Contents I. Introduction
A number of copper transmission lines for gigabit-level high-speed printed circuit boards (PCBs) having high interconnection density give rise to the serious bottleneck in high-speed signal transmission because of their electromagnetic interferences. An optical printed circuit board (OPCB) has been developed as a good solution to overcome these problems. However, the implementation of an optical interconnection using the OPCB has some limitations for guiding the optical beam perpendicularly between the vertical-cavity surface-emitting laser (VCSEL) or the surface-receiving photodiode (PD) and optical layers inside the OPCB. Many methods to efficiently deflect the light perpendicularly have been tried in the following ways: 45°-ended polymer waveguides [1], [2], 45°-ended fiber rods [3], and 45°-ended mirrors [4]. These structures have the additional optical loss induced by the beam divergence of the direct coupling from the VCSEL into the multilayered optical layers embedded in a thick PCB and from the optical layers to the PD window. Thus, an alternative scheme using 45°-ended polymer waveguides and microlens arrays was reported in order to reduce the layer difference of the optical coupling loss in the multilayered optical interconnection [5]. However, the alternative scheme requires many microlens array components of pieces for the optical layers of . Thus, these components with 45°-mirror planes are not easy to build the two-dimensional (2-D) multilayered optical interconnection structure because of the difficulty of implementing the high-density 2-D miniature optical deflecting components. Accordingly, as another solution, we already suggested a one-dimensional optical platform based on the OPCB using the 90°-bent fiber block [6]. In this letter, a 2-D optical platform which had features of low optical link loss, low optical crosstalk, and the passive assembly of all components was successfully demonstrated using the 2-D 90°-bent fiber block.
