Optical TOSLINK Trigger

I've tried an optical TOSLINK trigger, and discovered some non-obvious problems.
I was looking at an oversimplified clone part spec-sheet, when I should have been
looking at the original Toshiba.

The secret was that the receivers are self-leveling, and don't work correctly at DC.
I need to pump a dummy clock through it, and de-modulate at the other end...

This may actually work to advantage. Auto adjustment for optical losses (and any
misalignment across the tube). Might as well make lemonade with these lemons....