Anibal Fernández, F.

Baghsiahi, H.

Papakonstantinou, I.

Selviah, D.R.

Wang, K.

Yu, G.

English

UCL Discovery

Copyright © 2008 UCLDesign Rules for Polymer Waveguides and Measurement TechniquesKai Wang, David R. Selviah, Hadi Baghsiahiand F. Anibal FernándezOptical Devices & Systems, Department of Electronic & Electrical Engineering, UCL (University College London)Ioannis PapakonstantinouSharp Laboratories of Europe Ltd (formerly at UCL)Guoyu YuOpTIC Technium (Part of UCL)Chairman: Henning Schröder, Co-Chairman: David R. SelviahInternational IEEE Symposium on Photonic PackagingElectrical Optical Circuit Board and Optical BackplaneSponsored by Fraunhofer IZM, VDI/VDE, IEEE-CPMT and IEEE-LEOSMesse Munich, co-located with Electronica, Germany, 13th November 200821. Motivation: Optical versus Electronic interconnect Demonstrator Structure2. Waveguide fabrication techniques3. Measurement technique4. Crosstalk and loss measurement Straight waveguides Crossings Bends5. Optical system design2 Copyright © 2008 UCLOutline31. Motivation: Optical versus Electronic interconnect Demonstrator Structure2. Waveguide fabrication techniques3. Measurement technique4. Crosstalk and loss measurement Straight waveguides Crossings Bends5. Optical system design3 Copyright © 2008 UCLOutline4Optical versus Electronic Interconnect• Copper tracks become inefficient as data rates rise above 10 Gb/s• Latency delay• Skin effects in the conductors• Cross-talk• Electromagnetic Interference (EMI)• Reflection• Signal loss and manufacturing cost increases.• Optical interconnect has potential benefits• Less delay due to no RC components.• Low propagation loss 0.03 - 0.06 dB/cm at 850 nm wavelength inwaveguide < 50 50 m in cross-section.• Do not require impedance matching.• Wide bendwidth• Wavelength division multiplexing is achievable.Copyright © 2008 UCL5 Copyright © 2008 UCLDemonstrator SchematicOptical and ElectronicInterconnectsBackplaneMezzanine Board (DaughterBoard, Line Card)Optical Connector61. Motivation: Optical versus Electronic interconnect Demonstrator Structure2. Waveguide fabrication techniques3. Measurement technique4. Crosstalk and loss measurement Straight waveguides Crossings Bends5. Optical system design6 Copyright © 2008 UCLOutline7Fabrication Techniques and Waveguides SamplesCopyright © 2008 UCLStraight waveguides – Optical InterLinks  90° Crossings – Dow Corning90° Crossings – Heriot Watt University 50° Crossings – Exxelis 8Photolithographic Fabrication of Waveguides Copyright © 2008 UCL9End Facets of WaveguidesCopyright © 2008 UCLThrough Nomarski Microscope with both front and back illumination101. Motivation: Optical versus Electronic interconnect Demonstrator Structure2. Waveguide fabrication techniques3. Measurement technique4. Crosstalk and loss measurement Straight waveguides Crossings Bends5. Optical system design10 Copyright © 2008 UCLOutline11 Copyright © 2008 UCLOptical Loss Measurement850 nm VCSELIntegrating sphere photodetector150 μm pinholenW Power Meter50/125 μm step index fibremode scrambler RIndex matching fluid 0 dBm-1.63 dBm-1.63 dBm15.3 mm50 ×75 µm12Source: ULM Photonics GmbHSource: Microsemi CorporationSource: GRINTech GmbHVCSEL ArrayPIN ArrayGRIN Lens ArrayMT compatible interfaceVCSEL Array for Crosstalk Measurement Copyright © 2008 UCL131. Motivation: Optical versus Electronic interconnect Demonstrator Structure2. Waveguide fabrication techniques3. Measurement technique4. Crosstalk and loss measurement Straight waveguides Crossings Bends5. Optical system design13 Copyright © 2008 UCLOutline14 14• 70 μm × 70 μm waveguide cross sections and 10 cm long• In the cladding power drops linearly at a rate of 0.011 dB/µm• Crosstalk reduced to -30 dB for waveguides 1 mm apartCopyright © 2008 UCLDesign Rules for Inter-waveguide Cross TalkPD with 75 µm pinholeVCSEL x (µm)Normalized Transmitted Power (dB)0th 1st 2nd 3rd 4th 5th 6th -1styx z1 mmRecommendedUsed15 Copyright © 2008 UCLSchematic Diagram Of Waveguide Crossings at 90° and at an Arbitrary Angle, θ16 16 Copyright © 2008 UCLDesign Rules for Arbitrary Angle Crossings• Loss of 0.023 dB per 90° crossing consistent with other reports• The output power dropped by 0.5% at each 90° crossing• The loss per crossing (Lc) depends on crossing angle (θ),Lc=1.0779 · θ -0.8727.RecommendedUsedLoss per crossing (dB)Crossing angle (degree)Power drops 0.08 dB at 20°0.023 @ 90Width (μm) Optimum Radius (mm) Maximum Power (dB)50 13.5 -0.7475 15.3 -0.91100 17.7 -1.1850 µm × 50 µm 75 µm × 50 µm 100 µm × 50 µm Bend radius (mm)Transmitted power (dB)17 Copyright © 2008 UCLLoss of Waveguide BendsRecommendedUsed181. Motivation: Optical versus Electronic interconnect Demonstrator Structure2. Waveguide fabrication techniques3. Measurement technique4. Crosstalk and loss measurement Straight waveguides Crossings Bends5. Optical system design18 Copyright © 2008 UCLOutlineInput power (dBm/mW) -2.07 / 0.62Coupling loss (dB) 4.4 at both input and output endsPropagation loss (dB/cm)0.08Bend 90°Radii (mm) 15.000 15.250 15.500 15.725 16.000 16.250Loss per bend (dB) 0.94 0.91 0.94 0.94 0.95 0.95CrossingsCrossing angles (°) 22.27 29.45 36.23 42.10 47.36Loss per crossing (dB) 0.078 0.056 0.047 0.041 0.037Min. detectable DC power (dBm/mW)-15 / 0.03Min. DC power no BER at 231 (dBm/mW)-12 / 0.0619 Copyright © 2008 UCLPower Budget20 Copyright © 2008 UCLCalculated Waveguides OutputNo. CrossingsNo. BendsStraight (cm) Calculated outputwithout index matching (dBm)Calculated outputwith index matching (dBm)1 0 4 2.17 9.71 7.312 0 4 2.17 9.71 7.313 0 4 2.14 9.72 7.324 3 4 2.24 10.00 7.605 5 4 2.04 10.09 7.696 3 4 5.95 10.22 7.827 3 4 5.78 10.25 7.858 2 4 6.80 10.24 7.849 4 4 9.67 10.66 8.2610 0 4 12.99 10.89 8.4911 0 6 16.30 13.10 10.7012 0 6 20.19 13.48 11.0821 21System DemonstratorFully connected waveguide laid out using design rulesCopyright © 2008 UCL22Demonstrator Dummy BoardCopyright © 2008 UCLWaveguides were printed out using solder resist for visualization 23 Copyright © 2008 UCLDemonstrator with Optical Interconnects24 Copyright © 2008 UCLThe Shortest Waveguide Illuminated by Red Laser 25 Copyright © 2008 UCLWaveguide with 2 Crossings Connecting 1stto 3rd Linecard Interconnect26 Copyright © 2008 UCLOutput Facet of the Waveguide Interconnection 27Conclusions• Characterised photolithographically manufactured acrylate polymermultimode waveguide• Design rules derived from the experimentsCopyright © 2008 UCLAcknowledgment The authors thank EPSRC via IeMRC for funding Xyratex Technology Ltd Dave Milward, for managing the project, Ken Hopkins, and Richard Pitwon, for helpful discussions. Exxelis Ltd Navin Suyal and Habib Rehman, for waveguide fabrication. Cadence• Gary Hinde, for technical support.• Stevenage Circuits Ltd• Jonathan Calver, Jeremy Rygate and Dougal Stewart forfabricating waveguide dummy board.• David R. Selviah for being technical lead28The EndThanks for Your AttentionAny Questions?

Design rules for polymer waveguides and measurement techniques

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