Transcript Generation and processing of UWB Signals over fiber Béatrice Cabon IMEP Institut de Microélectronique Electomagnétisme et Photonique INPG-MINATEC, Grenoble, France Jianping Yao Microwave Photonics Research Laboratory School of Information.

Generation and processing
of UWB Signals over fiber
Béatrice Cabon
IMEP
Institut de Microélectronique Electomagnétisme
et Photonique
INPG-MINATEC, Grenoble, France
Jianping Yao
Microwave Photonics Research Laboratory
School of Information Technology and Engineering
University of Ottawa, Canada
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Part I
Photonic generation of UWB Signals
Outline
1. Introduction to UWB
2. Photonic generation of UWB pulses
1) Based on phase modulation to intensity
modulation (PM-IM) conversion
2) Based on a semiconductor optical amplifier (SOA)
3) Based on a nonlinearly biased MZM
3. Summary
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Introduction: concept
Frequency domain
Time domain
Narrow Band
Bluetooth
802.11a: 5 GHz
802.11 b/g
Cordless phones
Microwave ovens
GPS PCS
Emitted
Power
t
Frequency
Modulation
UWB: 3.1 – 10.6 GHz
Ultra Wideband
f
1
0
1
0
1
0
1
0
2. GHz
t
Pulse Polarity
Modulation
-41.3
dBm/MHz
1. 1.
2.
3.
5.
10.
f
3. GHz
10. GHz
Frequency (GHz)
Advantages of UWB:
Advantages of using direct-sequence impulse UWB:
1.
High data rate
1.
2.
Reduced multipath
fading
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
3.
Co-existing with other
wireless access
techniques
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Introduction : 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 pulses
s(t )  exp( t 2  2 )
ds dt
Gaussian monocycle (first-order derivative):
S ()  exp(2 )
jS ( )
2 S ()
Gaussian pulse:
d 2 s dt 2
Gaussian doublet (second-order derivative):
1
Waveform
0.5
0.5
1
0
monocycle
Gaussian
doublet
0
-0.5
0
-200 -100
0
100
200
-1
-200 -100
t (ps)
Spectrum
0
100
200
-1
-200
1
1
0.5
0.5
0.5
5
10
15
f (GHz)
20
0
0
5
10
f (GHz)
0
100
200
15
20
t (ps)
t (ps)
1
0
0
-100
15
20
0
0
5
10
f (GHz)
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PM-IM conversion
based on chromatic dispersion
0
0
0  m
Laser:
0  m
0
PM
RF: m
0  m 0  m
Dispersive
Medium
m
H (m )
Fig. 1. PM-IM conversion based on chromatic dispersion.
First peak
H (m )
Second notch
First notch
DC
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.
Fig. 2. The corresponding RF frequency response.
The frequency response is used to shape the spectrum of a Gaussian pulse to a doublet.
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UWB generation and
distribution over fiber
1 0 1 1
A
Antenna
1 0 1 1
Data Sequence
25 km
EOPM
LD
PC
Chromatic
dispersion based
UWB pulse
generation and
distribution system
B
PD
SMF Link
Central Station
Access Point
-50
6
FCC Mask for Indoor Comm.
4
0
-2
-4
-10
0
Fig. 1 BERT output pulse (a) the waveform, and (b) the
power spectrum.
13.5 GHz
-70
1.99
GHz
1.61
GHz
-80
-90
-8
(b)
10.6 GHz
40 ps
-6
(a)
3.1 GHz
2
Power (dBm)
Amplitude (mV)
-60
100
200
300
time (ps)
400
500
-100
0
5
10
Frequency (GHz)
(a)
15
(b)
Fig. 2. UWB doublet (a) the waveform, and (b) the
power spectrum.
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.
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UWB generation based on
frequency discrimination
Cross phase
modulation
P
Pulse laser
source
R
FBG
UFBG
t
CC
B
DD
A
TLS: Tunable laser source
PC: Polarization Controller
OA: Optical Amplifier
PD: Photodetector
FBG: Fiber Bragg grating
NLF: Nonlinear Fiber

H
Pump
Pump
PC
OA
OA
TLS
TLD
Probe
Probe
The phase modulation (PM) is realized at the
nonlinear fiber (NLF) via cross phase modulation
and PM-IM conversion is performed at the edges
of the FBG reflection spectrum (frequency
discriminator).
NLF
Circulator
Circulator
UWB Pulse
a
a
t
t
A
B
a
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.
Frequency
Discrimination
PD
PD
NLF
a
t
t
C
D
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UWB generation based on
on a semiconductor optical amplifier
6
10
10
Reflection (dB)
Amplitude (mV)
0
72 ps
-20
-40
-60
0
200
400
600
800
1000
0
-10
-10
-20
-20
-30
-30
-40
1548
1550
1552
Amplitude (mV)
FBG2
FBG1
0
Transmission (dB)
20
3
0
-3
-40
1554
-6
Time delay 
600
800
1000
-50
FBG1
MZM
EDFA
50
DCA
SOA
PD
Power (dBm)
LD1
50
400
Generated monocycle
FBG2
LD2
200
Time (ps)
BERT, 13.5 Gbit/s
10000000000000001
1549.01 nm
0
Wavelength (nm)
Time (ps)
PC
48 ps
-60
-70
AMP
1552.80 nm
Fig. 1. UWB pulse generation based on cross gain
modulation (XGM) in a semiconductor optical amplifier
(SOA) and time-delay by FBGs
-80
0
4
8
12
Frequency (GHz)
The spectrum of the
generated monocycle
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.
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Nonlinearly biased MZM
Mach-Zehnder Modulator (MZM):
Pout  Pin cos2 [
Pout / Pin
Vbias
2
(Vbias  V (t ))]
V
Doublet
Pin
Pout / Pin
By biasing the MZM at the
nonlinear regions, UWB
doublet pulses can be
generated.
B
V
V(t)
Pout
Doublet
A
Vbias
Vbias
V(t)
V
V(t)
30
Amplitude (mV)
Amplitude (mV)
30
20
10
0
-10
-20
10
0
-10
-20
-30
-30
-40
0
-40
0
400
800 1200 1600 2000
Time (ps)
270 ps
20
400
Experimental results: Pulse
width 270 ps, bandwidth 8
GHz, centered at 4.5 GHz,
Lower frequencies are
suppressed
800 1200 1600 2000
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.
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Summary


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 fiberoptic components, which have the potential for
integration.
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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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Part II
Processing of UWB Signals
Outline
1. MWP processing and modulation schemes
2. Low cost RoF links for UWB
3. Example of UWB: MB-OFDM
4. Up conversions of UWB signals
1) UWB/O
2) O/UWB
5. Summary
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1- MWP Processing and
modulation schemes
Direct modulation : low cost, easy implementation,
but limited bandwidth Optical
(30 GHz),
non-linearity, RIN, chirp
domain
Input:
Microwave signal
Optical source
Optical device
Photodetector
Ouput:
Microwave signal
External modulation : larger bandwidth (50 GHz for EOM),
larger electrical gain of the link, but expensive
Input:
Microwave signal
Advantages: Range and bandwidth extensions (MMW, UWB over fiber…)
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2- Low cost RoF links for UWB
 Direct modulation: SMF and MMF
 Critical considerations:
UWBin
Laser
Diode
VCSEL or DFB
UWBout
Fiber
Photodiode
+ TIA
- SMF Chromatic dispersion
- MMF Intermodal dispersion - Non-linearity
- Non-linear L-I curve
- Shot noise
- RIN
- Thermal noise
- Chirp
- Dark current
Central Station
Access Node
Ref : Y. Le Guennec et al, Technologies for UWB-Over-Fiber, LEOS’ 2006
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3- Example of UWB : MB-OFDM
MB-OFDM (Multi Band-Orthogonal Frequency Division Multiplexing):
 OFDM + TFC (Time Frequency Code) → Multi users possibility.
PSD (dB/MHz)
 Spectrum is divided into 14 sub-bands of 528 MHz wide, data rate up to 480 Mb/s
Band Group
#1
Band Band Band
#1
#2
#3
Band Group
#2
Band Band Band
#4
#5
#6
Band Group
#3
Band Band Band
#7
#8
#9
3432 3960
5016 5544
6600
4488
6072


7128
Band Group
#4
Band Band Band
#10 #11 #12
7656 8184
8712
Band Group
#5
Band Band
#13 #14
9240 9768 10296
F (MHz)
122 sub-carriers, 22 pilots
Frequency hopping (with TFC)
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4- MWP up-conversions of UWB
• UWB/O up-conversion
UWB – »baseband»
Laser
Diode
or
Modulator
UWB « frequency
converted»
• O/UWB up-conversion
Fiber
UWB –on optical carrier
Photodiode
+ TIA
UWB « frequency
converted»
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UWB/O up-conversion
Principles :
1)
PSD (dBc/Hz)
0
UWB - OFDM
-50
-0.4
0
0.4 Freq (GHz)
Non linear MWP mixing
Frequency
PD
hopping
fsc 1 fsc2 …..
fsci
loptical
2)
Non linear MWP mixing
PSD (dBc/Hz)
UWB
PD
Freq (GHz)
0
3.1
10.6
Freq (GHz)
60
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Example: Optical up-conversion
for frequency hopping over fiber
MB-OFDM frequency hopping using optical MW mixing
P
P
freq
FIF
Up - conversion
FH+ FIF
freq
IF = OFDM UWB signal
Ref : Y. Le Guennec et al, Technologies for UWB-Over-Fiber, LEOS’ 2006
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MWP mixing :
nonlinear modulations
in
PLO
in
PUWB
+
PD
Bias Tee
P out
IF
Pop
t
DC
I
a) Laser diode (LD)
in
PLO
in
PUBW
+
Bias Tee
EOM
DC
Popt
PD
P out
IF
V
b) Electro-optic external modulator (EOM)
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MWP mixing :
cascaded modulations
in
PLO
Bias Tee
DC
EOM
PD
P out
IF
Pop
Popt
t
P in
UWB
Allow
remote
inputs
I
c) LD + EOM, linear
P in
UWB
Bias Tee
EOM1
DC
Bias Tee
V
in
PLO
EOM2
PD
P out
IF
d) EOM + EOM, linear
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Up conversion O/UWB
Non linear MWP mixing
in
PUWB
I
photodiode
V
in
PLO
P out
IF
e) Photodiode (PD)
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Frequency hopping
with direct modulation
Optical microwave up-conversion of OFDM (802.11a)
 Direct modulation: low cost mixing solution, no additional
component
 Bias current close to the threshold current
P-I curve
12
Experimental OFDM up-conversion from
1.5 GHz to 5.8 GHz
10
18
8
6
4
2
0
0
10
20
30
40
50
60
70
80
I(mA)
90
EVM (% rms)
Popt(mW)
14
EVM LD
EVM LD
EVM LD
EVM LD
EVM LD
16
14
Prf=-10 dBm
Prf=-5 dBm
Prf=0 dBm
Prf=5 dBm
Prf=10 dBm
12
10
8
6
- Compromise between optimal mixing
4
in non linear zone and clipping
2
- Higher photodetected RIN to
consider in 528 MHz BW
0
10
20
30
Ibias (mA)
40
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23
Perspectives for
UWB/O at 60 GHz
UWB - PRBS 2 Gb/s
UWB signal around 40 GHz
signal on sub-carrier of 2 GHz
SMF
PMF
PMF
EOM
1
DFB
1550nm
EOM
2
SA
PDs
60GHz
X
UWB
EDFA
f sc =2 GHz
Linear
Regime
f LO =20 GH z
Min T
Optical carrier suppression
PD - sub-carrier at 2 fLO= 40
GHz
The 60 GHz optical heterodyne signal is generated by the double side band
suppressed carrier “DS-SC” method
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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
UWB signal up-converted
UWB signal , BW 3.4 GHz
at 8 GHz
RF:
IR-UWB
signal
256MBps NRZ
modulation on frequency
carrier of 2GHz
PLO=10 dBm
Wide-band
Circulator
Optical link
Local
Oscillator:
5 GHz
GHz
8
LD
PD
BW 6-10 GHz
Antenna
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Monocycle
input signal, time
domain
Monocycle – FFT
Frequency domain
BW=3.416 GHz
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Monocycle
0
-10 0
2
4
6
8
10
12
Power (dBm)
-20
-30
-40
-50
-60
-70
-80
-90
Frequency (GHz)
Up-conversion
Output power, LO=8GHz ; 10dBm
Power (dBm)
0
-10 2
-20
-30
-40
4
6
8
10
12
14
of UWB
at 8 GHz
Perspectives :
-50
-60
-70
-80
-90
60 GHz up-conversion
-100
Frequency (GHz)
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5- Summary

Two approaches to up-converting UWB signals
o
o
The first approach , UWB/O uses EOM and LD
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
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Acknowledgments

UROOF IST project,

The contributions of Giang NGUYEN, René GARY
and Yannis LE GUENNEC
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