Nanopower Fiber Optics / MOSFET Switch
Thank you all for your feedback and comments, which have enabled me to (hopefully) evolve the design to address its shortfalls yet meet the nanopower quiescent current goal.



The revised design uses a voltage divider reference for the comparator to address potential issues around noise and the comparator's on/off thresholds, while keeping steady voltage divider current at a bare minimum. The smaller 22K R10 resolves the time constant issue with FET output capacitance and the target baud rate when JP2 is disconnected. The final comparator voltage divider may require some minor tweaking but I'm now in the ballpark with the design.

Very helpful! Much appreciated.