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Generation and processing Generation and processing of UWB Signals over fiberof UWB Signals over fiber
Béatrice CabonBéatrice CabonIMEP
Institut de Microélectronique Electomagnétisme et Photonique
INPG-MINATEC, Grenoble, France
Jianping YaoJianping YaoMicrowave Photonics Research Laboratory
School of Information Technology and Engineering University of Ottawa, Canada
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1.1. Introduction to UWBIntroduction to UWB
2.2. Photonic generation of UWB pulsesPhotonic generation of UWB pulses1)1) Based on phase modulation to intensity Based on phase modulation to intensity
modulation (PM-IM) conversionmodulation (PM-IM) conversion
2)2) Based on a semiconductor optical amplifier (SOA)Based on a semiconductor optical amplifier (SOA)
3)3) Based on a nonlinearly biased MZMBased on a nonlinearly biased MZM
3.3. Summary Summary
OutlineOutline
Part IPart IPhotonic generation of UWB SignalsPhotonic generation of UWB Signals
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Introduction: conceptIntroduction: concept
Frequency (GHz)
GPS PCS Bluetooth802.11 b/gCordless phonesMicrowave ovens
802.11a: 5 GHz
-41.3 dBm/MHz
Emitted Power
1. 1. 2. 3. 5. 10.
UWB: 3.1 – 10.6 GHz
Advantages of UWB:
1. High data rate
2. Reduced multipath fading
3. Co-existing with other wireless access techniques
t
0101
f
2. GHz
Time domain Frequency domain
t
0101
f
3. GHz 10. GHz
Narrow Band
Frequency Modulation
Ultra Wideband
Pulse Polarity Modulation
Advantages of using direct-sequence impulse UWB:
1. Carrier free, without the need of frequency mixers and local oscillators
2. High multipath resolution
3. Ultra high precision ranging at centimeter level
4. Enhanced capability to penetrate through obstacles
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Introduction : FCC regulationIntroduction : FCC regulation
FCC regulation approved in 2002: (1) Bandwidth >500 MHz or fractional bandwidth >20% (2) The unlicensed bandwidth: 3.1-10.6 GHz(3) Maximum power density: -41.3 dBm/MHz
FCC spectral mask for indoor commercial UWB system
L. Yang, and G. B. Giannakis, IEEE Signal Processing Mag., vol. 21, no. 6, pp. 26-54, Nov. 2004
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Introduction: Ideal UWB pulsesIntroduction: Ideal UWB pulses
Waveform
Spectrum
-200 -100 0 100 2000
0. 5
1
-200 -100 0 100 200-1
-0. 5
0
0. 5
-200 -100 0 100 200-1
0
1
0 5 10 15 200
0. 5
1
0 5 10 15 200
0. 5
1
0 5 10 15 200
0. 5
1
t (ps) t (ps) t (ps)
f (GHz) f (GHz) f (GHz)
Gaussian pulse:
Gaussian monocycle (first-order derivative):
Gaussian doublet (second-order derivative):
2 2( ) exp( )s t t ds dt2 2d s dt
( )j S 2 ( )S
2( ) exp( )S
monocycle doubletGaussian
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PM-IM conversion PM-IM conversion based on chromatic dispersionbased on chromatic dispersion
Fig. 1. PM-IM conversion based on chromatic dispersion.
DispersiveMediumPM
00 m
0 m
0 0
0 m 0 m
m m
Laser:
RF:
( )mH
Fig. 2. The corresponding RF frequency response. The frequency response is used to shape the spectrum of a Gaussian pulse to a doublet.
DC
First peak
Second notch
First notch
( )mH
m
F. Zeng and J. P. Yao, "Investigation of phase modulator based all-optical bandpass microwave filter," IEEE Journal of Lightwave Technology, vol. 23, no. 4, pp.1721-1728, April 2005.
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Chromatic dispersion based UWB pulse generation and distribution system
F. Zeng and J. P. Yao, " An approach to UltraWideBand pulse generation and distribution over optical fiber," IEEE Photonics Technology Letters, vol. 18, no. 7, pp. 823-825, March 2006.
LD
PC
Central Station
EOPM PD
Access Point
Data Sequence
SMF Link
Antenna
AB
10
11 1
01
1
25 km
UWB generation and UWB generation and distribution over fiberdistribution over fiber
Fig. 1 BERT output pulse (a) the waveform, and (b) the power spectrum.
(a) (b)
0 5 10 15-100
-90
-80
-70
-60
-50
Frequency (GHz)
Po
we
r (d
Bm
)
3.1 GHz 10.6 GHz
1.61GHz
13.5 GHz
FCC Mask for Indoor Comm.
1.99GHz
0 100 200 300 400 500-10
-8
-6
-4
-2
0
2
4
6
time (ps)
Am
plitu
de (m
V)
40 ps
Fig. 2. UWB doublet (a) the waveform, and (b) the power spectrum.
(a) (b)
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TLD NLF PD
UFBG
PC
Circulator
t
PR
A
BC
D
OA
Pump
Probe
UWB Pulse
TLS PD
FBG
PC
Circulator
t
PR
A
BC
D
OA
Pump
Probe NLF
A
DC
B
t
a
t
a
t
a
t
a
A
DC
B
t
a
t
a
t
a
t
a
TLS: Tunable laser sourcePC: Polarization ControllerOA: Optical AmplifierPD: PhotodetectorFBG: Fiber Bragg gratingNLF: Nonlinear Fiber
Pulse laser source
UWB generation based on UWB generation based on frequency discriminationfrequency discrimination
F. Zeng and J. P. Yao, "Ultrawideband impulse radio signal generation using a high-speed electrooptic phase modulator and a fiber-Bragg-grating-based frequency discriminator," IEEE Photonics Technology Letters, vol. 18, no. 19, pp. 2062- 2064, Oct. 2006.
The phase modulation (PM) is realized at The phase modulation (PM) is realized at the nonlinear fiber (NLF) via cross phase the nonlinear fiber (NLF) via cross phase modulation and PM-IM conversion is modulation and PM-IM conversion is performed at the edges of the FBG performed at the edges of the FBG reflection spectrum (frequency reflection spectrum (frequency discriminator).discriminator).
Cross phase Cross phase modulationmodulation
Frequency Frequency DiscriminationDiscrimination
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EDFA
LD1
LD2
MZM
SOA
PD
BERT, 13.5 Gbit/s10000000000000001
PC
50
50DCA
AMP
FBG1
FBG2Time delay
0 200 400 600 800 1000-6
-3
0
3
6
Am
plitu
de (
mV
)
Time (ps)
48 ps
1552.80 nm
1549.01 nm
Q. Wang, F. Zeng, S. Blais, and J. P. Yao, "Optical Ultrawideband monocycle pulse generation based on cross-gain modulation in a semiconductor optical amplifier," Optics Letters, vol. 31, no. 21, pp. 3083-3085, November 2006.
Fig. 1. UWB pulse generation based on cross gain modulation (XGM) in a semiconductor optical amplifier
(SOA) and time-delay by FBGs
0 200 400 600 800 1000-60
-40
-20
0
20
A
mpl
itude
(m
V)
Time (ps)
72 ps
1548 1550 1552 1554-40
-30
-20
-10
0
10
-40
-30
-20
-10
0
10
FBG2
Tra
nsm
issi
on (
dB)
Ref
lect
ion
(dB
)
Wavelength (nm)
FBG1
UWB generation based on UWB generation based on on a semiconductor optical amplifieron a semiconductor optical amplifier
0 4 8 12
-80
-70
-60
-50
Pow
er (
dBm
)
Frequency (GHz)
Generated monocycle
The spectrum of the generated monocycle
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Nonlinearly biased MZMNonlinearly biased MZM
2 2cos [ ( ( ))]out in biasP P V V t
V
Mach-Zehnder Modulator (MZM):
Pin Pout
Vbias V(t)
V
A
inout PP /
biasV
V(t)
Doubletinout PP /
biasV V
B
V(t)
Doublet
Experimental results: Pulse width 270 ps, bandwidth 8 GHz, centered at 4.5 GHz, Lower frequencies are suppressed
0 400 800 1200 1600 2000
-40
-30
-20
-10
0
10
20
30
Am
plitu
de (
mV
)
Time (ps)
270 ps
0 400 800 1200 1600 2000
-40
-30
-20
-10
0
10
20
30
Am
plit
ud
e (
mV
)
Time (ps)
Q. Wang and J. P. Yao, "UWB doublet generation using a nonlinearly-biased electro-optic intensity modulator," IEE Electronics Letters, vol. 42, no. 22, pp. 1304-1305, October 2006.
By biasing the MZM at the nonlinear regions, UWB doublet pulses can be generated.
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Three approaches to generating UWB pulses were proposed and demonstrated:
o The first approach was based on PM-IM conversion using either a dispersive device or an optical frequency discriminator.
o The second approach was based on XGM in an SOA.
o The third approach was based on a nonlinearly biased MZM.
All approaches could be realized using pure fiber-optic components, which have the potential for integration.
SummarySummary
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Acknowledgments
The Natural Sciences and Engineering Research Council (NSERC) of Canada
The contributions of Fei Zeng, and Qing Wang.
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1.1. MWP processing and modulation schemesMWP processing and modulation schemes
2.2. Low cost RoF links for UWBLow cost RoF links for UWB
3.3. Example of UWB: MB-OFDMExample of UWB: MB-OFDM
4.4. Up conversions of UWB signalsUp conversions of UWB signals
1)1) UWB/OUWB/O
2)2) O/UWBO/UWB
5.5. Summary Summary
OutlineOutline
Part IIPart II
Processing of UWB SignalsProcessing of UWB Signals
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1- MWP Processing and modulation schemes
External modulation : larger bandwidth (50 GHz for EOM), larger electrical gain of the link, but expensive
Optical domain
Ouput:Microwave signal
Input:Microwave signal Optical source Photodetector
Optical device
Advantages: Range and bandwidth extensions (MMW, UWB over fiber…)
Input:Microwave signal
Direct modulation : low cost, easy implementation, but limited bandwidth (30 GHz), non-linearity, RIN, chirp
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2- Low cost RoF links for UWB2- Low cost RoF links for UWB
Direct modulation: SMF and MMF
Critical considerations:
Fiber
Laser Diode
UWBin
UWBout
Access Node
- Non-linear L-I curve- RIN- Chirp
- Non-linearity- Shot noise- Thermal noise- Dark current
- SMF Chromatic dispersion- MMF Intermodal dispersion
Photodiode + TIA
Central Station
VCSEL or VCSEL or DFBDFB
Ref : Y. Le Guennec et al, Ref : Y. Le Guennec et al, Technologies for UWB-Over-Fiber, , LEOS’ 2006LEOS’ 2006
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3- Example of UWB : MB-OFDM
Band#1
Band#2
Band#3
Band#4
Band#5
Band#6
Band#7
Band#8
Band#9
Band#10
Band#11
Band#12
Band#13
Band#14
3432 3960 4488 5016 5544 6072 6600 7128 7656 8184 8712 9240 9768 10296 F (MHz)
PS
D (
dB
/MH
z) Band Group
#1Band Group
#2Band Group
#3Band Group
#4Band Group
#5
122 sub-carriers, 22 pilots Frequency hopping (with TFC)
MB-OFDM (Multi Band-Orthogonal Frequency Division Multiplexing): OFDM + TFC (Time Frequency Code) → Multi users possibility. Spectrum is divided into 14 sub-bands of 528 MHz wide, data rate up to 480 Mb/s
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4- MWP up-conversions of UWB
• UWB/O up-conversion
• O/UWB up-conversion
Laser Diode
Modulatoror
UWB –on optical carrier
UWB « frequency converted»
Photodiode + TIA
Fiber
UWB « frequency converted»
UWB – »baseband»
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UWB/O up-conversionPrinciples :
1)
ffscisci
Freq (GHz)Freq (GHz)00
00
-50-50
PSD (dBc/Hz)PSD (dBc/Hz)
0.40.4-0.4-0.4 Non linear MWP Non linear MWP mixingmixing
ffsc 1 sc 1 ffsc2 …..sc2 …..
FrequencFrequencyy
hoppinghopping
Freq (GHz)Freq (GHz)
2)
3.13.1 10.10.66
00 6060
Freq (GHz)Freq (GHz)
PSD (dBc/Hz)PSD (dBc/Hz)
opticaloptical
PDPD
Non linear MWP Non linear MWP mixingmixing
PDPD
UWB - OFDMUWB - OFDM
UWBUWB
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FH+ FIF
Example: Optical up-conversion for frequency hopping over fiber
MB-OFDM frequency hopping using optical MW mixing
IF = OFDM UWB signalIF = OFDM UWB signal
freqfreq FIF
freqfreq
PP PP
Ref : Y. Le Guennec et al, Ref : Y. Le Guennec et al, Technologies for UWB-Over-Fiber, , LEOS’ 2006LEOS’ 2006
Up - conversion
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MWP mixing : nonlinear modulations
a) Laser diode (LD)
PD outIF
P
DC
Bias Tee+
inLOP
inUWBP
b) Electro-optic external modulator (EOM)
EOM PD outIF
P
DCBias Tee+
inLOP
inUBWP
I
Popt
Popt
V
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MWP mixing : cascaded modulations
c) LD + EOM, linear
inUWB
P
inLOP
EOM
DCBias Tee
PD outIF
P
Allow remote inputs
V
Popt
I
Popt
d) EOM + EOM, linear
inUWB
P
EOM1
DCBias Tee
PD outIF
PEOM2
inLOPBias Tee
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Up conversion O/UWB
e) Photodiode (PD)
inUWBP
inLOP out
IFP
Non linear MWP Non linear MWP mixingmixing
photodiodeV
I
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0
2
4
6
8
10
12
14
16
18
10 20 30 40 50
EVM LD Prf=-10 dBm
EVM LD Prf=-5 dBm
EVM LD Prf=0 dBm
EVM LD Prf=5 dBm
EVM LD Prf=10 dBm
Optical microwave up-conversion of OFDM (802.11a)
Direct modulation: low cost mixing solution, no additional component
Bias current close to the threshold current
Ibias (mA)
EV
M (
% r
ms)
P-I curve
- Compromise between optimal mixing in non linear zone and clipping
- Higher photodetected RIN to consider in 528 MHz BW
Frequency hopping with direct modulation
Experimental OFDM up-conversion from 1.5 GHz to 5.8 GHz
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Perspectives for UWB/O at 60 GHz
LinearLinearRegimeRegime
Min TMin TOptical carrier suppressionOptical carrier suppression
PD - sub-carrier at 2 fPD - sub-carrier at 2 fLOLO= 40 = 40 GHzGHz
The 60 GHz optical heterodyne signal is generated by the double side band suppressed carrier “DS-SC” method
UWB - PRBS UWB - PRBS 2 Gb/s2 Gb/s
signal on sub-carrier of 2 GHz signal on sub-carrier of 2 GHz
UWB signal around 40 UWB signal around 40 GHzGHz
SA
PMF EOM
1
EOM 2
PMF SMF
X
UWB fsc=2 GHz fLO =20 GH z
PDs 60GHz
DFB 1550nm
EDFA
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Input PRBS
2 Gb/s
Output
Up converted PRBS around 60 GHz
2 Gb/s
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O-UWB up-conversion : experimental results @ IMEP
RF: 256MBps NRZ
modulation on frequency carrier of 2GHz
LD
Optical link
PD
Local Oscillator:
5 GHz
Wide-band Circulator
Antenna
UWB signal up-converted UWB signal up-converted
at 8 GHzat 8 GHz
PPLOLO=10 dBm=10 dBm
UWB signal , BW 3.4 GHzUWB signal , BW 3.4 GHz
IR-UWB signal
8 GHz
BW 6-10 GHz
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Monocycle
input signal, time domain
Monocycle – FFT
Frequency domain
BW=3.416 GHz
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Up-conversion
of UWB
at 8 GHz
Perspectives : Perspectives :
60 GHz up-60 GHz up-conversionconversion
Monocycle
-90
-80
-70
-60
-50
-40
-30
-20
-10
0
0 2 4 6 8 10 12
Frequency (GHz)
Po
wer
(d
Bm
)
Output power, LO=8GHz ; 10dBm
-100
-90
-80
-70
-60
-50
-40
-30
-20
-10
0
2 4 6 8 10 12 14
Frequency (GHz)
Po
we
r (d
Bm
)
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5- Summary5- Summary
Two approaches to up-converting UWB signals
o The first approach , UWB/O uses EOM and LDo The second approach, O/UWB, uses a PD
all based on a non-linearity
Approaches allow transmission at 60 GHz for future picocellular WLAN’s applications