Optical EngineeringFan-out intensity optimization of bidirectional photopolymer hologram-based optical backplane bus
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Fabrication of the bidirectional optical backplane bus, employing arrays of multiplexed polymer-based waveguide holograms on a waveguiding plate, is reviewed. An analysis of its functionality is presented for the first time. After an objective function for the system is established, the fan-out intensity fluctuations among all the different channels are minimized by solving a set of nonlinear equations numerically. To further ensure the validity of our calculation, a different objective function is considered and the same optimized result is obtained. Particularly, we optimized the fan-out distribution for the case in which nine boards on one side of the optical bus are presented. It was found that a globally optimized diffraction efficiency distribution exists and the minimum fan-out intensity after optimization is about 1.5% of the incident power, which means a minimum laser diode power for this bidirectional optical bus has to be above 7.0 mW for a system speed of 1.2 Gbit/s and a bit error rate of 10-15. Finally, the surface normal fanout beams come out of both directions of the backplane. Therefore, the best hardware implementation scheme integrates the processor/memory boards on both sides of the backplane bus. As a result, the optimal member of processor/memory boards is 16, i.e., 9 ± (922), rather than 9.