Simplifying the deployment of optical interconnects

Optical interconnects make connections by replacing conventional electrical wiring with optical lines, resulting in lower noise and higher speed. However, the conventional method of connecting optical fibres requires high-precision polishing to align the tips of the fibres: the fibres need to be fixed into the connector and then have their fibre-end faces precisely polished so that their tips align flat for low-loss connections. Since the polishing process needs to be performed for each connector, the overall cost is high. Fujitsu Laboratories' design technology and Furukawa Electric's manufacturing technology contributed to developing a simple optical connector that offers the benefits of low signal loss without requiring costly polishing. The Fujitsu Laboratories and Furukawa Electric connector is capable of accommodating different lengths of optical fibre with a spring mechanism (this eliminates the need for the costly polishing process). This reduces the cost of connecting optical fibres by more than 50%.

Recently, data transmission volume inside servers has grown in line with increased server processing performance and, today, data speeds of 25Gbps or more are necessary for transmissions between the CPUs, and CPUs and memory. As a result of attenuation at high speeds, conventional electrical wiring suffers signal degradation which makes high-speed transmission between server boards difficult, even over short distances. However, optical fibres suffer little signal degradation and so there is much interest in optical interconnects. When used for communications between server boards, optical interconnects require numerous multi-fibre connectors, each of which connects and aligns multiple optical fibres to enable parallel signal transfers. A high volume is required to deploy optical interconnects inside servers, leading to cost problems.

The connectors features a spring mechanism for optical connectors that slightly deforms when connecting optical fibres, allowing for deforming in the optical connector itself to introduce minute bends into the optical fibres as a way to accommodate for differences in their lengths, so that their tips align. Additionally, laser-processing the tips of the optical fibres results in surfaces equivalent to those achieved through polishing, so that optical fibres can align flush without gaps. Combining these technologies eliminates the need for polishing and results in optical-fibre connections with signal loss levels on par with existing multi-fibre connectors (0.2dB or less).

Fujitsu Laboratories and Furukawa Electric jointly developed this optical connector for use on boards, and with an optical connector housing that accommodates four optical connectors in a compact space, this design allows for as many as 96 optical fibres to be connected. This technology will enable the cost of installing optical interconnects between boards inside servers to be lowers, and increase overall server performance in the future. Fujitsu Laboratories and Furukawa Electric are continuing development with the goal of applications in servers around 2016. This technology need not be limited to internal server communications; it also has additional potential uses for connecting optical fibres between rack-mounted devices.