Next-Generation Ultra-High-Speed DWDM Transport TNC2011, Prague, May 2011 Dr. Klaus Grobe, Dr. Jörg-Peter Elbers, Dr. Michael Eiselt ADVA Optical Networking Advanced Technologies

Outline Coherent 100G Software-Defined Optics Optical-Layer Switching

High-Speed Transmission (long-haul) OOK Re Im DPSK Re Im Re Im DP-QPSK Re Im DC-DP- QPSK or Re Im DP-16QAM Re Im DC-DP- QPSK 10G 40G 100G 400G 1T Intensity Modulation Phase Modulation Phase Modulation Phase Modulation, QAM Single / Dual Carrier QAM O-OFDM Direct Detection Self-coherent Detection Digital coherent Intradyne Detection Single Polarization Dual Polarization Optical Dispersion Compensation ADC, RX-DSP, 28 GBd, 40 nm ADC, RX-DSP, 60 GBd, 28 nm TRX-DSP

112G Coherent Dual-Polarization QPSK PBC PBS Driver Filter PC Digital Filter (FFE) 90° Hybr. QPSK Coder 0° CW LD LO Client I/F (CFP) FEC, Framing, Monitoring ADC 50 GHz DWDM with 2 (bit/s)/Hz spectral efficiency 1500…2000 km reach on uncompensated fiber Digital filter not yet available as standard components (expected end 2011)

Coherent digital DP-QPSK XI XQ YQ YI X0° X90° Y0° Y90° Carrier Recovery 56 GS/s ADC Clock Recovery CMA Equalizer Decider, Decoder |x|2 exp(-j2fst) Cubic Interpolator  arg(∙)/M DMX 1:N Xk X1 XN (∙)M  est Delay X´k exp(-j(∙)) Approx. Resample X Y hxx  b0 b1 bi bN Decider Adaptation Algorithm a(n) – c(n) ε(n) hyx hxy hyy CDC CD/NL Equalizer ADC Nonlinear Mitigation with Backward Propagation Dispersion Compensation FIR Filter Fixed Compensation Digital Coherent Intradyne PolMux-QPSK 4 x 56-GS/s ADC @ 7…8 Bit (1.6…1.8 Tb/s) Digital Filter & Square timing recovery Adaptable FFE for CD compensation Butterfly FFE w/ CMA for PMD compensation NL compensation w/ Backward Propagation Carrier phase estimation Clock Recovery Linear only FFT CMA Equalizer Disp. Compensation FOE IFFT Carrier Phase Est. NL Phase Shift N Spans Complex Decisions Linear and Nonlinear

400G / 1T Transmission: why, how? Why 400G, 1T in transport? Higher data rates to increase fiber capacity Combine low-rate channels to reduce number of managed entities Assumptions used hereinafter 480 Gb/s, 1200 Gb/s, including 15% SD-FEC overhead Nyquist WDM shaping: BWTotal = NSubcarrier · RS Only noise considered (“AWGN channel”) Overall power remains constant (limited by laser safety, non-linearity) Flex-grid channel granularity: 50 GHz

Channel Coding and Modulation 5 6 7 8 9 10 11 12 13 14 1 1.1 1.2 1.3 1.4 1.5 Net Coding Gain [dB] for BER=1e-15 Transmission rate G.709 soft 2 bit hard Shannon Limit for ideal FEC 100G Implementations 8000 km 2000 km 1 2 3 4 5 6 7 8 9 10 15 20 25 Spectral Efficiency [bits/s/Hz] SNR/bit [dB] BPSK QPSK 16QAM 64QAM 256QAM Shannon Limit Gaussian Ch. Fiber Capacity Limit [1] Additional NCG gets smaller with increasing overhead 1 dB gain by soft-decision FEC 2 effective bits are sufficient Single polarization, SSMF, 100-km spans, ideal Raman, no DC, 5-Ch WDM [1] Essiambre, et al., “Capacity Limits of Optical Fiber Networks,” JLT, vol. 28, no. 4, Feb. 2010

Software-Defined Optics The term software-defined optics was introduced to purposely make comparisons to existing software-defined radio (SDR) We interpret software-defined optics as software-based configuration or implementation of operating functions Multi-rate transceivers based on same hardware Differs from software control, i.e., tuning of operating set-points Change of constellation points increases bit rate Denser constellation packing reduces OSNR tolerance

400G Options Format Symbol Rate Bits / # Sub- carriers Req. BW Reach penalty vs. 100G DP-16QAM 60 GBd 8 1 100 GHz 7 dB DP-QPSK 4 2 150 GHz 1.2 dB 30 GBd PS-QPSK 40 GBd 3 200 GHz -1.8 dB DP-8QAM 6 5.2 dB DP-64QAM 12 50 GHz 14.4 dB DP-16QAM DP-QPSK PS-QPSK DP-8QAM DP-64QAM 100G DP-QPSK Capacity x Reach = const.

1T Options Format Symbol Rate Bits / # Sub- carriers Req. BW Reach penalty vs. 100G DP-16QAM 38 GBd 8 4 150 GHz 9.2 dB DP-8QAM 40 GBd 6 5 200 GHz 5.7 dB PS-16QAM 250 GHz 2.5 dB DP-QPSK 60 GBd 300 GHz 2.2 dB DP-16QAM 100G DP-QPSK Capacity x Reach = const. DP-8QAM PS-16QAM DP-QPSK

Channel Coding and Modulation What do we need to get there ? High speed DSPs/DACs/ADCs: power-limited Photonic Integration Photonics are dominating optical transceiver size & cost Options : InP, hybrid, CMOS photonics Technology Gates I/O speed ADC (8 bit) DAC (8 bit) Available 65 nm 50–100M 10 Gb/s 56 GS/s 2.2 W 2010 40 nm 100–150M 28–32 Gb/s 55-65 GS/s 1.2 W 0.5 W 2011 28 nm 150–200M >28-32 Gb/s 110-130 GS/s 1.7 W 0.7 W 2012/13 20 nm 200–250M <100 Gb/s 2014/15 Adapted from Fujitsu Microelectronics

SDO Example: Co-4C-DP-M-QAM DSP / DAC PBS 90° PD ADC DSP / DAC PD ADC DMX … DSP DSP / DAC 90° PD ADC DSP / DAC PBS PD ADC Laser DP-IQ Mod. Laser DP-IQ Mod. … Combiner Coh. RX DSP Laser DP-IQ Mod. Coh. RX DSP Laser DP-IQ Mod. Splitter MUX … Coh. RX DSP MZM  Coh. RX DSP PBS PS MZM rot. MZM  Laser Laser Laser Laser MZM IX QX IY QY

1 Tb/s with Software-Defined Optics e.g., 4C-DP-16QAM, 38 GBd, 200 GHz e.g., 4C-DP-8QAM, 40 GBd, 200 GHz e.g., 4C-DP-QPSK, 30 GBd, 150 GHz SC-DP-QPSK, 30 GBd, 50 GHz 0.25 1T 800G 400G 100G (200G) 0.2 0.15 Percentage of Routes 0.1 0.05 500 600 700 800 900 1000 1100 1200 1300 1400 Link Length [km]

Optical Layer - Switching ROADM - Functional Definitions Colorless Directionless Contentionless Flexgrid Colorless Directionless Contentionless Colorless Directionless Fixed A/D Directionless WSS WSS WSS WSS WSS Line WSS WSS WSS WSS WSS WSS WSS WSS WSS WSS WSS WSS WSS WSS WSS WSS WSS WSS A/D WDM WDM WSS WSS WSS TX TX TX TX TX Local channels fixed in color and direction Any direction Local channels fixed in color Any direction Any color Individual color only per A/D path Any direction Any color Color re-use on same A/D path Any direction Any color Color re-use on same A/D path Flexible channel Bandwidth 1xN WSS 1xN WSS 1xN WSS, Flexgrid WDM WSS WSS

Optical Layer – Switching Example : Flexible Grid mixed channel plan 200GHz 150GHz 75GHz 50GHz

Conclusion Capacity  Reach of Co-DP-QPSK nearly optimum Similar reach for higher bit rates requires optical improvements Raman amplification, better FEC, … New fibers (pure-silica, photonic-crystal, …) Flexible modulation (SDO) allows capacity / reach adaptation Gridless architecture to accommodate >50 GHz super-channels

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