Toshiba has introduced a pair of fast opto-couplers that will work from 2.2V, allowing them to work from the 2.5V rail of LVCMOS, for example, as well as up to 5.5V. Typical 3.3V data rates are: TLP2312 5Mbit/s TLP2372 20Mbit/s The threshold input current of 1.6mAmax and the supply current of 0.5mAmax at entire operating temperature ...

This story continues at High speed photo couplers work at 2.2V

Or just read more coverage at Electronics Weekly