Optical implementation of rearrangeable nonblocking double banyan interconnection network in free space

Abstract

The banyan network plays an important role in optical interconnection networks. A smart and compact double banyan network with cascading banyan network and inverse banyan network is proposed by using a polarizing beam-splitter (PBS), a phase spatial light modulator (PSLM), a half-wave plate (HWP), a double-faced reflective mirror (DFRM), and mirrors. The PBS features that the s-component (perpendicular to the incident plane) of the incident light beam is reflected, and the p-component (parallel to the incident plane) passes through it. Simultaneously, the bipartition graph algorithm (BGA) is adopted to ascertain the state of the node switch in each node stage (straight or crossover connection). According to switching logic, under control of external electrical signals, the PSLM functions to control routing paths of the signal beams, i.e. the polarization of each optical signal is rotated or not rotated 90° by a programmable PSLM. Since the proposed optical setup consists of only optical polarization elements, it is compact in structure, and possesses a low energy loss, a high signal-to-noise ratio and an available large number of optical channels. Finally, the discussions and the experimental results show that the double banyan network proposed here, owing to without signal blocking and conflict, may be used in optical communication and optical information processing.