FirstLight: Pluggable Optical Interconnect Technologies for Polymeric Electro-Optical Printed Circuit Boards in Data Centers

Multimode polymer waveguides are promising for use in board-level optical interconnects. In recent years, various on-board optical interconnection architectures have been demonstrated making use of passive routing waveguide components. In particular, 90 bends have played important roles in complex waveguide layouts enabling interconnection between non co-linear points on a board. Due to the dimensions and index step of the waveguides typically used in on-board optical interconnects, low-loss bends are typically limited to a radius of 10 mm. This paper therefore presents the design and fabrication of compact low-loss waveguide bends with reduced radii of curvature, offering significant reductions in the required areas for on-board optical circuits. The proposed design relies on the exposure of the bend section to the air, achieving tighter light confinement along the bend and reduced bending losses. Simulation studies carried out with ray tracing tools and experimental results from polymer samples fabricated on FR4 are presented. Low bending losses are achieved from the air-exposed bends up to 4 mm of radius of curvature, while an improvement of 14 m in the 1 dB alignment tolerances at the input of these devices (fibre to waveguide coupling) is also obtained. Finally, the air-exposed bends are employed in an optical bus structure, offering reductions in insertion loss of up to 3.8 dB. Index Terms-Board-level optical interconnects, multimode waveguide bends, polymer waveguides.

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confidence: 99%

Compact Multimode Polymer Waveguide Bends for Board-Level Optical Interconnects

Bamiedakis

Penty

White

2013

“…Many materials are available for forming the master. In our study, we employed EpoCore and EpoClad as the master materals for their excellent processibility by photolithography [15], [23], [25]. As they are also the materials used for forming the waveguides in the PCB, we enjoy the convenience of using the same materials for forming the master and the waveguides.…”

Section: Fabrication Processmentioning

confidence: 99%

“…for optical backplane application in mass storage systems [23]. In this paper, we report our effort in the development of a practical approach toward mass production of waveguide-embedded OPCBs.…”

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confidence: 99%

Industry Compatible Embossing Process for the Fabrication of Waveguide-Embedded Optical Printed Circuit Boards

Jin

Chiang

Chan

et al. 2013

We demonstrate a cost-effective embossing process for the fabrication of waveguide-embedded optical printed circuit boards (OPCBs). The process involves the application of a polydimethylsiloxane mold for the production of polymer waveguides on a copper-clad FR4 substrate followed by the conventional lamination process. The embossing process is carefully tailored for the commercial polymer materials that are developed specifically to withstand the high temperature and high pressure environment during lamination. With this process, we are able to produce highquality waveguide-embedded OPCBs with good repeatability. Our typical OPCB samples, each of which consists of 12 130-mm long fully embedded channel waveguides with a core size of approximately 50 × 50 μm and a pitch of 250 μm, show an average optical loss in the range 0.16-0.22 dB/cm at the wavelength 850 nm. The OPCBs survive the reflow process at 245 • C with a small change in the optical loss. The embossing process can be readily integrated with the existing PCB manufacturing process and thus offers a practical solution to mass production of OPCBs.Index Terms-Optical interconnect, optical polymer, optical printed circuit board (OPCB), polymer waveguide, waveguide fabrication.

“…Another challenge is the precise free-space coupling between components and linecards. In this work the waveguides will be planar integrated in commercial available display glass by thermal ion-exchange processing beyond the experimental stage of EOCB demonstrators recently demonstrated with areas of (233 x 303) mm² [13][14] [15]. Size enlargement has to be regarded as very challenging for all PCB processes in terms of handling and tolerance.…”

Section: Introductionmentioning

confidence: 99%

Large Optical Backplane With Embedded Graded-Index Glass Waveguides and Fiber-Flex Termination

Brusberg

Whalley²,

Pitwon

et al. 2016

Introduction of electro-optical circuit board (EOCB) technologies based on embedded glass waveguides in the system enclosure of current data storage, compute or switch platforms will be instrumental in accommodating the prohibitive bandwidth densities projected in exascale data centers, access networks and high performance computing environments in future. The main focus of this paper is, therefore, on the realization of large EOCB backplanes (350 x 465) mm²) with passive dual star interconnect topologies. The waveguides are embedded inside glass panels using a two-step thermal ion exchange process [1]. The fabricated embedded waveguides are then characterized for propagation and coupling losses across different wavelength ranges and for different coupling arrangements. The fabrication process for these large panels is briefly explained accompanied by the lamination process of four separate glass panels. The connectivity between backplane and peripheral cards is addressed using fiber flex termination with two possible waveguide interfaces -actively assembled pluggable interface and passively assembled adhesive bonded interface. A demonstration platform is also finally reported and the viability evaluated for optical connectivity and system efficiency is tested for the whole system containing fiber flex termination.Index Terms-Electro-optical circuit boards, ion-exchange, glass optical waveguides, graded index waveguides, optical interconnects, optical glass S. Whalley is with