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Recent advances and trends for digital coherent 100Gb/s ... Watch and SPS... · Page 3 . NEC...
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NEC Corporation www.nec.com/submarine/
Yoshihisa Inada Submarine Network Division
NEC corporation
Recent advances and trends for digital coherent 100Gb/s and beyond technologies in submarine optical cable
OFC MARKET WATCH Panel 2
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▐ Introduction
▐ 100G submarine cable systems
▐ Innovative technologies for beyond 100G systems
▐ Summary
Outline
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▐ Recent growth of international traffic demand has driven a drastic capacity enhancement of trans-oceanic submarine cable systems supported mostly by the break-through of digital coherent technologies with large spectral efficiency.
▐ The introduction of 100G/s technology has stimulated the investment for new build systems as well as capacity upgrade of legacy systems as it can deliver large capacity in a more cost-effective way.
▐ Recent advances and trends in submarine industry are presented and discussed based on our records and activities.
Introduction
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4th Generation (Digital Coherent)
Year
Cap
acity
(Bit/
s) /
Fibe
r Pai
r
2nd Generation (DWDM)
3rd Generation (Multi-level formats)
'98 ‘00 ‘02 ‘04 ‘06 ‘08 ‘10 ‘12 ‘14 ‘16 ‘18 ‘20
1T
10T
100G
10Gb/s System Based
10G x 192 10G x 128 10G x 96 10G x 64 10G x 32 10G x 16
40Gb/s System Based
40G x 88 40G x 64
40G x 176
100G x 100
100Gb/s System Based
beyond-100Gb/s 400G
1st Generation (WDM)
5G
1T 5th Gen.
(Super Channel) O
ptic
al
Reg
ener
ator
2.5G x 16
'96 '94
2.5G x 8
5G
Opt
ical
Am
plifi
er
Tun.
DC
M
Tun.
Las
er
You are here
Evolution of Capacity and Technologies
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Transmission Distance (km)
Capacity/fp
3,000km 6,000km 9,000km
5Tbps
10Tbps
20Tbps
12,000km
Technology Trend for 100G and Beyond
100G DP-BPSK [legacy cable] 100GHz spacing
100G DP-QPSK 50GHz spacing
Multi-carrier (Super-channel) 400G DP-16QAM
400G/1T DP-QPSK Superchannel
Technologies • SD LDPC FEC • Higher order modulation • Nyquist/ Super-channels • NL compensation • Advanced Fiber
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▐ Introduction
▐ 100G submarine cable systems
▐ Innovative technologies for beyond 100G systems
▐ Summary
Outline
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Submarine cable
Repeater
Line terminal equipment
Branching unit Power feeding
equipment
Components for Submarine Cable System
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Advanced Components for 100G Submarine System
Equipment Applied Key Technologies
SLTE Multi-level modulation (BPSK, QPSK, 16QAM) Polarization multiplexing and demultiplexing Digital coherent detection Digital compensation for linear effect (CD, PMD) Error Correction (LDPC based soft decision FEC)
Cable Low loss and Large Effective Area fiber Uncompensated dispersion map
Repeater Er-doped fiber amplifier (same as 10G/40G system) Increased output power Flat and wide gain characteristics
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Digital-Coherent Technology
►Unmatched sensitivity ►Hybrid Mixer Chip by PLC
►Tunable lasers ►Narrow linewidth
Coherent Receiver ►Digital Adaptive Impairment Compensation
► Polarization-mode dispersion ► Ultra-large Chromatic dispersion compensation
►Digital polarization demultiplexing (increased SE) ►Advanced SD-FEC
LSI digital signal processing
CDC Pol-Demux Phase recovery
DSP stages (100GbE)
Mixer
AD
C Digital
Signal Processing
01110010000101101001011
SD-FEC
11010111010101110011001
00010001111011001110010
01111100010011110011111
V1 V2 V3 V4 V5 V6 V7
C1 C2 C3
Modulation Format
Channel Spacing
SE [b/s/Hz]
Carriers Optical
Spectrum Constellation Map
100G DP-QPSK
50GHz 2 1 50GHz
X-pol Y-pol
Im Im
Re Re
X-pol
Y-pol
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LDPC Decoding Process
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LDPC based Soft Decision FEC
▐ First generation: Reed-Solomon (RS) FEC
▐ Second generation: Concatenated hard-decision FEC
▐ Third generation: Soft-decision FEC with iterative decoding (Large NCG > 10dB)
Bit
Err
or R
ate
Required OSNR
Target BER
Coding Gain
+0.98 -0.89 -1.19 +0.95 -0.56 -1.04 +0.84 -0.68 +0.99 +1.23 -1.04 +0.92 +1.23
+1 -1 -1 +1 -1 -1 +1 -1 +1 +1 -1 +1 +1
Log-likelihood ratio(LLR) calculation
Converged LLRs
V1 V2 V3 V4 V5 V6 V7
C1 C2 C3
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DP-QPSK: High Capacity and Long Reach
▐ Short-medium reach upgrades and transoceanic new builds ▐ Dual polarization + Quadrature phase keying provides high
spectral efficiency [2 bit/Hz/s - 2.67 b/s/Hz] ▐ Ultra-large dispersion compensation capabilities in the DSP
processor (up to 12,000km)
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DP-QPSK
6 7 8 9
10 11 12 13
6000 7000 8000 9000 10000 11000 Distance (km)
Q v
alue
(dB
)
Uncompensated Link
[ps/
nm]
[km]
Uncompensated [Large core fiber]
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DP-BPSK: Robustness against Fiber Nonlinearity
BPSK provides maximum robustness against phase noise
DP-BPSK DP-QPSK
4
6
8
10
12
14
-8 -6 -4 -2 0 2 4 Channel Power [dBm]
Q [d
B]
▐ Ultimate performance for transoceanic 100G upgrades ▐ Dual polarization + Binary phase keying provides strongest
tolerance to nonlinear effects in D+/D- submarine links DP-BPSK
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Dispersion Compensation
Channels travel at same speed
Large XPM
Severe Phase-noise
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Fiber Technology C
apac
ity/R
each
SMF [0.5 dB/km]
DSF [0.3 dB/km]
DMF [0.2 dB/km]
D+ [0.16 dB/km] EDFA
Digital Coherent
Single channel
DWDM
80s 10s 90s 00s
10G DWDM 2.5G DWDM
5G
40G DWDM
100G DWDM
NZ-DSF [0.2 dB/km]
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Repeater Technology
20s 10s 90s 00s
7dBm [5-10nm]
12dBm [>20nm]
15dBm [>30nm]
5dBm [2-5nm]
1480nm Pumps 980nm Pumps
18dBm [>35nm]
Analog
Digital Coherent
OOK DPSK
40G DWDM 100G DWDM 400G/1T DP-QPSK Nyquist QAM
>20dBm [>40nm]
10G DWDM 5G~2.5G WDM
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▐ Introduction
▐ 100G submarine cable systems
▐ Innovative technologies for beyond 100G systems
▐ Summary
Outline
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Repeater Bandwidth [nm]
FEC-NCG
Fiber Core Area [µm2]
Fiber Cores
CD-PMD SPM XPM
Spectral Efficiency Impairments Compensated
1
2
3
2
4
8
16
1 3 5 7
80
100
120
140
40
60
80
11 11.5 12
C C+L Raman
100G DP-QPSK, SSMF, C-EDFA
120
Multi-level Modulation
Key Technologies for Increasing Fiber Capacity
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30.3 km Type II fiber
20LDs50 GHz
IQ Mod
50 GHz
AWG3
IQ Mod
AWG4
IQ Mod
20LDs
AWG2
IQ Mod
OSA
PCWaveShaper
LO
PM-EDFA
ADC&
Off-lineDSP
Processing
30.3 km Type I fiber
× 7
SW
10:90
WaveShaper
PC
AWG1
10:90
OSA
Data1 LDPC
Data2 LDPC
Data3 LDPC
Data4 LDPC
12.5GHzF.S. PolMux
PolMux
12.5 GH
z IL
OTF190°
Hybrid
(a)
(b)
(c)
LSPC
2000 4000 6000 8000 100004
4.55
5.56
6.57
7.58
8.59
9.5
Transmission Distance (km)
Q (d
B)
CDCNLC
Error free transmission for 40 Channels Q versus distance
40×117.6 Gb/s PDM-16QAM OFDM Transmission over 10,181 km with Soft-Decision LDPC Coding
and Nonlinearity Compensation
Spectral Efficiency 1: Higher Order QAM
1545 1547 1549 1551 1553 15552
3
4
5
6
wavelength (nm)
Q (d
B)
CDCNLC
A B
Im
Re Re
Im QPSK 16QAM
2bit/symbol 4bit/symbol
Re
Im 8QAM
3bit/symbol
Number of bit per symbol can be increased
Baud-rate per channel can be relaxed Spectral efficiency can be increased Digital processing is required in
transmitter
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OFC 2012, PDP5.C.4
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Current WDM Super-channel Concept
▐ Optical super-channels enable; 400G and beyond signals with practical electronics Reduced channel spacing with digital pulse shaping and other technologies
▐ Next generation equipment will be based on both QAM and super-channel technologies.
Spectral Efficiency 2: Super-channels
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Next Generation FEC
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1) 40×117.6 Gb/s PDM-16QAM OFDM Transmission over 10,181 km with Soft-Decision LDPC Coding and Nonlinearity Compensation. OFC 2012, PDP5.C.4 2) High Capacity Field Trials of 40.5 Tb/s for LH Distance of 1,822 km and 54.2 Tb/s for Regional Distance of 634 km, OFC 2013, PDP5.A.4
▐ Adaptive overhead for on-demand performance Spectral efficiency is optimized to line
OSNR Latency can be reduced
▐ High performance LDPC Low Q limit < 5dB Still large complexity
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Compensation of Fiber Nonlinearity ▐ Optical fiber nonlinearity limits the maximum Q factor after transmission. ▐ Back-propagation algorithm can compensate the fiber nonlinearity. ▐ Approx. 1dB improvement was obtained in 100Gb/s-10,000km transmission.
Analog to
Digital
Digital “Back” Propagation
DSP domain (virtual fiber)
PD PD PD PD
90 degree hybrid Tx
Optical “Forward” Propagation
Physical domain (real fiber)
Data In Data Out
Virtual Link Optical Link
Power (dBm)
Q (d
B) Limited
by OSNR Nonlinearity
(SPM)
0 0.5 1 1.5
9
9.5
10
10.5
Power/channel (dBm)
Q (d
B)
CDCNLC
1dB
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-7 -6 -5 -4 -3 -26
6.5
7
7.5
8
8.5
9
Power
Q (d
B) f
rom
BE
R127 Gb/s, L=6455 km
▐ Experimental Tests on Dispersion managed systems with back-propagation NLC algorithm SMF+DCF link DMF link NZ-DSF link
-8 -6 -4 -2 0 27
8
9
10
11
12
Power/channel (dBm)
Q (d
B)
Residual Dispersion ∼ 7400 ps/nm (y-pol)
NEC-BP=OFFNEC-BP=ON
SMF+DCF link DMF link
-10 -9 -8 -7 -6 -5 -4 -3 -2
5
6
7
8
9
10
Power/channel (dBm)
Q (d
B) [
from
BE
R]
CD CompensationNL Compensation
w/o 10G
w 10G
NZ-DSF link
Compensation of Fiber Nonlinearity (Dispersion managed links)
1) Nonlinearity compensation using very-low complexity backward propagation in dispersion managed links. OFC2012, OTh3C4 2) 100G upgrade over legacy submarine dispersion-managed fiber link using fiber nonlinearity compensation and maximum-likelihood…, OFC2012, OTu2A 3) Low Complexity Nonlinearity Compensation for 100G DP-QPSK Transmission over Legacy NZ-DSF Link with OOK channels, ECOC2012, Mo1C5
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▐ Multi core fiber Capacity increase in proportion to the
number of core. Multi core EDFA is required for practical
deployment.
Multi core fiber
First demonstration of MC-EDFA-Repeatered SDM Transmission of 40×128-Gb/s PDM-QPSK Signals per Core over 6,160-km 7-core MCF, Opt. Exp, 21,789.
6,100km transmission over 7-core fiber
Space-division Multiplexing by New Fibers
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Outline
▐ Introduction
▐ 100G submarine cable systems
▐ Innovative technologies for beyond 100G systems
▐ Summary
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Summary
▐ Thanks to the advancement in digital coherent 100Gb/s technologies and the transmission optical fiber, the deployment of 100Gb/s is underway in many projects for trans-oceanic submarine cable systems.
▐ The adoption of 100Gb/s DWDM in submarine networks significantly
increases fiber capacity in a cost-effective way.
▐ 100Gb/s technologies can be also applied to legacy systems for efficient capacity upgrades.
▐ Advanced key technologies, including FEC, nonlinearity compensation,
digital multi-level modulation or optical super-channel, will enable larger capacity of submarine cable systems beyond 100Gb/s.