Generation and processing of UWB Signals over fiber

ISIS-IPHOBAC SUMMER SCHOOL, May 17-18, 2007, Budapest, Hungary"Broadband Architectures and Functions"

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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


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Acknowledgments

UROOF IST project,

The contributions of Giang NGUYEN, René GARY and Yannis LE GUENNEC

Documents

Generation and processing of UWB Signals over fiber