Re: isolation problem
Hi
If you will use a distance of meters, then fiber optic Transmitter and receiver are must. In this case, simple POF (plastic over fiber) can be a comparably cheap solution. Look to HFBR-1412 and HFBR-2412 series.
If the distance should not be big so much (around 1 millimeter) or you need big distance only to isolate input-output, then use a widebody optocoupler, like HCNW136.
A last solution can be to use a IR emitter and receiver (for several decade centimeters). Then refer to, for example, HSDL-4251.
Hope it helps.