making led on using opto coupler

hi all
i want to glow led using opto coupler. my actual project is to mount an opto coupler on the aluminium disc in an electric meter. aluminium disc has a small hole in it. when the disc makes a complete rotation and hole passes through the opto coupler mounted at specified place,it will let the tx Ir pass through the hole and the output of optocoupler should result in glow of led attached with opto coupler's output..
i don't exactly know which opto coupler to use .and what should be the circutry for led and opto coupler interfacing.

 

One thing to be clear on before you start this project is that if this meter is in use measuring residential or industrial usage, it is going to be illegal to open it up for access. Also, the conductors are exposed and live, meaning there is a lethal shock hazard.

Unless this is a watt-hour meter in a lab that can be worked on with power shut off, I would recommend against the project.