Submarine Networks – Today and Tomorrow Geoff Bennett

Director, Solutions and Technology Geoff Bennett Director, Solutions & Technology Nottingham, United Kingdom Today’s Rules

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Transatlantic Cable Capacity (circuits) 4500 4k 4k 4000 LEO Telstar 1 July 10th 1962 3500

3000 GEO 2500

2000 Intelsat 1 th 1500 April 6 1965 845 1000

500 36 48 138 138

0 TAT-1 TAT-2 TAT-3 TAT-4 TAT-5 TAT-6 TAT-7 1956 1959 1963 1965 1970 1976 1978

Transatlantic Cable Capacity (circuits) 45000

40000

35000

30000

25000

20000 40k 15000 Copper

10000 Fiber 4k 4k 5000 36 48 138 138 845

0 TAT-1 TAT-2 TAT-3 TAT-4 TAT-5 TAT-6 TAT-7 TAT-8 1956 1959 1963 1965 1970 1976 1978 1988

From TAT-10 onwards cable capacity moves to data rate, not telephone channels…

…because, by 1992, voice was just another type of data Source: Wikipedia

Europe

They carry >95% of Mediterranean international bandwidth

Asia

About 1.5 x 1015 bits per second Worldwide Growth (1.5 petabits per second)

Growth is forecast at 39% ICPs dominate globally CAGR from 2019-2026 Historically transatlantic and trans- Source: Telegeography 2020 pacific, but spreading to all routes

Not even close…

Dotcom Bubble

Coherent ($B) Coherent CapEx Post Bubble SLTE Upgrades ICP Surge

Cable laying ship

Plough Cable

Submarine cable

25 year design life

+10kV -10kV

• Sharks did used to attack galvanic telegraph cables • 1988 onwards – metal tape screening introduced Sharks! • No more problems with sharks!

On average there are over 100 cable outages per year – but you rarely hear about them

Cable vendor gets 100% Closed Closed cable SLTE Coherent! transponder revenue Cables contracts expire Upgrades

2014→ Spectrum Sharing New cables are • One network operator for the cable designed to be “Open” – Possibly different operators per fiber pair

Transponders – Possibly different operators on a single fiber pair Vendor A Vendor A Vendor B • Challenges . . – How to “accept” the new cable is RFS? Wet Plant + . Vendor Z – How to manage spectrum for multiple tenants

Vendor A Vendor B Infinera Cable Landing Station Transponder(s) Transponder(s) Transponder(s)

ASE and/or Idlers Some or all transponders will be located in PoP/DC

Power Management ROADM Controller Wet plant PoP or  monitoring Data Center

Backhaul “Glass through” To the Wet Plant

© 2020 Infinera. All rights reserved. Company Confidential. 18 Submarine Cable Capacity Evolution Poll Question Submarine Cable Types Ultra Long Haul 1 Dispersion Managed Cable (→2010) 2 Uncompensated (2014→)

+ve -ve +ve -ve +ve Positive Dispersion

Deployed up to 2010 Deployed 2014-2019

Examples: Hundreds of cable systems worldwide Examples: SeaBRAS-1, MONET, BRUSA, MAREA, AAE-1 etc.

3 Festoon/Unrepeatered 4 Space Division Multiplexing (2020→)

No Amp Chain

RFS 2020 onwards Examples: Dozens of cable systems worldwide Examples: Dunant – others in planning Relatively Short Distance

1 Dispersion Managed Cable (→2010)

+ve -ve +ve -ve +ve

Deployed up to 2010

Examples: Hundreds of cable systems worldwide

These cables were designed Chromatic dispersion has to be and deployed before coherent managed by alternating positive technology was available and negative dispersion fibers along the cable

• Example: Transatlantic cable – Dispersion Managed – Transponder Evolution – Four fiber pairs – Design capacity: 800 Gb/s per fiber pair (80 waves at 10Gb/s per wave) LC-PCS 60 Coherent 200G

50 Coherent 48Tb/s 100G Coherent 40Tb/s 40 32Tb/s 30 40G Coherent 20 10G IM-DD 12.8Tb/s 10 Total Cable Capacity (Tb/s) Capacity Cable Total 3.2Tb/s

0 2005 2010 2012 2016 2020

The Cable System The Field Trial Results 6,644 km Production Gear – Hero Capacity 6,644 km One-Way Results (16QAM) Bilbao 6.21 bit/s/Hz Spectral Efficiency 26.2 terabit/s capacity Virginia Beach 13,210 km Loopback Results (8QAM) 4.46 bit/s/Hz Spectral Efficiency ▪ MAREA Cable System 18.6 terabit/s capacity ▪ Virginia Beach, USA to Bilbao, Spain Commercial Margin Capacity ▪ 6,644km 24.2 Tb/s ▪ Large Area, +ve dispersion cable

Amplifier Location

←C-Band EDFA→ • Submarine cables need amplifiers ←C-Band EDFA→ • Amplifiers must be powered ←C-Band EDFA→ ←C-Band EDFA→ Let’s look at some key facts

+10-15 kV -10-15 kV

Amplifier power is Amplifiers are only Copper conductor Transponder inserted at cable about 1.2% efficient has resistance of performance end points about 0.75 Ω/km depends on high OSNR – so high amp power levels

Amplifier Location C+L doubles fiber ←C-Band EDFA→ ←C-Band EDFA→ XTb/s capacity at the pair capacity, but has ←C-Band EDFA→ cost of 4 fiber pairs ←C-Band EDFA→ no effect on total cable capacity C Band only

Amplifier Location

←C-Band EDFA→ ←L-Band EDFA→ XTb/s capacity at the Limited by ability to ←C-Band EDFA→ cost of 2 fiber pairs ←L-Band EDFA→ power the amp chain

C+L Band

Amplifier Location

←C-Band EDFA→ All of these work to limit the ←C-Band EDFA→ ←C-Band EDFA→ number of fiber pairs in the cable ←C-Band EDFA→

Maximize capacity Maximize capacity Cable design goals per fiber pair per cable

• Shorter amp spacing • Higher order modulation • Longer amp spacing • LC-PCS • Higher amp power • Fewer fiber pairs • Lower amp power • More fiber pairs • Examples: • Pump sharing • Example: Dunant • MAREA, BRUSA, etc.

MAREA Dunant

State of the art State of the art SDM cable UNCOMPENSATED cable

• 6,600 km cable • 6,600 km cable • 8 fiber pairs • 12 fiber pairs • 24 Tb/s per fiber pair* • 25 Tb/s per fiber pair** • Total capacity 192 Tb/s • Total capacity 300 Tb/s *In service **Planned © 2020 Infinera. All rights reserved. Company Confidential. 30 Challenges for Submarine Transponder Design Poll Question Cable and Transponder Life Cycles

Submarine cable design lifetime Coherent optical engine technology cycle

25 Years 4 Years

The cable you lay this year may not be the “ideal cable” for future transponders

BUT… Regardless of cable type, each generation of transponder delivers more capacity

You need a comprehensive toolkit

7nm DSP Analog ASIC PIC 20% 33%

Ultra High Baud Rate LC-PCS Subsea Modulations High Gain SD-FEC (32-96 Gbaud) (ME-8QAM, etc) • Compact DCO • 1.6Tb/s Optical Engine • 2λ x up to 800Gb/s CHM6 Nyquist Subcarriers DBA Super-Gaussian Encryption

Gain Sharing

Groove (GX) C L

1 2 3 4

. . .

. 1529 1567 1569 1610

192 192 192 192 Shared Wavelocker SD-FEC Gain Sharing Lightning Tolerance C+L Band DRX XTC

Carrier 1 Carrier 2 Carrier 1 Carrier 2 Carrier 1 Carrier 2 Carrier 1 Carrier 2

Subcarriers Subcarriers Subcarriers Subcarriers

Laser 1 Laser 2 Laser

1st Gen: No shaping 2nd Gen: Nyquist shaping ICE4: Nyquist subcarriers ICE6: Nyquist subcarriers • Higher spectral efficiency • Higher spectral efficiency • Add subcarriers • Driven by FlexGrid • Enhanced clock recovery • High Baud rate carrier • Linear tolerance • Low Baud rate subcarriers • Non-linear tolerance © 2020 Infinera. All rights reserved. Company Confidential. 37 Two options for increasing capacity*

*For both per-wavelength and total fiber capacity

QPSK 16QAM

Time Time 2 Bits/symbol 4 Bits/symbol Symbols per Second

Increase the modulation order Increase the Baud rate (ie. bits per symbol) (ie. symbols per second)

Chromatic Dispersion is a function of Square of the Baud Rate Compensating CD creates noise inside (2xBaud Rate = 4xCD) the transceiver (lower modem SNR)

Coherent Transceiver

CD Compensation NOISE

Chromatic Chromatic Dispersion

Baud Rate

Uncompensated cables rely on high CD can be a big problem for CD to mitigate nonlinear effects trans-oceanic (14,000km+)

200Gb/s @ 16QAM 800Gb/s @ 64QAM 4 x 8 GBaud 8 x 12 GBaud

Most DWDM vendors

Single carrier A B 32 Gbaud → 66 Gbaud

FWM SPM

Nyquist Sub-carrier Optimized Performance

Distortion Penalty Distortion While maintaining economic advantage of higher Baud rate

X1 Spectral Efficiency X3

PM-QPSK PM-8QAM PM-16QAM PM-32QAM PM-64QAM

X30 Optical Reach X1

Maybe we could increase PM-QPSK Let’s draw the symbols that a the distance between receiver would see constellation points… PM-QPSK PM-64QAM

PM-64QAM

The closest other The closest other symbols symbols for QPSK are a for 64QAM are really close! long way away But the further from the constellation origin, the higher the power of the symbol – which triggers non-linear effects

64QAM 1 Imagine if we could “smooth out” the sawtooth 32QAM

16QAM Shannon Limit Fiber Capacity Fiber

8QAM Imagine if we could “move the QPSK 2 curve” closer to the Shannon Limit BPSK

Optical Reach These are two aspects of Probabilistic Constellation Shaping

We know the outer symbols are a problem More bits per symbol, shorter reach

DM Fewer bits per symbol, longer reach So we use a clever Start with a Distribution Matcher to 64QAM manipulate the probabilities constellation of using certain symbols

1 By adjusting the probability distribution we can smooth out the sawtooth edges 2 The capacity-reach performance is moved closer to the Shannon Limit More bits per symbol,

shorter reach Fiber Fiber Capacity

Shannon Limit

Fewer bits per symbol, longer reach

Optical Reach

Goal: Team to carry 800 lbs DBA → 10085 10090 110100 100115 100115 100110 10090 10085 as far as they can in 1 hour

Impairments 10085 10090 100110 100115 100115 100110 10090 10085

ICE6 : 800Gb/s waves, 8x12GBd subcarriers DBA Enables: Option 1: 100 lbs per person Higher data rate over a given distance Weaker members slow the team down Option 2: The strongest members carry a little more than the weaker members Go further at a given data rate Result: The whole team goes further

Current options revolve around the two different parts of the Shannon Equation

The “bandwidth term” The “log term” S C = B log 1 + (2 N )

Bandwidth term

This is why SDM is so interesting for the near future Capacity Log term

1: Maximize ROI from existing cables 2: More to extract from new cables

Submarine network demand continues to grow Amplifier Location Amplifier Location ←C-Band EDFA→ ←C-Band EDFA→ ←L-Band EDFA→ ←C-Band EDFA→ ←C-Band EDFA→ ←C-Band EDFA→ ←L-Band EDFA→ ←C-Band EDFA→ S C = B log 1 + 2( N ) 3: C+L delivers more capacity per 4: SDM points the way to a Petabit PCS brings us close to fiber pair, not per cable transatlantic cable the Shannon Limit

Imagine a future Petabit transatlantic cable

Somehow you 40 fiber pairs must deal with… 25 Tb/s per FP 2,500

400 Gb/s per  …transponders*

*At each end

S C = B log 1 + (2 N )

There may be a Shannon …but not on power Limit on fiber capacity… or volume

Imagine a 400G QSFP28 module that can span the Atlantic

Instead of one wavelength per transponder and then muxing them…

  . .

Transponders   Mux or ROADM

Implement many wavelengths on a single chip and mux them

  . . 

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