Fiber Nonlinearities and 1 Tb/s Systems
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This document summarizes research on 400 Gb/s and 1 Tb/s transmission systems and fiber nonlinearities. It discusses: 1. Fiber nonlinear limits on spectral efficiency and distance as a function of launch power, channel count, and linear vs. nonlinear regimes. 2. Experimental results demonstrating a 1 Tb/s super channel over 138 km using 5x224 Gb/s signals with digital signal processing for nonlinear compensation. 3. A field trial of the 1 Tb/s super channel and 112 Gb/s QPSK signals over 138 km and 330 km respectively in the GIGA network in Brazil, showing improved bit error rate with nonlinear compensation.
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Fiber Nonlinearities and 1 Tb/s Systems
- 1. 400 Gb/s & 1 Tb/s systems and fiber nonlinearities Jacklyn D. Reis, PhD Luis H. H. de Carvalho, BSc Carolina Franciscangelis, BSc Victor Parahyba, BSc Júlio C. M. Diniz, MSc Daniel M. Pataca, PhD Fábio D. Simões, PhD Neil G. Gonzalez, PhD Júlio César R.F. de Oliveira, PhD CPqD, Campinas, São Paulo, Brazil 23-25 February 2014 Day 1
- 2. 1. Fiber Nonlinear Limits 2. 1 Tb/s Super Channel 3. Field Trial with Nonlinear Compensation 1. 1 Tb/s super channel 138 km 2. 112 Gb/s DP-QPSK 338 km Outline
- 3. Nonlinear Limits in Optical Networking • Spectral efficiency times distance [bit/s/Hz]*km • Longer distance • Higher launch power • Higher optical channels • Linear Regime ASE • Nonlinear Regime Kerr nonlinearities686 JOURNAL OF LIGHTWAVE TECHNOLOGY, VOL. 28, NO. 4, FEBRUARY 15, 2010 Fig. 35. Spectral efficiency after transmission for various distance. All links are without dispersion compensation. impairments. It is possible to avoid this recorrelation of WDM channels by using dispersion compensators that are “channel- ized,” i.e., that compensate dispersion independently for each WDM channel without compensating the relative time delay be- Fig. 36. Spectral efficiency for four signal and noise scenarios for the 2000 km transmission of Fig. 35. (ch: channel.) Essiambre et al, IEEE/OSA JLT’10. 1 2 3 4 5 6 7 8 9 10 100 1000 10000 30000 Distance(km) Net Spectal Efficiency (b/s/Hz) 1000 (bit×km)/(s×Hz) 4000 (bit×km)/(s×Hz) 10000 (bit×km)/(s×Hz) 40000 (bit×km)/(s×Hz) Fig. 2. System reach vs. throughput trade-off in main record transmission experiments based on coherent detection published in the last five years. gh-order format generation and N-WDM spectral shaping can both be obtained with l techniques [4, 8], but current consensus strongly favors the use of transmitter (Tx) Nespola et al, OptEx’14. Liu et al, IEEE SPMag’14
- 5. Simulation model • Electrical + optical components for simulation super channels / WDM systems implemented in Matlab • DSP normalization, CD equalizer (2x), LMS (2x), blind phase search, synchronization, EVM/SNR ADC Analog Filtering Downsample Quantizer DSP Jitter DAC Symbols Upsample Quantizer AWGN Analog Filtering ZOH Upsample Jitter ClippingNyquist ADC Analog Filtering Downsample Quantizer DSP Jitter DAC Symbols Upsample Quantizer AWGN Analog Filtering ZOH Upsample Jitter ClippingNyquist Transmitter λtx DAC PBS DAC PBC Mod Mod Out Receiver DigitalSignalProcessing Ix Qx 2x4 90º Hyb ADC ADC λrx PBS In PBS Iy Qy 2x4 90º Hyb ADC ADC A 1:N A W G A W G
- 6. Maximum reach without amplification • If 7% HD FEC with 3.8x10-3 (SNR≈21.1 dB) Maximum reach of 175 km with linear compensation only • Launch power ≈ 4 dBm (single polarization) Receiver DSP Ix Qx 2x4 90º Hyb ADC ADC λN Prx = -31 dBm Ptx = -31 dBm + ILfiber Transmitter λ1 DAC Mod Out DAC A -21 dBm -11 dBm -16 dBm -6 dBm -1 dBm +4 dBm
- 7. -1 dBmSignal+SPM SPMSPM +19 dBm Maximum reach without amplification • Output optical spectrum for different input power (or transmission distance). • Nonlinear generation from -21 (50 km-SSMF, top left) dBm up to 19 dBm (250 km, bottom right) launch power -21 dBm-16 dBm-11 dBm-6 dBm+4 dBm+9 dBm+14 dBm
- 8. Maximum reach without amplification • Considerations on launch power and receiver sensitivity • If receiver sensitivity is lower than -33 dBm, than the input power has to increase • Input power is upper bounded by fiber nonlinearities (~4 dBm up to 100 km – SSMF) • To avoid increasing the launch power to support the loss budget, amplification prior the coherent receiver may be used to enhance sensitivity
- 9. Multi-carrier transmission at 50 GHz grid • Nx43 Gbaud – 64QAM at 50 GHz frequency grid after 100 km of SSMF (0.2 dB/km, 16 ps/nm/km, 1.3 W-1km- 1) 9 −100 −50 0 50 100 −100 −90 −80 −70 −60 −50 −40 −30 −20 −10 0 Output Optical Spectrum Frequency to 193.4 THz [GHz] OpticalPower[dBm/Hz] −100 −50 0 50 100 −100 −90 −80 −70 −60 −50 −40 −30 −20 −10 0 Output Optical Spectrum Frequency to 193.4 THz [GHz] OpticalPower[dBm/Hz] −100 −50 0 50 100 −100 −90 −80 −70 −60 −50 −40 −30 −20 −10 0 Output Optical Spectrum Frequency to 193.4 THz [GHz] OpticalPower[dBm/Hz] −100 −50 0 50 100 −100 −90 −80 −70 −60 −50 −40 −30 −20 −10 0 Frequency to 193.4 THz [GHz] OpticalPower[dBm/Hz] Transmitter Receiver DSP Ix Qx 2x4 90º Hyb ADC ADC λN 100 km SSMF 0.2 dB/km 16.5 ps/nm/km 1.3 (kmW)-1 A W G Transmitter TransmitterTransmitter λ1 DAC Mod Out DAC A
- 10. −9 −6 −3 0 3 6 −30 −27.5 −25 −22.5 −20 −17.5 −15 Nch x 43 Gbaud −64 QAM at 100 km −SSMF Launch Power [dBm] EVMRMS [dB] 1 Channel 2 Channels BER = 10 −3 3 Channels 4 Channels Multi-carrier transmission at 50 GHz grid • Intra-channel SPM versus inter-channel XPM at 50 GHz • From 1 Channel to 4 Channels 3 dB penalty on launch power BER = 10-3 due to XPM
- 11. 1T SUPER CHANNEL PART II
- 12. Optical pre-filtering • Experimental setup • WDM scenario: 3 channels, 35-GHz spacing. • Optical filtering: Nyquist optical filter, bandwidth variation. • Use of conventional DSP, without ICI or ISI compensation. • Results analysis • Measured performance at central channel (worst scenario). • Q-Penalty in reference to “non-filtered” 224G RZ PDM-16QAM. • Best performance @ 26GHz bandwidth (ICI vs ISI trade-off). Test Channel VOA 2x1 Neighbors SCOPE(40-GS/s) (a) EDFA 3 dB WaveShaper Mod. RZ PDM-16QAM Mod. RZ PDM-16QAM LO OfflineDSP (b) ICR
- 13. Experimental Setup Fig. 1: Experimental setup. (a) 1.12-Tb/s transmitter; (b) 224G RZ-PDM-16QAM optical eye and constellations; (c) 1.12-Tb/s spectrum in a 175-GHz flexi-grid WSS channel; (d) Recirculation loop; (e) DSP-Rx block diagram.
- 14. Back-to-back characterization (per-carrier) • Measured performance @ 1e-3 BER • 224Gb/s RZ PDM-16QAM (Reference): 26 dB (6-dB implementation penalty). • Reference after filtering: 25.5 dB (0.5-dB matched filter improvement). • 1.12-Tb/s Superchannel (5-Carriers): 26.3 dB (0.8-dB multiplexing penalty). • 1.12-Tb/s after 5 ROADMs@175-GHz: 27.4 dB (1.1-dB penalty). • Required OSNR @ FEC Limit: 3.8e-3 BER • 1.12-Tb/s Superchannel (5-Carriers): 23.3 dB.
- 15. Transmission results Launch-Power after 700km BER with NLC after 1000 km Transmission performance OSNR performance (per-carrier) • Launch-Power test • Per-carrier investigation. • Optimum value: -1 dBm/carrier • Transmission results • 700 km and 7 ROADM passes • Using conventional DSP • 1000 km and 10 ROADM passes • Employing nonlinear compensation. • OSNR performance • Without NLC • After 700 km: 25.3 dB • Transmission penalty: 2 dB • With NLC • After 1000 km: 23.9 dB • Transmission penalty: 0.6 dB • Improvement of 1.4 dB in transmission penalty by employing NLC • Transmission reach improved from 700 to 1000 km.
- 17. Field Trial: GIGA Network • Campinas to Jundiaí ~138 km • Campinas to São Paulo ~330 km
- 18. 1 Tb/s Super Channel: 5 x 224 Gb/s DP-16QAM RZ+PF DAC free 6 b/s/Hz SE (175 GHz grid) ECOC’13
- 19. −5 −4 −3 −2 −1 0 0 0.002 0.004 0.006 0.008 0.01 0.012 Launch Power per Channel [dBm] BER 1 Tb/s Super Channel: 5x224 Gb/s DP−16QAM −Campinas −Jundiai BER = 3.8x10 −3 Asymmetric SSF 1 +MLSE Symmetric SSF 16 Asymmetric SSF 1 Linear Compensation 1 Tb/s: 5 x 224 Gb/s DP-16QAM 138 km • BER Improvement at Optimal Power 3.5x
- 20. 112 Gb/s: DP-QPSK 330 km • BER Improvement at Optimal Power 1.5x / 2.8x • Nonlinear tolerance 2 dB improvement w/o MLSE −8.5 −7.5 −6.5 −5.5 −4.5 −3.5 −2.5 −1.5 −0.5 0 0.001 0.002 0.003 0.004 0.005 0.006 0.007 0.008 0.009 0.01 Launch Power [dBm] BER 112 Gb/s DP−QPSK −Campinas −Sao Paulo Linear Compensation Asymmetric SSF 1 Symmetric SSF 16 Asymmetric SSF 1 +MLSE BER = 3.8x10 −3
- 21. Conclusions • DSP plays a major role on high-speed optical networking • Fiber nonlinear effects limit the launch power • Shorter capacity • Shorter distance • Digital nonlinear compensation • At least 2 dB improvement on nonlinear tolerance • Network parameters in deployed fibers • Chip implementation is yet to appear