2014 11...

© 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

Da

ta tra

ffic

(p

eta

byte

/ m

on

th)

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

DW

DM

lin

e c

ard

re

ve

nu

es (

$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 2019To

tal

us

ed

su

bm

ari

ne

ca

pa

cit

y (

Gb

ps

)

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

Su

bm

ari

ne b

an

dw

idth

p

erc

en

tag

e

To

tal u

sed

in

tern

ati

on

al

ban

dw

idth

(G

bp

s)

0%

10%

20%

30%

40%

2011 2012 2013 2014 2015 2016 2017 2018 2019 2020

Trans-AtlanticTrans-PacificUS-Latin AmericaIntra-AsiaEurope-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

2016 1988 1992 1996 2000 2004

565 Mbit/s

2.5G

10G

40G

1994 1998 2002 1986 1990

8 x 2.5G

16 x 2.5G

40 x 2.5G

80 x 2.5G 16 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

Fib

er

Ca

pa

city (

Gb

it/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 10 00

I

Q

11 01

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

Po

we

r (d

Bm

)

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

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-5

0

5

1525 1535 1545 1555 1565 1575 1585 1595

Pow

er

(dB

m)

Wavelength (nm)

Booster output spectrum

0.1nm RBW

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-5

0

5

1525 1535 1545 1555 1565 1575 1585 1595

Pow

er

(dB

m)

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

Q facto

r befo

re S

D-F

EC

(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 dB45 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

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-55

-50

-45

-40

1543 1545 1547 1549 1551 1553 1555 1557 1559

Pow

er

(dB

m)

Wavelength (nm)

0.01nm RBW 8 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

Per

channel pow

er

(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

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0

5

1525 1535 1545 1555 1565 1575 1585 1595

Wavelength (nm)

Pow

er

(dB

m)

Preamp output spectrum

0.1nm RBW

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0

5

1525 1535 1545 1555 1565 1575 1585 1595

Wavelength (nm)

Pow

er

(dB

m)

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)

Eff

ective

no

ise fig

ure

(dB

)

-4

-3

-2

-1

0

1

2

3

1540 1550 1560 1570 1580 1590 1600 1610

Wavelength (nm)

Re

lative

ga

in (

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… Fib

er

att

enuation (

dB/k

m) 1.0

0.8

0.4

0.2

1.2 1.7 1.6 1.5 1.4 1.3

Optical wavelength (µm)

C band

Old fibers

Modern fibers


Fib

er

att

enuation (

dB/k

m)

0.8

0.4

0.2

1.2 1.7 1.6 1.5 1.4 1.3

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

L C S O 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...

Technology