Information superhighways exploit optical-pulse propagation in silica
fibre. Will the computers at the ends of the highway likewise exploit
the optical representation of information? In the 1960s the first sche
mes for all-optical digital computers were proposed. In the 1990s emph
asis has shifted to optical interconnection of arrays of semiconductor
smart pixels. This paper presents reasons for this shift and, by comp
lete contrast, possible applications for natural materials such as bac
teriorhodopsin.