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Recent Research Activities on Specialty Fibers
Ming-Jun Li
Science and Technology Division, Corning IncorporatedE-mail: [email protected]
WOCC’2007Newark, NJ, April 27-28, 2007
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Acknowledgement• X. Chen • D. A. Nolan• G. E. Berkey• J. Wang• J. Koh• S. Li• S. Gray• S. R. Bickham
• A.B. Ruffin• D.T. Walton• L. A. Zenteno• J. A. West • K. W. Koch • J. Coon• Kevin W. Bennett
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Outline• Introduction
• Recent research and development at Corning– Single polarization fiber– High Power Laser Fiber– Nonlinear Fiber– Microstructured Fiber– High Numerical Aperture Fiber
• Conclusions
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Outline• Introduction
• Recent research and development at Corning– Single polarization fiber– High Power Laser Fiber– Nonlinear Fiber– Microstructured Fiber– High Numerical Aperture Fiber
• Conclusions
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Specialty Fibers and Applications• Specialty optical fiber is modified, usually by design and by doping, for a
specialized function
• Examples of specialty fibers– Attenuating fiber: control attenuation– Ytterbium-doped double-clad fiber: high power fiber lasers– Erbium-doped fiber: fiber amplifiers for telecommunications– High NA fiber: capture more input with low bend-induced loss– Metallized fiber: coated with metals for high temperatures– Photonic crystal fiber: use photonic crystal structure to modify fiber
properties– Mid-infrared fiber: low loss optical transmission in 2 to 10 μm . – Photosensitive fiber: fiber gratings by UV exposure– Polarization maintaining fiber: keep linear polarized light
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Corning Specialty Fiber’s ProductsCorning Specialty Fiber’s Products
• PM 480• PM 630• PM 850• PM 980• PM 1300• PM 14XX• PM 1550
• PM 480• PM 630• PM 850• PM 980• PM 1300• PM 14XX• PM 1550
Corning Specialty Fiber
Polarization Control Erbium Power Delivery
Polarization MaintainingSingle Polarization
• SP 1060 (NEW)• SP 1310 (NEW)• SP 1550 (NEW)• SP 850 (Development)
• SP 1060 (NEW)• SP 1310 (NEW)• SP 1550 (NEW)• SP 850 (Development)
•RC PM 1550•RC PM 14XX•RC PM 1300•RC PM 980•Low Birefringence Fibers•High NA•PM 400 Visible (NEW)
Other Capabilities
Special Single-mode Fibers
High Index /Bend
Insensitive
• SMF-28e Photonic Fiber(NEW)
• RGB 400 (NEW)• RC Std SMF Fiber
• SMF-28e Photonic Fiber(NEW)
• RGB 400 (NEW)• RC Std SMF Fiber
•HI 780•HI 980•HI 1060•HI 1060 FLEX•RC HI 980•RC HI 1060•RC HI 1060 FLEX•RC 1300•RC 1550
•ER 1550C•ER 1550C3•ER 1550C3 LC (NEW)•ER 1600L3•RC ER 1550C3•RC ER 1600L3
• Yb Double Clad (NEW)• Polymer Clad Silica
(NEW)• High NA Silica Core
In Development
• Yb Double Clad (NEW)• Polymer Clad Silica
(NEW)• High NA Silica Core
In Development
• Hermetic Coatings• Polyimide Coatings• Reduced Cladding Fibers• Photonic Band Gap Fibers
In Development
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Outline• Introduction
• Recent research and development at Corning– Single polarization fiber– High Power Laser Fiber– Nonlinear Fiber– Microstructured Fiber– High Numerical Aperture Fiber
• Conclusions
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What is Single Polarization (SP) Fiber?• Fiber in which only one polarization mode propagates, while
the other polarization mode is attenuated• Difference between SP and PM fiber
SP fiber PM fiber
x
y
Delayx (fast)
y (slow)
– Guide one polarization only– No PMD, PDL
– Guide two polarizations– For long fiber, mode coupling
can cause PMD, PDL
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Applications of Single Polarization Fiber• Medical and military application
– High power single polarization fiber lasers• Long haul networks
– Eliminates the need to deal with PMD, PDL, etc.• Coherent communication
– Eliminate polarization instability • Optical interconnection
– Reduce component costs • Fiber sensors
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Design Concepts of SP Fiber • High birefringence to separate the two polarization modes
• Fiber structure to let one polarization propagate, the other polarization be cutoff
• Two design approaches:– Using stress birefringence– Using geometry birefringence
yx nnB −=
claddingycladdingx nnnn <> ,
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Corning Patented Design with Dual Air Holes
• Use air holes to create geometry birefringence • The air holes are also used to achieve differential cutoff
wavelengths
CoreAir hole
Cladding
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1550 nm SP FiberPower distribution along minor axis
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
-10.00 -8.00 -6.00 -4.00 -2.00 0.00 2.00 4.00 6.00 8.00 10.00
Radius (μm)
Pow
er (a
.u)
Pow
er distribution along major axis
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9 1-10.00-8.00
-6.00-4.00
-2.000.00
2.004.00
6.008.00
10.00
Radius (μm
)
Power (a.u)
Mode field diameter (μm)
Minor Major2.8 10.2
Wavelength (nm)1500 1520 1540 1560 1580 1600
Spe
ctra
l Sig
nal (
dB)
-100
-95
-90
-85
-80
-75
-70
-65
1550 window
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1310 nm SP FiberPower distribution along minor axis
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
-10.00 -8.00 -6.00 -4.00 -2.00 0.00 2.00 4.00 6.00 8.00 10.00
Radius (μm)
Pow
er (a
.u)
Power distribution along m
ajor axis
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9 1-10.00-8.00
-6.00-4.00
-2.000.00
2.004.00
6.008.00
10.00
Radius ( μm
)
Power (a.u)
Mode field diameter (μm)
Minor Major2.4 8.7
Wavelength (nm)
1250 1270 1290 1310 1330 1350
Spe
ctra
l Sig
nal (
dB)
-100
-95
-90
-85
-80
-75
-70
-65
1310 window
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1060 nm SP FiberPower distribution along minor axis
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
-10.00 -8.00 -6.00 -4.00 -2.00 0.00 2.00 4.00 6.00 8.00 10.00
Radius (μm)
Pow
er (a
.u)
Pow
er distribution along major axis
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9 1-10.00-8.00
-6.00-4.00
-2.000.00
2.004.00
6.008.00
10.00
Radius ( μm
)
Power (a.u)
Mode field diameter (μm)
Minor Major2.7 9.6
Wavelength (nm)1020 1040 1060 1080 1100
Spe
ctra
l Sig
nal (
dB)
-85
-80
-75
-70
-65
-60
1060 window
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Polarization Dependent Loss
Wavelength (nm)1420 1440 1460 1480 1500 1520 1540
PDL
(dB
)
01020304050607080
L = 101.3 cmL = 53.9cmL = 27.8 cm
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Application of SPF in High Power LasersBuilt in Single Polarization Double Clad Fiber
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Outline• Introduction
• Recent research and development at Corning– Single polarization fiber– High Power Laser Fiber– Nonlinear Fiber– Microstructured Fiber– High Numerical Aperture Fiber
• Conclusions
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High Power Narrow-linewidth Fiber LaserHigh Power Narrow-linewidth Fiber Laser• Many applications require
•• A major limiting factorA major limiting factor
SBS threshold in LMA fiber ~ 100 W
High PowerHigh Power & Narrow Narrow linewidthlinewidth
SBSSBSStimulated Stimulated BrillouinBrillouin ScatteringScattering
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Corning’s allall--glassglass,, LMA double-clad fiber
LMA fiber crossLMA fiber cross--sectionsection
LMA core
1st clad
2nd clad
LMA Core: Yb/Al/Ge/SiO2
Inner clad: Ge-SiO2
Outer clad: B/F-SiO2
Core: 30Core: 30--60 um, core NA: 0.0460 um, core NA: 0.04--0.060.06Pump NA (1Pump NA (1stst clad to 2clad to 2ndnd clad): clad): ≥≥ 0.30.3
Index
LMA index profileLMA index profile
SiO2
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Advantages of OVD LMA fiber makingAdvantages of OVD LMA fiber making
• All-glass double-clad structure – no polymer in optical path, ideal for high-power
• Lowest fiber background loss & high Yb QE– all vapor-phase doping, warranted hi-purity & low-defect
• SBS mitigation, gain guiding etc – Dopants (Al, Yb) profile capability
• High-NA for pump– Up- and down-dope capability
• low-NA for Yb-doped core with high Yb/Al content – Core compositional flexibility
• All-glass double-clad structure – no polymer in optical path, ideal for high-power
• Lowest fiber background loss & high Yb QE– all vapor-phase doping, warranted hi-purity & low-defect
• SBS mitigation, gain guiding etc – Dopants (Al, Yb) profile capability
• High-NA for pump– Up- and down-dope capability
• low-NA for Yb-doped core with high Yb/Al content – Core compositional flexibility
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Reducing the interaction length:- Increase Yb doping concentration
•• Corning has the highest YbCorning has the highest Yb--doping (1doping (1--2wt%) concentration with 2wt%) concentration with uncompromised quantum yield/background loss in the worlduncompromised quantum yield/background loss in the world
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High-Yb fiber with the lowest background loss
Loss in core region Loss in MM pump region
Low-loss characteristics of Yb-doped OVD fibers
0
1
23
4
5
6
78
9
10
1050 1100 1150 1200 1250 1300 1350 1400Wavelength (nm)
Loss
(dB
/km
)
Low-loss characteristics of Yb-doped OVD fibers
0
1
23
4
5
6
78
9
10
1050 1100 1150 1200 1250 1300 1350 1400Wavelength (nm)
Loss
(dB
/km
)
Pumping (innerclad) region Attenuation (141-0383)
0
10
20
30
40
50
60
70
80
90
100
600 800 1000 1200 1400 1600
Wavelength (nm)Lo
ss (d
B/k
m)
MCVD solution-doping data
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Stimulated Brillouin Scattering
• Intense pump-light creates acoustic wave, via ‘electrostrictive effect’• Acoustic wave creates an index grating • Light is scattered by the grating in the backward direction• Frequency of scattered light is downshifted in due to the Doppler shift
Incident Light ω
Scattered Light ω−Ω
Acoustic Wave Ω
Index Grating
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A New Comprehensive SBS Analysis• SBS Threshold: input power at which the SBS power starts to
rise exponentially
: fiber optical effective area: overlap integral
K: polarization factorg(νmax): maximum effective gain coefficient
αu: acoustic mode lossLeff : effective length
aouI
Optical Profile DesignPolarization control
Brillouin Frequency change
effA
Optical Profile DesignAcoustic Profile design
aoueff
ueffth ILLg
KAP
),( maxνα
∝
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Reduce Optical/Acoustic Overlap by Fiber DesignReduce Optical/Acoustic Overlap by Fiber Design
• Overlap integral gives us a new criterion for designing high SBS threshold fibers
• Minimize acousto-optic overlap– index profiles to modify optical/acoustic modes– choose dopants to modify acoustic velocity
• Overlap integral gives us a new criterion for designing high SBS threshold fibers
• Minimize acousto-optic overlap– index profiles to modify optical/acoustic modes– choose dopants to modify acoustic velocity
↓↓↑↑↑↑↑Acoustic refractive index
↑↑↓↓↑↑↑Optical refractive index
AlAl22OO33F2B2O3TiO2P2O5GeO2Dopant
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Fiber Profile for Reduced SBSFiber Profile for Reduced SBS
Radius (μm)0 5 10 15 20 25 30
Aco
ustic
Del
ta (%
)
-0.6-0.4-0.20.00.20.40.60.8
Acoustic Delta ProfileRefractive index/
Dopant concentration
Radius (μm)0 5 10 15 20 25 30
Fiel
d A
mpl
itude
-1.0
-0.5
0.0
0.5
1.0LP01L01L02
• Triangular acoustic index profile pushes acoustic waves to edge of core
• Acousto-optic overlap integral is reduced
• Predicted SBS threshold increase of ~7dB
Al
Ge Ge B/FYb
LMA Profile Schematic
coreinner
cladding
outercladding
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Measured SBS Thresholds in Large Mode Area Fibers
0
5
10
15
20
25
30
35
0.0 50.0 100.0 150.0 200.0 250.0 300.0Output power (Watts)
Bac
kwar
d po
wer
mon
itor (
mW
)
Step Index
Low SBS
SBS threshold is improved by 6 dB
Dual pump configuration
30 μm core12 m long
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Outline• Introduction
• Recent research and development at Corning– Single polarization fiber– High Power Laser Fiber– Nonlinear Fiber– Microstructured Fiber– High Numerical Aperture Fiber
• Conclusions
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Nonlinear Fiber Design Considerations• Small effective area - High nonlinearity
Nonlinear coefficient
• Low loss – High figure of merit• Right amount chromatic dispersion• Cutoff below the operating window-Single mode• Low polarization mode dispersion• High SBS threshold for non-Brillouin applications
effAn22
λπγ =
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Figure of Merit• Conventional figure of merit
• New figure of merit considering SBS
αγ
=0F γ: nonlinear coefficient, α: attenuation
BgPF γα
γ== 0 gB: Brillouin gain
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Profile Designs
Step Index Profile W-profile
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Typical Fiber CharacteristicsParameter
Effective areaDispersionDispersion slopeCutoff wavelengthAttenuation
Typical Value
15-25 μm2
0-20 ps/nm/km0-0.06 ps/nm2/km1200-1500 nm0.4-0.7 dB/km
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Reducing SBS in Nonlinear Fibers• SBS Threshold:
: fiber optical effective area: overlap integral
K: polarization factorg(νmax): maximum effective gain coefficient
αu: acoustic mode lossLeff : effective length
aouI
Optical Profile DesignPolarization control
Brillouin Frequency change
effA
Optical Profile DesignAcoustic Profile design
aoueff
ueffth ILLg
KAP
),( maxνα
∝
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Profile Design
• Ring profile design to reduce overlap between optical and acoustic fields
• SBS threshold is similar to standard single mode fiber
-0.5
0
0.5
1
1.5
2
0 2 4 6 8
Radius (microns)
% D
elta
DDC fiber DS fiber
-25
-20
-15
-10
-5
0
5
10
15
5 7 9 11 13 15
Input power (dBm)
Ref
lect
ed p
ower
(dB
m)
13 km ring profile10 km graded-index
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Decrease Dopant Level Along the Fiber
• Broaden the Brillouin spectrum and reduce the gain• SBS improvement of 7 dB demonstrated
CoreClad
Ge dopant decreases along the fiber (a)
-40
-30
-20
-10
0
10
20
30
-8 -6 -4 -2 0 2 4 6 8 10 12 14 16 18 20 22 24 26
Input Power (dBm)
Bac
k-sc
atte
ring
pow
er (d
Bm
)
(a)
(b)
(d)
(c)
(a) Conventional CDF. (b) Conventional DDF. (c) SBS-DDF launched at high dispersion side. (d) SBS_DDF lunched at low dispersion side.
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Outline• Introduction
• Recent research and development at Corning– Single polarization fiber– High Power Laser Fiber– Nonlinear Fiber– Microstructured Fiber– High Numerical Aperture Fiber
• Conclusions
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Photonic band-gap fiberPBGF
Photonic band-gap fiberPBGF
Bragg fiber Bragg fiber
Photonic crystal fiberPCF or “holey” fiber
Photonic crystal fiberPCF or “holey” fiber
Micro-structured air/silica or highly nonlinear fiber
Micro-structured air/silica or highly nonlinear fiber
Solid- & Hollow-Core Photonic Crystal Fibers
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Why Photonic Crystal Fiber?Air-Silica Fiber
High Index Contrast Microstructured Cladding
Band-Gap EffectsSmall Core
High Birefringence
Endless Single Mode
High Nonlinearity
High NA
Fiber lasers
Components
Low loss transmission
UV and NIR guides
Unique sources
Large SM guides
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Potential for Low Loss
PROPERTY CONVENTIONAL FIBER
HOLLOW-COREPBGF
(POTENTIAL)
HOLLOW-COREPBGF
(CURRENT) Loss
(dB/km)
Surface modes
0.15-0.17 < 0.1 13
Lowest-loss, small-core PBGF
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Comparison of Effective Nonlinearity of PBGF0.15
0.10
0.05
0 Δ
λ/L
(nm
/cm
)
0.12 4 6 8
12 4 6 8
102
Peak power (MW)
Corning fiber HC-1550-01
γ =
2πn2
λ Aeff γ Blaze = 2.5×10−8(W ⋅cm)−1
γ Corning = 2.4 ×10−9 (W ⋅cm)−1 γ SMF = 3×10−5(W ⋅cm)−1
Nonlinearityparameter
Spectral broadening
measurement at zero-
dispersion point
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High Birefringent PBGF
Wavelength (nm)1550 1570 1590 1610 1630
Bea
tleng
th (m
m)
0.06
0.07
0.08
0.09
0.10
0.11
Bire
frin
genc
e
0.015
0.017
0.019
0.021
0.023
0.025
0.027BeatlengthBirefringence
(b)
Birefringence is 0.016-0.025, highest values reported on PBGF
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Outline• Introduction
• Recent research and development at Corning– Single polarization fiber– High Power Laser Fiber– Nonlinear Fiber– Microstructured Fiber– High Numerical Aperture Fiber
• Conclusions
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High NA Fiber Applications• Laser Power Delivery• Illumination• Industrial Sensors • Medical• Interferometers• Short-Haul Data and Video
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Polymer Clad Silica Fibers
0
10
20
30
40
50
60
70
400 500 600 700 800 900 1000 1100 1200 1300Wavelength (nm)
Atte
nuat
ion
(dB/
km)
ETFEBuffer
Fluorinatedpolymer Cladding
Silica Core
Typical AttenuationCOR-400-VIS39 (Low OH)
• Features:– High Numerical Aperture (0.39)– Low attenuation– High Purity Silica Core
• Low OH and High OH available– Excellent Epoxy Adhesion for
Connectorization– Variety of Core Sizes available
(200, 400µm)– OVD Manufactured Fiber
Consistency– Other Geometries, NA, and
Buffers Possible by Special Request
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All Glass High NA Fibers• Features:
– OVD high purity glass technology • Glass core• Glass cladding
– High Numerical Aperture • 0.3-0.4 depending on wavelength
window– High temperature operating range
• Up to 125 oC with polymer coating • Higher temperatures special
coating– Low attenuation
• Prototypes are being developed
Coating
Silica Cladding
Silica Core
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Conclusions• Corning offers a broad product portfolio
• World-class research capability– Advanced fiber design– Leading fiber making technology
• New specialty fibers are being developed– Offer unique features for different applications
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