ultrahigh speed nyquist pulse transmission and 3m (multi ......ultrahigh‐speed nyquist pulse...
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ISUPT 2013October 22, 2013
Ultrahigh‐speed Nyquist Pulse Transmission and 3M (Multi)
Technology
Ultrahigh‐speed Nyquist Pulse Transmission and 3M (Multi)
Technology
Masataka Nakazawa
Research Institute of Electrical CommunicationTohoku University
2-1-1 Katahira, Aoba-ku, Sendai-shi, 980-8577 Japan
OutlineOutline
(1) Technological overview of optical communication infrastructure
(2) Ultrafast and high spectral efficiency optical transmission
• 1024~2048 QAM transmission• Optical Nyquist pulse TDM transmission
(3) Multi-core fibers for SDM transmission• Mode-coupling measurements along an MCF using
a 7 channel OTDR
(4) Summary
Technological overview of optical fiber transmissionTechnological overview of optical fiber transmission
100M
Lin
k C
apac
ity
/ fib
er(s
) [
bp
s]
1.6G2.4G
1980 1990 2000
400M
10GTDM
Moore’s Law
2010 2020
100T
1G
1P
1E
1T
1G
1P
1E
1T
40G
WDM
10Gx80
EDFA
120
100
80
60
40
20
0
Inte
rnet
tra
ffic
[Gb
it/s
]
Year1999 2000 2001 2002 2003 2004 2005 2006 2007 2008
Increase in Internet Traffic in Japan
1st InnovationEDFA, WDM
2nd Innovation•Multi-level coherent transmission
•Multi-core fiber•Multi-mode control
1 Tbit/s@2009
40% increase per year
100G
Optical power limitationBandwidth limitation of
optical amplifiers
Physical dimensions for modulation and multiplexingPhysical dimensions for modulation and multiplexing
WDM: Wavelength Division MultiplexingSDM: Space Division Multiplexing
Quadrature
Time
SDM
By courtesy of P. Winzer
First “M”: Multi-level modulationFirst “M”: Multi-level modulation
QAM (Quadrature Amplitude Modulation):
Two carriers with the same frequency are amplitude-modulated independently.
The phase of the two carriers is 90 deg. shifted each other.
2N QAM processes N bits in a single channel, so it has N timesspectral efficiency compared with OOK.
Constellation map for 16 (=24) QAM
0000 0100 10001100
0101 1101 10010001
11110011 0111 1011
01100010 1110 1010
rθ
同位相(I)
直交位相(Q)
In-phase (I)
Quadrature-phase (Q)
0 1
With OOK
In-phase (I)
Quadrature-phase (Q)
Challenges to 1024 and 2048 QAMChallenges to 1024 and 2048 QAM
Constellation of back-to-back signal
1024 QAM
2048 QAM
SNR requirement for FEC limit (BER = 2x10-3)
512 QAM:Eb/N0=21 dB → SNR=30.5 dB (1 Symbol =9 bit)
1024 QAM:Eb/N0=24 dB → SNR=34 dB (1 Symbol =10 bit)
2048 QAM:Eb/N0=27 dB → SNR=37.4 dB (1 Symbol =11 bit)
10 15 20 25 3010
-6
10-5
10-4
10-3
10-2
10-1
512QAM
2048 QAM
1024QAM
Eb /N0 [dB]
FEC threshold
2048 = 211
= 48 x 48 – 256= 2304 – 64 x 4
-100
-80
-60
-40
-20
0
-3 -2 -1 0 1 2 3
Po
we
r [d
Bm
]
RF frequency [GHz]
PCEDFA
IQ Mod.
(fOFS=2.03 GHz)OFS
Optical Filter (3.5 nm)
12Gsample/s
PC AttAmplifier
PC
IQ Mod.
OFS
3 Gsymbol/s 1024 QAM signal・Nyquist raised cos. filter (roll off = 0.35)・Pre-equalization with FDE(FFT size = 16384, Frequency resolution = 0.73 MHz)
PBC
XY
PC
PD
Synthesizer
FeedbackCircuit
LocalOscillator
DBM
(Tunable Fiber Laser)
PC
PC fsyn=2.03 GHz
90°Optical Hybrid75 km SLA
Digital Signal Processor
Etalon
Att Prec
A/DB-PD X
Y
Optical filter (0.7 nm)A/DB-PD
A/DB-PD A/DB-PD
90°
90°PCRaman
Pump-1 dBm
PC: Polarization ControllerOFS: Optical Frequency ShifterPBC: Polarization Beam CombinerSSMF: Standard Single-mode FiberDBM: Double Balanced MixerB-PD: Balanced Photo-Detector
Att
75 km SLA
Raman Pump -1 dBm
fQAM signal
2.03 GHz
Inte
nsi
ty
Pilot signal
C2H2 FrequencyStabilized Fiber Laser
Arbitrary WaveformGenerator
LO
Demodulation Bandwidth= 4.05 GHz
40 Gsample/s
・Linewidth: 4 kHz
・Linewidth: 4 kHz
Back propagation
(Step size : 9.375 km)
Y. Koizumi et al., Opt. Exp., 20, 12508 (2012)
Polarization-multiplexed 3 Gsymbol/s, 1024 QAM (60 Gbit/s) coherent optical transmission systemPolarization-multiplexed 3 Gsymbol/s, 1024 QAM (60 Gbit/s) coherent optical transmission system
-30 -25 -20 -15 -10
Back-to-back (X)Back-to-back (Y)After 150km transmission (X)After 150km transmission (Y)
10-5
10-4
10-3
10-2
10-1
BER
Received Power [dBm]
Back-to-back
After 150 km transmission
BER characteristics
FEC threshold
Experimental results for 60 Gbit/s 1024 QAM transmissionExperimental results for 60 Gbit/s 1024 QAM transmission
BE
R
60 Gbit/s
4.05 GHz x 1.07 = ≒ 13.8 bit/s/Hz
Spectral efficiency (single-channel)
Roll-off factor = 0.35Signal bandwidth: 3 Gsymbol/s x (1+) = 4.05 GHz
Trend in high speed, high capacity coherent transmission
Trend in high speed, high capacity coherent transmission
High-speed transmissionOTDM/ETDM
Spectrally efficient transmissionMulti-level modulation
Driving force for high-speedoptical networking100 Gbit/s Ethernet
Driving force for ultra-efficient/large capacity FTTH
OOK, DPSK, DQPSK
M-PSK, QAM, OFDM
Frequency
Time
OTDM/RZ-QAM
RZ-OTDM
QAM
Realization of high-speed, high spectral efficiency transmission
OpticalNyquist pulse transmission
= 0
= 1 = 0.5
Proposal of optical Nyquist pulse and its TDMProposal of optical Nyquist pulse and its TDM
= 0
= 1 = 0.5
Nyquist filter has a sinc-function-like impulse response with zero crossing at every symbol period Intersymbol interference (ISI) can be suppressed even in smaller bandwidth
Tf
Tf
TfT
Tf
fR
2
1||,0
2
1||
2
1,)1||2(
2sin1
2
12
1||0,1
)(
T: Symbol period: roll-off factor
Interleaving of Nyquist pulseOptical Nyquist pulse (Impulse response of Nyquist filter)
2)/2(1
)/cos(
/
)/sin()(
Tt
Tt
Tt
Tttr
Nyquist filter
Nyquistfilter
Baseband data signal(QPSK, QAM, …)
f f+fs +2fs-fs-2fs+fs-fs
tt
1/fs
t
11, 0 | |
2
1 1 1( ) 1 sin (2 | | 1) , | |
2 2 2 2
10, | |
2
fT
H f T f fT T
fT
Transferfunction:
Bandwidth limited data signal(not a “pulse”)
ffc Pulse
shaper
ffc+Nfs
fc-Nfs
t
Transform-limited optical pulses (Gaussian, sech, …)
Optical Nyquist “pulse”
2
sin( / ) cos( / )( )
/ 1 (2 / )
t T t Tr t
t T t T
11, 0 | |
2
1 1 1( ) 1 sin (2 | | 1) , | |
2 2 2 2
10, | |
2
fT
R f T f fT T
fT
Waveform:
Spectrum:
Comparision between Nyquist filtering and optical Nyquist pulses
Comparision between Nyquist filtering and optical Nyquist pulses
K. Kasai et al., OECC 2007 PDP and IEICE Electron. Express vol. 5, 6 (2008).
M. Nakazawa et al., Opt. Express vol. 20, 1129 (2012).
6.25 ps
DemultiplexerMultiplexer
Optical Fiber
MultiplexedOTDM signal
Time
25 ps
Ultrahigh-speed OTDM transmission using optical Nyquist pulses[1]
Ultrahigh-speed OTDM transmission using optical Nyquist pulses[1]
[1] M. Nakazawa et al., Opt. Express, 20, 1129 (2012).
40G 160G40G
40G
40G
40G
40G
40G
40G
Optical Nyquist pulse train
No
rmal
ized
po
wer
3.125 ps
No
rmal
ized
po
wer
160 Gbaud OTDM waveform
No
rmal
ized
po
wer
40 GHz optical Nyquist pulse( = 0.5)
Demultiplexed signal
Ultrafast optical sampling
1540 nm1.6 ps
MUX
PC EDFADemod.
EDFA
PDATT
DI
Prec40 GHzMLFL
PLL EDFA
OpticalDelay PC 15 nm
CLK
1563 nm800 fs
CLK
EDFA
HNL-DFF2 km
40 GHz
1 nm
EDFA
2 nm
40 GHzMLFL
ErrorDetector
40 GHzPPG
40 Gbit/s215-1 PRBS
Q
Q
40 G 640 Gbaud
10 nm
HNLF 100m
PC
PC
PC
EDFA
SMF50 km
PC
x7
DPSK Modulator
IDF25 km
640 Gbit/s DPSK transmitter
525 km transmission link
40 Gbit/s DPSKrecieverDFF
500 m640 G 40 Gbit/sDEMUX
EDFA 15 nm
Pulseshaper
PC PBS//
⊥
Pulseshaper
EDFA
OpticalDelay
OpticalNyquist pulse generator
10 nm
640 G 1.28 Tbit/s polarization-multiplexed
NOLM
1.28 Tbit/s/ch - 525 km polarization-multiplexed DPSK transmission with 640 Gbaud optical Nyquist pulse
1.28 Tbit/s/ch - 525 km polarization-multiplexed DPSK transmission with 640 Gbaud optical Nyquist pulse
MLFL: Mode-Locked Fiber LaserHNL-DFF: Highly NonLinear-Dispersion Flattened FiberCLK: Clock RecoveryPPG: Pulse Pattern GeneratorIDF: Inverse Dispersion Fiber
DI: Delay InterferometerATT: Optical attenuatorPD: Balanced Photo DetectorNOLM: Nonlinear Optical Loop Mirror
K. Harako et al., Opt. Express, 21, 21603 (2013).
Optical Nyquist pulse for 640 Gbaud transmissionOptical Nyquist pulse for 640 Gbaud transmission
Optical Nyquist pulse waveform and spectrum
-90
-80
-70
-60
-50
-40
-30
-20
-10
1530 1540 1550
Power [dBm]
Wavelength [nm]
0
5
10
15
20
25
Power [
mW]
Time [ps]1.56 ps/div
Growth of depolarization-induced crosstalk
0
0.02
0.04
0.06
0.08
0.1
0 100 200 300 400 500 600
Crosstalk
Transmission Distance [km]
4 dB
Gauss
Nyquist
L2 fitting
For 640 Gbaud• Due to narrower spectral width of the
Nyquist pulse, the growth rate of the depolarization-induced crosstalk is much lower than a Gaussian pulse.
• Crosstalk was 4 dB lower than that of a Gaussian pulse after 525 km propagation.
1.28 Tbit/s/ch-525 km polarization-multiplexed transmission experiments
1.28 Tbit/s/ch-525 km polarization-multiplexed transmission experiments
-32 -30 -28 -26 -24 -22 -20 -18
Bit Error Rate
Received Optical Power [dBm]
10-10
10-3
10-4
10-5
10-6
10-7
10-8
10-9 Single-pol
Pol-MUX
Back to
back
Optical Nyquist pulse Gaussian pulse
-32 -30 -28 -26 -24 -22 -20 -18
Bit Error Rate
Received Optical Power [dBm]
10-4
10-5
10-6
10-7
10-8
10-9
10-10
10-3
Back to
back Single-pol
Pol-MUX
1530 1540 1550 1560
10dB/div
Wavelength [nm]
Gauss (600 fs) signal
crosstalk
1525 1535 1545 1555
10dB/div
Wavelength [nm]
Nyquist (640 Gabud)
crosstalksignal
Spectral efficiency: 1.28 Tbit/s960 GHz x 1.07( = 0.5)
= 1.25 bit/s/Hz for DPSK (Typical SE is 0.5 bit/s/Hz for DPSK)
225 m150 m200 mCladding diameter
12719# of cores
H. Takara et al. (NTT, Fujikura, Hokkaido Univ., DTU), ECOC2012, Th3.C.1.
T. Hayashi et al. (Sumitomo), OFC2011, OWJ3, PDPC2.
J. Sakaguchi et al. (NICT, Furukawa, Optoquest), OFC2012, PDP5C.1.
Reference
0.199 dB/km0.18 dB/km0.23 dB/kmLoss
-55~-49 dB/km- 92 dB/km- 42 dB/kmCrosstalk
80 m2
45 m
88 m272 m2Aeff
37 m35 mCore pitch
Multi-core fibers for SDM transmissionMulti-core fibers for SDM transmission
Space-division multiplexed transmission using MCFSpace-division multiplexed transmission using MCF
D. Qian et al. (NEC America, Corning, etc.), FiO2012, FW6C.3.
H. Takara et al. (NTT, Fujikura, DTU, Hokkaido Univ.), ECOC2012, Th3.C.1.Ref.
3 km52 kmDistance
Spatial optical coupling
1.05 Pbit/s (195 Gbit/s x 385 WDM x [12 core (PDM-32 QAM) + 2 mode (PDM-QPSK)])
Fan in/fan out deviceMCF coupling
1.01 Pbit/s (456 Gbit/s PDM-32QAM x 222 WDM x 12 core)
Total Bit rate
Mode coupling measurement along MCF using multi-channel OTDR[1]
Mode coupling measurement along MCF using multi-channel OTDR[1]
12
34
56
7
Time
Optical pulse
Pulse width:
Input power: P0
Pbs1Pbsm
MCF
Fiber length
Backscattered power
Pbs1
Pbs2 Pbs3
Pbsm / Pbs1
KSlope: 2h1,m
Local mode coupling due to structural imperfection
Fiber length
)(
)(
1,1
1,1111
mmmmm
mm
PPhPdz
dP
PPhPdz
dP
Mode coupling between core 1 and core m:
KLhP
Pm
bs
bsmm ,1
1,1 2
From Pbsm/Pbs1, mode coupling coefficient h1,m and its longitudinal variation can be measured[2] .
[1] M. Nakazawa et al., Opt. Exp., 20,12530 (2012), [2] M. Nakazawa et al., JOSAA, 1, 285 (1984).
Mode coupling measurement resultsMode coupling measurement results
Original backscattered signals
Mode coupling ratio from center to outer cores
0.20 dB/km
(Input: Center core)
Mode coupling coefficient
2.9 kmLength
217 mCladding
diameter
46 mCore pitch
MCF under test
M. Nakazawa et al., OFC2012, OTh3I.3
Mode-division-multiplexed transmission using MIMOMode-division-multiplexed transmission using MIMO
Q
kk tntxhty
1
)()()(Receivedsignal
x(t): Input signal, n(t):Noise, Q:Number of modes
Distortion in mode k: kcjkkk eah
(1) SISO (Single Input Single Output) (One Tx, One Rx)
ak: Loss of mode kk: Group delay of mode kk: Coupling ratio to mode k
(2) MIMO (Multiple Input Multiple Output) (M Tx, N Rx)
hijk: Distortion when transmitted from Tx j to Rx i via mode k
Received signal at Rx i
)()()( ttt nHxy Matrix representation Estimate H from x(t) and y(t)
NitntxHtntxhtyM
jijij
M
j
Q
kijijki 1,)()()()()(
11 1
Tx 1
Tx 2
Tx M
Rx 1
Rx 2
Rx N
。。。
。。。
Mode 1
Mode 2 Mode k
Mode multiplexer / demultiplexerMode multiplexer / demultiplexer
Free space opticswith phase plates[1]
Fiber coupler[2]
LCOS(Liquid Crystal on Silicon)[3]
[1] S. Randel et al., Opt. Exp. 19, 16697 (2011).[2] N. Hanzawa et al., OFC2011, OWA4.[3] C. Koebele et al., Opt. Exp. 19, 16593 (2011).
Mode-division-multiplexed transmission experimentsMode-division-multiplexed transmission experiments
5 modes x 100 Gbit/s - 40 km PDM-QPSK transmission using LP01 + LP11a + LP11b + LP21a + LP21b (2x2 MIMO + 4x4 MIMO + 4x4 MIMO)[1]
6 modes x 40 Gbit/s - 130 km PDM-QPSK transmission using LP01+LP11a+ LP11b+ LP21a+ LP21b+ LP02 (12x12 MIMO)[2]
[1] C. Koebele et al. (ALU), ECOC2011, Th.13.C.3.[2] R. Ryf et al. (ALU), FiO2012, FW6C.4.
SummarySummary
Recent advances toward the realization of an ultrahigh SE and ultrahigh-capacity SDM transmission are presented with a special focus on the following novel technologies:
1. Ultramulti-level coherent transmission up to 1024 levels
2. Ultrafast coherent pulse transmission with OTDM RZ/QAM
3. Nyquist pulse transmission
4. MCF characterization with longitudinal mode-coupling measurement
Fiber capacity at a Pbit/s level is expected to be achieved with SDM by taking full advantage of the high spectral efficiency and high spatial density in MCF.