We present a review of our work on the micro/nano-scale design, fabrication and integration of optical waveguide arrays and devices for applications in a newly-conceived optical module system that we call "optical printed circuit board" (O-PCBs) and VLSI micro/nano-photonic integrated circuit. The O-PCBs consist of planar circuits and arrays of waveguides and devices of various dimensions and characteristics to perform the functions of transporting, switching, routing and distributing optical signals on flat modular boards. The VLSI micro/nano-photonic integrated circuits perform similar functions on a chip scale. O-PCBs consist of planar circuits and arrays of waveguides and devices of various dimensions and characteristics to perform the functions of transporting, switching, routing and distributing optical signals on flat modular boards. Fundamentally it contrasts with the electrical printed circuit board (E-PCB), which is designed to perform transporting, processing and distributing electrical signals. We have assembled O-PCBs using optical waveguide arrays and circuits made of polymer materials and have examined information handling performances when they are interconnected with the micro-laser arrays, detector arrays and optoelectronic devices. For VLSI nano-scale photonic inte-gration and applications, we designed power splitters and waveguide filters using photonic band-gap crystals and plasmonic waveguide structures. We discuss scientific issues and technological issues concerning the minia-turization, interconnection, and integration of micro/nano-photonic devices and circuits and discuss potential utilities of O-PCBs and VLSI micro/nano-photonics for applications in computers, telecommunication systems, transportation systems, and bio-sensing microsystems.