Butt-coupled optoelectronic modules for high-speed optical interconnects

Optical interconnects have gradually replaced electrical interconnects in the long-distance telecom, local-area, and rackto-rack link classes. We believe that this transition will also happen in the card-backplane-card datacom link class, both for bandwidth*length reasons and for density reasons. In analogy to the transition from individually wired boards to integrated printed circuit boards, we believe that eventually board-level optical interconnects will be based on an integrated technology such as board-embedded waveguides. In order to bring optical waveguide technology into mainstream product development plans, however, numerous challenges on many levels have to be met. Problems to be tackled span from the base level of materials (stability, processability) and devices (reliability, lifetime), over the subsystem level of packages (concepts, cost-efficient assembly and alignment) all the way up to the system level (link architecture, system packaging, heat management). A sustainable solution can only be reached if the development of all individual technology components is done with the whole system in mind. Important figures of merit are the cost per gigabit per second, the power per gigabit per second, and the maturity/reliability of the technology. We will give an overview of our optical interconnect activity, with respect to these challenges. We will discuss the options, explain our technology decisions and present some results of our multi-disciplinary activity.

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“…3). In both cases we have operated the modules at 10 Gbps and used them in on-board and off-board links [38,39]. A part of this work (Fig.…”

Section: Coupling Into and Out Of The Optical Channelmentioning

confidence: 99%

Challenges for the introduction of board-level optical interconnect technology into product development roadmaps

2006

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“…For the manufacturing accuracy of the adapter and optical modules we assume a standard deviation on the order of 1 µm. This estimate is based on both the manufacturing accuracy known from standard commercial polymer ferrules for multimode fiber bundles and on the optical transceiver modules, which we have already demonstrated [21].…”

Section: Discussionmentioning

confidence: 99%

“…We typically use the passive alignment system with an intermediate adapter [21] that provides a link between the mechanical alignment structures in the PCB and the optical elements. One type is an 'MT adapter', which provides an industrystandard MT-pin interface that accepts any element conforming to this standard, be it transmitters, receivers, ribbon cables, or connectors, see Figure 4.4 .…”

Section: Passive Alignment Adaptersmentioning

confidence: 99%

Embedded micro-mirrors for compact routing of multimode polymer waveguides

Lamprecht¹

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Performance scaling of computing devices leads to higher bandwidth requirements for the processor package. The limited scalability of high-speed electrical interconnects [79] drives research on optical interconnects and optical printed circuit board (PCB) technologies [2, 14, 22, 52, 80]. The first part of this thesis is concerned with simplifying polymer waveguide routing and compact integration schemes for optical printed circuit boards. The discussed subjects are: Embedded micro-mirrors for in-plane and out-of-plane redirection of the light path (a), and mechanical alignment fiducials for the assembly of optical components (b). Both are then eventually integrated in a compact electrooptical flex board (c). The developed embedded micro-mirrors (a) are an integral part of the waveguide layer. The micro-structures that make up their bodies are fabricated directly onto the lower cladding by UV-laser patterning of a photosensitive resin. Vertical and 45°tilted micro-structures are eventually used as in-plane and out-of-plane micromirrors, respectively. A wet-chemical deposition process is developed to apply the reflective metal layer selectively on the micro-structures. In-plane micro-mirrors with a surface roughness of R a = 20 nm and reflectivity of R = 0.5 are realized. The fabrication processes are compatible to polymer waveguide and PCB manufacturing equipment. The presented mechanical fiducial marker approach (b) enables a precise and adjustment-free mounting of external components to an optical printed circuit board. The achieved positioning accuracy of inserted mechanical adapters is σ axis < 5 µm with respect to the waveguide axis. This yields an acceptable missalignment induced coupling loss of less than 0.5 dB. An electro-optical flex board (c), which integrates the mechanical fiducial markers (b) and the out-of-plane micro-mirrors (a), is fabricated as basis for a compact electrooptical module. The optoelectronic element, which can be a VCSEL-(vertical cavity surface emitting laser) or PD-(photodiode) array, will be vertically coupled to the underlying array of twelve polymer waveguides by the embedded out-of-plane micro-mirrors. The second part of this work is concerned with the analysis of light propagation in waveguide links. Herein proposed is an experimental approach to characterize the modal power coupling in simple waveguide elements. The used modal power coupling matrix relates the input and output modal power distribution of the waveguide elements. A generic optical waveguide link can then be represented as a concatenation of pre-characterized simple waveguide elements. To measure the modal power coupling matrix, the launch of specific modes at the input facet is required. Therefore, an intensity-and a phase-controlling spatial light modulator (SLM), are used to generate the specific modal field profiles. Therewith, lower order modes are successfully launched in a circular step-index fiber. In order to analyze the modal power distribution at the endfacet of the waveguide, an approach based on o...

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“…In a previous publication [1,3,7], we reported in more detail on a 1x4 array of either a transceiver or receiver package where the optical coupling resembles the layout of today's commercial transceiver/receiver optical subassemblies as used for fiber based parallel optical interconnects, namely the VCSEL/PD array is butt coupled and in plane with the optical channels. For today's fiber cables, in plane optical coupling is above and parallel to the PCB whereas with PWG, in plane optical butt coupling of the transceiver package may be in the PCB.…”

Section: Optical Transceiver Packages Coupled To Waveguidesmentioning

confidence: 99%