High-Speed Optical Transmission Systems

High-Speed Optical Transmission Systems
Hochbitratige optische Übertragungssysteme von heute und morgen
Prof. Dr.-Ing. Christian-Alexander Bunge
Hochschule für Telekommunikation Leipzig
bunge@hft-leipzig.de
Local Area Network (LAN)
mehrere 10m, ~1Gb/s
Metronetz
~100km
Vermittlungsstelle
grauer
Kasten
Zugangsnetz
~1km, ~10Mb/s
Hochbitratige optische
Verbindungen
Backbone
>100km
Backbone
>100km
Metronetz
Backbone
>100km
Backbone
>100km
Metronetz
Backbone
>100km
Backbone
>100km
Metronetz
Überblick
‣ Einführung
‣ Übertragungssystem
‣ Konzepte
‣ Sender, Signalerzeugung
‣ Empfänger
‣ Direkt-Detektion vs. kohärent
‣ begrenzende Effekte, Degradationen
‣ Dispersion, Nichtlinearitäten
‣ Streckenauslegung
Wochenübersicht 2014
vormittags
10:15h
–
13:00h
nachmittags
14:00h
–
17:00h
Mo
Di
Mi
Do
Fr
VL
Systeme
VL
Empfänger
UE
Sender
UE
Übertrag.Effekte
VL
Übertrag.Effekte
VL
Sender
VPI/
Simulation
–
Einführung
UE
Empfänger
Zeit zum
Nacharbeiten /
ReCap
ZeitVL
zum
NachÜbertrag.arbeiten /
Effekte
ReCap
zur Prüfung
mündliche Prüfung
45 min pro Student
möglichst Gruppenprüfung mit 2 oder max. 3 Studenten
Terminabsprache ca. 2–3 Wochen vor dem Prüfungstermin
Anmeldung bei mir:
Christian-Alexander Bunge
Hochschule f. Telekommunikation Leipzig
Gustav-Freytag-Str. 43-45
04277 Leipzig
Tel.: (0341) 306 22 41
E-Mail: bunge@hft-leipzig.de
Organisatorisches...
Vormittags (10h-13h): Vorlesung
Christian-Alexander Bunge
Hochschule f. Telekommunikation Leipzig, Gustav-Freytag-Str. 43-45, 04277 Leipzig, Tel.: (0341) 306 22 41, bunge@hft-leipzig.de
Nachmittags (14h-17h): Simulationspraktikum/
Selbststudium
Lilli Kuen
HFT 516, lilli.kuen@mailbox.tu-berlin.de
Organisatorisches...
‣
Allgemeine Informationen, Skript:
‣
http://www1.hft-leipzig.de/ice/bunge_de.html
‣
http://www.hft.tu-berlin.de
!
‣
Literaturempfehlungen
‣
Agrawal, G. P.: Fiber-Optic Communication Systems, John Wiley & Sons, 2008
‣
Voges, Petermann: Optische Kommunikationstechnik, Springer-Verlag, 2002.
Stand der Technik: Was ist möglich?
32 Tb/s (320x114 Gb/s) PMD-RZ-8QAM transmission
over 580 km of SMF-28 ultra-low-loss fiber
461
tions using
, where (a)
recovery.
ZHOU et al.: RZ-SHAPED PDM-8QAM MODULATION FORMAT
by
intr
T
tica
tim
pol
me
can
U
nol
suc
(32
coh
bit/
T
fro
Lab
Re
Fig.et11.
Experimental
setup for 32 Tb/s
-band transmission
experiment.
aus: X. Zhou
al. „32
Tb/s (320x114Gb/s)
PMD-RZ-8QAM
transmission
over 580 km of SMF-28 ultra-low-loss fiber,” J. of Lightw. Technol. Vol. 28, No. 4, Feb. 2010.
Table 1: Some current spectral efficiency records at per-channel bit rates beyond 40 Gb/s. DQPSK: Differential quadrature phase shift keying;
QAM: Quadrature amplitude modulation; OFDM: Orthogonal frequency-division multiplexing.
10x112-Gb/s PDM 16-QAM transmission over 630 km
2. Experimental Setup
The fiber
experimental
system6.2-b/s/Hz
is shown in Fig. 1. Ten
lasers were operated
on a 16.67-GHz grid in the C band between
of
with
spectral
efficiency
193.35 THz and 193.50 THz (1549.31 nm to 1550.51 nm). A tunable external-cavity laser (ECL) was used as the
source for the respective WDM channel under test, due to the required narrow linewidth for 16-QAM. The
measured linewidth of the ECL was ~100 kHz. The remaining lasers were distributed feedback (DFB) lasers with
linewidths of about 2 MHz. Two transmitters were used, corresponding to odd and even channels on a 33.33-GHz
© 2009 OSA/OF
Log (Bit-Error Ratio)
a2595_1.pdf
PDPB8.pdf
Theory
1 Ch. no Interleaver
1 Ch. w/ Interleaver
WDM w/ Interleaver
-2
y
x
x
y
y
-3
-4
-5
-6
14 16 18 20 22 24 26 28 30 32
© 2009 OSA/OFC/NFOEC 2009
OSNR in 0.1 nm (dB)
Fig. 1: Experimental setup.
y
x
y
978-1-55752-869-8/09/$25.00 ©2009 IEEE
x
y
Relative Power (dBm)
Fig. 4: Bit-error-ratio results in back-to-back operation.
Fig. 5: Signal constellations for both polarizations. Top left: Single
channel without the interleaver (OSNR= 35 dB). Top right: Channel in
WDM environment (OSNR=23 dB). Bottom: After transmission.
-2
10
-10
-20
1
Bit-Error Ratio
a2595_1.pdf
PDPB8.pdf
x
x
2 ! 10-3 FEC Limit
-3
10
-30 Downloaded on February 28,2010 at 17:24:15 EST from IEEE Xplore. Restrictions apply.
Authorized licensed use limited to: Technische Universitaet Berlin.
(0.1-nm resolution bandwidth)
193.30 193.35 193.40 193.45 193.50 193.55
Frequency (THz)
-4
10
193.30 193.35 193.40 193.45 193.50 193.55
Frequency (THz)
7: Bit-error-ratio results
after 630-km
transmission. aus:
A,. Gnauck
et al.
„ 10x112-Gb/s
16-QAM transmission over 630 km of fiber withFig.6.2-b/s/Hz
spectral
efficiency,”
Fig.
5: Signal
constellations
for both
polarizations. TopPDM
left: Single
channel without the interleaver
(OSNR=
35 dB).
Top right: Channel
Optical
Fiber
Conference
(OFCin2009), Post-Deadline Paper
PDP8, San Diego, USA, 2009.
-3
Fig. 6: Optical spectrum after 630-km transmission.
20.2 dB to achieve a BER of 1 ! 10 . This value is 3.2 dB off the theoretical limit for PDM 16-QAM (solid li
Dämpfung und optische Fenster
100
Dämpfung [dB/km]
10
Gesamtdämpfung
OH-Absorption
1
Rayleighstreuung
0,1
IR-Absorption
UV-Absorption
0,01
600
800
1000
1200
1400
1600
Wellenlänge [nm]
Entwicklung der optischen Übertragungsstrecken
1. Generation
LED
MMF
MMF
Reg.
MMF
Reg.
MMF
50 Mb/s-100 Mb/s
Reg.
10 km
2. Generation
1,3µm Laser
SMF
SMF
Reg.
SMF
Reg.
SMF
100 Mb/s-1,7 Gb/s
Reg.
50 km
3. Generation
1,55µm Laser
SMF
SMF
Reg.
SMF
2,5 Gb/s-10 Gb/s
Reg.
ca. 100 km
4. Generation
DFB-Laser
λ2
Tx2
λn
Txn
Rx1
SMF
EDFA
SMF
Rx2
……
Tx1
……
λ1
ca. 100 km
Rxn
2,5 Gb/s-40 Gb/s
pro Wellenlänge
erreichte Übertragungslängen und -kapazitäten
Kanaldatenrate
Gesamtkapaz.
Grundsätzlicher Aufbau einer Übertragungsstrecke
Daten
Sender
Block
Coding
Empfänger
Line
Coding
Line
Coding
Line Coding:
Gleichstromanteil
Anzahl Marks und Spaces
Redundanz
z B. differentielle Kodierung
Block Coding:
Fehler-Korrektur
Redundanz
Robustheit erhöhen
z. B. FEC, Turbo-Kodes
Block
Coding
Daten
Aufbau einer optischen Übertragungsstrecke
Modulator
Sender
TIA
Signalverarbeitung
Empfänger
Demodulator
DatenRückgewinnung
Daten
TaktRückgewinnung
Takt
Multiplex-Techniken
Zeit-MUX
Wellenlängen-MUX
Zeitmultiplex (TDM-System)
Kanal 1
t
Kanal 2
t
Kanal 3
t
Kanal 4
t
Kanäle 1, 2, 3 und 4
t
ETDM- vs. ODTM-Sender
AM
010..
..110
010..
BitwortErzeugung ..110
AM
010..
BitwortErzeugung ..110
AM
……
010..
BitwortErzeugung ..110
……
optische
Pulsquelle
Δτ
AM
n⋅Δτ
Verzögerungsleitungen
∑
ETDM- vs. ODTM-Sender
010..
BitwortErzeugung ..110
AM
010..
BitwortErzeugung ..110
AM
……
010..
BitwortErzeugung ..110
……
optische
Pulsquelle
Δτ
AM
n⋅Δτ
AM
Verzögerungsleitungen
010..
..110
∑
Wellenlängenmultiplex (WDM-System)
λ1
Tx1
λ2
Tx2
Wellenlängenspektrum
(a)
λ1+λ2+…+λn
……
λn
Txn
Prinzip
(b)
Aufteilung der Information: spektral vs zeitlich
f
f
t
TDM
t
(O)FDM
(:A,6,*B+9C>7D<:--),-'E76+)F6,G)*B
Frequenz-Multiplex, Sub-Carrier-Multiplexing
2/
#+,(()-./
20
#/!!"
21
#/!!1
H
!"
#$%&'()*
3.&'4565)7
8
8
8
H
#+,(()-.1
3.&'4565)7
#0!!1
!/.;"/<
#=!!1
9:4'7,4*,(5%'44)*
!0.;"0<
8
8
8
3.&'4565)7
8
8
8
3.&'4565)7
#=!!"
!>=?@
H
9:4'7,4*,(5%'44)*
3.&'4565)7
3.&'4565)7
#0!!"
3.&'4565)7
#+,(()-.0
8
8
8
3.&'4565)7
8
8
8
3.&'4565)7
=13.&'4565)7
9:4'7,4*,(5%'44)*
!
!=.;"=<
!"!##$%&'()*+,-'#../&'0-123'43'53'%678,*+9:6
;,<+7-,'=&'>6)?,'=@
Spektren
bei FDM
Illustration of OSSB modulation using dual-electrode MZ modulator.
Fig. 2.
HUI et al.: SCM FOR HIGH-SPEED OPTICAL TRANSMISSION
Fig. 3. Measured OSSB spectrum with four subcarrier channels.
shown in Fig. 2, in order to generate OSSB, the composite signal
was applied to both of the two balanced electrodes with a
phase shift in one of the arms using a 90 hybrid splitter. A direct
Spektren bei OFDM
f
fT + n · f
... ...
⇥T
fT =
2
f
fn = N · f
Spektren bei OFDM
A(t) = Rect
t
t0
Tbit
⇥
t
sin f · Tbit
Ã(f ) = F{A(t)} ⇥
f · Tbit
Ãges (f ) =
i
f
f
si · Ã(f ) · exp(⇧ · 2 fi )
Modulation
DAC
cos(2πfRFt)
DAC
Re
I
Bias
elektrische
+
+
Modulation
sin(2πfRFt)
Im
×
Optical Optical
Modulator Filter
Laser
Q
Carrier
Loss-Compensated
Fiber Link
Equalization Demodulation
×
Splitter
el. De-Re
-sin(2πf t)
Multiplex
Q
×
Im
ADC
Photodiode
RF
Serial to Parallel
I
ADC
cos(2πfRFt)
elektrische
Signalverarbeitung
FFT
Fig. 1. Optical OFDM system block diagram.
N parallel
Data Channels
Zeros
elektrische
Inverse
FFT
Signalverarbeitung
×
Distortion
Products
Parallel to Serial
N parallel
Data Channels
waveform containing a superposition of all of the sub-carriers. This waveform is modulated
onto an RF-carrier, fRF, using an I-Q modulator, producing a real-valued waveform
comprising a band of sub-carriers displaced from DC (see inset). Next, this band is modulated
ontoOFDM-System:
an optical carrier using aVorteil
linear optical
modulator. In contrast
to our–earlier
orthogonaler
Signale
FFTsystem [13],
the output of the optical modulator is filtered to remove all frequencies other than the upper
side-band (or lower sideband if preferred) and an attenuated (suppressed) optical carrier.
Modulationsformate: wie Information kodiert wird
3.1 Overview
In this chapter, the methods for the optical signal generation are introduced. The focus is set on modulation
formats employing the amplitude modulation of the optical carrier, because of their importance in today’s
optical transmission systems. The generation and transmission characteristics of conventional and novel
modulation
formats
are presented. Systems
High-Speed
Optical
Transmission
– TU Berlin – Dr.-Ing. C.-A. Bunge
SYS/
Modulationsformate
~
E(t)
=~
e · A · e |[!0 t+'(t)]
3.2 Optical signal generation
6
Kanalkapazität nach Shannon
‣ Rb: Bitrate
Rb = RS · RC log2 M
‣ RS: Symbolrate
‣ normalerweise RS≤B bei Vermeidung von Symbolinterferenz
(Nyquist-Theor.)
‣ Rc: Redundanz
‣ Rc≤1, ohne Fehlerkorrektur Rc=1
‣ M: Anzahl der Symbolzustände (binär, quaternär,...)
Übertragungskapazität
‣ maximale Bitrate, die man übertragen kann
‣ Abhängig u.a. von:
‣ Leistung
‣ Bandbreite
CKanal = B · log10 (1 + SNR)
‣ Rauschen
‣ Modulationsformat
‣ Multiplexing
‣ Spektrale Effizienz
CKanal
ES =
⌫

bit
s · Hz
Beispiele für Modulationsformate
NRZ- vs.
for a RZ pulse with a reduced duty cycle ( <0.3) an
is an increased robustness to fiber nonlinearities cause
the wider ones, enabling a fast reduction of the pulse p
using OTDM-techniques [172]. The reduced pulse width
RZ-Spektrum
making this technique less interesting for the implemen
3.3 NRZ-based modulatio
e⇥ciency (>0.4 bit/s/Hz).
Figure 3.3: 40 Gb/s NRZ signal: a) optical spectrum
b)40
signal
and chirp
Figure 3.7:
Gb/sshape
RZ signal:
a) optica
RZ-Formate im Vergleich
NRZ
RZ33
RZ50
RZ67
3.4 RZ-based modulation fo
spectral width between the two first spectral side-bands amounts to 40 GHz. Compared to the RZ
RZofCSRZ
Duo-Binär
(DB)
3.6a)Carrier-Suppressed
a spectral reduction with a factor
2 occurs.und
The CSRZ
pulses possess
a RZ signal shape
ptical phase di⇥erence of between adjacent bits (Fig. 3.9b). This inter-pulse phase condition c
ficial for an increased nonlinear tolerance [178].
Figure 3.9: 40 Gb/s CSRZ signal: a) optical spectrum b) signal shape and chirp
Figure 3.5: 40 Gb/s duobinary signal: a)
JOURNAL OF LIGHTWAVE TECHNOLOGY, VOL. 17, NO. 10, OCTOBER 199
Ein- und Zwei-Seitenband-Modulation
JOURNAL OF LIGHTWAVE TECHNOLOGY, VOL. 17, NO. 10, OCTOBER 1999
Zwei-Seitenband (DSB)
(a)
(a)
Ein-Seitenband (SSB)
nsitivity versus MZ modulator bias angle for
Gb/s over 400 km at a BER of 10 9 .
D(B)PSK - DQPSK
halbe Symbolrate bei gleicher Bitrate
Konstellationsdiagramme
(u)
(u)
11
01
0
1
(u)
(u)
00
(D)PSK
10
(D)QPSK
Kohärenter Empfang
Iph
halbdurchlässiger Spiegel
Signal @
Etrans
Fotodiode
PD = | 0
1
Lokaloszillator @
ELO
Iph
0
1
|Etr ans + ELO |2
Iph / Etrans ELO exp(|!trans t + ')
1|
⇥0
Quadratur-Amplitudenmodulation: QAM
(u)
(u)
(u)
(u)
QAM16
QAM64
weitere Beispiele
Fig. 2. Modified design of the proposed 8QAM modulator.
TECHNOLOGY, VOL. 28, NO. 4, FEBRUARY 15, 2010
1. Schematic illustration of the proposed 8QAM modulator where the conation diagrams are based on simulation by assuming ideal modulators.
the coherent receiver, with a special emphasis on the proed cascaded multimodulus blind equalization algorithm.
Section IV, we describe experimental results employing
modulation and detection techniques described before,
luding the generation and intradyne detection of 114 Gb/s
M-RZ-8QAM signal and 32-Tb/s transmission over 580-km
-band EDFA-only optical
ULL SMF-28 fiber utilizing
plification. Finally, we present the conclusions in Section V.
II. HIGH-SPEED 8QAM MODULATOR DESIGN
have two potential problems when used in a real system. First,
the MZM2 inside the dual-parallel MZM is only driven with
0.7 V , and therefore, is less tolerant to the transmitter-side
band-limiting effects (limited electrical driver amplifier bandwidth and optical modulator electro/optic (E/O) response bandwidth) than the usual case with full 2 V drive. This is due to
the fact that the MZM has a nonlinear E/O response function
when biased at the null point, where V
given by
denotes the driving electrical voltage. Second, the common PM
will linearly transfer the amplitude jitter of the driving electrical
signal into phase jitter of the generated optical signal, making it
very sensitive to the transmitter-side band-limiting effects.
The two issues described before can be solved by a modification in the design, as shown in Fig. 2. In the modified design, the
required amplitude modulation imbalance between the upper
and the lower branches in the dual-parallel MZM is achieved
by introducing an extra 5.7 dB power attenuation in the lower
branch (or the higher branch). Note that this power attenuation
smitted and received WDM spectra on a 25-GHz grid after
8-QAM
16-QAM
smission. Upper right: Optimization of Raman gain and
n theory, PDM-8QAM can tolerate 1.5 dB more noise than
M-8PSK [1], [34] because it encodes the signal in all four
mensions of an optical carrier, and is probably the optimal
Überblick zu degradierenden Effekten
Rauschen
AM
p(E)
‣ zufällige Signalschwankungen
‣ Laserrauschen (Phasen,
MPN)
‣ spontane Emission (ASE)
PM
0
M
0
M
p(E)
‣ Quantenrauschen
‣ Empfängerrauschen
-M
‣ thermisches Rauschen
‣ Schrotrauschen
Rb,max = B · log2
PSignal
1+
PRauschen
⇥
Konstellationsdiagramme, Übertragungsqualität
Selbst- und Kreuzphasenmodulation: SPM und XPM
XPM
λ1
XPM
λ2
λ3
I
SPM
SPM
λ
Vierwellenmischung (Four-Wave Mixing, FWM)
λ1
λ2
mit
12 = 2 1
21 = 2 2
I
λ12
2
1
λ21
aber u. a. auch:
2121 = 21 + 2
FWM
FWM
λ
1
IXPM-IFWM
t
Anfang: Dacc=0
I-XPM
I-FWM
t
Mitte: Dacc>0
t
Ende: Dacc=0
Bitfehlerwahrscheinlichkeit
‣ Anzahl der falsch detektierten Bits im Vergleich zur
Gesamtanzahl der Bits:
!
NFehler
BER =
Ngesamt
‣ Bitfehlerrate hängt von der Signalqualität ab, u.a. vom
Rauschen:
!
PSignal
SNR =
PRauschen
‣ Im Optischen wird Rauschen vornehmlich durch das ASERauschen bestimmt. Wenn EDFAs in der Strecke sind,
dominiert ASE i.A.:
PSignal
PSignal
OSNR =
=
PASE
SASE · ⌫
Power-Budget
‣ Verluste
‣ Faser
‣ Stecker, Spleiße
‣ Variation, Alterung
Ptrans
Faserdämpfung
Steckerdämpfung
Spleiße
Dispersion
‣ Signalverschlechterung,
Verzerrung
‣ Margin
Verzerrungen
Margin
Pmin
Systemauslegung, Margins
‣ Empfängerempfindlichkeit
‣ minimale Leistung am Empfänger, damit Bitfehlerrate noch
eingehalten wird
‣ untere Grenze für Empfangsleistung
‣ Maximalleistung am Sender gegeben u.a. durch:
‣ Augensicherheit
‣ Nichtlinearitäten
‣ Differenz ergibt das Budget
Zusammenfassung
‣ Aufbau einer optischen Übertragungsstrecke
‣ Multiplextechniken
‣ Zeitmultiplex, Wellenlängenmultiplex
‣ Modulationsformate
‣ vor allem: Amplituden- und Phasenmodulation
‣ degradierende Effekte
‣ Systemparameter