The purpose of this study is to apply a free-space optical interconnection to a reconfigurable board-to-board connection where the wiring patterns connecting boards are optically formed without electrical-optical conversion. We regard a photorefractive bi-directional connection module (PBCM) based on a mutually pumped phase conjugate mirror as a key device to construct such a connection network and employ PBCMs at input/output interfaces of each board. Although optical behaviors of PBCM are influenced by the exposure conditions, we especially focus on the diameter of beams illuminating photorefractive media placed inside PBCM so as to find some geometrical restrictions in a design of networking system. Through numerical analyses, we show a sample configuration of PBCM for the board-to-board interconnection and present a conceptual design of input/output interface.
We have studied PRCM as a basic device that could achieve a free-space optical communication with the spatial parallelism using mainly photorefractive crystal and four-wave mixing technique. The asynchronous PRCM, which is newly introduced in this paper, has the diffraction grating generated by two control beams independent of the signal beam. Thus, the signal is transmitted at the velocity of light and can be branched with no delay from the multiple nodes connected on the transmission bus line. We also propose a new two-way communication device, to which double phase conjugator technology was applied, as opposed to the one-directional device of optical signals from the transmitting side to the reception side. We conduct a basic evaluation on the branching and transmission characteristics of signals at the spatial optical switch element.