Optical interconnects
In general, it requires energy to convert electrical signals to and from optical signals.  However, depending on the type of optical fiber that you use, you can send that signal for much longer distances without losing the integrity of that signal.

One great advantage of using an optical link between devices is the electrical isolation that is afforded.  For example, we use 1mm optical fiber and simple optical transmitters and receivers to provide signal transport and isolation for low-speed serial signals between devices that can be many thousands of volts apart from each other.

One supplier of low-cost 1mm plastic fiber and user-friendly optical transmitters and receivers is Industrial Fiber Optics.