IN LEITERPLATTEN INTEGRIERTE OPTISCHE VERBINDUNGSTECHNIK AUF DÜNNGLASBASIS

Transcription

1 IN LEITERPLATTEN INTEGRIERTE OPTISCHE VERBINDUNGSTECHNIK AUF DÜNNGLASBASIS Dr. Henning Schröder phone:

2 Outlook n Motivation n Manufacturing n Waveguide integration n EOCB fabrication n Technology transfer roadmap n Demonstrators n Summary

3 Evolution of Optical Interconnects on Board-level Source: Katharine Schmidtke, March 19th, 2014; PhoxTroT 1st Optical Interconnect in Data Centers Symposium, Berlin, Germany

4 Today panel size thin glass is worldwide available and of highest quality n Displayglass can be: n delivered on large panel formate n structured using mature techniques n Supplier n Schott AG (Germany) n Corning (USA) n Asahi (Japan) n Properties n Isolator with very smooth surface n Reliable at high thermal load and dimensional stabile n Low loss buried optical waveguides can be realized Source: Schott

5 Benefit: Optical Interconnects on PCB provide highest intra-system bandwidth n Optical interconnects for data transmission at board level offer n Reduction in power consumption n Increased energy efficiency n Higher system density n Bandwidth scalability: fiber-based optical engines are commercially available n BOA (Finisar) n MicroPod (Avago) Development of an electrooptical backplane with pluggable optical board-to-board connectors

6 Why glass? Benefits of using glass for packaging TIA IC Glass Interposer PD VCSEL Driver IC Glass Interposer EOCB Embedded Optical Waveguide Layer n CTE close to Si and III-V-components n Through vias do not need passivation layer in contrast to silicon n High thermal load and dimensional stability n Transparent material integration of optics n Cost effective glass panels (e.g. display glass)

7 Thin glass can be used for photonic board integration and interposer TIA IC Glass Interposer PD VCSEL Driver IC Glass Interposer EOCB Embedded Optical Waveguide Layer Embedded optical layer in printed circuit board Glass interposer for electrooptical transceivers

8 Glass overview Source: Schott Source: Corning

9 FEM simulation of waveguide process Model-based process parameter determination Data base Glass diffusion characteristics FEM simulation Ion-exchange with mask 1) Determination of glass material parameters 2) FEM simulation of ionexchange waveguide process 3) FEM mode solver (number of modes and characteristics) FEM simulation Mode solver FEM simulation Ion-exchange without mask

10 Thermal ion exchange technology results in graded index buried multimode optical waveguides Ag+ ion-exchange Al sputtering Litho+etching Salt melt (AgNO 3 ) Glass Glass Glass Al removal Na+ ion-exchange Salt melt (NaNO 3 ) Glass Glass Glass waveguide panel (199 x 160 mm) Cross section refractive index profile of MM-GI-WG 10

11 Combined PCB and display processes enable optical waveguide panel size technology Dip-Coater LDI Furnace Laser cutter Aluminum diffusion mask layer on glass panel (297 x 210 mm²). 11

12 Important for Silicon Photonics integration: The higher the wavelength the lower the optical loss n Waveguide characterization results Waveguide cross section 250µm 500µm Index profile Insertion loss [db] λ=850 nm λ=1310 nm Linear (λ=850 nm) Linear (λ=1310 nm) Propagation loss y = 0,41x + 2,70 2 y = 0,05x + 2,15 Elliptical gradient-index profile with maximum below the glass surface (20..25µm) and n of Length [cm] Full mode confinment (50/125µm MMF) Propagation loss (λ=850nm) = 0.41dB/cm Propagation loss (λ=1310nm) = 0.07dB/cm 12

13 Single-mode electro-optical circuit board EU collaborative project PhoxTroT Ø Development of SM electro-optical backplane Partiell embedding of glass panels for mid-board optical interface 140x140mm² glass panel Design and development of out-of plane coupling interface VCSEL waveguide Simulation Waveguide photodiode Waveguide SOI grating coupler SOI grating coupler waveguide

14 Electro-optical backplane PCB design is crucial in terms of performance and reliability n PCB boundary conditions n 4 conventional electrical PCB layers n Outer board area of 281 x 233 mm², board thickness of 3.5 mm n Embedded 500µm thick glass waveguide layer n SEPPLANE1 design: one glass waveguide panel (199mm x 160mm) n SEPPLANE2 design: two glass waveguide panels (79.25mm x 160mm) n Waveguide groups with point-to-point geometries, bends, openings 14

15 Electro-optical backplane fabrication uses slightly adopted standard processes for the optical package n CTE missmatch between materials n Copper: α = K -1 n Glass D263Teco: α = K -1 n FR4 pregreg: α = K -1 n Low temperature bonding applied n 50µm adhesive foil for bonding optical layer n Lamination temperature is below 100 C n Low build-in stress during lamination n Optical package is pre-fabricated n with embedded glass waveguide panel n in the core layer n between prepreg layers with cavities Optical package of SEPPLANE2 with two glass panels 15

16 Low temperature PCB panel lamination of subpackages results in hybrid EOCB Glass waveguide panel (199 x 160 mm) n n n n Electrical through holes outside the glass panel area for interconnect the electrical layers Cavities opened by milling for accessing optical layer Backplane electrically fully functional glass undamaged 16

17 Hybrid EOCB can be automatically assembled with MT compatible receptacle mounts n Design provides standard optical interface n High precision MT receptacle mounts are actively aligned and automated assembled (ficontec) over the waveguides in the glass panel n Direct fiber-optic MT patchcord connection to waveguides within the EOCB n Optical connector housing assembly passivley 17

18 Technology transfer strategy today Process development at Fraunhofer EOCB prototyping at Fraunhofer Project based collaborate EOCB manufachturin g with PCB manufactures, Delivery of structured thin glass sheets Process transfer to - Contract manufactures of structured thin glass sheets - innovative PCB manufactures, licensing

19 Electro-optical backplanes need to carry multiple line cards n Design of the current demonstrator platform n sub-rack chassis n 5 line cards n electro-optical backplane with pluggable optical board-to-board connectors 19

20 Electro-optical backplane fabrication is fully functional n Electrical through holes outside the glass panel area for interconnect the electrical layers n Cavities opened by milling for accessing optical layer n Backplane electrically fully functional - glass undamaged Source: H. Schröder et al. Photonics West 2015, USA In co-operation with: 20

21 New designed optical board-to-board connectors use MT compatible receptacles Line card Backplane Source: H. Schröder et al. Photonics West 2015, USA

22 Precise board assembly of the MT compatible receptacle mounts needs automated active alignment n Assembly equipment used n ficontec pick-and-place assembly equipment with translational axes and two rotatory axes and additional 3-axis manual translation stage for positioning second MT patchcord in front of the same waveguide group for launching purpose n Adhesive dispensing and UV curing and top and bottom vision control cameras Pick-and-place assembling equipment by ficontec 22

23 The MT compatible receptacle mounts can be plugged easily with backplane receptacles n After assembling of all 16 MT receptacle mounts for SEPPLANE1 ready for connectorization Assembled MT receptacle mounts 23

24 Fiber patch cords are inserted into the backplane receptacles n Fiber based n 90 light deflection of optical signals n from the horizontal EOCB waveguides to the vertical test card n Custom short fibre jumpers were designed and developed n These jumpers split out 2 groups of 12 fibres from a single vertical 2x12 MT ferrule to the lowest rows of 2 separate 6x12 MT ferrules n Different backplane connector designs n to accommodate 1 or 2 adjacent MT receptacle mounts n Fiber plugs for test purposes 24

25 4 Different backplane receptacle designs were realized n Backplane receptacle built-up n Head section (black section) designed to support a compliant MT ferrule and its own shutter designed to interlock with that of the engaging plug n The receptacle housing (white section) incorporates the short fiber-optic patchcord n 4 varieties of backplane receptacle à different board positions, connector configurations and orientations Head section Housing 25

26 For the first time 32 Gb/s/ch have been demonstrated at ECOC 2014 for the glass based optical backplane n Live demonstration n Anritsu booth n MP1800A pattern generator n 32 Gb/s/ch n Bit error < n 850 nm Source: H. Schröder et al. Photonics West 2015, USA

27 Several realized prototypes show successful collaboration results n Ilfa GmbH, Seagate n Contag GmbH 27

28 The fitting plugs at the line cards interconnect the optical engines by fiber patch cords n Line-card with connector plug n Mounted on the edge of the line-card n Plug housing is designed to support an MT type ferrule with shutter to prevent dust contamination and for eye safety n Engagement features integrated for accurate coupling to another compliant MT ferrule housed in the receptacle section mounted on the backplane Housing Shutter Line-card 28

29 2 Demonstrator versions based on 2 backplane layouts n Features: n 7U sub-rack chassis n 5 pluggable line cards based on the Euro-card form factor supporting 850 nm optical engines and pluggable optical connectors n Pluggable connector system comprising connector plug, different backplane receptacles and MT receptacle mount for direct passive optical connectivity n Optical backplane

30 The higher the wavelength the lower the link loss n Bidirectional insertion loss measurements n Insertion loss at λ=850nm: 10.7 db n Insertion loss at λ=1310nm: 3.9 db Insertion loss between point 1 Fiber patch cord Fiber patch cord Optical connector Optical waveguide Optical connector

31 BERT measurements show bit error free operation Eye diagrams for 10.3 Gb/s with PRBS test with signals convoyed at 1310 nm over 12 waveguides on the optical backplane

32 Next step: Single-mode glass waveguides Waveguide cross section 125µm n Index profile Propagation loss 0 y [µm] n=1.52 n=1.523 Insertion loss [db] y=0.05x x [µm] Elliptical gradient-index profile with maximum below the glass surface (5µm) and n of Length [cm] Propagation loss (λ=1550nm) = 0.05dB/cm

33 Conclusion n EOCB will overcome bandwidth limitations in next generation power efficient data center systems n Thin glass based photonic waveguide integration is successfully developed and demonstrated for multimode (and singlemode!) n Glass waveguide panel embedding without build-in stress or glass damaging was demonstrated n Fully functional and reliable pluggable optical board-toboard connector was assembled n Performance demonstrated up to 32 Gb/s/ch n Transfer to PCB manufactures will be next step 33