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Optical backplanes utilizing multimode polymer waveguides

Optical links are expected to overcome the limitations imposed by electrical links even for short transmission distances as they have done in telecommunications trunk networks. For board-to-board and board-to-multiboard communication we have developed an optical backplane for applications in mobile systems. Compared to fiber based realizations it is compact, rugged and has the potential to be fabricated at low cost. The main features of the optical backplane in planar technology are free space expanded beam transmission between boards and backplane and guided wave transmission within the backplane. No optical connectors are required. Due to the expanded beams and highly multimode waveguides large coupling tolerances of several 100 micrometers are achieved. Low loss polymer backplane waveguides (3 dB/m) allow transmission lengths of more than 19'. Demonstrators for board-to-board interconnections and star networks have been realized. Transmission experiments at 1 GBit/s have been successfully performed. Environmental tests prove the thermal stability of the polymer waveguides.