Three-dimensional guided-free-space multistage optoelectronic fanout interconnection using wavelength division multiplexing and space division multiplexing

An integrated 3-D guided-free-space 4-stage optoelectronic fan-out (6 X 6, 2 X 6, 6 X 6 and 2 X 6) interconnect using WDDM is proposed and demonstrated together with 2 X 4 X 5 3-D optoelectronic fan-out using SDDM. This channel separation is one order of magnitude smaller than that using wavelength-selective detecting technique in WDDM. Signal to noise ratio of 57 dB is experimentally determined, with two channel 40 (2 X 4 X 5) fan-outs having a channel separation of 600 micrometers in SDDM. The interconnection scheme presented herein allows each pixel within a transmitting plane to communicate simultaneously and reconfigurably with many pixels in the subsequent planes in a truly three-dimensional feature. This system can utilize vertical cavity surface emitting laser diodes, photo detecting planes and planarized guided-free-space fan-out interconnects, allowing compact multi-stage integration. By using two-dimensional spatially separated or multiplexed hologram arrays on a thin light guiding plate, the interconnection capability is greatly enhanced as compared to other techniques. This novel optoelectronic interconnect should find widespread applications in microelectronics systems and fiber-optic communication networks. In this paper, we report the demonstration of a new solution that employs guided-free-space optical parallel fan-out interconnects. It takes advantage of such exclusive characteristics of optical interconnects as high packing density, massive single- wavelength fan-out and wavelength multiplexibility. Unlike the previously reported research, the interconnection scheme presented herein allows each pixel in a transmitting plane to communicate simultaneously and reconfigurably with many pixels in the subsequent planes with a truly three-dimensional (3-D) feature. Moreover, WD(D)M configuration can be maintained while extending into space-division-demultiplexing (SDDM) based on the fact that each VCSEL is spatially separated in the transmitting plane. As a result, each channel does not need to have many laser diodes operating at different wavelengths in order to facilitate the spontaneous communications with many pixels in the detecting planes. This new approach significantly reduces the fabrication requirements imposed on the laser diodes (with multiple output wavelengths) and on the photodetectors (with wavelength-selectivity). A one-to-one 2-D interconnect scheme is extended into a one-to-many 3-D one.