The Cost of 10-Gb/s and 100-Gb/s Coexistence TNC2013, Maastricht, June 2013 Dr. Klaus Grobe, Steven Searcy, Dr. Sorin Tibuleac, ADVA Optical Networking

© 2013 ADVA Optical Networking. All rights reserved. Confidential. 22 Content 10G and 100G Transport Technology Recap Challenges of combined 10G / 100G Transport

© 2013 ADVA Optical Networking. All rights reserved. Confidential G and 100G Transport Technology Recap

© 2013 ADVA Optical Networking. All rights reserved. Confidential. 44 High-Speed Transmission (long-haul) 40G10G100G 400G … 1T ADC, DSP, 30 GBd, 40 nm TRX-DSP and/or ADC, DSP, 60 GBd, 28 nm Intensity Modulation Single Polarization Direct Detection Optical Dispersion Compensation Phase Modulation Self-coherent Detection Phase Modulation Digital coherent Intradyne Detection Dual Polarization QPSK, QAM, QPR Single / Dual / Multi Carrier Re Im DP-QPSK Re Im DP-16QAM Re Im 4C-DP- QPSK Re Im 4C-DP- QPSK Re Im 4C-DP- QPSK Re Im 4C-DP- QPSK Re Im DBPSK Re Im OOK/DD

© 2013 ADVA Optical Networking. All rights reserved. Confidential G IM-DD Source S+HSink PD Driver LD G A A DC A A Span Accumulated CD Residual CD A A DC A A ROADM A A DC A A A A A A ROADM 50 GHz DWDM with 0.2 (bit/s)/Hz spectral efficiency Up to 3000 km reach on compensated fiber (unless pre-distorted) FEC w/ coding gain ~9 dB, leading to EOL OSNR <14 dB PMD tolerance 30 ps DGD, CD tolerance 1200 ps/nm

© 2013 ADVA Optical Networking. All rights reserved. Confidential G Coherent Dual-Polarization QPSK 50 GHz DWDM with 2 (bit/s)/Hz spectral efficiency Up to 3000 km reach on uncompensated fiber (less when compensated) SD-FEC w/ coding gain >11 dB, leading to EOL OSNR <14 dB PMD tolerance 100 ps DGD, CD tolerance 60,000 ps/nm PBCPBS QPSK Coder + Driver PC Digital Filter (FFE) 90° Hybrid 0°0° 90° CW LD PC PBS LO Sink Source ADC 90° QPSK Coder + Driver 90° Hybrid 0°0° 90°

© 2013 ADVA Optical Networking. All rights reserved. Confidential G Intradyne Digital DP-QPSK Linear only ADC Clock Recovery Fixed Compensation CMA Equalizer Carrier Recovery(FOE, CPE) Decider, Decoder CD Compensation(FIR Filter) FFT CD Compensation IFFT NL Phase Shift Linear and Nonlinear N Spans Bulk CD / NL Compensation Carrier recovery in digital domain Adaptive bulk compensation of CD Adaptive PMD and residual-CD compensation, and polarization demultiplexing with MIMO eq. Optional NL compensation

© 2013 ADVA Optical Networking. All rights reserved. Confidential. 88 BER Comparison Why is 100G is good as (or better than) 10G? Inherently better OSNR of QPSK over IM/DD FEC better by ~2 dB Almost lossless PDM Photonic layer better by ~1 dB when uncompensated ~4 dB

© 2013 ADVA Optical Networking. All rights reserved. Confidential. 99 Challenges of combined 10G / 100G Transport

© 2013 ADVA Optical Networking. All rights reserved. Confidential. 10 Impact of IM-DD Aggressor Channels Co-propagating IM-DD channels reduce the Q-Factor performance of QPSK Penalty caused by XPM-induced Nonlinear Phase Noise – X-NLPN Penalty can be reduced by Low IM-DD power (-2 dBm or smaller) Guardband between IM-DD and QPSK (e.g., 200 GHz) 5 x DQPSK Center Ch. QPSK + 4 x 10G IM-DD Power per Neighbor Channel [dBm] Q-Factor [dB] Co-propagating IM-DD generates X-NLPN

© 2013 ADVA Optical Networking. All rights reserved. Confidential Gb/s performance is also impacted by different optical layers A penalty can occur even if X-NLPN is suppressed Penalty caused by Higher EDFA noise-figure XPM In DCF itself (small) In transmission fiber, caused by compensation of channel walk-off Optical Layer based on DCF generates XPM and NF penalty Impact of Photonic Layer Span Loss [dB] Reach [km] G DP-QPSK 10G IM/DD + 100G DP-QPSK

© 2013 ADVA Optical Networking. All rights reserved. Confidential. 12 Impact of CD Compensation Method Chongjin Xie, ECOC2009, P Per-Channel Launch Power [dBm] OSNR for BER=10 -3 [dB] w/ DCF w/o DC w/ Ch-FBG Periodic Group-Delay (PGD) CD compensators can have almost 0, or even negative, OSNR penalty Better XPM suppression No XPM generation No channel walk-off compensation Channelized FBGs are PGD compensators, their use is recommended over DCF. Frequency [THz] Group Delay [ps] PGD

© 2013 ADVA Optical Networking. All rights reserved. Confidential. 13 Impact of 100G CPE Receiver allows optimizing block size of Carrier Phase Estimation Longer blocks better for linear noise limitation Shorter block lengths reduce penalty in nonlinear scenarios Settings of 2, 4, … 32 Limited crosstalk penalty w/o guardband In some designs, performance is improved with a guardband (200 GHz) Van den Borne et al., ECOC Symbols 5 Symbols 7 Symbols 9 Symbols log(BER) Launch Power [dBm]

© 2013 ADVA Optical Networking. All rights reserved. Confidential. 14 Uncompensated photonic layer Requires 10G w/ electronic pre-distortion Limited alien-wavelength support for standard 10G Negligible penalty, specially if small guardband is provided Cheaper photonic layer Compensated photonic layer Use channelized FBGs, adapt CPE block length Alien-wavelength support for all 10G Negligible penalty, specially if small guardband is provided Photonic layer more expensive Selective CD compensation… Coherent (QPSK/QAM) overlay… Options for mixed 10G / 100G

© 2013 ADVA Optical Networking. All rights reserved. Confidential. 15 Selective 10G CD Compensation In Degree-N or extra leveling nodes 10G sub-bands, DC adapted to these bands Per-link compensation, can simplify network-wide CD compensation Combined w/ guardband, gives optimum performance for both Consumes WSS ports, reduces node degree or add/drop scalability May require extra nodes A A A A A A 1:9 WSS 1:9 DC A A A A 1:9 WSS 1:9 DC A A WSS 1:9 Local A / D Leveling Node Add/Drop Node

© 2013 ADVA Optical Networking. All rights reserved. Confidential. 16 Coherent-only Overlay Requires duplicated fibers and systems (in-line amplifiers) Considered most future-proof, regarding 400G, 1T, … Ideally, uses new fibers optimized for coherent QPSK / QAM G.652D G.654

© 2013 ADVA Optical Networking. All rights reserved. Confidential. 17 Cost of 10G/100G Coexistence Method Generalized Cost Potential Advantages 1 Coherent overlay Double cost of photonic layers (incl. fibers). Potential network (fiber) under-utilization. Example: at beginning of life (low channel count), almost doubles cost. At EOL, adds <10% cost. Considered the only save solution for 400+ Gb/s (super-) channels 2 IM/DD with inbuilt EDC No general 10-Gb/s alien-wavelength support. 10-Gb/s EDC can increase peak-to-average ratio and thus increase IM/DD aggressor characteristic. Can avoid compensated photonic layer 3 Use of FBGs instead of DCFs Adds accumulated phase ripple to IM/DD channels and hence limits their maximum reach: penalty for 10G <1 dB Eliminates XPM from DCF. Reduces X-NLPN (maintains walk- off). 4 Guard bands between 10G and 100G channels Decrease of system and network capacity and added complexity in wavelength planning. Example: 96-Ch system, 4 channels spared as guard band, then 4% capacity are blocked. Can achieve optimum performance for IM/DD and QPSK. Combine with Method 3. Combine with CPE adaptation. 5 Selective CD compensation and channel separation in ROADMs Requires additional ROADM ports and decreases node degree, or increases node blocking. Example: separating IM/DD and QPSK per node reduces maximum degree of standard ROADM technology from Degree-8 to Degree-4. Can achieve optimum performance for IM/DD and QPSK. Combine with Method 4. Combine with CPE adaptation. 6 Power-level reduction for IM/DD Can be complex (software / Control Plane). Reduces IM/DD performance. Still requires CD compensation for IM/DD unless combined with Method 2. Can lead to negligible X-NLPN- induced penalty for QPSK.

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