Technische Universität Hamburg-Harburg · Alcatel Corporate Research Center now with Alcatel USA...
Transcript of Technische Universität Hamburg-Harburg · Alcatel Corporate Research Center now with Alcatel USA...
UV trimming of arrayed waveguide gratings
Technische Universität Hamburg-Harburg
Frank KnappeTechnical University Hamburg-Harburg
Jörg GehlerAlcatel Corporate Research Center
now with Alcatel USA
December 2000
Technische Universität Hamburg-HarburgOutline
- Objective
- Influence of phase errors
- Mesurement of phase distributions
- Compensation of phase errors with UV trimming
- Results
- Conclusion/Prospect
Technische Universität Hamburg-HarburgObjective I
N = 25 … 250
Technische Universität Hamburg-HarburgObjective II
- Used for:multiplexer/demultiplexerchannel equalizerchannel switching
- important characteristics:crosstalkchromatic dispersionbirefringencePDLPMD
Technische Universität Hamburg-HarburgObjective III
-70
-60
-50
-40
-30
-20
-10
0
1542 1547 1552 1557 1562
Wavelength [nm]
Tra
nsm
issio
n[d
B] Crosstalk: 27dB
Technische Universität Hamburg-HarburgInfluence of phase errors I
- Full characterization of a device by the complex transfer function
- amplitude spectrum is given by the focussing slab regions
- more critical: phase spectrum
- fast fluctuations responsible for crosstalk
- slow fluctuations responsible for chromatic dispersion
H. Yamada et al "Measurement of Phase and Amplitude Error Distributionsin Arrayed-Waveguide Grating Multi/Demultiplexers Based on Dispersive Waveguide”,Journal of Lightwave Technol. , p.1309 (2000)18
Technische Universität Hamburg-HarburgInfluence of phase errors II
H. Yamada et al "Measurement of Phase and Amplitude Error Distributionsin Arrayed-Waveguide Grating Multi/Demultiplexers Based on Dispersive Waveguide”,Journal of Lightwave Technol. , p.1309 (2000)18
Technische Universität Hamburg-HarburgInfluence of phase errors III
H. Yamada et al "Measurement of Phase and Amplitude Error Distributionsin Arrayed-Waveguide Grating Multi/Demultiplexers Based on Dispersive Waveguide”,Journal of Lightwave Technol. , p.1309 (2000)18
Technische Universität Hamburg-HarburgCompensation techniques I
- thin flim heatersH. Yamada et al "10 GHz spaced arrayed-waveguide grating multiplexer with
phase-error-compensating thin-film heaters,” Electron. Lett. , p.360 (1995)
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H. Yamada et al "Statically-phase-compensated 10 GHz-spaced arrayed-waveguidegrating multiplexer", Electron. Lett. , p.1580 (1996)
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H. Yamada et al "Low-crosstalk arrayed-waveguide grating multi/demultiplexer withphase compensatingplate”, Electron. Lett. , p.1698 (1997)
31
32
33
�-Si strip loaded waveguides
phase compensating plates
permanent power consumptionadditional clean room processesincreased insertion losses
problems:
Technische Universität Hamburg-HarburgCompensation techniques II
- most AWG’s are based on silica on silicon
- refractive index can be increased (or decreased) by UV illumination
nL
- required phase changes: ~ 0.5 rad
- realistic values for n: 5e-4 … 1e-3
- required trimming length: ~ 250 µm
- = 2 /� � � � �
�
Technische Universität Hamburg-HarburgCompensation techniques III
- Why no H loading?
- AWG’s + attached fibers to big for loading chamber
- no H -induced shift of central wavelength
- no H outdiffusion to take into account
- Problem: such values for n also possible without H loading ?
2
2
2
2�
Technische Universität Hamburg-HarburgCompensation techniques IV
1,45
1,455
1,46
1,465
1,47
57 58 59 60 61 62 63 64 65
µm
refr
acti
ve
ind
ex
UV illuminated
non-UV illuminated
UV-illuminated
�n ~ 10-3
Technische Universität Hamburg-Harburg
Laser1,3 µm
AWG
WDM1.3/1.5
samplingtrigger
Voltmeter
waveformrecorder
cube-cornermirror
LED1,55 µm
polarisationcontroller
Measurement of phase distribution I
K. Takada et al "Measurement of phase error distribution in silica-based arrayed waveguidegrating multiplexers by using Fourier transform spectroscopy”, Electron. Lett. , p.1671 (1994)
J. Gehler and K. Lösch, "Dispersion measurement of AWG´s by Fourier-transform spectroscopy”,ECOC´99, Nice, P2.30, 1999
30
-3
-2
-1
0
1
2
3
0 2 4 6 8 10
Optical path change [mm]
Inte
ns
ity
[a.u
.]
Technische Universität Hamburg-HarburgMeasurement of phase distribution II
H. Yamada et al "Measurement of Phase and Amplitude Error Distributionsin Arrayed-Waveguide Grating Multi/Demultiplexers Based on Dispersive Waveguide”,Journal of Lightwave Technol. , p.1309 (2000)18
Technische Universität Hamburg-Harburg
-2
-1.5
-1
-0.5
0
0.5
1
1.5
2
0 10 20 30 40 50 60 70
Arrayed waveguide number
Ph
ase
[rad
]
phase as fabricated
desired phase distribution
Aim
Technische Universität Hamburg-HarburgExperimental Setup
Technische Universität Hamburg-HarburgExperimental procedure I
-2
-1,5
-1
-0,5
0
0,5
1
1,5
2
2,5
3
0 10 20 30 40 50 60
Arrayed waveguide number
Ph
as
e[r
ad
]
trimming step 1
trimming step 2
trimming step 3
Technische Universität Hamburg-HarburgExperimental procedure II
-0,5
-0,45
-0,4
-0,35
-0,3
-0,25
-0,2
-0,15
-0,1
-0,05
0
0 10 20 30 40 50 60
Arrayed waveguide number
Ph
as
e[r
ad
]
trimming step 1
trimming step 2
trimming step 3
Technische Universität Hamburg-Harburg
-2
-1.5
-1
-0.5
0
0.5
1
1.5
2
0 10 20 30 40 50 60
Arrayed waveguide number
Ph
ase
[rad
]
before UV-trimming
after UV-trimming
Results I
Technische Universität Hamburg-Harburg
-70
-60
-50
-40
-30
-20
-10
0
1542 1547 1552 1557 1562
Wavelength [nm]
Tra
nsm
issio
n[d
B]
before UV-trimming
after UV-trimming
Results II
Technische Universität Hamburg-HarburgConclusion
- UV trimming using frequency doubled Ar-laser
Power: 35 mW @ =244 nm, trimming speed: 0.5 µm/s
- UV-induced index change: n =10
- Reduction of crosstalk level by 8 dB to below -35 dB
- residual crosstalk mainly caused by amplitude errors in the waveguidegrating
- phase correction up to 5 rad without perceptible additional losses
- chromatic dispersion reduced from -0.7ps/nm to 0.1ps/nm
�
�-3
Technische Universität Hamburg-HarburgProspect
- faster trimming
- main requirement: On-line phase measurement
- computer controlled trimming
- UV-written AWG’s ?