1 [email protected]Fujitsu Laboratories of America ● Sunnyvale ● CA Enabling Technologies for Board Enabling Technologies for Board- Level Level Optical Interconnects Optical Interconnects Alexei L. Glebov Advanced Optoelectronics Technology Department Fujitsu Laboratories of America 1240 E. Arques Ave., Sunnyvale, CA presented at joint IEEE CPMT & LEOS SCV chapter meeting January 11, 2006 [email protected]Fujitsu Laboratories of America ● Sunnyvale ● CA Fujitsu Laboratories of America Fujitsu Laboratories of America Fujitsu Laboratories of America (FLA) is a wholly owned subsidiary of Fujitsu Laboratories (Japan) FLA was established on April 20, 1993 Location: Sunnyvale, California ~ 100 employees
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Enabling Technologies for Board-Level Optical Interconnectsewh.ieee.org/soc/cpmt/presentations/cpmt0601.pdf · Enabling Technologies for Board-Level Optical Interconnects Alexei L.
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1st Wave of Optical Interconnect Development 1st Wave of Optical Interconnect Development
Success story: 1st optical backplane deployed in a large-scale telecommunication platform or supercomputer was deployed in 1994 by AT&T in DACS Vi-2000 digital access and cross-connect system. From ECTC 1993 by Grimes et al.
155 Mbps
For telecom market was OK
BUT, no broad electronics market was ready to adapt optical boards at that point
Transition from Electrical to Electro-Optical BackplaneTransition from Electrical to Electro-Optical Backplane
Standard electronic packageOptical Backplane
Fabrication of additional lightguiding layer on PCBAssembly (Integration) of Tx and Rx on linecardsLight coupling to lightguiding layer through optical
VCSELs - most popular light sources for OI nowGrown epitaxially from III-V materials on wafer levelTypical wavelengths: 850 and 980 nmVCSELs with λ=1.3-1.5 µm are available10 Gb/s are commercial, up to 20 Gb/s in research
Source: Fuji Xerox, Ulm Photonics
VCSEL structure
Source: Fuji Xerox
10 Gb/s, 850nm multi-mode VCSEL
VCSEL arrays
Open Questions:VCSEL reliability (getting better)Max speed maybe 20 Gb/s, for reasonable cost (?)LatencyPower/thermal managementCost
Alternative Transmitters for OI in ResearchAlternative Transmitters for OI in Research
External ModulationSi PhotonicsElectronic-Photonic IC (EPIC)
External Modulation of CW light source
Intel’s solution for Si-based transceiver.“In 2005, Intel researchers further demonstrated that this silicon modulator is capable of transmitting data up to 10 gigabits per second (Gbps).”
For 850 nm both Si and InGaAs detectors can be usedSi PIN is less expensive but has lower responsivity and bandwidthFor 1310 and 1550 InGaAs detectors are usedInGaAs PIN can support up to 40 Gb/s transmissionSiGe detectors are in research to replace InGaAs in Si photonics
Bit Error Rate (BER) is strongly dependent on the optical signal intensity at the detector Thus, low total insertion loss of the module is crucial!
Schematic of PIN photodiode
Spectral response of different diodes
1.5 Gb/s optical link BER vs. received optical powerWang et al. JLT v. 22, p. 2158, 2004
Different fabrication techniquesTypical dimensions 30-50 µmThe dimensions can go down to 5 µmExpected propagation losses <0.1 dB/cmHigh thermo-mechanical stabilityIntegration compatible
Can be embedded on boards or fabricated separately and then laminated
Polymer Materials for OI Waveguide FabricationPolymer Materials for OI Waveguide Fabrication
Low absorption lossRefractive Index stability Refractive Index variabilityPhotopatternable for lithographyAdhesion to various materialsSurface planarizationThermal stabilityLow water uptakeLow stressCTE matchTemperature compatibility with FR4 processingViscosity adjustment for thickness controlAnd so on ….
Source: L. Eldada, Dupont Photonics
Some optical polymers - candidates for waveguide fabrication
Basic requirements for vertical mirrors:Symmetric for in and out couplingTurning light up and downPrecise mirror plane positioning control ( ± 2-3 µm) for 20-30 µm WGHigh reflectivity (80-90%)Full integration with waveguides
Light coupling schemes for chip on board surface mountIn chip-to-chip board level OI the board also contains embedded waveguides with integrated mirrors, so the board fabrication is very similar.
However, instead of connector assembly we have to deal with chip assembly and alignments.
“The future of optical components technology will be determined by electronic-photonic convergence and short-reach (< 1km) interconnections. Needless to say, this path requires significant technological development.”
“Electronics-photonics must converge”
“The roadmap's conclusion was that III-V materials have typically led in terms of performance; silicon has followed with its trend towards high-volume low-cost manufacturing; and organics have greatest potential for supporting hybrid integration and packaging.”
Some Additional LiteratureSome Additional Literature
D. A. B. Miller “Rationale and Challenges for Optical Interconnects to Electronic Chips”, Proc. IEEE, v. 88, p. 728 (2000)M. W. Haney, H. Thienpont, T. Yoshimura, “Introduction to the issue on optical interconnects”, J. Select. Topics Quant. Electron., vol. 9, p. 347-349 (2003); and other papers in the volume.Agarwal et al. “Latency reduction in optical interconnects using short optical pulses”, J. Select. Topics Quant. Electron., vol. 9, p. 410 (2003)Cho et al. “Power consumption between high speed electrical and optical interconnects for interchipcommunication”, J. Lightwave Technology, v. 22, p. 2021 (2004)Huang et al. “Optical Interconnects: Out of the box forever?”, J. Select. Topics Quant. Electron., vol. 9, p. 614 (2003)L. Eldada, “Polymer integrated optics: promise vs. practicality,” Proc. SPIE, vol. 4642, p. 11 (2002)T. Yoshimura et al, “Self-organized lightwave network based on waveguide films for 3D optical wiring within boxes,” J. Lightwave Technol., vol. 22 , p. 209 (2004)“Handbook of Optical Interconnects” edited by S. Kawai, Taylor & Francis (2005)“Selected papers on optical interconnects and packaging”, SPIE milestone series, volume MS 142, editor S. H. Lee (1997)Glebov et al., “Optical Interconnect modules with fully integrated reflector mirrors”, IEEE Phot. Tech. Lett., v. 17, p. 1540 (2005)Glebov et al. “Backplane photonic interconnect modules with optical jumpers”, Proc. SPIE, v. 5731, p. 63 (2005)