A parallel optical interface is a form of fiber-optic technology aimed primarily at communications and networking over relatively short distances (less than 300 meters), and at high bandwidths.
Parallel optic interfaces differ from traditional fiber-optic communication in that data is simultaneously transmitted and received over multiple fibers.
Needless to say, there are many ways to perform this multiplexing provided the fundamental coding at the fiber level meets the channel requirement.
[1] It displaces copper backplanes that are commonly used for large switching equipment design.
[2] Parallel optics is often the most cost-effective solution for getting 40 Gigabit per second transmission of data over distances exceeding 100 meters.