Performance comparison of parallel optical interconnects for enterprise servers
There is an emerging need in the computing industry for higher bandwidth, longer distance, and increased density interconnections within clusters of high performance enterprise-class computer systems. Many of these servers share a common set of high level requirements which lend themselves to the use of parallel optical interconnects to either supplement or replace existing copper data buses. In this paper, we describe the results of application testing performed on 12-fiber parallel optical cables and connectors, including a relative comparison between three different multimode cable assembly sources. Assembly loss and effects of both axial and off-axis pull forces are measured for cable samples mated to a laser transmitter array. Significant variations exist in the performance of the same type of cable assembly from different manufacturing sources, particularly concerning their susceptibility to pull forces; we also investigate the effects of fiber strain relief to improve performance of these links. While currently available 12-fiber array connectors are not equivalent in performance to standard duplex connectors, this work suggests areas for future improvement and data communication application requirements which should be considered when using parallel fiber optic arrays.
Polymer optical waveguide-based computer backplanes and interconnect
In recent years, there has been an increasing interest in the design and development of optical waveguides for computer backplanes and intra-card communications. The transition from high speed copper interconnects to optical links is driven by those applications which can most benefit from a greatly increased bandwidth-distance product; this includes rack mounted blade servers, data communication switches and routers, high end enterprise servers, and supercomputers. Typically the candidate applications require hundreds of optical links, each operating at 10 Gigabit per second or higher, for aggregate bandwidths on the order of multi-terabits per second across distances of one to ten meters across a backplane. In this paper, we review some recent developments in polymer-based optical interconnect for these applications. In particular, we report experimental results for arrays of multi-mode acrylate polymer waveguides, fabricated either on the surface of a printed circuit board or embedded within a multi-layer board. Transmission speeds up to 12.5 Gigabit per second have been demonstrated on a single link, with optical attenuation as low as 0.04 dB/cm. Packaging considerations for vertical cavity laser and photodiode arrays will be discussed, including tolerances for passive alignment between waveguides and active components. Finally, we review several recently issued patents for optical backplane connector concepts and their potential applications within the next 3 years.
Strategies for glass based photonic system integration
There is a clear tendency to integrate more and more opto-electronic and micro-optical components like optical fibers, laser diodes, modulators, isolators, beam-splitting components and micro lenses in also increasingly dense and complex assemblies. The paper will discuss thin glass as a very promising base material for that kind of photonic packaging on interposer and board level including optical interconnection using fibers.