Planar waveguides and embedded microelements such as 45o vertical mirrors, lateral mirrors, bends, and microlenses comprise main building blocks of the waveguide-based optical printed circuit boards (PCB) for board-level optical interconnects (OI). These microelements enable a variety of three dimensional (3D) routing architectures which are required to support high density interconnects in optical boards. Optical polymers have proved to be the materials of choice for large-scale OI modules with propagation dimensions exceeding 100 mm. In order to meet the loss budget available for the integrated OI modules, the polymers are expected to have optical losses less than 0.05 dB/cm. Both channel and slab waveguides can be used to transmit the signals between the input and output ports. In the case of channel waveguides, the critical issues are the waveguide core shaping, propagation losses and ability to form various passive elements such as bends, crossings and reflective mirrors. In the case of slab waveguides, two dimensional waveguide microlenses have to be designed to collimate the light beams for propagation at longer distances with the controllable beam divergences. The 45o micromirrors can be used to couple the light signal in and out of the waveguiding layer and enable 3D routing of the optical signal in the waveguiding layers. In this work, we present the experimental and computational results on the development of different waveguide devices and microelements for the board level OI.