h igh s peed, p luggable o ptical b ackplane c onnector t echnology richard pitwon, ken hopkins,...
TRANSCRIPT
HIGH SPEED, PLUGGABLE OPTICAL
BACKPLANE CONNECTOR TECHNOLOGY
HIGH SPEED, PLUGGABLE OPTICAL
BACKPLANE CONNECTOR TECHNOLOGY
Richard Pitwon, Ken Hopkins, Dave MilwardXyratex Technology Ltd
International Symposium on Photonic Packaging
Electrical Optical Circuit Board and Optical Backplane
organized by Fraunhofer IZM & VDI/VDE-IT
Munich, GermanyNovember 2006
David R. Selviah, Ioannis PapakonstantinouKai Wang, F. Anibal FernándezUniversity College London (UCL)
Purpose
British government funded initiative to investigate incorporation of optical backplanes into high bandwidth systems and develop solutions
THE STORLITE PROJECT
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University College London
Investigation into performance enabling polymer waveguide
structures and characterisation
Xyratex
Investigation into optical backplane connector technology and prototype
solution development
Exxelis Ltd
Optical PCB manufacture
Duration
June 2003 – November 2005
RESEARCH OBJECTIVES
• Investigation of current state of the art in optical PCB technology research
• Polymeric waveguide fabrication and characterisation
• Optical PCB Design Rules
• Investigation into low-cost technology drivers
• Method of pluggable daughtercard connection to an optical backplane
• Development of prototype solutions
• Parallel optical transceiver and pluggable optical backplane connector
• Development of prototype demonstration assembly
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RESEARCH AND DEVELOPMENT OVERVIEW
• High speed parallel optical transceiver
• Opto-mechanical registration interface
• Low-cost optical backplane connection
mechanism
• Low cost precision optical alignment and
assembly method
• Optical PCB interface coupling method
• Prototype demonstration unit
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HIGH BANDWIDTH BACKPLANE ENVIRONMENTS
48 Drive RAID Storage System
12 Drive SBOD Storage System
16 Drive EBOD Storage System
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HIGH BANDWIDTH BACKPLANE
Power Module
Multi Layer Interconnect Backplane
Controller
Module
Dual PortDisk Drives
Air FlowChannels
High Speed Connectors
To Controllers
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BACKPLANE ENGAGEMENT MODEL
Orthogonal daughtercard
engagement to backplane
Embedded optical channels to
carry high speed serial signals
between cards
Copper layers to carry power,
control signals and low speed
signals
High bandwidth backplane
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Daughtercard
VCSEL
PROPOSED COUPLING PRINCIPLE
Optical Waveguides
Backplane
Surface emitting photonics used
on daughtercard interface
Butt-coupling scheme allows for
minimum number of
intermediary optical interfaces
Copper Planes
Copper Traces
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PARALLEL OPTICAL TRANSCEIVER DESIGN
• Quad duplex parallel optical transceiver
• 10.3 Gbps per channel (82 Gb/s aggregate bandwidth)
• Electronic daughtercard connector
• Flexible and rigid PCB sections
• Optical backplane interface
Flexible mid-section
Rigid base section
Rigid optical
interface
Electronic
connector
Active opto-mechanical
coupling interface
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PHOTONIC INTERFACE
DESIGN
Source: ULM Photonics GmbH
Source: Microsemi Corporation
Source: GRINTech GmbH
VCSEL ArrayVCSEL Array
PIN ArrayPIN Array
GRIN Lens ArrayGRIN Lens Array
MT compatible
interface
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OPTOELECTRONIC PCB WITH MT – SOCKET
INTERPOSER
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(a)
(b)
MT-socket interposer
MT-plugCeramic lens holder
MT-pins
MT - SOCKET INTERPOSER ON THE TOP OF
BACKPLANE
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3.8870 ± 0.00010.35650 ± 0.00001
0.66
±
0.01
0.02 mm0.53125 mm
3.8825 ± 0.005 mm
0.25 mm
ACTUAL ALIGNMENT OF THE
COMPONENT
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waveguides
registration features
3886 µm
SUPPORT DAUGHTERCARD DESIGN
4 XFP ports
PCB material
Rogers 4350 on
outer layers
Transceiver receptacle
4 Port 10 GbE LAN Physical Relay board
Host interface
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CHARACTERISATION SETUP
MT patchcord for
stand alone testing
Physical layer relay
board
• Test traffic: 10 GbE LAN (10.3 Gbps)
• VCSEL bias current: 11.91 mA
• VCSEL modulation current: 9.8 mA
• Divergence: 25°
• Output optical power: 0.43 mW
• Average optical jitter: 31.2 ps (Pk – Pk)
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CONNECTOR MECHANISM
Principal Function
Elevation and retraction of optical interface
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ALIGNMENT METHOD BASED ON MT
CONCEPT
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daughtercard MT-pin
4 VCSEL array
MT-pin
4 PD array
x
z
y
θφ
backplanearray of 12waveguides
MT-holes
POLYMER OPTICAL WAVEGUIDE TECHNOLOGY
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POLYMER WAVEGUIDE CHARACTERISTICS
Waveguide Material
UV-curable polymeric acrylate (Truemode®)
Propagation loss @ 850 nm: 0.04 dB/cm
Heat degradation resilience: up to 350°C
Waveguide properties
Size: 70 µm x 70 µm
Core index: 1.556
Cladding index: 1.526
Numerical aperture: 0.302
Waveguide Array
Centre to centre pitch: 250 µm
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PROTOTYPE DEMONSTRATOR CONSTRUCTION
Separate passive
electrical backplane
Passive Electrical Backplane
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Daughtercard Guide Features
PROTOTYPE DEMONSTRATOR CONSTRUCTION
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Daughtercard Power Supply
PROTOTYPE DEMONSTRATOR CONSTRUCTION
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Daughtercard to Optical Backplane Coupling Evaluation
PROTOTYPE DEMONSTRATOR CONSTRUCTION
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Optical Backplane Integration
Separate optical PCB
PROTOTYPE DEMONSTRATOR CONSTRUCTION
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Complete Demonstration Unit
PROTOTYPE DEMONSTRATOR CONSTRUCTION
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TEST AND CHARACTERISATION
Optical Coupling Characterisation
Test traffic: 10 GbE LAN (10.3 Gbps)
Wavelength: 850 nm
Reference Signal – No Waveguide
Jitter : 0.34 UI
Relative Loss: 0 dB
10 cm Waveguide with Isapropanol
Jitter 0.36 UIRelative Loss 4.5 dB
10 cm Waveguide – Diced and Polished
Jitter 0.56 UIRelative Loss 6.9 dB
10 cm Waveguide – Diced Only
Jitter 0.89 UIRelative Loss 7.9 dB
Arrangement:
Active connector – waveguide - patchcord
Multimode MT fibre
patchcord
Active prototype
connector
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TEST AND CHARACTERISATION
Arrangement:
Test traffic source (10 GbE LAN)
Fibre cable
XFP Port 1 (Rx)
Daughtercard 1
Connector 1 (Tx)
Optical PCB
Connector 2 (Rx)
Daughtercard 2
XFP Port 2 (Tx)
Fibre cable
Traffic Capture
High Speed Network Link Evaluation
Bit Error Rate < 10-12
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CONTOUR MAP OF VCSEL AND PD
MISALIGNMENT
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(a) Contour map of relative insertion loss compared to the maximum coupling position for VCSEL misalignment at z = 0.
(b) Same for PD misalignment at z = 0. Resolution step was Δx = Δy = 1 µm.
Dashed rectangle in the middle of the maps corresponds to the expected relative insertion loss according to the calculated misalignments along x and y in text slides.
The minimum insertion loss was 4.4 dB, corresponded to x = 0, y = 0, z = 0
TOLERANCES ALONG X, Y AND Z FOR CONNECTOR
COMPONENTS
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X y Z
MT-plug 3 μm (pin-to-pin) 3 μm (pin-to-GRIN) ________
MT-socket 3 μm (hole-to-hole)3 μm (hole-to-
waveguide)________
OPCB features
+2.5 μm (increase in registration wall-to-wall spacing due to
overexposure) 2.5 μm (due to 5 μm
extra spacing between feet of
interposer)
1 μm (core thickness control)
+10 μm (accuracy of dicing in respect to the dicing
lines on the board) +2.5 μm (backstop shift
due to overetching)
Tolerance of MTinterposer socket
towaveguides
8 μm or 3 μm ifoverexposure widening
isknown and reproducible
4 μm
+12.5 μm or +10 μm if overexposure widening
is known and reproducible
Combined tolerance
of VCSEL and PIN to
waveguides
11 μm or 6 μm ifoverexposure widening
isknown and reproducible
7 μm
+12.5 μm or +10 μm if overexposure widening
is known and reproducible
RELATIVE INSERTION LOSS OF VCSEL AND PD AS THEY MOVE AWAY FROM THE OPCB
WAVEGUIDES.
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0
0.5
1
1.5
2
2.5
3
3.5
4
0 20 40 60 80 100 120 140 160 180 200
axial distance z (μm)
Inse
rtio
n L
oss
(dB
)
VCSEL
Photo Detector
CROSSTALK MEASUREMENT
1
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Power received at the end of 0th waveguide as a function of the lateral distance of the VCSEL from its center. The boundaries and the centers of the waveguides on the
backplane are marked. In the cladding power drops at a rate of 0.011 dB/µm
-250 0 250 500 750 1000 1250 1500
-35
-30
-25
-20
-15
-10
-5
0
x (m)
Rel
ativ
e p
ower
at
0th
wav
egu
ide
(dB
)
VCSEL
0th 1st 2nd 3rd 4th 5th 6th
PD
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Signal-to-cross-talk (SCR) levels that 0th waveguide experiences from its adjacent waveguides.
-70 -50 -30 -10 0 10 30 50 700
5
10
15
20
25
30
35
x (m)
SXR
(dB
) 1st
2nd
3rd
4th
5th
6th(b)
CROSSTALK MEASUREMENT
2
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SCR experienced by waveguides number 1 and 4 and of waveguides number 2 and 3 from the array of four in the connector if all are in use. Dashed-dot lines determine the
boundaries of the maximum expected cross-talk based on current connector tolerances.
-80 -60 -40 -20 0 20 40 60 800
5
10
15
20
25
x (m)
SCR
(dB
)
1 and 4 waveguides in connector
2 and 3 waveguides in connector
CROSSTALK MEASUREMENT
3
STABILITY TESTING OF THE MT – SOCKET INTERPOSER 1
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Insertion loss and signal to cross-talk (SCR) as a function of mating cycle for 75 engagements.
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Histogram of insertion loss
STABILITY TESTING OF THE MT – SOCKET INTERPOSER 2
Purpose
Industrial collaborative effort to develop commercial technology drivers for optical backplane and connector technology and drive the proliferation of optical backplane technology into the industrial sector
THE CANDEO PROJECT
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Xyratex
Commercial development of proprietary parallel optical
transceiver technology
Samtec
Commercial development of optical backplane engagement mechanism
CANDEO CURRENT STATUS
• High speed parallel optical transceiver design modified for
commercial design
• Single stage optical backplane engagement mechanism
developed
• Commercial form factor module designed and developed
• First mechanical prototype on exhibition by Samtec and Xyratex
at Electronica 2006, Samtec booth 419 in Hall B4
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Phase I(currently underway)Phase I(currently underway)
INTEGRATED OPTICAL AND ELECTRONIC PCB MANUFACTURING
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Academic PartnersUniversity College London (UCL) – Waveguide design, modelling, measurementHeriot-Watt University – Direct UV laser waveguide fabrication Loughborough University – Laser ablation, surface treatment, printing waveguide fabrication, flip-chip assembly
Industrial PartnersXyratex – End user and project manager BAE Systems – End userRenishaw – End user Exxelis – Polymer chemistry, lithographic waveguide fabricationCadence – PCB layout toolsRsoft Design – Optical modeling toolsXaar – print head technology
Purpose
To compare multimode, polymer waveguide manufacture techniques for large area optical backplanes and to develop design rules.
SUMMARY
Xyratex White Papers • An Optical Backplane Connection System with Pluggable Active Board Interfaces(available from Xyratex website)
• Pluggable Optical Backplane Connector Technology (available)
• Optical vs Copper Cost and Performance Evaluation (pending)
www.xyratex.com
Xyratex White Papers • An Optical Backplane Connection System with Pluggable Active Board Interfaces(available from Xyratex website)
• Pluggable Optical Backplane Connector Technology (available)
• Optical vs Copper Cost and Performance Evaluation (pending)
www.xyratex.com
Intellectual Property 7 patent applications related to optical PCB interconnect and communication structures and methodologies
Intellectual Property 7 patent applications related to optical PCB interconnect and communication structures and methodologies
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SUMMARY
UCL Publications (available from UCL website)
Papers published on waveguide devices
• Sources misalignment x, y, z
• Detector misalignment x, y, z
• Straight tapered waveguide
• Bends
• Propagation loss
• Thermal optics switch
• Power splitter
• Precision low cost alignment
www.ee.ucl.ac.uk/%7Eodevices/
UCL Publications (available from UCL website)
Papers published on waveguide devices
• Sources misalignment x, y, z
• Detector misalignment x, y, z
• Straight tapered waveguide
• Bends
• Propagation loss
• Thermal optics switch
• Power splitter
• Precision low cost alignment
www.ee.ucl.ac.uk/%7Eodevices/
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Thank You for Your Attention
Richard C A PitwonSenior Photonics Engineer
Ken HopkinsHardware Architect
Dave MilwardDevelopment Manager
E-mail: [email protected]
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David R SelviahF. Anibal Fernández Senior Academics
Ioannis PapakonstantinouPostgraduate Researcher
Kai WangResearch Fellow
E-mail: [email protected]
Acknowledgements
UK Department of Trade and Industry
EPSRC
ExxelisDr Navin Suyal
Prof. Frank Tooley