1 © 2010 exfo inc. all rights reserved. lasers à fibre basés sur soa et applications en tests et...
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1© 2010 EXFO Inc. All rights reserved.
Lasers à fibre basés sur SOA et applications en tests et mesures
Michel LeblancChef de groupe, Ingénierie Systèmes14 Mai 2010
2© 2010 EXFO Inc. All rights reserved.
Plan de la présentation
Lasers SOALasers SOAPourquoi développer des lasers?
Caractéristiques recherchées
Investigation
ApplicationsApplications Test de composantes
Mesures CD et PMD
Mesures de PMD distribuée
3© 2010 EXFO Inc. All rights reserved. 3© 2010 EXFO Inc. All rights reserved.
› Caractérisation de composants (CWDM, DWDM)› Mesures de perte d’insertion, réflectivité et dépendance en polarisation vs
› Réflectomètre optiques (OTDR) accordable en longueur d’onde› Caractérisation d’un lien à plusieurs longueurs d’onde› Mesure CD› Mesure PMD
Le laser accordable dans les tests et mesures …
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Principales caractéristiques souhaitées
› Caractérisation de composants (CWDM, DWDM)› Plage spectrale étendue (1 seul laser pour tout tester!)› Laser étroit mais pas trop! (linewidth control)› Balayage continu sans saut de mode› Faible bruit (low SSE)› Stabilité de puissance
› Réflectomètre optiques (OTDR) accordable en longueur d’onde› Opération en mode pulsé (pulse variable, taux de répétition variable)› Laser étroit mais pas trop! (linewidth control)
5© 2010 EXFO Inc. All rights reserved. 5© 2010 EXFO Inc. All rights reserved.
Laser à fibre basé sur SOA (SFL)
OutputTBF
Isolator
SM fiber
PC1
Coupler
Semiconductorgain medium
PC2
Basic SFL design
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Laser à cavité externe (ECL)
Basic ECL design
Diffraction Grating
SM fiber Gain Chip
Pivot Point
Collimating lens
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Largeurs de raie des lasers
Power
Coherence control (100 MHz)
Multimode SFL (1-10 GHz)Power
Single-mode ECL (typ. 100 kHz)
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Avantages potentiels du laser SFL
› Opération multimodes élimine le besoin d’obtenir un balayage ‘’mode-hop free’’› Largeur de raie de quelques GHz contrôlée par design réduit les effets d’interférence› Faible ASE possible sans ajout de complexité dans le design› Possibilité de combiner plusieurs milieux de gain dans un même laser› Fonctionnement en mode pulsé avec un seul SOA possible
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Laser avec filtre large
Cavity design 1 TBF BW ~ 200 - 300 pm
I2 Output
SOA
TBF
I1SMF
25%
75%
PC1 PC2
C
Ref: H. Chen, F. Babin, G.W. Schinn, AOE 2006, Shanghai, China (2006)
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Caractéristiques spectrales
0
0.02
0.04
0.06
0.08
0.1
0.12
0.14
0.16
0 2 4 6 8 10Frequency (GHz)
Inte
nsit
y (a
.u.)
MLM
SLM
FSR=8GHz
-90
-70
-50
-30
-10
10
1450 1475 1500 1525 1550 1575 1600 1625 1650
Wavelength (nm)
Pow
er (d
Bm
)
Res: 1nm(a) (b)
SLM
Spectrum
Measured by OSA Measured by scanning Fabry-Perot interferometer
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Caractéristiques spectrales
-90
-80
-70
-60
-50
-40
0 50 100 150 200 250 300 350 400 450 500
Frequency (MHz)R
elat
ive
Inte
nsit
y (d
B)
-90
-80
-70
-60
-50
-40
0 50 100 150 200 250 300 350 400 450 500
Frequency (MHz)
Rel
ativ
e In
tens
ity
(dB
)
-90
-80
-70
-60
-50
-40
0 50 100 150 200 250 300 350 400 450 500
Frequency (MHz)
Rel
ativ
e In
tens
ity
(dB
)
(a) 1440nm (b) 1500nm
(c) 1550nm (d) 1614nm
Baseband noise vs wavelength
(e) 1615nm
-90
-80
-70
-60
-50
-40
0 50 100 150 200 250 300 350 400 450 500
Frequency (MHz)
Rel
ativ
e In
tens
ity
(dB
)
-90
-80
-70
-60
-50
-40
0 50 100 150 200 250 300 350 400 450 500
Frequency (MHz)
Rel
ativ
e In
tens
ity (
dB)
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Caractéristiques spectrales
-50
-40
-30
-20
-10
0
10
20
1420 1440 1460 1480 1500 1520 1540 1560 1580 1600 1620 1640 1660
Wavelength (nm)
Pow
er (
dBm
)
Tunable range: 1435-1645nm
SLM region
MLM region
Tunable range for SLM and MLM
-10
-5
0
5
10
15
20
25
30
1420 1440 1460 1480 1500 1520 1540 1560 1580 1600 1620 1640
Wavelength (nm)
Gai
n (d
B)
SOA Gain
SOA ASE
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Laser avec filtre étroit
SOA
G
M1
M2
L PC1
PC2
50%
50%
Output
SMF
1
23 TBF
I2
C2
C1
Narrow filter bandwidth can produce a MLM lasing oscillation for the entire laser operation wavelength region
Cavity design 2 TBF BW ~ 16 pm
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Caractéristiques spectrales
-0.001
0.004
0.009
0.014
0.019
0.024
0.029
0.034
0.039
0.044
0.049
0.054
0.059
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
Frequency (GHz)
Inte
nsit
y (a
.u.)
FSR = 8GHz
1450nm
1475nm
1500nm
1525nm
1550nm
1575nm
1600nm
1624nm
-90
-80
-70
-60
-50
-40
-30
-20
-10
0
10
20
1430 1450 1470 1490 1510 1530 1550 1570 1590 1610 1630
Wavelength (nm)
Pow
er (
dBm
)
OSA Res: 1nmTuning range: 1445-1620nm
Tunability linewidth vs
• Linewidth ~ 1.5 GHz• Low SSE ~ 50 - 60 dB
MLM SFL w/ a narrow linewidth
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Modulation de fréquence d’un laser SOA monomode:- contrôle de largeur de raie
Cavity Configuration for Frequency Modulation (FM) laser operation in a SFL
Collaboration avec COPL, Université Laval, Simon Lambert-Girard, Michel Piché
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Modulation de fréquence d’un laser SOA monomode
Left: measured laser spectrum for sine modulation by PM for fax = 16.017 MHz, fm = 16.000 MHz, Vpp = 0.6 V
Right: simulation.
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Modulation de fréquence d’un laser SOA monomode
Synthetic laser linewidths compare with Gaussian lineshapes w/ a SOA current modulation (modulation depth = 20 %, fax = 16.009 MHz):
Left: sine modulation, fm = 16.02 MHz,
Middle: optimized modulation, fm = 16.02 MHz
Right: optimized modulation, fm = 16.03 MHz
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Mise en oeuvre
et applications
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Mise en oeuvre: laser toutes-bandes (all-band)
SOA chosen as gain medium since it can be designed for optimized gain in almost any desired region
PM fiber used throughout to ensure stability Tuning filter (TBF) is shared between the two individual cavities
SOA1 centred at 1350 nm
SOA2 centredat 1530 nm
SOAs’ 3-dB BW >70 nm
Laser design and characteristics
TBF
SOA 1
SOA 2
OC 1
OC 2
OC 3
50/50
25%
75%
25%75
%
Output
Ref: R. Baribault, H. Chen, G. He, D. Gariepy, F. Babin, G.W. Schinn, OFMC 2005, Teddington, UK (2005)
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Conception du filtre accordable (TBF)
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Caractéristiques spectrales
Linewidth S/SSE
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Analyseur de composants passifs
Passive Component Analyser (PCA)
This tunable SOA-based SFL source (TLS) serves as
basis for a swept- PCA for IL, ORL and PDL measurements as a function of wavelength.
PSA generates 4 SOPs for use with Mueller matrix method.
TLSCAL
MODULE
DETECTORS
DUT
REF
MEASURE
PSA
PSA – Polarisation State Adjuster
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Mesure typique – composant CWDM
Typical Results
16 Channel CWDM Demux
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Mise en oeuvre: laser pulsé pour OTDR accordable
SOA
PMF
Delay Line(PMF)
M
TBF
Control
PMF
BSB A
Cir
C
FUT
APD
1 2 3
4
Low SSE design
Ref: US Patent US2009/0310627 H. Chen, G.W. Schinn
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Laser pulsé
(1) Principle
-0.015
0.005
0.025
0.045
0.065
0.085
0.105
0.125
0.145
0.165
0.185
0.205
0.225
0 200 400 600 800 1000 1200 1400
Time (ns)
Inte
nsit
y (a
.u.)
-0.015
0.005
0.025
0.045
0.065
0.085
0.105
0.125
0.145
0.165
0.185
0.205
0.225
0 200 400 600 800 1000 1200 1400
Time (ns)
Inte
nsit
y (a
.u.)
-0.015
0.005
0.025
0.045
0.065
0.085
0.105
0.125
0.145
0.165
0.185
0.205
0.225
0 200 400 600 800 1000 1200 1400
Time (ns)
Inte
nsit
y (a
.u.)
ASE from SOA not in cavity Light pulse from SOA based laser but without delay line(high SSE)
100ns light pulse from SOA based laser but with delay line
Low SSE
(2) Measurements
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Laser pulsé
Results – light pulse, linewidth and S/SSE
-80
-70
-60
-50
-40
-30
-20
-10
0
1455 1475 1495 1515 1535 1555 1575 1595
Wavelength (nm)
Pow
er (
dBm
)
Res. 1nm
-57
-54
-51
-48
-45
-42
-39
-36
-33
-30
-27
-24
-21
1549.62 1549.67 1549.72 1549.77 1549.82 1549.87
Wavelength (nm)
Pow
er (
dBm
)
Res. 0.01nm
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Mesures de CD avec un OTDR
SOA
PMF
Delay Line(PMF)
M
TBF
Control
PMF
BSB A
Cir
C
FUT
APD
1 2 3
4
FresnelReflection
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Mesure de CD
Different light pulse arrivals for different
Measured GD and CD for 25 km DSF
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Mesures de PMD avec un OTDR
Principle design for products
Delay Line(120-m PMF)
M
C1
BS
25%
75%
PMF
FUT
APD1
APD2
PBSPS
SOATBF
Controllingand
Signal Processing
Fresnel
Reflection
PMF
Tunable Tunable pulsed laserpulsed laser
PMD measurementPMD measurement
I/OI/O--SOP SOP ScramblerScrambler
Tunable OTDRTunable OTDR
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Mesure de PMD
Acquisition SettingAcquisition Setting• I/O-SOP: 2000• Wavelength: 400• range: 1530.6 - 1569.6nm • 20.52 GHz,• PMD· 0.118
ResultResult
• This method gives: PMDse = 5.74 ( 0.30) ps
• RTM measurement: PMDRTM = 5.75 ps
1.53 1.54 1.55 1.56 1.570
0.5
1RMS-Difference =Local Differences
< T T' > 0.274
PMDse 5.74ps
( Wavelength [m] , I/O-SOP ) k
RMS-Difference = 0.274
•Method based on newly developed Scrambled SOP Analysis•Measure Transmission difference for many SOP and pairs•RMS difference related to PMD•(method standardized at TIA)
Ref: H. Chen, N. Cyr, B. Ruchet, M. Leclerc, G.W. Schinn, ECOC 2007, Berlin, Germany (Sept. 2007)
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Mesure de PMD distribuée
› Same theory as single-ended PMD with tunable OTDR› Use Rayleigh backscattering instead of Fresnel reflection› Lot of data crunching…
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Mesure de PMD distribuée
› Measure PMD contribution of each section
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Mesure de PMD distribuée
› Predict new total PMD if a section is replaced
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Conclusions
› Le développement d’instruments de tests et mesures avancés requiert l’utilisation de lasers ayant des caractéristiques particulières
› EXFO a développé des lasers uniques et intégré ceux-ci dans plusieurs équipements commercialisés
› EXFO continue à développer d’autres lasers pour certains produits présentement en développement.
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Contributeurs
› EXFO› Hongxin Chen› Gregory W. Schinn› François Babin (now with INO)› Normand Cyr› Robert Baribault› Daniel Gariépy› Gang He› Bernard Ruchet› Michel Leclerc
› COPL› Simon Lambert-Girard› Michel Piché