Gradient-index lens optical backplane

An optical backplane design based on gradient-index lenses is described. This design is based on a tapped bus architecture and offers an affordable and efficient card-to-card communication method. It was found that the use of gradient-index lenses reduced the alignment tolerances by a factor of 10 over an equivalent free-space model. Results from simulation and from the construction of a five-node, proof-of-concept demonstration unit are presented. The excess loss measured for the 25 different combinations varied from a low of 0.7 dB to a high of 4.0 dB.