© UCL 2004
17TH IEEE/LEOS Conference
Puerto Rico, 7-11 of November, 2004
Modeling Of Optical Coupling To Multimode Polymer Waveguides: Axial And Lateral
Misalignment Tolerance
Guoyu Yu and David R. SelviahDepartment of Electronic and Electrical Engineering
University College London
Outline• Modelling strategy• VCSEL modelling • Coupling optics• Receiver modelling • Results and Discussion
2© UCL 2004
Modeling Diagram
0110
PRBS Driver VCSEL Guide Receiver
Eye
Power
Power meter reading varies with relative lateral and axial misalignment between VCSEL and waveguide
Time information such as eye diagram and thus system BER obtained to meet general specification
BER
3© UCL 2004
Spatial Field Distribution
Polarisation direction
LG00 LG10
LG11 LG01
843 843.5 844 844.5 845 845.5 846
-70
-65
-60
-55
-50
-45
-40
10 Gb/s VCSEL Spectrum at Drive Current i=2.5 mA
Wavelength (nm)P
ow
er
(dB
m)
VCSEL active area
diameter=7 µm
4© UCL 2004
Polar Plot of 4 modes
LG00 LG10
LG11 LG01
5© UCL 2004
Weighted 4 modes
6© UCL 2004
VCSEL Output
0 2 4 6 8 100
1
2
3
4
5
constant output power
Rdiff
=50
typicalbias current range
90°C
13°C
optic
al p
ower
(mW
)
current (mA)
0
2
4ULM002Q02S3066100
vol
tage
(V)
Small-signal transfer function at 25 oC, bias
of 5 and 10 mA
Transient response of single-mode VCSEL
Simulated (left) VCSEL LI output
compared with data from manufacture
(right)
7© UCL 2004
Spatial Output
8© UCL 2004
Spatial Output
9© UCL 2004
Results
Single Mode Four Modes
10© UCL 2004
Power Contour at -1 dB
• The lateral and axial tolerance increase monomatically with the increased guide width (10-60 µm).
• For guide of 100 µm width, tolerance is not improved due to modal noise.
• The lateral and axial tolerance increase monomatically with the increased guide width (10-60 µm).
• Axial tolerance is not as good as single mode due to mode divergence.
Single Mode Four Modes
From inner most, guide with=10, 20, 30, 40, 50, 60, 70 micron
From inner most, guide with=10, 20, 30, 40, 50, 60, 70 micron
11© UCL 2004
0 100 200 300 400 500 600 700 800 900 1000-50
-40
-30
-20
-10
0
10
20
30
40
50
Larger Guides
0 100 200 300 400 500 600 700 800 900 1000-50
-40
-30
-20
-10
0
10
20
30
40
50
0 100 200 300 400 500 600 700 800 900 1000-50
-40
-30
-20
-10
0
10
20
30
40
50
0 100 200 300 400 500 600 700 800 900 1000-50
-40
-30
-20
-10
0
10
20
30
40
50
Guide Width=80m Guide Width=100m
Guide Width=80m Guide Width=100m
1 mode 1 mode
4 modes 4 modes
12© UCL 2004
Experiment
0 10 20 30 40 50 60 70-14
-12
-10
-8
-6
-4
-2
0
Model: w=50 µm, xi=100 µm, zi=100 µm.
Experiment: x scan range: 0-62 µm.
13© UCL 2004
Conclusion
Acknowledgement
•Increased guide width result in improved lateral and axial misalignment tolerance if the guide width is less than receiver aperture size.
•Modal noise will affect the tolerance level when guide width is greater than receiver aperture size.
•EPSRC and Xyratex for financial support
•Anibal Fernandez and Frank Tooley for useful discussion
14© UCL 2004
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15© UCL 2004
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