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Simulation and ExperimentalStudy of SCM/WDM Optical
Systems
Renxiang HuangUniversity of Kansas
May 23, 2001
OutlineOutline
Introduction to SCM technologyIntroduction to SCM technology Demand for more bandwidthDemand for more bandwidth
TDM,WDM strategiesTDM,WDM strategies
SCM and WDM combinationSCM and WDM combination
Numerical simulation modelNumerical simulation model Goals and general requirementsGoals and general requirements
Description of the simulation modelDescription of the simulation model Transmitter Optical fiber nonlinear model Receiver
OutlineOutline
Simulation results BPSK, 4-subcarrier each with 2.5Gb/s datarate, self-coherent
detection QPSK, 2-subcarrier each with 2x2.5Gb/s datarate, self-
coherent detection ASK, 4-subcarriers each with 2.5Gb/s datarate, direct
detection using narrowband optical filter Traditional NRZ modulated OC192 system
Experiment
Conclusions and future work
Introduction: Introduction: Demand for more BandwidthDemand for more Bandwidth
Faster Internet access High speed data transmission Video Conferencing High resolution image transmission Other new services
More fiber everywhereMore fiber everywhere
Higher data-rate each wavelength----------TDMHigher data-rate each wavelength----------TDM
More wavelengths in the fiber--------------- WDMMore wavelengths in the fiber--------------- WDM
Introduction: TDM,WDM strategiesIntroduction: TDM,WDM strategies
TDM strategyTDM strategy Simple modulation format: IMDD binary systemSimple modulation format: IMDD binary system
Short bit length, more bits in unit timeShort bit length, more bits in unit time
Electrical TDM and optical TDM, Electrical TDM and optical TDM, solitonsoliton
Grooming may be a big problemGrooming may be a big problem
Difficult in transmission through fiber: chromatic dispersion,Difficult in transmission through fiber: chromatic dispersion,PMD, fiber nonlinearityPMD, fiber nonlinearity
Does not scale well beyond OC192Does not scale well beyond OC192
Introduction: TDM,WDM strategiesIntroduction: TDM,WDM strategies
WDM strategyWDM strategy Multiple wavelengths in a single fiberMultiple wavelengths in a single fiber
Better utilization of optical fiber transmission windowBetter utilization of optical fiber transmission window
Lower Lower bitratebitrate & lower power per wavelength & lower power per wavelength
From CWDM to DWDM: increase bandwidth efficiencyFrom CWDM to DWDM: increase bandwidth efficiencyexample:example:2.5Gb/s per-channel data rate and 50GHz channel spacing, the
bandwidth efficiency is 0.05 bit/Hz.
Technical difficulties: Technical difficulties: lightwavelightwave sources, optical filters, sources, optical filters,dispersion management, dispersion management, nonliearnonliear crosstalkcrosstalk, …., ….
Introduction: SCM/WDM and OSSBIntroduction: SCM/WDM and OSSB
SCM leverages mature microwave technologySCM leverages mature microwave technology
Two-step modulation: RF modulation at sub-carriers, opticalTwo-step modulation: RF modulation at sub-carriers, opticalmodulation at wavelengths.modulation at wavelengths.
OSSB is preferred: less dispersion penalty, higher bandwidthOSSB is preferred: less dispersion penalty, higher bandwidthefficiencyefficiency
fOf 3- f 2 - f 1 - f 4+f 3+f 2+f 1+f 4-
a. O ptical DSB SCM
b. O ptical SSB SCM
fO f 4+f 3+f 2+f 1+
op tic a l d e tec tionus ing filte r
Introduction: SCM/WDM and OSSBIntroduction: SCM/WDM and OSSB
SCM/WDM combinationSCM/WDM combination Large number of channels, low channel speed, easy groomingLarge number of channels, low channel speed, easy grooming
and scaling, lower dispersion penaltyand scaling, lower dispersion penalty
Advanced modulation format, phase modulation possibleAdvanced modulation format, phase modulation possible
NonliearityNonliearity-introduced distortion-introduced distortion
b. W DM
a. W DM/SCM
f 4+f 3+f 2+f 1+
1λ 2λ
1λ 2λ
An exemplary setup of SCM/WDM systemAn exemplary setup of SCM/WDM system
λm
λ1
f1
Σ
f2ch.2
fn
ch.n
.
.
Receiver
ch.1
Opt
ica
l WD
M M
UX
Opt
ica
l WD
M D
MU
XAdd/drop
f1
Σ
f2
ch.2
fn
ch.n
.
.
Receiver
ch.1
Transmitterf1
Σ
f2
ch.2
fn
ch.n
.
.
λ1ch.1
Transmitterf1
Σ
f2ch.2
fn
ch.n
.
.
λm
ch.1
50GHz
λ1 λ2 λ3 λ4λ
5GHz
Numerical model for SCM/WDM systemsNumerical model for SCM/WDM systems
Goals and general requirementsGoals and general requirements To be able to handle different types ofTo be able to handle different types of multi multi-wavelength-wavelength
SCM/WDM systemsSCM/WDM systems
Include both dispersion and fiber Include both dispersion and fiber nonlinearitynonlinearity
To be able to handle a variety of modulation formats, OSSB,To be able to handle a variety of modulation formats, OSSB,ASK, BPSK, QPSK and binary IMDDASK, BPSK, QPSK and binary IMDD
Combine Combine waveform waveform distortion and noise: distortion and noise: sensitivitysensitivity
Transmitter simulation model
C hanne l 4 da ta2 .488G b it/s
C hanne l 4 R Fosc illa to r
(17 .5G Hz)
C hanne l 1 da ta2 .488G b it/s
C hanne l 1 R Fosc illa to r(3 .6 G Hz)
channe l 3 (13G Hz)
channe l 2 (8 .3G Hz)
T ransmitter fiilte r
T ransmitter filte r
S C M T ra nsm itter B lock D ia gram
RFmu ltip lexer
M Z m odu la tor
90degreephase shift
B ias
LDPower
amplifie rW D M coup le r
f ro m o ther laser sourses
tof iber
27-1 PRBS Random relative delay between different sub-carriers
and wavelengths 6-order Butterworth filter for band-limiting 64 to 256 samples per bit depending on the required
simulation bandwidth
Baseband signal generation
Baseband signal generation
2 0 0 4 0 0 6 0 0 8 0 0 1 0 0 0 1 2 0 0 1 4 0 0 1 6 0 0 1 8 0 0
0
5 0 0
1 0 0 0
1 5 0 0
2 0 0 0
2 5 0 0
3 0 0 0
3 5 0 0
4 0 0 0C h a n n e l N u m b e r = 1 C h a n n e l W a v e le n g t h = 1 5 5 0 n mN u m b e r o f s a m p l e s / b i t = 6 4
(a)eyediagram of baseband signal after the electrical filter
0 0 . 5 1 1 . 5 2 2 . 5 3 3 . 5 4 4 . 5 5
x 1 04
- 2 0 0 0
- 1 0 0 0
0
1 0 0 0
2 0 0 0
3 0 0 0
4 0 0 0
I c h a n n e l T R A N S M I T F I L T E R O U T P U T P U L S E - - > I N T E N S I T Y a f t e r f i l t e r i n g
Pu
lse
in
te
ns
ity
(
mw
)
T i m e ( p s )
C h a n n e l N u m b e r = 1 B i t R a t e = 2 . 4 8 G b / sC h a n n e l W a v e l e n g t h = 1 5 5 0 n mC a r r i e r f r e q u e n c y = 2 . 6 G H z
- 6 - 4 - 2 0 2 4 6 8- 3 0
- 2 5
- 2 0
- 1 5
- 1 0
- 5
0
5
1 0
•Signal eyediagram
•Signal waveform
•Baseband Spectrum
)sin()()cos()()( tnTtfyAtnTtfxAts csnccsnc ωω ∑∑∞
∞−
∞
∞−
−−−=
cA peak signal value
nx and ny information bits (0, 1 or -1)
)(tf normalized baseband bit shape function
cω subcarrier frequency
ASK: BPSK: QPSK:0or 1=nx 1-or 1=nx 1-or 1=nx
0=ny 0=ny 1-or 1=ny
If f(t) represents a rectangular bit shape , the PSD of the complex envelope of MPSK is
))sin(
()(2
S
SSc
fT
fTTAfP
ππ
= , where ST is the symbol time.
The 3dB bandwidth of BPSK and QPSK are both 0.88R if they have the same symbolrate R. Each symbol in QPSK represents 2 bits, so the spectrum efficiency is doubled.
Sub-carrier generation
4-subcarrier BPSK composite signal4-subcarrier BPSK composite signal
0 . 5 1 1 . 5 2 2 . 5 3 3 . 5 4 4 . 5 5
x 1 04
- 5 0 0 0
- 4 0 0 0
- 3 0 0 0
- 2 0 0 0
- 1 0 0 0
0
1 0 0 0
2 0 0 0
3 0 0 0
4 0 0 0
5 0 0 0
T R A N S M I T F IL T E R O U T P U T P U L S E - - > IN T E N S IT Y a f t e r c o m b i n e r
Pu
lse
in
te
ns
ity
(
mw
)
T i m e ( p s )
- 3 0 - 2 0 - 1 0 0 1 0 2 0 3 0
- 4 5
- 4 0
- 3 5
- 3 0
- 2 5
- 2 0
- 1 5
- 1 0
- 5
0
5
T R A N S M I T F I L T E R T O T A L S P E C T R A L I N T E N S I T Y
Pu
lse
in
te
ns
ity
(
mw
)
F r e q u e n c y ( G H z )
h a n n e l N u m b e r = 4
i t R a t e = 2 . 4 8 G b / s
h a n n e l W a v e l e n g t h = 1 5 5 0 n m
Waveform
Spectrum
0oAC
90o
AC
DC90o
Hyb
rid
Microwavesignal Bias
Ligh
twav
ein
Ligh
twav
eou
t
Dual-drive MZ modulator and OSSB signal generationImplementation
Dual-drive MZ modulator and OSSB signal generationTheory
Modulator output )](cos[)](cos[2
)( 21 ttttA
tE ooo φωφω +−+=
1φ , 2
φ phase delay of the two arms
Set tt Ω+= cos)(1βπγπφ and )cos()(2
θβπφ +Ω= tt ,
π
γV
Vdc= DC bias of one arm,
π
βV
Vac ||= optical modulation index.
When 21=γ , and
2
πθ = ,
)......(2)cos()(2)]cos())[sin((2
)( 210 βπωβπωωβπ JtJttJE
tE oooi
o +Ω−++−=
OSSB Spectrum
Nonlinear distortion of unlinearized modulator Generate CTB but no CSO
CTB is proportional to the square of modulation index
- 4 0 - 3 0 - 2 0 - 1 0 0 1 0 2 0 3 0 4 0 5 0
- 9 0
- 8 0
- 7 0
- 6 0
- 5 0
- 4 0
- 3 0
- 2 0
- 1 0
0
T R A N S M I T F I L T E R T O T A L S P E C T R A L I N T E N S I T Y b e f o r e F P
Pu
lse
in
te
ns
ity
(
mw
)
F r e q u e n c y ( G H z )
N u m b e r = 4
= 2 . 4 8 G b / s
W a v e l e n g t h = 1 5 5 0 n m
0 2 4 6 8 1 0 1 2 1 4- 1 0 0
- 8 0
- 6 0
- 4 0
- 2 0
0
2 0
4 0
0 2 4 6 8 1 0 1 2 1 4 1 6- 1 0 0
- 8 0
- 6 0
- 4 0
- 2 0
0
2 0
Carrier suppression
Increase modulation efficiency Reduce modulator-induced nonlinearity
FPI
Biascontrol
FPI reflection FPI transmission
Signal in
Signal out
Carrier suppression
0.5 1 1.5 2 2.5 3 3.5 4 4.5 5
x 104
0
500
1000
1500
2000
2500
3000
3500
4000
TRANSMIT FILTER OUTPUT PULSE --> INTENSITY before FP
Pu
lse
inte
ns
ity (
mw
)
Time (ps )
-40 -30 -20 -10 0 10 20 30 40
-90
-80
-70
-60
-50
-40
-30
-20
-10
0
TRANSMIT FILTER TOTAL SPECTRAL INTENSITY before FP
Pu
lse
inte
ns
ity (
mw
)
Frequency (GHz)
th=1550 nm
-80 -60 -40 -20 0 20 40 60 80-6
-5
-4
-3
-2
-1
0
-40 -30 -20 -10 0 10 20 30 40
-90
-80
-70
-60
-50
-40
-30
-20
-10
0
TRANSMIT FILTER TOTAL SPECTRAL INTENSITY after FP
Pu
lse
inte
ns
ity (
mw
)
Frequency (GHz)
ber=4 Gb/s
elength=1550 nm
Before carrier suppression FP filter After carrier suppression
0.5 1 1.5 2 2.5 3 3.5 4 4.5 5
x 104
0
200
400
600
800
1000
1200
1400
1600
1800
TRANSMIT FILTER OUTPUT PULSE --> INTENSITY after FP
Pu
lse
inte
ns
ity (
mw
)
Time (ps )
amplitude
waveform
Optical fiber simulation model
Standard s ingle mode fiberInline amp lifie r
(ED FA )Standard s ingle mode fiber
Inline amp lifie r(ED FA )
Standard s ingle mode fiberPreamplifie r
(ED FA )
Standard s ingle mode fiberInline amp lifie r
(ED FA )
Standard s ingle mode fiberPreamplifie r
(ED FA )
F iber pa th w ithou td ispersion compensa tion
F iber pa th w ith d ispersioncompen sa tion
D ispers ionC ompensa tion
(fiber o r gra ting)
D ispers ionC ompensa tion
(fiber o r gra ting)
Optical fiber simulation model
Span length ranges from 40 to 80 km. 3 dB loss margin reserved foreach span (If the dispersion compensation is implemented, the additional loss is 6dB)
Attenuation of each span is compensated by optical amplification.
Neglect nonlinearity of Dispersion Compensator
SMF parameter: α=0.25 dB/km, n2=2.36e-20, Aeff = 71um2 , D= 18ps/nm/km. Dispersion slope 0.093 ps/nm^2/km. PMD coefficient 0.1 or0.5ps/sqrt(km) .
Solve Nonlinear Schrodinger Equations, neglect SRS and SBS.
Using Split-step Fourier method.
Optical fiber simulation model
- 2 0 - 1 0 0 1 0 2 0 3 0 4 0- 1 0 0
- 9 0
- 8 0
- 7 0
- 6 0
- 5 0
- 4 0
- 3 0
- 2 0
- 1 0
0
(a) spectrum before the optical fiber
- 4 0 - 3 0 - 2 0 - 1 0 0 1 0 2 0 3 0 4 0 5 0- 1 0 0
- 9 0
- 8 0
- 7 0
- 6 0
- 5 0
- 4 0
- 3 0
- 2 0
- 1 0
0
(b) optical spectrum a fter 80 km fiber tra nsmission
Figure 2.12 op tical spectrum before and a fter 80 km fiber transm ission, optical
pow er is 3 dB m
Simulation model for receiverSimulation model for receiver
RF coupleropticaldetector
PreamplifierEDFA
Channel 1 RFossilator(3.6GHz)
LPF
LPF
Q calculation
Q calculation
Sychronization
Sychronization
Channel 4 RFossilator
(17.5GHz)
WDMDemultiplexer
WDM demultiplexer: 6th-order Butterworth filter, 30GHzbandwidth.
EDFA preamplifier: fixed output 1dBm total
Analytic formula to calculate ASE noise
Photo-detection: square-law operation + low-pass filter.
- 3 0 - 2 0 - 1 0 0 1 0 2 0
- 1 0 0
- 9 0
- 8 0
- 7 0
- 6 0
- 5 0
- 4 0
- 3 0
Simulation model for receiverSimulation model for receiver
High pass filter: reduce DC component after O/E conversion Carrier recovery: Mth Power loop for MPSK carrier recovery
Input: )2cos()( θθπ ++= kctfAts , for SS TktkT )1( +≤≤ , ST symbol time
MM
MMMk
ππππθ 2)1(,.....,
23,
22,
2,0 −=
θ : phase delay due to the transmission and transmitter bias
Select the first term using a bandpass filter, divide the frequency by M
)2cos()( θπ += tfKtC c
Simulation model for receiverSimulation model for receiver
)( =tsM )2cos( ++ θπ MtMfA cM higher order harmonics
Bandpass filter
CompositeRF signal
mixer narrow band filter
Select 2nd order harmonic
frequencydidvider recovered
subcarrier
(a) (b)(d)(c) (e)
Channel selection
2nd power loop for BPSK carrier recoveryAn example
0.5 1 1.5 2 2.5 3 3.5 4
x 10-9
-8
-6
-4
-2
0
2
4
(a)
(c)
(b)
(d)
(e)
DemodulationDemodulation
-8 -6 -4 -2 0 2 4 6
-6 0
-5 0
-4 0
-3 0
-2 0
-1 0
0
0 . 5 1 1 .5 2 2 .5 3 3 .5 4 4 .5 5
x 1 04
-0 .0 8
-0 .0 6
-0 .0 4
-0 .0 2
0
0 .0 2
0 .0 4
0 .0 6
0 .0 8
0 . 1C ha n ne l W a ve le ng th 1 5 5 0 n mC a rrie r fre q u e nc y=3 .6 0 3 8 G Hz
2 0 0 4 0 0 6 0 0 8 0 0 1 0 0 0 1 2 0 0 1 4 0 0 1 6 0 0 1 8 0 0
0
0 .0 2
0 .0 4
0 .0 6
0 .0 8
0 . 1
0 .1 2
Spectrum Waveform Eyediagram
Mixer output
Baseband filter output
-4 -3 -2 -1 0 1 2 3 4-1 2 0
-1 1 0
-1 0 0
-9 0
-8 0
-7 0
-6 0
0 . 5 1 1 . 5 2 2 .5 3 3 .5 4 4 .5 5
x 1 04
0
0 .0 2
0 .0 4
0 .0 6
0 .0 8
0 . 1
0 .1 2
2 0 0 4 0 0 6 0 0 8 0 0 1 0 0 0 1 2 0 0 1 4 0 0 1 6 0 0 1 8 0 0
0
0 .0 2
0 .0 4
0 .0 6
0 .0 8
0 . 1
0 .1 2
Waveform EyediagramSpectrum
PMD-induced polarization walk-offPMD-induced polarization walk-off between carrier and sub-carriersbetween carrier and sub-carriers
ωθτ
∆∆=∆
τ∆ DGD in seconds,
θ∆ relative wave vector rotation in radians ω∆ optical frequency change that produced the rotation, in radians/seconds
Consequence: Decrease the beating efficiency between carrier and sub-carriers by cos( ∆θ )
PMD definition:
PMD-induced PMD-induced waveform waveform distortiondistortion• In a Gaussian pulse IMDD system, the limitation from PMD is estimated by
22
)(
020.0
DGD LB ≈
• For SCM system, assume the pulse width is the period of the sinusoid sub-carriers at 12GHz or 18GHz
• With DGD of 0.5 kmps/
L = 240km and 550km for 12GHz and 18GHz sub-carriers
B: data rate, L: maximum transmission distance
• With DGD of 0.1 kmps/
L = 6000km and 13000km for 12GHz and 18GHz sub-carriers
DGD (ps/sqrt(km))
0 .1 0 .1 5 0 .2 0 .2 5 0 .3 0 .3 5 0 . 4 0 .4 5 0 . 5
2 0 0 0
4 0 0 0
6 0 0 0
8 0 0 0
1 0 0 0 0
1 2 0 0 0
L(k
m)
Analytic estimation of receiver sensitivityAnalytic estimation of receiver sensitivity
Approximations: All noises considered additive with Gaussian statistics
Signal-ASE beat noise dominant
5dB EDFA noise figure
Neglect waveform distortion
Linear approximation for MZ modulator
Calculated receiver sensitivity -31dBm for 4-subcarrier BPSK, 10Gb/s total capacity
-34dBm for 2-subcarrier QPSK , 10Gb/s total capacity
-46dBm for single channel IMDD OC48, 2.5Gb/s capacity
-40dBm for single channel IMDD OC192, 10Gb/s capacity
4-subcarrier BPSK, self-coherent detection(2.5Gb/s per sub-carrier,10Gb/s total capacity)
0 .2 0 .3 0 .4 0 .5 0 .6 0 .7 0 .8 0 .9 1-3 2
-3 0
-2 8
-2 6
-2 4
-2 2
-2 0
-1 8
Bandwidth/datarate
Sen
sitiv
ity (
dBm
)Optimal receiver bandwidth 0.7 ξ datarate
4-subcarrier BPSK, self-coherent detection(2.5Gb/s per sub-carrier,10Gb/s total capacity)
RF channel spacing should be larger than 4.2 GHz
2.5 3 3.5 4 4.5 5
x 109
-32
-30
-28
-26
-24
-22
-20
-18
-16
-14
-12
RF channel spacing (Hz)
Sen
sitiv
ity (
dBm
)
4-subcarrier BPSK, self-coherent detection(2.5Gb/s per sub-carrier,10Gb/s total capacity)
Lowest frequency sub-carrier should be larger than 2.6 GHz
1.6 1.8 2 2.2 2.4 2.6 2.8 3 3.2 3.4 3.6 3.8
x 109
-30
-25
-20
-15
-10
-5
0
5
10
Subcarrier 1 Frequency(Hz)
Rec
eive
r S
ensi
tivity
(dB
m)
480km
560km
640km
Carrier suppression can improve the sensitivity on a roughly dB-per-dB base
4-subcarrier BPSK, self-coherent detection(2.5Gb/s per sub-carrier,10Gb/s total capacity)
0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45 0.5-32
-30
-28
-26
-24
-22
-20
-18
-16
-14
-12
OMI
Sen
sitiv
ity (
dBm
)
No suppression
with 5dB suppression
4-subcarrier BPSK, self-coherent detection(2.5Gb/s per sub-carrier,10Gb/s total capacity)
-30 -25 -20 -15 -10 -5 0-35
-30
-25
-20
-15
-10
Suppression ratio (dB)
Sen
sitiv
ity (
dB
m)
0 km
-30 -25 -20 -15 -10 -5 0-28
-26
-24
-22
-20
-18
-16
-14
Suppression ratio (dB)
Sen
sitiv
ity (
dB
m)
420 km
-25 -20 -15 -10 -5 0-25
-20
-15
-10
Suppression ratio (dB)
Sen
sitiv
ity (
dB
m)
500 km
increase OMI increase OMI
increase OMI
4 BPSK subcarrier SCM system resultsPMD
km
ps
DC OMI OP
dBm
RFMI Freq1 L:
1
wavelength
L:
4
wavelength
0.1ps Yes 0.3 5 0.9 0.9 1.15 1.35 2.6 920 450
0.1ps yes 0.4 5 0.9 0.9 1.15 1.35 2.6 680 300
0.1ps yes 0.3 3 0.9 0.9 1.15 1.35 2.6 640 350
0.1ps yes 0.4 3 0.9 0.9 1.15 1.35 2.6 520 400
0.1ps yes 0.3 0 0.9 0.9 1.15 1.35 2.6 350
0.1ps yes 0.4 0 0.9 0.9 1.15 1.35 2.6 250
0.1ps yes 0.3 -3 0.9 0.9 1.15 1.35 2.6 250
0.1ps yes 0.4 -3 0.9 0.9 1.15 1.35 2.6 200
0.1ps no 0.3 5 1.12 1.05 1.05 0.9 2.6 600 200
0.1ps no 0.4 5 1.12 1.05 1.05 0.9 2.6 600 200
0.1ps no 0.3 3 1.12 1.05 1.05 0.9 2.6 560 250
0.1ps no 0.4 3 1.12 1.05 1.05 0.9 2.6 400 250
0.1ps no 0.3 0 1.12 1.05 1.05 0.9 2.6 350
0.1ps no 0.4 0 1.12 1.05 1.05 0.9 2.6 350
0.1ps no 0.3 -3 1.12 1.05 1.05 0.9 2.6 350
0.1ps no 0.4 -3 1.12 1.05 1.05 0.9 2.6 250
4 BPSK subcarrier SCM system resultsPMD
km
ps
DC OMI OP
dBm
RFMI Freq1 L:
1
wavelength
L:
4
wavelength
0.5ps yes 0.3 5 0.9 0.9 1.15 1.35 2.6 440 350
0.5ps yes 0.4 5 0.9 0.9 1.15 1.35 2.6 360 350
0.5ps yes 0.3 3 0.9 0.9 1.15 1.35 2.6 360 350
0.5ps yes 0.4 3 0.9 0.9 1.15 1.35 2.6 280 350
0.5ps yes 0.3 0 0.9 0.9 1.15 1.35 2.6 250
0.5ps yes 0.4 0 0.9 0.9 1.15 1.35 2.6 250
0.5ps yes 0.3 -3 0.9 0.9 1.15 1.35 2.6 250
0.5ps yes 0.4 -3 0.9 0.9 1.15 1.35 2.6 150
0.5ps no 0.3 5 1.12 1.05 1.05 0.9 2.6 500 200
0.5ps no 0.4 5 1.12 1.05 1.05 0.9 2.6 440 200
0.5ps No 0.3 3 1.12 1.05 1.05 0.9 2.6 440 250
0.5ps No 0.4 3 1.12 1.05 1.05 0.9 2.6 360 250
0.5ps No 0.3 0 1.12 1.05 1.05 0.9 2.6 300
0.5ps No 0.4 0 1.12 1.05 1.05 0.9 2.6 250
0.5ps No 0.3 -3 1.12 1.05 1.05 0.9 2.6 250
0.5ps No 0.4 -3 1.12 1.05 1.05 0.9 2.6 200
2-subcarrier QPSK, self-coherent detection(5Gb/s per sub-carrier,10Gb/s total capacity)
-60 -40 -20 0 20 40 60
-140
-120
-100
-80
-60
-40
-20
0Channel Number=2 Bit Rate=2.48 Gb/sChannel Wave length=1550 nm
200 400 600 800 1000 1200 1400 1600 1800
0
0.05
0.1
0.15
0.2
0.25
0.3 Channel Number=2 Channel Wavelength=1000000000 nmNumber of samples /bit=64
Optical spectrum Eye diagram
PMD DC OMI OP(dBm) RFMI Freq1 L
0.1ps Yes 0.3 5 1 1 4 1100
0.1ps Yes 0.4 5 1 1 4 950
0.1ps Yes 0.3 3 1 1 4 1200
0.1ps Yes 0.4 3 1 1 4 900
0.1ps Yes 0.3 0 1 1 4 750
0.1ps Yes 0.4 0 1 1 4 550
0.1ps Yes 0.3 -3 1 1 4 500
0.1ps Yes 0.4 -3 1 1 4 350
0.1ps No 0.3 5 1 1 4 400
0.1ps No 0.4 5 1 1 4 400
0.1ps No 0.3 3 1 1 4 450
0.1ps No 0.4 3 1 1 4 450
0.1ps No 0.3 0 1 1 4 250
0.1ps No 0.4 0 1 1 4 250
0.1ps No 0.3 -3 1 1 4 250
0.1ps No 0.4 -3 1 1 4 250
2-subcarrier QPSK, self-coherent detection(5Gb/s per sub-carrier,10Gb/s total capacity)
PMD DC OMI OP(dBm) RFMI Freq1 L
0.5ps Yes 0.3 5 1 1 4 750
0.5ps Yes 0.4 5 1 1 4 650
0.5ps yes 0.3 3 1 1 4 700
0.5ps yes 0.4 3 1 1 4 500
0.5ps yes 0.3 0 1 1 4 500
0.5ps yes 0.4 0 1 1 4 350
0.5ps yes 0.3 -3 1 1 4 350
0.5ps yes 0.4 -3 1 1 4 250
0.5ps no 0.3 5 1 1 4 400
0.5ps no 0.4 5 1 1 4 400
0.5ps no 0.3 3 1 1 4 450
0.5ps no 0.4 3 1 1 4 450
0.5ps no 0.3 0 1 1 4 250
0.5ps no 0.4 0 1 1 4 250
0.5ps no 0.3 -3 1 1 4 250
0.5ps no 0.4 -3 1 1 4 250
2-subcarrier QPSK, self-coherent detection(5Gb/s per sub-carrier,10Gb/s total capacity)
SCM system, direct-detectionUsin g narrow-band optical filters
PreamplifierEDFA
WDMDemultiplexer
Narrowbandoptical filter
photodiodeNarrowbandoptical filter
Narrowbandoptical filter
Narrowbandoptical filter
photodiode
photodiode
photodiode
LPF Bit synchronization Q
LPF Bit synchronization Q
LPF Bit synchronization Q
LPF Bit synchronization Q
SCM system, direct-detectionUsin g narrow-band optical filters
-2 0 -1 0 0 1 0 2 0 3 0
-6 0
-5 0
-4 0
-3 0
-2 0
-1 0
0
2 0 0 4 0 0 6 0 0 8 0 0 1 0 0 0 1 2 0 0 1 4 0 0 1 6 0 0 1 8 0 0-0 .1
-0 .0 5
0
0 .0 5
0 .1
0 .1 5
0 .2
0 .2 5
0 .3
0 .3 5
0 .4C ha nne l Num b e r=4 C ha nne l W a ve le ng th=1 0 0 0 0 0 0 0 0 0 nmNum b e r o f s a m p le s /b it=6 4
After narrowbandoptical filter
-15 -10 -5 0 5 10 15 20-70
-60
-50
-40
-30
-20
-10
200 400 600 800 1000 1200 1400 1600 1800
0
0.1
0.2
0.3
0.4
0.5
Before baseband filter
after baseband filter
Impact of optical filter bandwidth
1 1 .5 2 2 .5 3 3 .5 4 4 .5 5-3 4
-3 3
-3 2
-3 1
-3 0
-2 9
-2 8
Optical filter bandwidth (GHz)
Rec
eiv
er s
ens
itivi
ty (
dBm
)
SCM system, direct-detectionUsin g narrow-band optical filters
0 200 400 600 800 1000 1200-35
-30
-25
-20
-15
-10
-5
0
5
10
Rec
eive
r S
ensi
tivity
(dB
)
Fiber Length(km)-45 -40 -35 -30 -25 -20 -15 -10
-35
-30
-25
-20
-15
-10
-5
Rec
eive
r S
ensi
tivity
(dB
)
Carrier Suppression(dB)
increase OMI P=-3dBm0dBm
5dBm3dBm
DC OMI OP RFMI L
Yes 0.3 3 1 1 1 1 50
Yes 0.3 0 1 1 1 1 200
Yes 0.3 -3 1 1 1 1 250
Yes 0.3 -6 1 1 1 1 250
No 0.3 3 1 1 1 1 250
No 0.3 0 1 1 1 1 550
no 0.3 -3 1 1 1 1 500
No 0.3 -6 1 1 1 1 350
Maximum transmission distancedirect-detected SCM system
OC192 TDM system using NRZ modulation
DC OMI OP (dBm) Length (km)
Yes 0.5 3 950
Yes 0.5 0 1100
Yes 0.5 -3 800
Yes 0.5 -6 500
No 0.5 3 100
No 0.5 0 100
No 0.5 -3 100
No 0.5 -6 100
Experiments for one wavelength foursubcarriers BPSK SCM system
3 .6 G Hz
a m p lifie r
F ib er
D etecto rP re-a m p
Pow
erco
mbi
n
D atagenerato r
8 .3 G Hz
17 .5G H z
L P F
L P F
E D F AP re-a m p .
S co p e
13 GH zP
ower
Spl
itter
2 .4 88G b /s
B E Rtester
L P F
L P F
3.6 G Hz
8 .3 G Hz
13 GH z
17 .5G H z
Pow
er S
plitt
erE D F A
P o st-a m p
00
900
L a ser
D C B ias
OSSB
Nor
mal
ized
Opt
ical
spe
ctra
l den
sity
(dB
)
Frequency ( GHz)-50 -40 -30 -20 -10 0 10 20 30 40
-35
-30
-25
-20
-15
-10
-5
0
Detected composite signal RF spectrumDetected composite signal RF spectrum
-55
-50
-45
-40
-35
-30
-25
-20
0 2 4 6 8 10 12 14 16 18 20 22
F requen cy (G H z)
Inte
nsi
ty (d
Bm
)
Measured eye diagramsback-to-back and over 75km SMF
fc=8.3GHz, back-to-back, P=-23.5 dBmfc=8.3GHz, over fiber, P =-23 dBm
fc=3.6GHz, over fiber, P =-22.6 dBmfc=3.6GHz, back-to-back, P =-24.9 dBm
fc=13GHz, back-to-back, P =-27.6 dBmfc=13GHz, over fiber, P =-24 dBm
fc=17.5GHz, over fiber, P =-21.5 dBmfc=17.5GHz, back-to-back, P =-22.7 dBm
-34 -32 -30 -28 -26 -24 -2210-10
10-9
10-8
10-7
10-6
10-5
10-4
10-3Channel #1 ( fc = 3.6GHz)
* back/backo over 75km SMF
-36 -34 -32 -30 -28 -26 -2410-10
10-9
10-8
10-7
10-6
10-5
10-4
10-3Channel #2 ( fc = 8.3GHz)
* back/backo over 75km SMF
-36 -34 -32 -30 -28 -26 -2410-10
10-9
10-8
10-7
10-6
10-5
10-4
10-3 Channel #3 ( fc = 13GHz)
* back/backo over 75km SMF
-34 -32 -30 -28 -26 -24 -2210-10
10-9
10-8
10-7
10-6
10-5
10-4
10-3 Channel #4 ( fc = 17.5GHz)
* back/backo over 75km SMF
BE
R
Optical power ( dBm)
BE
R
BE
RB
ER
Optical power ( dBm)
Optical power ( dBm) Optical power ( dBm)
Measured BERback-to-back (stars) and over 75km SMF (circles)
Effects of carrierEffects of carrier suppresion suppresion
-39
-37
-35
-33
-31
-29
0 2 4 6 8R F p o w er to m o du la to r (dB m )
Re
ceiv
ed s
ens
itivi
ty (dB
m)
n o carr ie r suppression
w ith carr ier su ppression
Effect of channel spacingEffect of channel spacing
-35
-34
-33
-32
-31
-30
-29
-28
-27
-26
4.4 4.6 4.8 5 5.2 5.4 5.6 5.8
FR channel separation (GHz)
Rec
eive
r se
nsiti
vity
(dB
m)
Comparison between SCM and TDMComparison between SCM and TDM
-35
-30
-25
-20
-15
-10
-5
SM F Equ iva len t F ib er Length ( km)R
ecei
ver
sen
siti
vity
(dB
m)
TD M
S C M
0 20 40 60 80 100 120 140 160 180 200
3 4 0 6 8 0 1 0 2 0 1 3 6 0 1 7 0 0 2 0 4 0 2 3 8 0 2 7 2 0 3 0 6 0 3 4 0 00
A ccum u la ted d ispersion (ps/n m)
Conclusion remarks
Built a simulator for SCM/WDM systemsBuilt a simulator for SCM/WDM systems
Simulated multi-wavelength SCM systems: 4-subcarrier BPSK, 2-subcarrier QPSK and 4-subcarrier ASK
Optimized system parameters
BPSK format is recommended for 300km to 350 km transmissionwithout dispersion compensation.
QPSK format is recommended for up to 750 km transmission withdispersion compensation and 450km without dispersion compensation.
ASK system is not recommended because of the stringent requirementof optical filters.
Experimentally measured the performance of single-wavelength 4-Experimentally measured the performance of single-wavelength 4-subcarriersubcarrier BPSK system BPSK system
Furture work
MultiMulti-wavelength SCM test bed-wavelength SCM test bed
Experimental investigation of QPSK and M-Experimental investigation of QPSK and M-aryary
Impact ofImpact of Raman Raman amplification on SCM systems amplification on SCM systems
Single-Single-sideband sideband RF modulationRF modulation
Detailed PMD analysisDetailed PMD analysis
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