this is a simple Optical Convertor/Transmitter you can install in your FTA tuners that already have a SP/DIF (Co-Axial) Digital Audio Output.
you could use this circuit in conjunction with a SP/DIF(PCM) Modulator for those tuners that do not have SP/DIF already in them. you will not get dolby digital through it, but you will have an Optical connection to your audio receiver/amp.
this circuit could also be used as a Optical receiver witha simple part substitution.
this was made with Sharp and Toshiba phototransmitters/receivers in mind.
this is a .jpg photo of my exact worksheet. works very-very well in my coolsat, should work well in all others. pay close attention to the power you use for the Phototransmitter the tolerance MAX is +/-0.25v I retained a tolerance of 0.05v direct form the switched side of the power supply. DO NOT take your power from any support circuits in your iRD, this will cause damage unless you buffer and Isolate all the connections. as I said, this is a simple circuit, please feel free to modify it as your need warrants, this circuit is the buildingblock of ALL Optical Audio transmission and has a thousand uses.