conference & convention enabling the next generation of networks & services Ultra Ultra Long Long-Haul and High Haul and High-Capacity Capacity 40 Gbps DWDM Transmission Systems 40 Gbps DWDM Transmission Systems over Trans-Pacific Distance over Trans over Trans-Pacific Distance over Trans Pacific Distance Pacific Distance Takanori Inoue Takanori Inoue, Yoshihisa Inada, Lei Xu, , Yoshihisa Inada, Lei Xu, Takehiro Nakano, Ting Wang and Takaaki Ogata Takehiro Nakano, Ting Wang and Takaaki Ogata NEC Corporation NEC Corporation
conference & convention enabling the next generation of networks & services Outline 1. Introduction 2. 40Gbps System Design for Long Distance Transmission � Modulation Format � Modulation Format � Dispersion Map Optimization 3. 40Gbps Transmission Performance Assessment � Straight Line Experiment � Loop Experiment 4. Conclusion
conference & convention enabling the next generation of networks & services Introduction • 10Gbps DWDM technologies for submarine cable systems have been fully matured covering trans-pacific distance. - Channel spacing: 25GHz (Spectral efficiency: 0.4bit/s/Hz) - EDFA gain bandwidth: 40nm (~200ch) - Maximum Reach: <12000km • • Submarine cable system deployment with 40Gbps Submarine cable system deployment with 40Gbps technologies is indispensable to meet the growing capacity demand for international communication. - Higher capacity capability (Higher spectral efficiency) - Lower cost per bit - Reduction of power dissipation - Equipment down-sizing (Reduction of footprint) - Seamless connection between terrestrial 40Gbps system
conference & convention enabling the next generation of networks & services 10G to 40G Comparison Difference between 10G and 40G parameters Bit Rate 10Gbps 40Gbps Electrical Bandwidth 10GHz 40GHz Optical Spectrum Width 20GHz (0.16nm) 80GHz (0.64nm) Tolerance to CD Typ. +/- 200 ps (DPSK) 1/16 of 10G Tolerance to PMD Typically 10 ps 1/4 of 10G Required OSNR 6dB higher than 10G Optical nonlinear penalty Higher than 10G Key technologies for 40G system design • Baud rate reduction by multi-level modulation and polarization multiplexing • Coherent detection ( 2~3 dB sensitivity improvement ) • Active CD and PMD compensation by digital signal processing • Optimum design of transmission line (Fiber, Dispersion map)
conference & convention enabling the next generation of networks & services Modulation Formats for 40G Modulation Baud- Min. channel Optical Constellation Max. Format Rate spacing Spectrum Map Distance RZ-DPSK 40Gbps 100GHz < 6500km Im 100GHz (SE=0.4bit/s/H Re z ) RZ-DQPSK 20Gbps 50GHz < 5000km Im 50GHz (0.8bit/s/Hz) Re DP-RZ-QPSK 10Gbps 25GHz < 6500km Im Im X-pol (1.6bit/s/Hz) Re Re 50GHz Y-pol X-pol Y-pol DP-RZ-BPSK 20Gbps 50GHz < 9000km X-pol Im Im (0.8bit/s/Hz) Re Re X-pol Y-pol 50GHz Y-pol SP-RZ-QPSK 20Gbps 50GHz < 9000km X-pol Im (0.8bit/s/Hz) Re 50GHz
conference & convention enabling the next generation of networks & services Long Distance Transmission Capability Constellation Map (-4dBm/ch) DP-RZ-QPSK System Length: 6500km, 60km span 13 12 SP-RZ-QPSK DP-RZ-BPSK 11 or [dB] 10 10 Q factor 9 DP-RZ-BPSK DP-RZ-QPSK 8 7 RZ-DQPSK 6 -9 -8 -7 -6 -5 -4 -3 -2 -1 0 1 SP-RZ-QPSK Channel Power [dBm] DP-RZ-BPSK and SP-RZ-QPSK are promising for ultra long-haul.
conference & convention enabling the next generation of networks & services Transmission Line Design for 40Gbps ▐ RZ-DPSK / RZ-DQPSK ● Comparable with dispersion map for 10Gbps DPSK ▐ DP-RZ-QPSK ● All SMF without in-line DCF is one of the ideal transmission lines for digital coherent system, if only considering system performance. ● DMF is considered to be still one of the practical candidate for transmission line of digital coherent system with following issues, transmission line of digital coherent system with following issues, ■ CD compensation capability with DSP: around +/-40,000 ps/nm ■ Co-existing transmission with 10Gbps and/or analog 40Gbps signals All SMF RZ-DPSK 40G DP-RZ-QPSK 40G RZ-DPSK, RZ-DQPSK RZ-DQPSK 14 13 All SMF RZ-DPSK 13 12 Q value [dB] Q value [dB] 12 11 11 10 DMF 10 RZ-DQPSK 9 (SpanD=-2 ps/nm/km ) 9 8 8 -5 -4 -3 -2 -1 0 1 2 3 4 5 -1 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8 1 Block Averaged Dispersion [ps/nm/km] Block Averaged Dispersion [ps/nm/km]
conference & convention enabling the next generation of networks & services 40Gbps Transmission Performance Assessment • Straight line experiment – First generation 40Gbps transponder (RZ-DPSK and RZ-DQPSK) – 4300 km DMF transmission line (span length: 43 km) – 4300 km DMF transmission line (span length: 43 km) – 6500 km DMF transmission line (span length: 70 km) – 3400 km NZDSF Transmission line (span length: 46 km) • Loop experiment – Second generation 40Gbps transponder (DP-RZ-QPSK) – DMF transmission line (span length: 73km)
conference & convention enabling the next generation of networks & services 40Gbps Transponder (First Generation) Main features Various interfaces � STM-256/OC-768, STM-64/OC-192, 10GbE LAN PHY RZ-DPSK / RZ-DQPSK modulation formats � Enhanced FEC codes � Cover ITU-T grid with 100GHz/50GHz grid Cover ITU-T grid with 100GHz/50GHz grid � � Tunable Dispersion Compensation Module (TDCM) � 4x40G SLTMs in one SLT shelf � 40G Transponder Type SLTM40 SLTM40-Q SLTM40-XG Tributary Interface STM-256/OC-768 STM-64/OC-192 10GbE Line Bit Rate 43.02Gbps 44.57Gbps Modulation format RZ-DPSK, RZ-DQPSK FEC coding gain (BER=1x10 -13 ) 8.2dB
conference & convention enabling the next generation of networks & services RZ-DPSK/RZ-DQPSK 6,500 km DMF Straight Line Transmission • DMF line designed for commercial 10G Trans DMF line designed for commercial 10G Trans-Pacific systems Pacific systems (70 km span) (70 km span) 100GHz spaced 40Gbps RZ-DPSK 50GHz spaced 40Gbps RZ-DQPSK 40km span 50km span 60km span 70km span 40km span 50km span 60km span 70km span 80km span 90km span 100km span 70km span (Exp.) 80km span 90km span 100km span 70km span(Exp.) 14 14 13 13 Q SNR at -2dBm/ch 40km span Q SNR at -3dBm/ch 12 12 Q factor [dB] Q factor [dB] 40km span 11 11 10 10 100km span 9 9 FEC Detection Limit FEC Detection Limit 8 8 7 7 -9 -8 -7 -6 -5 -4 -3 -2 -1 0 1 2 3 4 5 6 -9 -8 -7 -6 -5 -4 -3 -2 -1 0 1 2 3 4 5 6 Repeater Output Power [dBm/ch] Repeater Output Power [dBm/ch] Optimum Channel Power:-2dBm Optimum Channel Power:-3dBm Q value: 11.1dB Q value: 10.5dB
conference & convention enabling the next generation of networks & services Experimental Setup for 40Gbps DP-RZ-QPSK Signal Transmission 40G Digital Coherent 40G DP-RZ-QPSK TX1 40G DP-RZ-QPSK TX1 Test-bed 10G(1) 10G(1) 10G(2) 10G(2) Coherent RX Coherent RX LD1 LD1 QPSK mod QPSK mod PM CPL PM CPL RZ RZ LD3 LD3 PBC PBC 10G(3) 10G(3) 10G(4) 10G(4) mod mod PD PD LD5 LD5 Pol. Pol. QPSK mod QPSK mod PD PD PD PD Diversity Diversity Diversity Diversity ADC ADC ADC ADC LD7 LD7 LD7 LD7 er Interleaver Interleaver er 90 degree 90 degree DMUX DMUX PD PD 40G DP-RZ-QPSK TX2 40G DP-RZ-QPSK TX2 Hybrid Hybrid 10G(1) 10G(1) 10G(2) 10G(2) PD PD LD2 LD2 QPSK mod QPSK mod PM CPL PM CPL LD4 LD4 RZ RZ Local Local DSP DSP PBC PBC 10G(3) 10G(3) 10G(4) 10G(4) mod mod LD LD (PC) (PC) LD6 LD6 SW1 SW1 QPSK mod QPSK mod LD8 LD8 84 CW 84 CW Light Source Light Source GEQ GEQ SW2 SW2 DMF DMF 73km 73km DMF DMF DMF DMF DMF DMF DMF DMF DMF DMF DEC DEC 73km 73km 73km 73km 73km 73km 73km 73km 73km 73km Optimized Dispersion Map
conference & convention enabling the next generation of networks & services 40Gbps DP-RZ-QPSK Signal Performance on DMF Transmission Line 50GHz spaced 40Gbps DP-RZ-QPSK signal 12 Q SNR 11 ctor [dB] 10 Q Meas All-SMF 9 9 (60km span, Ref.) (60km span, Ref.) Q facto DMF(73km Span) 8 7 FEC Detection Limit 6 4000 5000 6000 7000 8000 Distance [km] X pol. Y pol. X pol. Y pol. Constellation 6300km 4370km Map
conference & convention enabling the next generation of networks & services 40Gbps DWDM Development Direction Suppression of nonlinear propagation impairment will be the most vital for 40Gbps DWDM systems over trans-Pacific distances. Capacity/fp Low Loss / Low NL SMF Low Loss / Low NL SMF DP-RZ-QPSK (Digital) 7.68Tbps 25GHz spacing 25GHz spacing Raman Amp. / Remote Amp. Raman Amp. / Remote Amp. Raman Amp. / Remote Amp. Raman Amp. / Remote Amp. DMF Next Gen. FEC (e.g. LDPC) Next Gen. FEC (e.g. LDPC) 5.12Tbps Nonlinear tolerant modulation 3.84Tbps RZ-DQPSK (e.g. DP-RZ-BPSK) 50GHz spacing 50GHz spacing LEAF/DMF New DMF (Low Loss, Low NL) 2.56Tbps RZ-DPSK (Analog) (Reference) 100GHz spacing 1.28Tbps 10G-25GHz LEAF/DMF 1.92Tbps EDFA (40nm) 12,000km 3000km 6000km 9000km Transmission Distance (km)
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