Simulation and Experimental Study of SCM/WDM Optical Systems · Introduction: TDM,WDM strategies TDM strategy Simple modulation format: IMDD binary system Short bit length, more bits

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)


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.


- 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


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


)( =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


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

)


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


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


-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


Sen

sitiv

ity (

dB

m)

420 km

-25 -20 -15 -10 -5 0-25

-20

-15

-10


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


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


SCM system, direct-detectionUsin g narrow-band optical filters

PreamplifierEDFA

WDMDemultiplexer

Narrowbandoptical filter

photodiodeNarrowbandoptical filter



photodiode

photodiode

photodiode

LPF Bit synchronization Q





-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

)


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)


-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)


-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)


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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Documents

Simulation and Experimental Study of SCM/WDM Optical Systems · Introduction: TDM,WDM strategies TDM strategy Simple modulation format: IMDD binary system Short bit length, more bits