPSK-MPPM, the system complexity is reduced at the cost of the degradation of BER performance, which can improve the practicality of hybrid modulation technology in FSO system.展开更多
The explosive increase in data traffic requires networks to provide higher capacity and long-haul transmission capabilities.This paper introduces new results on high-order modulation and efficient Digital Signal Proce...The explosive increase in data traffic requires networks to provide higher capacity and long-haul transmission capabilities.This paper introduces new results on high-order modulation and efficient Digital Signal Processing algorithms to reduce various transmission limitations in coherent receiving systems.Polarization Division Multiplexed Quadrature Phase Shift Keying(PDM-QPSK)is deployed to reach high bit rates,provides modified digital clock recovery,and allows BER-Aided Constant Modulus Algorithm(BA-CMA)equalising.A Soft Decision-Forward Error Correction(SD-FEC)algorithm and a joint scheme with timing recovery and adaptive equaliser are used to achieve better performance.A compact coherent transceiver is also developed.These techniques have been applied in the largest 100 G Optical Transport Network(OTN)deployment in the world,the backbone expansion project for Phase 3 of the China Education and Research Network(CERNET),with a total transmission length of 10 000 km.展开更多
Accurate characterization of high-power laser parameters,especially the near-field and far-field distributions,is crucial for inertial confinement fusion experiments.In this paper,we propose a method for computational...Accurate characterization of high-power laser parameters,especially the near-field and far-field distributions,is crucial for inertial confinement fusion experiments.In this paper,we propose a method for computationally reconstructing the complex amplitude of high-power laser beams using modified coherent modulation imaging.This method has the advantage of being able to simultaneously calculate both the near-field(intensity and wavefront/phase)and far-field(focal-spot)distributions using the reconstructed complex amplitude.More importantly,the focal-spot distributions at different focal planes can also be calculated.To verify the feasibility,the complex amplitude optical field of the highpower pulsed laser was measured after static aberrations calibration.Experimental results also indicate that the near-field wavefront resolution of this method is higher than that of the Hartmann measurement.In addition,the far-field focal spot exhibits a higher dynamic range(176 dB)than that of traditional direct imaging(62 dB).展开更多
The scientific monitoring and reliable telecommunications(SMART)initiative,led by a joint task force including ITU,aims to integrate electronic sensors into undersea telecommunications cables for real-time and high-se...The scientific monitoring and reliable telecommunications(SMART)initiative,led by a joint task force including ITU,aims to integrate electronic sensors into undersea telecommunications cables for real-time and high-sensitivity subsea monitoring.The current integrated sensing and communication(ISAC)solution to the SMART application still relies on wavelength band multiplexing of sensing information via Ethernet switches,leading to optical communication bandwidth waste.To achieve the dense and low-interference ISAC for SMART network applications,we demonstrate the co-transmissions of coherent optical digital subcarrier modulation(DSCM)communication signals and temperature sensing information in the SMART system.Besides the co-transmission capability,the special design of the sensing transmission format is made to enable the compatible DSP with DSCM communications,which shares the same wavelength channel.Moreover,due to the different physical locations of the in-line sensing joints to the communication transceivers in the SMART system,it is hard to align the wavelength of the communication laser and the sensing one,which cannot ensure the precise allocation of sensing information into the frequency blanks of DSCM communication signals.To deal with these two issues,the sensing information at inline joints is proposed to be modulated in the manner of optical single-sideband(SSB)modulation and frequency modulation(FM),and then the precise allocation into the frequency blanks of DSCM communication signals can be realized,along with the full compatibility to demodulate the sensed temperature using the traditional frequency offset estimation in coherent DSP.Experiments on a two-span repeatered single-mode fiber link validate the integration of 20 GBaud optical DP-QAM16 transmissions and real-time temperature sensing at a sensing joint.Advanced communications are enabled by implementing space-time coding on DSCM communication signals,with 0.2 dB Q factor improvement.As for the sensing functionality,the temperature sensing resolution at 0.0625°C,which reaches the limitation of the employed electronic thermometer DS18B20,has been obtained by using the communication-compatible DSP.We believe the proposed ISAC scheme along with the corresponding DSP flowchart makes sense for monitoring the subsea via the advanced SMART cables.展开更多
Analytical formulas for a class of tunable random electromagnetic beams propagating in a turbulent atmosphere through a complex optical system are derived with the help of a tensor method. One finds that the far field...Analytical formulas for a class of tunable random electromagnetic beams propagating in a turbulent atmosphere through a complex optical system are derived with the help of a tensor method. One finds that the far field intensity distribution is tunable by modulating the source correlation structure function. The on-axis spectral degree of polarization monotonically increases to the same value for different values of order M in free space while it returns to the initial value after propagating a sufficient distance in turbulence. Furthermore, it is revealed that the state of polarization is closely determined by the initial correlation structure rather than by the turbulence parameters.展开更多
基金supported by the National Natural Science Foundation of China(No.61373124)
文摘A hybrid polarization division multiplexed-differential phase shift keying-multipulse pulse position modulation(PDM-DPSK-MPPM) scheme for multi-hop free-space optical(FSO) communication is investigated. The analytical bit error rate(BER) of the proposed system in Gamma-Gamma turbulence channels is derived and verified using computer simulation. The results show that both multi-hop and hybrid modulation schemes are efficient techniques to improve the performance of FSO links. Compared with the traditional binary phase shift keying(BPSK) and MPPM, the hybrid scheme can improve the bandwidth-utilization efficiency and reliability of the system. Compared with the coherent demodulation of PDM-QPSK-MPPM, the system complexity is reduced at the cost of the degradation of BER performance, which can improve the practicality of hybrid modulation technology in FSO system.
基金supported by the National Natural Science Foundation of China under Grant No. 60932004the National High Technical Research and Development Program of China (863 Program) under Grants No. 2012AA011301,No. 2012AA011303
文摘The explosive increase in data traffic requires networks to provide higher capacity and long-haul transmission capabilities.This paper introduces new results on high-order modulation and efficient Digital Signal Processing algorithms to reduce various transmission limitations in coherent receiving systems.Polarization Division Multiplexed Quadrature Phase Shift Keying(PDM-QPSK)is deployed to reach high bit rates,provides modified digital clock recovery,and allows BER-Aided Constant Modulus Algorithm(BA-CMA)equalising.A Soft Decision-Forward Error Correction(SD-FEC)algorithm and a joint scheme with timing recovery and adaptive equaliser are used to achieve better performance.A compact coherent transceiver is also developed.These techniques have been applied in the largest 100 G Optical Transport Network(OTN)deployment in the world,the backbone expansion project for Phase 3 of the China Education and Research Network(CERNET),with a total transmission length of 10 000 km.
基金supported by the Project of the Ministry of Industry and Information Technology(Grant No.TC220H05L)the National Natural Science Foundation of China(NSFC)(Grant Nos.61905261,61827816 and 11875308)+1 种基金the Shanghai Sailing Program(Grant No.18YF1426600)the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDA25020306).
文摘Accurate characterization of high-power laser parameters,especially the near-field and far-field distributions,is crucial for inertial confinement fusion experiments.In this paper,we propose a method for computationally reconstructing the complex amplitude of high-power laser beams using modified coherent modulation imaging.This method has the advantage of being able to simultaneously calculate both the near-field(intensity and wavefront/phase)and far-field(focal-spot)distributions using the reconstructed complex amplitude.More importantly,the focal-spot distributions at different focal planes can also be calculated.To verify the feasibility,the complex amplitude optical field of the highpower pulsed laser was measured after static aberrations calibration.Experimental results also indicate that the near-field wavefront resolution of this method is higher than that of the Hartmann measurement.In addition,the far-field focal spot exhibits a higher dynamic range(176 dB)than that of traditional direct imaging(62 dB).
基金National Natural Science Foundation of China(62475178)Yangtze River Delta Region Integration Project(2024CSJGG2600).
文摘The scientific monitoring and reliable telecommunications(SMART)initiative,led by a joint task force including ITU,aims to integrate electronic sensors into undersea telecommunications cables for real-time and high-sensitivity subsea monitoring.The current integrated sensing and communication(ISAC)solution to the SMART application still relies on wavelength band multiplexing of sensing information via Ethernet switches,leading to optical communication bandwidth waste.To achieve the dense and low-interference ISAC for SMART network applications,we demonstrate the co-transmissions of coherent optical digital subcarrier modulation(DSCM)communication signals and temperature sensing information in the SMART system.Besides the co-transmission capability,the special design of the sensing transmission format is made to enable the compatible DSP with DSCM communications,which shares the same wavelength channel.Moreover,due to the different physical locations of the in-line sensing joints to the communication transceivers in the SMART system,it is hard to align the wavelength of the communication laser and the sensing one,which cannot ensure the precise allocation of sensing information into the frequency blanks of DSCM communication signals.To deal with these two issues,the sensing information at inline joints is proposed to be modulated in the manner of optical single-sideband(SSB)modulation and frequency modulation(FM),and then the precise allocation into the frequency blanks of DSCM communication signals can be realized,along with the full compatibility to demodulate the sensed temperature using the traditional frequency offset estimation in coherent DSP.Experiments on a two-span repeatered single-mode fiber link validate the integration of 20 GBaud optical DP-QAM16 transmissions and real-time temperature sensing at a sensing joint.Advanced communications are enabled by implementing space-time coding on DSCM communication signals,with 0.2 dB Q factor improvement.As for the sensing functionality,the temperature sensing resolution at 0.0625°C,which reaches the limitation of the employed electronic thermometer DS18B20,has been obtained by using the communication-compatible DSP.We believe the proposed ISAC scheme along with the corresponding DSP flowchart makes sense for monitoring the subsea via the advanced SMART cables.
基金supported by the National Natural Science Foundation of China (No. 11504172)the Natural Science Foundation of Jiangsu Province (No. BK20150763)the Project Funded by the Priority Academic Program Development of Jiangsu Higher Education Institutions
文摘Analytical formulas for a class of tunable random electromagnetic beams propagating in a turbulent atmosphere through a complex optical system are derived with the help of a tensor method. One finds that the far field intensity distribution is tunable by modulating the source correlation structure function. The on-axis spectral degree of polarization monotonically increases to the same value for different values of order M in free space while it returns to the initial value after propagating a sufficient distance in turbulence. Furthermore, it is revealed that the state of polarization is closely determined by the initial correlation structure rather than by the turbulence parameters.
