Serial COM Network + Arduino
I'm not sure about the way you have opto1's diode wired - I'm thinking it should have its junction with opto2's emitter grounded.

If you trace the circuit through you have bus->R5->diode->transistor->bus - this cannot possibly do anything sensible - no current can pass through that circuit because there is no third connection to ground or power.

Maybe you have drawn it wrong but as it stands nobody is likely to help unless it is fixed because nobody can really know what you are trying to achieve. Maybe I'm wrong?