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Submarine Networks –Today and TomorrowGeoff Bennett
Director, Solutions and Technology
Geoff BennettDirector, Solutions & TechnologyNottingham, United Kingdom
Today’s Rules
Have a Question? Ask all questions in the Questions Tab
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Poll Question
5© 2020 Infinera. All rights reserved. Company Confidential.
Poll Question
From Telegraph to Telephone to Data
7© 2020 Infinera. All rights reserved. Company Confidential.
Telegraph → Telephone
0
500
1000
1500
2000
2500
3000
3500
4000
4500
TAT-1 TAT-2 TAT-3 TAT-4 TAT-5 TAT-6 TAT-7
36 48 138 138
845
4k 4k
Transatlantic Cable Capacity (circuits)
1956 1959 1963 1965 1970 1976 1978
Telstar 1July 10th 1962
LEO
Intelsat 1April 6th 1965
GEO
Before 1956 calls were made over radio telephony
8© 2020 Infinera. All rights reserved. Company Confidential.
Copper vs Fiber Capacity Levels
0
5000
10000
15000
20000
25000
30000
35000
40000
45000
TAT-1 TAT-2 TAT-3 TAT-4 TAT-5 TAT-6 TAT-7 TAT-8
36 48 138 138 845 4k 4k
40kCopper
Fiber
Transatlantic Cable Capacity (circuits)
1956 1959 1963 1965 1970 1976 1978 1988
9© 2020 Infinera. All rights reserved. Company Confidential.
Transatlantic Fiber Optic Cable Evolution
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
10© 2020 Infinera. All rights reserved. Company Confidential.
Today there are a lot of submarine cables!
Europe
Mediterranean
Asia
They carry >95% of
international bandwidth
telegeography.com
11© 2020 Infinera. All rights reserved. Company Confidential.
How much traffic is carried by Submarine Cables?
Growth is forecast at 39% CAGR from 2019-2026
ICPs dominate globally
Worldwide Growth
Source: Telegeography 2020
Historically transatlantic and trans-pacific, but spreading to all routes
About 1.5 x 1015 bits per second(1.5 petabits per second)
12© 2020 Infinera. All rights reserved. Company Confidential.
Are we in another bubble?
Not even close…
Dotcom Bubble
Post Bubble
Coherent
Coherent
SLTE Upgrades ICP SurgeCap
Ex($
B)
The anatomy of a submarine cable
14© 2020 Infinera. All rights reserved. Company Confidential.
Laying the cable
Cable laying ship
PloughCable
Submarine cable
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Amplifiers in Submarine Cables
+10kV -10kV
50-80km
25 year design life
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Danger to Submarine Cables
Sharks!
• Sharks did used to attack galvanictelegraph cables
• 1988 onwards – metal tape screening introduced
• No more problems with sharks!
On average there are over 100 cable outages per year – but you rarely hear about them
17© 2020 Infinera. All rights reserved. Company Confidential.
Circa 2009Before 2010
Open Cables: Key Trend in Submarine Cables
Cable vendor gets 100% transponder revenue
Closed Cables
Closed cable contracts expire
SLTE
UpgradesCoherent!
2014→
New cables are designed to be “Open”
Vendor A
Wet Plant +Vendor A
Vendor B...
Vendor Z
Transp
on
ders
Accelerated Innovation
Spectrum Sharing
• One network operator for the cable
– Possibly different operators per fiber pair
– Possibly different operators on a single fiber pair
• Challenges
– How to “accept” the new cable is RFS?
– How to manage spectrum for multiple tenants
18© 2020 Infinera. All rights reserved. Company Confidential.
Open Cable Network Architecture
BackhaulTo the Wet Plant
Power Management Controller
ASE and/or Idlers
Vendor A Transponder(s)
Vendor B Transponder(s)
Infinera Transponder(s)
ROADM
Cable Landing Station
PoP orData Center
“Glass through”
Some or all transponders will be located in PoP/DC
Wet plant monitoring
Submarine CableCapacity Evolution
Poll Question
22© 2020 Infinera. All rights reserved. Company Confidential.
Submarine Cable Types
+ve -ve +ve -ve +ve
Dispersion Managed Cable (→2010)
Deployed up to 2010
1
Examples: Hundreds of cable systems worldwide
Uncompensated (2014→)
Deployed 2014-2019
2
Positive Dispersion
Examples: SeaBRAS-1, MONET, BRUSA, MAREA, AAE-1 etc.
Festoon/Unrepeatered3
No Amp Chain
Examples: Dozens of cable systems worldwide
Space Division Multiplexing (2020→)
RFS 2020 onwards
4
Examples: Dunant – others in planning
Ultra Long Haul
Relatively Short Distance
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Dispersion Managed Cables
+ve -ve +ve -ve +ve
Dispersion Managed Cable (→2010)
Deployed up to 2010
1
Examples: Hundreds of cable systems worldwide
These cables were designed and deployed before coherent
technology was available
Chromatic dispersion has to be managed by alternating positive
and negative dispersion fibers along the cable
24© 2020 Infinera. All rights reserved. Company Confidential.
Capacity Evolution over Dispersion Managed Cables
• 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)
0
10
20
30
40
50
60
2005 2010 2012 2016 2020
3.2Tb/s
10GIM-DD 12.8Tb/s
40GCoherent
32Tb/s
100GCoherent 40Tb/s
200GCoherent 48Tb/s
LC-PCSCoherent
Tota
l Cab
le C
apac
ity
(Tb
/s)
25© 2020 Infinera. All rights reserved. Company Confidential.
MAREA: A Coherent-Optimized Submarine Cable
The Field Trial ResultsThe Cable System
MAREA Cable System
Virginia Beach, USA to Bilbao, Spain
6,644km
Large Area, +ve dispersion cable
Production Gear – Hero Capacity6,644 km One-Way Results (16QAM)6.21 bit/s/Hz Spectral Efficiency26.2 terabit/s capacity
13,210 km Loopback Results (8QAM)4.46 bit/s/Hz Spectral Efficiency18.6 terabit/s capacity
Commercial Margin Capacity
24.2 Tb/s
6,644 km
Virginia Beach
Bilbao
Where Next for Increasing Cable Capacity?
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Submarine Amplifiers and Capacity
←C-Band EDFA→
←C-Band EDFA→
←C-Band EDFA→
←C-Band EDFA→
Amplifier Location
• Submarine cables need amplifiers
• Amplifiers must be powered
Amplifier power is inserted at cable end points
+10-15 kV -10-15 kV
Amplifiers are only about 1.2% efficient
Copper conductor has resistance of about 0.75 Ω/km
Transponder performance depends on high OSNR – so high amp power levels
Let’s look at some key facts
28© 2020 Infinera. All rights reserved. Company Confidential.
Technology Option: Light C+L Bands
←C-Band EDFA→←C-Band EDFA→
←C-Band EDFA→
←C-Band EDFA→
XTb/s capacity at the cost of 4 fiber pairs
Amplifier Location
←C-Band EDFA→
←C-Band EDFA→←L-Band EDFA→
←L-Band EDFA→ XTb/s capacity at the cost of 2 fiber pairs
Amplifier Location
C+L doubles fiber pair capacity, but has
no effect on total cable capacity
Limited by ability to power the amp chain
C Band only
C+L Band
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What is SDM? → How do we maximize capacity?
←C-Band EDFA→
←C-Band EDFA→
←C-Band EDFA→
←C-Band EDFA→
Amplifier Location
Cable design goalsMaximize capacity
per fiber pairMaximize capacity
per cable
• Shorter amp spacing
• Higher amp power
• Higher order modulation
• Fewer fiber pairs
• Examples:
• MAREA, BRUSA, etc.
• Longer amp spacing
• Lower amp power
• Pump sharing
• LC-PCS
• More fiber pairs
• Example: Dunant
All of these work to limit the number of fiber pairs in the cable
30© 2020 Infinera. All rights reserved. Company Confidential.
SDM Comparison: MAREA vs Dunant
• 6,600 km cable
• 8 fiber pairs
• 24 Tb/s per fiber pair*
• Total capacity 192 Tb/s
• 6,600 km cable
• 12 fiber pairs
• 25 Tb/s per fiber pair**
• Total capacity 300 Tb/s*In service **Planned
MAREA Dunant
SDM RoadmapFuture transatlantic cable
40 fiber pairs @ 25Tb/sPetabit scale cable
State of the art UNCOMPENSATED cable
State of the art SDM cable
Challenges for Submarine Transponder Design
Poll Question
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Cable and Transponder Life Cycles
Submarine cable design lifetime
25 Years
Coherent optical engine technology cycle
4 Years
The cable you lay this year may not be the “ideal cable” for future transponders
Regardless of cable type, each generation of transponder delivers more capacityBUT…
35© 2020 Infinera. All rights reserved. Company Confidential.
The only real solution…
You need a comprehensive toolkit
36© 2020 Infinera. All rights reserved. Company Confidential.
ICE6: 5th Generation Coherent Optical Engine
PIC7nm DSP Analog ASIC
• Compact DCO
• 1.6Tb/s Optical Engine
• 2λ x up to 800Gb/s
XTCDRX
Groove (GX)
CHM6
Ultra High Baud Rate
(32-96 Gbaud)
20% 33%
High Gain SD-FECSubsea Modulations
(ME-8QAM, etc)
LC-PCS
192
.1
192
.2
192
.3
192
.4
Gain Sharing
SD-FEC Gain SharingShared Wavelocker Lightning Tolerance
1529 1567 1569 1610
C L
C+L Band
Nyquist Subcarriers DBA Super-Gaussian Encryption
37© 2020 Infinera. All rights reserved. Company Confidential.
TERMINOLOGY: Nyquist Subcarriers: What and Why?
La
se
r 1
La
se
r 2
Carrier 1 Carrier 2
La
se
r 1
La
se
r 2
Carrier 1 Carrier 2
Subcarriers Subcarriers
La
se
r 1
La
se
r 2
Carrier 1 Carrier 2
1st Gen: No shaping 2nd Gen: Nyquist shaping
• Higher spectral efficiency
• Driven by FlexGrid
ICE4: Nyquist subcarriers
• Higher spectral efficiency
• Enhanced clock recovery
• Linear tolerance
• Non-linear tolerance
ICE6: Nyquist subcarriers
• Add subcarriers
• High Baud rate carrier
• Low Baud rate subcarriers
Carrier 1 Carrier 2
La
se
r 1
La
se
r 2
Subcarriers Subcarriers
38© 2020 Infinera. All rights reserved. Company Confidential.
Two options for increasing capacity*
*For both per-wavelength and total fiber capacity
4 Bits/symbol2 Bits/symbol
QPSK 16QAM
Increase the modulation order
(ie. bits per symbol)
TimeTime
Symbols per Second
Increase the Baud rate
(ie. symbols per second)
39© 2020 Infinera. All rights reserved. Company Confidential.
Baud Rate Dependencies: Chromatic Dispersion
Baud Rate
Ch
rom
atic
Dis
per
sio
nChromatic Dispersion is a function of Square of the Baud Rate
(2xBaud Rate = 4xCD)
CD can be a big problem for trans-oceanic (14,000km+)
Coherent Transceiver
CD Compensation NOISE
Compensating CD creates noise inside
the transceiver (lower modem SNR)
Uncompensated cables rely on high CD to mitigate nonlinear effects
40© 2020 Infinera. All rights reserved. Company Confidential.
Dis
tort
ion
Pen
alty
Baud Rate (Gbaud)
4 8 16 33 66
FWM SPM
Single carrier32 Gbaud → 66 Gbaud
Most DWDM vendors
Nyquist Sub-carrierOptimized PerformanceWhile maintaining economic
advantage of higher Baud rate
200Gb/s @ 16QAM4 x 8 GBaud
A
800Gb/s @ 64QAM8 x 12 GBaud
B
Baud Rate Dependency: Nonlinear Effects
41© 2020 Infinera. All rights reserved. Company Confidential.
Higher Order Modulation
PM-QPSK PM-8QAM PM-16QAM PM-32QAM PM-64QAM
Spectral EfficiencyX1 X3
X1X30 Optical Reach
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Why do we lose so much reach at higher orders?
PM-64QAM
PM-QPSK
PM-QPSK PM-64QAM
Let’s draw the symbols that a receiver would see
Maybe we could increase the distance between constellation points…
The closest other symbols for QPSK are a
long way away
The closest other symbols for 64QAM are really close!
But the further from the constellation origin, the higher
the power of the symbol –which triggers non-linear effects
43© 2020 Infinera. All rights reserved. Company Confidential.
Fib
er C
apac
ity
Optical Reach
The challenge with “hard” modulations
Shannon Limit
Imagine if we could “smooth out” the sawtooth
BPSK
8QAM
16QAM
32QAM
64QAM
QPSKImagine if we could “move the curve” closer to the Shannon Limit
1
2
These are two aspects of Probabilistic Constellation Shaping
44© 2020 Infinera. All rights reserved. Company Confidential.
Probabilistic Constellation Shaping (PCS)
Start with a 64QAM
constellation
We know the outer symbols are a
problemMore bits per symbol,
shorter reach
Fewer bits per symbol, longer reach
DM
So we use a clever Distribution Matcher to
manipulate the probabilities of using certain symbols
45© 2020 Infinera. All rights reserved. Company Confidential.
Remember the “sawtooth” curve?Fi
ber
Cap
acit
y
Optical Reach
Shannon Limit
By adjusting the probability distribution we can smooth out the sawtooth edges
More bits per symbol, shorter reach
Fewer bits per symbol, longer reach
1
The capacity-reach performance is moved closer to the Shannon Limit
2
46© 2020 Infinera. All rights reserved. Company Confidential.
100 100 100 100 100 100 100 10085 90 110 115 115 110 90 85DBA →
ICE6 : 800Gb/s waves, 8x12GBd subcarriers
Goal: Team to carry 800 lbsas far as they can in 1 hour
Option 1: 100 lbs per person
Weaker members slow the team down
Option 2: The strongest members carry a little more than the weaker members
Result: The whole team goes further
PCS and Subcarriers: Dynamic Bandwidth Allocation
100 100 100 100 100 100 100 100
Impairments
DBA Enables:Higher data rate over a given distance
Go further at a given data rate
100 100 100 100 100 100 100 100100 100 100 100 100 100 100 10085 90 110 115 115 110 90 85
47© 2020 Infinera. All rights reserved. Company Confidential.
But there is a theoretical limit
C = B log2( )1 +S
N
Current options revolve around the two different parts of the Shannon Equation
The “bandwidth term” The “log term”
This is why SDM is so interesting for the near future
Bandwidth term
Log term
Cap
acit
y
Capability
The Future of Submarine Networks
49© 2020 Infinera. All rights reserved. Company Confidential.
A Situation Report
Submarine network demand continues to grow
C = B log2( )1 +S
N
PCS brings us close to the Shannon Limit
1: Maximize ROI from existing cables 2: More to extract from new cables
What do we know? What does that mean?
←C-Band EDFA→
←C-Band EDFA→←L-Band EDFA→
←L-Band EDFA→
Amplifier Location
3: C+L delivers more capacity per fiber pair, not per cable
←C-Band EDFA→
←C-Band EDFA→
←C-Band EDFA→
←C-Band EDFA→
Amplifier Location
4: SDM points the way to a Petabit transatlantic cable
50© 2020 Infinera. All rights reserved. Company Confidential.
What does a future transponder look like?
Imagine a future Petabit transatlantic cable
40 fiber pairs
25 Tb/s per FP
400 Gb/s per
2,500
Somehow you must deal with…
…transponders*
*At each end
51© 2020 Infinera. All rights reserved. Company Confidential.
What can we do to help?
C = B log2( )1 +S
N
There may be a Shannon Limit on fiber capacity…
…but not on power or volume
Imagine a 400G QSFP28 module that can span the Atlantic
52© 2020 Infinera. All rights reserved. Company Confidential.
Large Scale Photonic Integration
Implement many wavelengths on a single chip and mux them
...
Instead of one wavelength per transponder and then muxing them…
...
Tran
spo
nd
ers
Mux or ROADM
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