2014 11 13-raman-amplification-for-wdm-transmission-acp-2014-a_th4_e-6-invited-paper-presentation-xtera

© 2014 Xtera Communications, Inc. Proprietary & Confidential 1
Raman Amplification for Ultra-Large
Bandwidth and Ultra-High Bit Rate
Submarine and Terrestrial Long-Haul
WDM
Herve Fevrier - Chief Strategy Officer – Xtera Communications
ACP 2014 (Shanghai, China)
11-14 November 2014

Content
• Background
• Responding to Bandwidth Needs
• 150 x 100G Field Trial
• 400G Field Trial
• Recent Unrepeatered 100G Transmission Results
• Raman Repeater: Innovation Going Under Water
• Exploiting Spectral Dimension for Higher Network Capacities

• Sir Venkata Raman earned the Nobel prize in Physics in 1930
– Prize motivation: “For his work on the scattering of light and for
the discovery of the effect named after him”
• Raman effect
– Inelastic scattering
• Applications
– Raman spectroscopy
– Raman amplification
• Laser sources and amplifiers
• Optical communications
– 1962: SRS observation
– 1973: Raman in optical fibers
• Xtera Communications Inc. (1998)
– Mohammed Islam (founder – worked on soliton transmission with L. Mollenauer)
– “Ideas in a different light”  Raman for:
• Different spectral windows
• A broader spectrum
• And obviously reach
Raman History

• Founded in 1998
• Opening new windows:
The S-band (2000-2001)
• Broadening the spectrum:
100 nm window
(2002-2005)
– 1st commercial
deployment 2004:
2.4 Tbit/s
Xtera Communications: The first steps

Technical Responses to
Insatiable Bandwidth Demand

The Bandwidth Demand is Insatiable
0.001
0.01
0.1
1
10
100
1,000
10,000
100,000
1,000,000
1985 1990 1995 2000 2005 2010 2015 2020
Year
Datatraffic(petabyte/month)
Minnesota Internet Traffic Studies
(MINTS) for US IP traffic
High
Low
Swanson-Gilder for US IP traffic
Cisco Visual Networking Index
Forecast and Methodology
2007-2012 and 2012–2017
For global IP traffic
 Doubling about every 18 months (≈2 dB per year)

With 100G Being The Dominant Line Rate
Global 10G, 40G, 100G & 100+G DWDM line card revenue
(After Ovum)
0,00
1,75
3,50
5,25
7,00
8,75
Year
2019
10G revenues
40G revenues
100G revenues
100G+ revenues
2011 2012 2013 2014 2015 2016 2017 2018
DWDMlinecardrevenues($B)

It’s All About…

The Internet Growth
2B 11/10/2010
1B 10/05/2005
After Internet Society Annual Report
2012 Internet Penetration
Global IP traffic will grow from 43 PB/month
in 2012 to 120PB/month in 2017 (23%
CAGR)
After Cisco VNI (2013)

• Undersea is approx. 35% of
total used international
bandwidth.
• It is dominated by Internet
bandwidth.
• The traffic matrix is becoming
more balanced.
Undersea Communications Forecast
0,0%
20,0%
40,0%
60,0%
80,0%
100,0%
0
100 000
200 000
300 000
400 000
2011 2013 2015 2017 2019
Totalusedsubmarinecapacity(Gbps)
Used for Internet (%)
Used for private networks (%)
Used for switched voice (%)
Total Used Submarine Capacity (Gbps)
31,3%
32,5%
33,8%
35,0%
36,3%
37,5%
0
250 000
500 000
750 000
1 000 000
2011201220132014201520162017201820192020
Submarinebandwidth
percentage
Totalusedinternational
bandwidth(Gbps)
0%
10%
20%
30%
40%
2011 2012 2013 2014 2015 2016 2017 2018 2019 2020
Trans-Atlantic
Trans-Pacific
US-Latin America
Intra-Asia
Europe-ME & Egypt

Total Used International Bandwidth (Gbit/s)
in China
0
17 500
35 000
52 500
70 000
2011 2012 2013 2014 2015 2016 2017 2018 2019 2020

Data Center Interconnect Traffic is Booming!!
Source: Ovum

Response from the
Optical Communications Industry
Enabled by
• Faster opto-electronics
• Wavelength multiplexing in C band
• Polarization multiplexing
• Multi-level modulation formats
0.1
10
100
1000
20161988 1992 1996 2000 2004
565 Mbit/s
2.5G
10G
40G
1994 1998 20021986 1990
8 x 2.5G
16 x 2.5G
40 x 2.5G
80 x 2.5G16 x 10G
10 Gbit/s
100 Gbit/s
40 x 10G 160 x 2.5G
10,000
1
100,000
2006 2008 2010 2012 2014
Year
17.6 Tbit/s
8.8 Tbit/s
Single-wavelength
system
800 Gbit/s 80 x 10G
80 x 40G
88 x 100G
44 x 400G
FiberCapacity(Gbit/s)

Five multiplexing dimensions available:
• Time
– Faster opto-electronics (enabling 10G, 40G, 100G…)
– Current practical limit: about 30 Gbaud devices
• Frequency
– Multiplexing more optical carriers at different frequencies
– Conventional EDFA-based WDM technology limited to C
band (≈ 38 nm)
• Polarization
– Propagation of several states of optical polarization, each
supporting a data stream
– Practical today’s implementation: two polarizations
• Quadrature
– Multi-level modulation format
– BPSK, QPSK, 8QAM, 16QAM, 64QAM… leading to reach
reduction
• Space
– More transmission media are made available in parallel
– Different flavors of Spatial Division Multiplexing (SDM):
ribbon fiber, multi-core fiber, multi-mode fiber
How to Keep up With Bandwidth Demand?
✔
✔
✔ 1100
Q
1101
I
16-QAM
1110
1111
0101
0111
1000
I
Q
1101
QPSK
0
I
Q
1
BPSK

Five multiplexing dimensions available:
• Time
– Faster opto-electronics (enabling 10G, 40G, 100G…)
– Current practical limit: about 30 Gbaud devices
• Frequency
– Multiplexing more optical carriers at different frequencies
– Conventional EDFA-based WDM technology limited to C
band (≈ 38 nm)
• Polarization
– Propagation of several states of optical polarization, each
supporting a data stream
– Practical today’s implementation: two polarizations
• Quadrature
– Multi-level modulation format
– BPSK, QPSK, 8QAM, 16QAM, 64QAM… leading to reach
reduction
• Space
– More transmission media are made available in parallel
– Different flavors of Spatial Division Multiplexing (SDM):
ribbon fiber, multi-core fiber, multi-mode fiber
Two Remaining Dimensions
Evolution or Revolution?
✔
✔
✔

Evolution With Optical Spectrum Expansion As
Enabled With Raman Optical Amplification
All-Raman provides x 3 in terms of spectrum
All-Raman provides x 2 in terms of reach
All-Raman provides x 6 in terms of Capacity x Reach
Maximizing spectral efficiency
AND spectrum
without compromising reach -30
-25
-20
-15
-10
-5
0
5
1515 1535 1555 1575 1595 1605
Power(dBm)
1625
Wavelength (nm)
100 nm of continuous
optical bandwidth
in the field since 2004

Terrestrial

Field Trial: 150 x 100G
• Deployed more than ten years ago
• Multiple ODFs in the path
• G.652 fiber with multiple splice points as a
result of construction activities in the
metropolitan area
• Length: 79.2 km per span
• 19 fibers/spans equipped (1,504 km total)
• Average span loss: 21.8 dB
• Existing standard connectors (SC/PC)
• Average fiber attenuation: 0.275 dB/km
• Shows three lumped loss of 1.2 ~ 1.9 dB
Bi-directional OTDR example of Verizon span
Challenging environment
G.652 field fiber
79.2 km per span
IL: 20 - 23 dB

150 x 100G System Configuration
Wide-band
booster
Aged network fiber
79.2-km span
Loss: 20 - 23 dB
x19
Backward
Raman
pump
module
Forward
Raman
pump
module
Gain
Flattening
Filter
(GFF)
Optional modules
Span # 01
20.3dB
Span # 02
22.5dB
Span # 03
22.8dB
Span # 04
22.2dB
Span # 05
21.5dB
Span # 06
20.4dB
Span # 07
22.6dB
Span # 08
20.1dB
Span # 09
21.4dB
Span # 11
22.9dB
Span # 12
20.5dB
Span # 13
21.3dB
Span # 14
22.1dB
Span # 15
21.8dB
Span # 16
23.1dB
Span # 10
21.6dB
Span # 17
22.2dB
Span # 18
22.4dB
Span # 19
22.1dB
19 x 7 x
Backward
Raman pump
module
GFF Type I 5 x GFF Type II 5 x
Forward
Raman pump
module
Total distance: 1,504 km (19 spans)
45 C-Band
(odd) DFBs
30 L-Band
(odd) DFBs
45 C-Band
(even) DFBs
30 L-Band
(even) DFBs
100G
Comb
100G
Comb
L-100G MXP
C-100G MXP
C-100G MXP
C-100G MXP
90/10
100-GHz
PM-AWG

• Input channels are pre-emphasized to provide flat Q over spectrum at
receive side.
• Ripple is controlled by multiple backward Raman pumps and passive link
Gain Flattening Filters (GFFs).
• Ripple is < 5 dB after 19 spans.
150 x 100G Transmission: Measured OSA Spectra
-30
-25
-20
-15
-10
-5
0
5
1525 1535 1545 1555 1565 1575 1585 1595
Power(dBm)
Wavelength (nm)
Booster output spectrum
0.1nm RBW
-30
-25
-20
-15
-10
-5
0
5
1525 1535 1545 1555 1565 1575 1585 1595
Power(dBm)
Wavelength (nm)
After 19 spans – 1,504 km
0.1nm RBW

• After 19 spans, margin (from SD-FEC threshold) is ~5 dB Q.
• 3 x distance can be bridged (4,500km) before regeneration.
150 x 100G Transmission: Q Over Distance
Q over Distance
0 200 400 600 800 1000 1200
Distance (km)
1400 1600
6
8
10
12
14
16
18
QfactorbeforeSD-FEC(dB)
1590.83 nm
1564.27 nm
1562.64 nm
1532.68 nm
Q factor threshold

• 15 Tbit/s (150 x 100G) field trial over 1,504 km with all-distributed
Raman amplification
– Over the Verizon legacy network fiber (average attenuation of 0.275 dB/km)
– Average Q = 11.4 dB (5 dB margin from the SD-FEC threshold)
– Excellent agreement between modeling and field measurements
– Very stable operation over 100 hours
– No active gain flattening devices as required in EDFA-based systems
• Transmission of 4 x 100G at 33.3 GHz spacing along with 50 GHz spaced
channels
– 22.5 Tbit/s capacity (50% capacity increase)
– Measured Q = 10.2 dB
• Room for improvement:
– Booster output OSNR as low as 30 dB due to setup constraints
– Non-optimized Nyquist filtering
– System operating in the “linear regime”: further improvement expected from
stronger booster and distributed Raman pump power
100G Field Trials Summary

PM-16QAM Receiver
LOIX
QX
IY
QY
Aged network fiber
79.2 km
IL: 20 - 23 dB
45 C-Band
(odd) DFBs
30 L-Band
(odd) DFBs
45 C-Band
(even) DFBs
30 L-Band
(even) DFBs
100G
Comb
100G
Comb
8 ECL (odd)
8 ECL (even)
64 GS/s DAC
64 GS/s DAC
Nyquist shaped
16QAM signals
Optical Modulator
Optical Modulator
C-100G MXP
L-100G MXP
C-100G MXP
L-100G MXP
Tunable
filter
ECL
x19
Off-Line DSP for CD, PMD, and Signal Recovery
Digital
Storage
Oscilloscope
BPD
BPD
BPD
BPD
Pol-Diverse
90 Degree
Optical
Hybrid
Commercial All-Distributed Raman Wide-Band ULH System (61 nm)
PM-16QAM Transmitters
100-GHz
PM-AWG
90/10
Wide-band
Booster
C-100G MXP
Optional modules
(12x GFFs and
5x forward Raman
pumps in total)
backward
Raman
pumps
WSS
Pol.
Mux
(a)
(b)
PM-16QAM 400G Tx PM-16QAM 400G Rx
All-Raman System
Setup for 400G Field Trial

Spectra of PM-16QAM 400G Channels
#2#1 #3 #4 #5 #6 #7 #8
At transmitter
• Eight 400G channels at 100 GHz
• Dual-carrier PM-16QAM
• 100 GHz between 400G channel
• 50 GHz between 200G subcarriers
At receiver (1,504 km)
• OSNR: 19.5 dB / 0.1 nm
-65
-60
-55
-50
-45
-40
1543 1545 1547 1549 1551 1553 1555 1557 1559
Power(dBm)
Wavelength (nm)
0.01nm RBW8 x 400G channels – 100GHz spacing
(16 x 200G subcarriers – 50GHz spacing)
100G channels
50GHz spacing

• Error-free transmission of eight PM-16QAM 400G channels (spaced
100 GHz apart) over 1,504 km aged SSMF in field
– The line system configuration was the one of the 100G field trial
 No optimization carried out for 400G trial
• Key technical enablers:
– All-distributed Raman amplification
– High-gain FEC coding
• 16QAM signals can be supported by existing carriers’ long-haul fiber
networks by reducing OSNR degradation during signal propagation with
all-distributed Raman amplification and by increasing FEC coding gain.
• In Verizon’s opinion, the trial result may delay carriers’ need to light new
pair of fiber to meet the growing traffic demand for several years.
400G Field Trial Summary

Verizon infrastructure representative of end-of-life numbers
Results for 1,504 km, 61 nm transmission with high margins
• First trial: 100G
– 150 x 100G PM-QPSK (50 GHz) on 1,500 km: 15T / 4,500+ km
• Second trial: 400G (4 x 100G)
– MC 4 x 100G PM-QPSK (33 GHz) on 1,500 km: 20T / 3,000+ km
• Third trial: 400G (2 x 200G)
– DC PM-16QAM (2 x 200G)
• 50 GHz spacing: 30T / 2,000+ km
• 37.5 GHz spacing: 40T /1,500+ km
• With 100-nm spectrum
(as deployed in 2004-2009):
– 24T / 4,500+ km
– 48T / 2,000+ km
– 64T / 1,500+ km
Validation Field Trial – Summary

XWDM [Capacity – Reach] Metric
240 x 100G
• 100 nm spectrum
• PM-QPSK channels
• 50 GHz channel spacing
• 2 bit/s/Hz spectral efficiency
120 x 400G
• 100 nm spectrum
• PM-16QAM 200G carriers
spaced 50 GHz apart
• 4 bit/s/Hz spectral efficiency
160 x 400G
• 100 nm spectrum
• PM-16QAM 200G carriers
spaced 37.5 GHz apart
• 5.3 bit/s/Hz spectral efficiency
 16QAM on more than 2,000 km of aged fiber (0.28 dB/km)

Submarine
Unrepeatered

• Maximizing the reach at 100G
– 1 x 100G on 520 km of ULL fiber, with ROPA
– 4 x 100G on 523 km of Vascade EX2000 fiber, with ROPA
• Maximizing the capacity over long unrepeatered distances
– 150 x 100G on 334 km of ULL fiber, without ROPA
– 150 x 100G on 390 km of ULL fiber, with ROPA
Recent Unrepeatered
100G Transmission Results

390 km, 150 x 100G Unrepeatered Transmission
With ROPA
ROPA
Forward
Raman
pumping
Backward
Raman
pumping
Direction of
transport
273 km
ULL fiber
117 km
ULL fiber
Perchannelpower(dBm)
Gain from
forward
Raman
pumping
Gain from backward
Raman pumping
Fiber attenuation
150 wavelengths
Gain
from
ROPA
0 50 100 150 200 250 350 400
Transmission distance (km)
300
10
0
-10
-20
-30
-40

390 km, 150 x 100G Unrepeatered Transmission
With ROPA
ROPA
Forward
Raman
pumping
Backward
Raman
pumping
Direction of
transport
273 km
ULL fiber
117 km
ULL fiber
-25
-20
-15
-10
-5
0
5
1525 1535 1545 1555 1565 1575 1585 1595
Wavelength (nm)
Power(dBm)
Preamp output spectrum
0.1nm RBW
-25
-20
-15
-10
-5
0
5
1525 1535 1545 1555 1565 1575 1585 1595
Wavelength (nm)
Power(dBm)
Booster output spectrum
0.1nm RBW

Submarine
Repeatered

Optical Repeater for
Subsea Cable Systems Launched at
Innovation:
Electrical Improved powering enabling Raman amplification.
Optical Modular optical design. Spectrum increased by 50%.
Mechanical Marine grade titanium. Compact, light and strong.
Manufacturability Flexible and simplified manufacturing process.
-1
0
1
2
3
4
5
1540 1550 1560 1570 1580 1590 1600 1610
Wavelength (nm)
Effectivenoisefigure(dB)
-4
-3
-2
-1
0
1
2
3
1540 1550 1560 1570 1580 1590 1600 1610
Wavelength (nm)
Relativegain(dB)

Optical Benefits from Raman in Repeaters
• Better noise performance
• Lower nonlinearities
• Broader spectrum
• Optical synthetizer
• Active gain tilt controller
 Longer repeater spacing
 Longer reach
 Wider spectrum for higher capacity

Status of Xtera Repeatered Projects
• 4 projects:
– 1 short
– 2 regional
– 1 long haul
• Deployments:
– 1 in 2014
– 2 in 2015

Exploiting Spectral Dimension for Higher
Network Capacities

• People have worked incredibly on spectral efficiency since 1989
– 4 x 2.5G in the C-band
– 40 x 10G in the C-band
– …BUT…
– The industry still uses only the C band
Wireline So Far…
Fiberattenuation(dB/km)
1.0
0.8
0.4
0.2
1.2 1.71.61.51.41.3
Optical wavelength (µm)
C band
Old
fibers
Modern
fibers

Fiberattenuation(dB/km)
0.8
0.4
0.2
1.2 1.71.61.51.41.3
Optical wavelength (µm)
Old
fibers
Modern
fibers
The Wireline Spectrum Opportunity
Band Description Wavelength range
O band Original (“1.3 µm window”) 1260 to 1360 nm
E band Extended 1360 to 1460 nm
S band Short wavelengths 1460 to 1530 nm
C band Conventional ("erbium window") 1530 to 1565 nm
L band Long wavelengths 1565 to 1625 nm
U band Ultra-long wavelengths 1625 to 1675 nm
LCSO E U

1. Today: Xtera has the full portfolio for 15 Tbit/s line capacity over ultra-
long distances (150 x 100G in 61 nm spectrum).
2. XWDM scenario (within end 2015):
– Terrestrial: 100 nm / 64 Tbit/s
3. Improved spectral efficiency to reach 1 Tbit/s per nm
4. Opening 50 nm in the S-band
5. Opening 50 nm in the O-band
6. Finally get to 100 nm for repeatered submarine
The result is a unified converged optical network.
– 100 Tbit/s for Long Haul and Ultra Long Haul
– 50 Tbit/s for Regional (up to approx. 1,000 km)
– 50 Tbit/s for Local
Notes: We cannot use the E band for already deployed fiber infrastructure
Xtera Scenario of the Future

The Future is a Highway with 4 Lanes!
1 lane of 50 nm
Regional traffic
1 lane of 50 nm
Local traffic
2 lanes of 50 nm
Long-haul traffic
Expanding line system spectrum for exploiting fiber bandwidth.

The “next revolution” will happen but it may take 10 or 15 years
and in the meantime… an evolution fueled by Raman technology
can cope with 200 Tbit/s per fiber pair.
Conclusion
Sir Chandrasekhara Venkata Raman
(1888 – 1970)
First Asian scientist to receive the
Nobel prize in physics (in 1930)

Maximizing Network Capacity, Reach and Value
Over land, under sea, worldwide

2014 11 13-raman-amplification-for-wdm-transmission-acp-2014-a_th4_e-6-invited-paper-presentation-xtera

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