Integration technologies for pluggable backplane optical interconnect systems

Integration technologies for board-to-board optical interconnect systems are presented. In the module architecture, optical transmitters and receivers are placed on the line cards and the signals are routed to the optically passive backplane through optical jumpers. The backplane contains a light guiding layer with embedded polymer waveguides (WGs) and 45-deg reflector micromirrors. The WGs are fabricated by direct lithographic patterning and have propagation losses as low as 0.05 dB/cm. The wedge dicing technology is developed for fabrication of the 45-deg micromirrors with 0.5-dB excess losses. The pluggable optical connectors with microlens adaptors couple the light from the optical jumpers into the backplane WGs. Evaluation of the connector alignment tolerances demonstrates a very weak dependence of the coupling efficiency on the axial displacement and a more significant effect of the radial shifts. The presented results show that the displacement tolerances can be substantially improved with auxiliary lenses formed on the substrate. Prototype optical interconnect modules with integrated channel WGs, mirrors, and assembled connectors are fabricated with insertion losses of 5 to 6 dB. The modules successfully pass the high-speed transmission tests at data rates up to 11 Gbits/s.