Nyquist wavelength-division multiplexing （N-WDM） allows high spectral efficiency （SE） in long-haul transmission systems. Compared to polarization-division multiplexing quadrature phase-shift keying （PDM-QPSK）, m...Nyquist wavelength-division multiplexing （N-WDM） allows high spectral efficiency （SE） in long-haul transmission systems. Compared to polarization-division multiplexing quadrature phase-shift keying （PDM-QPSK）, multilevel modulation, such as PDM 16 quadrature-amplitude modulation （16-QAM）, is much more sensitive to intrachannel noise and interchannel linear crosstalk caused by N-WDM. We experimentally generate and transmit a 6 x 128 Gbit/s N-WDM PDM 16-QAM signal over 1200 km single-mode fiber （SMF）-28 with amplification provided by an erbium-doped fiber amplifier （EDFA） only. The net SE is 7.47 bit/s/Hz, which to the best of our knowledge is the highest SE for a signal with a bit rate beyond 100 Gbit/s using the PDM 16-QAM. Such SE was achieved by DSP pre-equalization of transmitter-side impairments and DSP post-equalization of channel and receiver-side impairments. Nyquist-band can be used in pre-equalization to enhance the tolerance of PDM 16-QAM to aggressive spectral shaping. The bit-error ratio （BER） for each of the 6 channels is smaller than the forward error correction （FEC） limit of 3.8 × 10-3 after 1200 km SMF-28 transmission.展开更多
A 12-bit 2.6 GS/s radio frequency digital to analog converter(RF DAC)based on 1 um GaAs heterojunction bipolar transistor(HBT)process is presented.The DAC integrates a 4:1 multiplexer to reduce the data rate of input ...A 12-bit 2.6 GS/s radio frequency digital to analog converter(RF DAC)based on 1 um GaAs heterojunction bipolar transistor(HBT)process is presented.The DAC integrates a 4:1 multiplexer to reduce the data rate of input ports,which greatly facilitates the application.DAC core adopts 4+8 segmented current steering structure.R-2R ladder network is used for 8 least significant bit(LSB)to realize binary current weighting and thermometer coding is used for 4 most significant bit(MSB).Return-to-zero(RZ)technology is used to expand the effective bandwidth of DAC output to the third Nyquist band.The proposed DAC has a better output power flatness and spurious-free dynamic range(SFDR).Compared to traditional DAC,measured results demonstrate that the output power of this RZ DAC is increased by 33 dB and the SFDR is enhanced by 27 dB near the second Nyquist band.展开更多
文摘Nyquist wavelength-division multiplexing （N-WDM） allows high spectral efficiency （SE） in long-haul transmission systems. Compared to polarization-division multiplexing quadrature phase-shift keying （PDM-QPSK）, multilevel modulation, such as PDM 16 quadrature-amplitude modulation （16-QAM）, is much more sensitive to intrachannel noise and interchannel linear crosstalk caused by N-WDM. We experimentally generate and transmit a 6 x 128 Gbit/s N-WDM PDM 16-QAM signal over 1200 km single-mode fiber （SMF）-28 with amplification provided by an erbium-doped fiber amplifier （EDFA） only. The net SE is 7.47 bit/s/Hz, which to the best of our knowledge is the highest SE for a signal with a bit rate beyond 100 Gbit/s using the PDM 16-QAM. Such SE was achieved by DSP pre-equalization of transmitter-side impairments and DSP post-equalization of channel and receiver-side impairments. Nyquist-band can be used in pre-equalization to enhance the tolerance of PDM 16-QAM to aggressive spectral shaping. The bit-error ratio （BER） for each of the 6 channels is smaller than the forward error correction （FEC） limit of 3.8 × 10-3 after 1200 km SMF-28 transmission.
基金supported by Open Project of State Key Laboratory of Millimeter Waves (K201727)Open Project of National and Local Joint Engineering Laboratory of RF Integration and Micro-Assembly Technology (KFJJ20170203)+1 种基金National Science Foundation (61571235, 61504065)Scientific Research Foundation of Nanjing University of Posts and Telecommunications (NUPTSF NY215138)
文摘A 12-bit 2.6 GS/s radio frequency digital to analog converter(RF DAC)based on 1 um GaAs heterojunction bipolar transistor(HBT)process is presented.The DAC integrates a 4:1 multiplexer to reduce the data rate of input ports,which greatly facilitates the application.DAC core adopts 4+8 segmented current steering structure.R-2R ladder network is used for 8 least significant bit(LSB)to realize binary current weighting and thermometer coding is used for 4 most significant bit(MSB).Return-to-zero(RZ)technology is used to expand the effective bandwidth of DAC output to the third Nyquist band.The proposed DAC has a better output power flatness and spurious-free dynamic range(SFDR).Compared to traditional DAC,measured results demonstrate that the output power of this RZ DAC is increased by 33 dB and the SFDR is enhanced by 27 dB near the second Nyquist band.
