The companies note that, over recent years, the volume of data transmission inside servers has grown in line with greater server processing performance. Today, high-speed data speeds of 25 Gbps or more are required for transmissions between CPUs and between CPUs and memory. Conventional electrical wiring suffers from signal degradation due to attenuation at high speeds, even over the short distances on a server board. Optical fiber, which suffers little signal degradation and is robust to interference, has therefore led to much attention being focused on optical interconnects.
Current designs for optical interconnects inside servers use parallel designs that require numerous multifiber connectors. The connectors are too expensive for this application, the companies assert. Further, with existing multifiber connectors, the fibers need to be fixed into the connector and then have their fiber endfaces precisely polished so their tips align flat to achieve low-loss connections. The polishing process adds significantly to the overall cost.
Fujitsu Laboratories and Furukawa Electric say they have developed a connector that eliminates the need for costly polishing. The new design includes a spring mechanism inside the optical connector that introduces minute bends into the optical fibers as a way to accommodate small differences in their lengths so their tips still align. Laser processing the tips of the optical fibers results in surfaces equivalent to those achieved through polishing so the optical fibers can align flush.
The combination of these technologies obviates the need for polishing while resulting in optical-fiber connections with signal loss levels on par with existing multifiber connectors (0.2 dB or less), the companies claim. The new connector simplifies the task of installing high-capacity optical interconnects in a server and is expected to reduce by more than half the cost to connect optical fibers in this application. The technology is expected to increase data transmission speeds between boards, thus increasing overall server performance.
Fujitsu Laboratories and Furukawa Electric jointly developed the optical connector for use on boards. But with an optical connector housing that accommodates four optical connectors in a compact space, the new design allows for as many as 96 optical fibers to be connected. The partners are continuing development with the goal of applications in servers around 2016. They say the technology need not be limited to internal server communications; it also has additional potential uses for connecting optical fibers between rack-mounted devices.
The new multifiber connector technology is being presented in detail at SPIE Photonics West 2014 in San Francisco.