1. © UCL 2004 17 TH 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. Selviah Department of Electronic and Electrical Engineering University College London Outline Modelling strategy VCSEL modelling Coupling optics Receiver modelling Results and Discussion

2. © UCL 2004 2 Modeling Diagram 0110 PRBS Driver VCSELGuide 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 3 Spatial Field Distribution Polarisation direction LG00 LG10 LG11LG01 VCSEL active area diameter=7 µm

4. © UCL 2004 4 Polar Plot of 4 modes LG00 LG10 LG11 LG01

5. © UCL 2004 5 Weighted 4 modes

6. © UCL 2004 6 VCSEL Output Small-signal transfer function at 25 o C, 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 7 Spatial Output

8. © UCL 2004 8 Spatial Output

9. © UCL 2004 9 Results Single Mode Four Modes

10. © UCL 2004 10 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

11. © UCL 2004 11 01002003004005006007008009001000 -50 -40 -30 -20 -10 0 10 20 30 40 50 Larger Guides Guide Width=80  m Guide Width=100  m Guide Width=80  m Guide Width=100  m 1 mode 4 modes

12. © UCL 2004 12 Experiment Model: w=50 µm, xi=100 µm, zi=100 µm. Experiment: x scan range: 0- 62 µm.

13. © UCL 2004 13 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 14 VCSEL Cylindrical geometry uniform current injection linear gain

15. © UCL 2004 15 Receiver