Server backplane with optical wavelength diversity links

Data centers have become the major technology for collecting and processing information. The data-rates required for transferring the information through the server's backplane has been increasing from year to year at an almost exponential pace. Therefore a technology-shift from the electronic to the optic domain has already been initiated in order to meet the required data-rate demands for next-generation servers. The future technology that is analyzed in the paper is free space optics (FSO). FSO technology uses laser links between the server cards and the backplane and provides a lower bound on propagation delay due to the low index of refraction of air, when compared with waveguide or fiber technologies. However, turbulence occurs due to the high temperature of the chips and to ventilation inside the server, which results in deterioration of the communication performance. In this paper, we examine the feasibility of wavelength diversity as a means to mitigate the effect of turbulence on the server communication link performance. It is shown that using the diversity scheme cuts the outage probability by half for the same total transmitter power by comparison with the single wavelength scheme. Therefore, the power consumption (and operational costs) of the data center could be reduced dramatically if a wavelength diversity scheme were adopted. The authors believe that this is the first time that a laboratory experiment has been performed modeling a server backplane with FSO communication using wavelength diversity.