Meeting The Challenge of Cloud Scale Connectivity Abhijit Chitambar Ph.D. Principal Product Manager Infinera
Coherent Optical Transport Market Trends Transition to >100G Wavelengths is Underway CSPs Still Dominant, ICPs Grow Fastest Private Backbones Take Over 350 300 250 200 Tb/s 150 Trans-Atlantic Bandwidth Private: 70% CAGR Internet: 21% CAGR 100 50 0 2012 2013 2014 2015 2016 2017 2018 2019 2020 Sources: Telegeography, Dell Oro, Cignal AI Overall subsea capacity growth ~40-50%/year
Multiple Dimensions for Cloud Scale Transport Maximizing reach for a given baud and modulation Reach Three Axes of Scalability Baud Power Power GHz/nm 66Gbaud, 75GHz GHz/nm 150G 300G 33Gbaud, 37.5GHz C Band L Band Modulation Maximizing benefits of parallelism Increasing reliability & availability 8QAM 16QAM QPSK Reliability/Availability Parallelism/ Integration
Innovation in Multiple Dimensions: Baud Rate & Modulation Schemes 100GBaud/32QAM, 1Tb/Wave Capable Constellation Shaped 1024QAM (Source: Infinera ECOC 2017) (Source: Infinera ECOC 2017) Single wavelength 66GBd/1024QAM transceiver Highest coded bit rate of 1.32Tb/s ever reported in optical communications domain CS applied to maximize the link capacity at any given reach Achieved net bit rate of 680Gbs/s after 400km transmission over SMF: largest transmission distance ever for 66GBd 1024QAM Experimental CS-1024QAM Constellation ECOC 2017 Paper
Digitally Synthesized Nyquist Sub-carriers Super-channel carriers are split into Nyquist subcarriers Lower baud rate of subcarriers increases tolerance to nonlinearities such as XPM Increased tolerance to nonlinearities results in increased reach Super-channel carriers 37.5 GHz 35 GHz 35 GHz 35/n GHz subcarriers Super-channel with subcarriers Non Linear Tolerance NLT Increased Overall Fiber Capacity & Reach Q Value X Y B Available Today! Subcarriers Baud Rate A With Subcarriers Single Carrier Launch Power Single Carrier
SD-FEC Gain Sharing Available Today! Q Factor Strong Channel Commissioning Limit [CL] Q Factor Strong Channel Both channels now exceed CL CL Weak Channel Launch Power Could need lower SE modulation format Weak Channel Launch Power Mitigates nonlinearities Enables use of higher order modulation format Increased Overall Fiber Capacity & Reach
Tighter Channel Spacing Available Today! Roll-off Factor Conventional: 10-20% Requires larger guard band between channels subcarriers: 2-6% roll-off factor (Source: Infinera ICE4) 10-20% roll-off Wave locking Lasers with independent wave lockers have independent frequency shifts with time Must increase guard band to prevent collisions Monolithic PICs with shared wave lockers have correlated shift Minimal guard band required to prevent collisions within super-channel Independent frequency shifts Result Required guard band can be substantially smaller 20-30% higher spectral efficiency at same baud rate & modulation Correlated frequency shifts
Reliability: Eliminating Lightning Impacts on Aerial Fibers Available Today! The Challenge Optical Ground Wire (OPGW) + Widely available on power transmission lines + Cost-effective vs. buried cables Susceptible to lightning-induced outages due to fast State-of-Polarization (SOP) transients Sensitivity rises at higher modulations (8QAM+) Solution (Source: Infinera ICE4) >7.0 Mrad/s tolerance, exceeds allobserved events (~100% protection) Aided by Nyquist subcarriers Infinera ICE4 Typical commercial products Data from a North American span 1 ~500 km of aerial fiber >7 events per day during April-September Maximum observed angular velocity = 5.1 Mrad/s 1. Charlton, et. al. Optics Express25(9), 9689 (2017).
Proof Points and Key-Takeaways 22Gbaud/8QAM, 23.2 GHz ch. spacing 18.2T Capacity SE >4.5 b/s/hz Modulation Reach Baud >7.0 Mrad/s tolerance exceeds all observed events (~100% protection) Aided by Nyquist subcarriers 23 super-channels/138 carriers/ 552 sub-carriers 27.6T over 1000Kms Parallelism/ Integration Cloud scale connectivity driven by Innovations across multiple dimensions Proof points with commercially available products: Nyquist sub-carriers, SD-FEC Gain Sharing, Tight channel spacing, SOP tracking for lightening protection New technologies with higher Baud Rates and Constellation Shaping delivering increased capacity-reach
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