hdp user group international, inc. optical...

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HDP User Group International, Inc.Optical Interconnect

© HDP User Group International, Inc.

Date of Presentation•Project in the Definition Stage

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Optical Backplane Interconnect


Purpose

Chances for optical interconnect

To meet the ever increasing bandwidth demands, we need higher data rate, higher channel density and longer interconnect link length in telecom and datacom systems.

For electronic interconnect, there are some fundamental obstacles (such as loss, crosstalk, reflection and parasitics) to block it meeting the increasing bandwidth demands

In the near future, the cost of electronic interconnect will exceed the cost of optical interconnect, and optical interconnect will be the preferred solution for short-range interconnect (rack-to-rack, backplane, inter-board, and even inter-chip).

Optical PCB technology has been researched for many years, and some groups have already built some optical backplane prototypes. Optical backplanes will be very likely to be applied in high speed systems in the future 5~10 years.

3© HDP User Group International, Inc.

Challenges for optical interconnect

Although optical PCB technology has been researched for many years, some related technologies are still not mature

Waveguide fabrication at production scale Optical PCB fabrication Optical coupling (such as device-board and board-to-backplane) Assembly Optoelectronic devices in standard ”IC-like” packages used in

optical PCB Reliability (waveguide, connector, OE device, packaging materials,

and system-level qualification) Test vehicles… Testing methods, equipments and applied standards

These obstacles need to be removed before optical PCB technology can be Applied in industry.



The key objectives of the project is to:

Survey the technologies bottleneck in optical interconnect . Compare key technologies with experimental qualification or

proof-of-concept demos. Define an optical backplane Interconnect prototype. Assemble an optical backplane Interconnect demonstrator

and test. Establish optical backplane Interconnect practice application

guidelines. Pave the way for deployment of optical backplane

interconnect technologies into applications where it is superior to electronic signal transmission.

Project Goals

1. Complete survey on existing and emerging short-range (backplane level and board level) optical interconnect technologies for technology benchmark and roadmap including

Technical status and available components for Devices and O/E-packages (inc. OE-devices, driving electronics, OE-packages) Coupling interfaces (incl. device-board, board-to-BP, board-to-board, off-board/BP) Substrates and integration technologies (inc. OE boards, OE-Backplanes, materials) Current technical status in each building block Design practice Qualification & Standards

Technology Roadmap Applications and product examples Benefits, challenges, limitations Technical problems or roadblocks Competing technologies or alternatives Significant IPs & Patents


2. Design, manufacture and qualify optical interconnect model design/ test vehicle to analyze the feasibility, reliability and cost effectiveness of O/E technology

Target application/ product case (electrical benchmark if possible) Definition & specifications Design, modelling & simulation Selection of devices, couplers & connectors, materials, package types &

methods Fabrication of test vehicles Qualification & reliability testing Cost model & analysis

3. Publish report on Technology benchmark & roadmap, project results and design guidelines.


Technical Discussion


Structure of one optical backplane system

1 5

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3 34 7

6

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Legend:1. Couping interface (device-Board)2. Waveguide in board3. Board to Backplane Connection4. Waveguide in Backplane5. Transceiver module (VCSEL/PD,

laser driver, TIA)6. Board7. Backplane


Some requirements for optical backplane

Optical interconnect need to co-exist with electrical interconnect on a substrate;

The methods used for manufacturing optical backplane and the tolerance involved should be compliant with those of electrical backplane ;

Assembly should be simple; Optical alignment (optical device to connector, connector to board, board to

backplane) should be passive; Optical Connectors need to be pluggable and co-exist with electronic

Connectors on a board, and have reasonable alignment tolerance; Thermal, mechanical, chemical stability； Cost of optical solution should be comparable to that of electrical solution。


Key technologies and challenges involved in optical Backplane:

Waveguide and optical PCB manufacturing Optoelectronic device Optical coupling device and optical connector Assembly Testing and reliability assessment of optical PCB assembly


1. Waveguide and optical PCB manufacturing Waveguide material

polymer (Acrylate , Epoxy, Polysiloxane, Siloxane …) glass

Waveguide fabrication techniques Photolithography Injection molding Direct laser writing Laser ablation…

Requirements for waveguide and optical PCB fabrication technology Low intrinsic loss and waveguide propagation loss Thermal, mechanical, chemical stability Low waveguide aging loss (during at least 10 years) Compatibility for processes and materials


Routing capability (straight, bends, crossings, tapering, splitting) Large area waveguide processing capability High density waveguide processing capability (single layer and multilayer) Lamination compatibility (adhere to various materials, particularly FR4) Temperature compatibility with standard PCB lamination and soldering

process High accurancy of waveguide fabrication and PCB lamination process Testing and quality control during process Maturity of the technology

El ecr i cal l ayer

Cor eCl addi ng

wavegui de

del t a Y

del t a X

W

H

Pi t ch X

Pi t ch Y


2. Optoelectronic deviceKey indexes for OE device:

Power consumption (mW/Gpbs) Channel data rate Number of channels per module (parallel, not WDM) Dimension Optical port density Transmitter output power Receiver sensitivity Operating wavelength Reliability Package and interface

Electrical interface: BGA, LGA… Optical interface：MT, free space…

Cost


The optical interface of OE device is a pivotal aspect, and it is very dependent on the coupling structure between OE device and board.

a optical sub-unit [2]a assembled 12-channel transmitter module [1]

[1] IBM’s research, “Polymer-Waveguide-Based Board-Level Optical Interconnect Technology for Datacom Applications”, IEEE.

[2] Project “FutureBoard”, “Electro-optical circuit boards using thin-glass sheets with integrated optical waveguides”, SPIE.


3. Optical coupling device and optical connector Optical coupling (transmitter-to-waveguide, board-to-backplane,

waveguide-to-receiver) is one of the key challenges of optical PCB Technology. The coupling loss should as low as possible.

There are two typical coupling scheme for optical coupling between waveguides and OE devices: Butt-coupling Using beam 90°deflecting optics

Butt-coupling Beam 90°deflection

Better choice

El ect r i cal l ayer

OE devi ce El ect r i calcont act s

Opt i call ayer

I C chi p

def l ect i ngopt i cs

El ect r i cal l ayer

Opt i call ayer

OE devi ce El ect r i calcont act s

I C chi p


Reflection mirror for beam 90°deflection can be on waveguide or on coupling device.

reflection mirror on waveguide reflection mirror on coupling device

mi cr o l ens

Ref l ect i on mi r r orWavegui de cor e

coupl i ng devi ce

Ref l ect i on mi r r orWavegui de cor e

mi cr o l ens

coupl i ng devi ce

Better scalability

for multilayerapplication


Requirements for coupling device and connector Low coupling loss; High precision alignment structure ; Small geometric dimensions, require small board space, allow small

slot pitch; Simple assembly method, passive alignment; Co-exist with electrical backplane connectors in the same slot. Pluggable, reworkable The tolerance involved is compliant with current PCB manufacturing

tolerance Reliable high precision connection with immunity to movements

between board and backplane


4. Assembly

Simply assembly method, compatible with electronic PCB manufacturing.

Small misalignment guaranteeing low coupling loss transmitter-to-board (waveguide) Board (waveguide)-to-Backplane (waveguide) Board-to-Receiver

Mechanical robustness of the overall interconnection system


5. Testing and reliability assessments

Waveguide, O-PCB, OE-Module and O-PCB-A testing procedures, equipment, standards and methods

Short- and long-term reliability assessment Failure modes and mechanisms under changing environmental

conditions (ATS, HTS, DHH,…) Pb-free compliance, Telcordia compliance,…

Reliability challenges in the overall O/E interconnection system Test vehicle for reliability assessment

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Project Execution Plan


Project will be divided into four phases: Phase1: Benchmark survey and specification definition Phase2: Piece-part technologies research Phase3: Demonstrator integration and test Phase4: Project report


Phase 1: Benchmark survey and specification definition

Tasks list: Benchmark survey of available technologies Choose feasible candidates of piece-part technologies Specification definition of demonstrator and sub-units Definition of test vehicles, standards and methods


Phase 2: Piece-part technologies research

Tasks List Optical interface

Selection of optical Interface configurations for Optoelectronic device, optical coupling device and connector, waveguide and optical PCB

Parameters definition of each optical interface Waveguide material and components

Selection of waveguide material Selection of waveguide fabrication technologyWaveguide component fabrication and test

Opto-electric PCBO/E board design & simulation (optical, thermo-mechanical,..) Selection of optical layer integration technologyOpto-electric PCB fabrication and test


Phase 2: Piece-part technologies research (continued)

Tasks list (continued): Optoelectronic devices and transceiver (Tx/Rx) modules

Design Fabrication and test

Optical modeling & simulation Performance estimations for coupling concepts Ray trace simulation of coupling efficiency & alignment tolerance

Optical coupling device and optical connectorDesign Fabrication, assembly and test

Each piece-part technology of this phase maybe needs some runs of optimization.


Phase 3: Demonstrator integration and test

Tasks List Demonstrator redefinition Subassemblies fabrication and test

Optoelectronic transceiver modulesWaveguides and O/E PCBsOptical coupling device and optical connector

Demonstrator integration and test


Phase 4: Project report

Tasks List Establish optical backplane Interconnect practice application

guidelines Complete project report Issue project report

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Project Execution Timetable

Project Task When Complete ActualPhase 1: Benchmark survey and specification definitionBenchmark survey of available technologies TBD Date/Month/YY

Choose feasible candidates of piece-part technologies TBD Date/Month/YY

Specification definition of demonstrator and sub-units TBD Date/Month/YY

Definition of test vehicles, standards and methods TBD Date/Month/YY

Phase 2: Piece-part technologies researchOptical interface TBD Date/Month/YY

Waveguide material and components TBD Date/Month/YY

Opto-electric PCB TBD Date/Month/YY

Optoelectronic device and transceiver (Tx/Rx) modules TBD Date/Month/YY

Optical modeling & simulation TBD Date/Month/YY

Optical coupling device and optical connector TBD Date/Month/YY

Phase 3: Demonstrator integration and testDemonstrator redefinition TBD Date/Month/YY

Subassemblies fabrication and test TBD Date/Month/YY

Demonstrator integration and test TBD Date/Month/YY


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Project Task When Complete ActualPhase 4: Project reportEstablish optical backplane Interconnect practice application guidelines

TBD Date/Month/YY

Complete project report TBD Date/Month/YY

Issue project report TBD Date/Month/YY


Resources


Task Cost PrincipalBenchmark survey

Optoelectronic device and transceiver module

Optical coupling device and connector (optoelectronic device to daughter card & daughter card to backplane)

Optical waveguide material

Optical waveguide fabrication and test

Optical-electrical hybrid PCB fabrication and test (daughter card & backplane)

Prototype assembly and test

Team MembersPotential Participants:• 3M, Denny G. Aeschliman, [email protected]• Alcatel-Lucent, Joe Smetana, [email protected] • Albemarle, Guillaume Artois, [email protected]• Celestica, Thilo Sack, [email protected]• Cisco, Wei Xie, [email protected]• Cisco, Li Li, [email protected]• Cisco, John Duffy, [email protected]• Cisco, Jie Xue, [email protected]• Conpart, Helge Kristiansen, [email protected] • Ericsson, Alessandro Alquati, [email protected]• Fujitsu, Tetsuro Yamada, [email protected]• Huawei, Danny Tu, [email protected]• Huawei, Sang Liu, [email protected]• Huawei, Xi Jin, [email protected]• Huawei, Shaoyong Xiang, [email protected]• Juniper Networks, Mark Marino, [email protected] • Meadville, Chris Katzko, [email protected]• Meadville, Marika Immonen, [email protected]• Meadville, Tarja Rapala, [email protected]• NSN, Dietmar Breisacher, [email protected]• National Semiconductor, Hau Nguyen, [email protected]• Optical Interlinks, Bruce Booth, [email protected]• Promex, Dick Otte, [email protected]• Rogers Corporation, Diana Williams, [email protected]• Reflex Photonics, David Rolston, [email protected]


Participating companies and contact persons:TBD

Project leader:TBD

HDP User Group Staff Facilitator:Jack Fisher


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Active Optical cable (AOC)


Advantages and disadvantages of AOC compared to electrical cable:

AdvantagesHigh BandwidthHigh density Small size and light weight Low power consumption

DisadvantagesCostly Low reliability


There are mainly two kinds of standard AOC, QSFP and CXP.


CXP MSA Finisar’s QSFP MSA product: Quadwire

Huawei’s proposal on AOC project based on Huawei’s requirements in recent years (with CXP AOC as reference):

Lower power consumption: < 10mW/Gbps per Tx-Rx channel pair (@12.5Gbps)

Higher density: < ¾ size of CXP Higher data rate: > 12.5Gbps Fiber length up to 100m


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