No. The PS2 optical digital output is not currently supported by SMS.
The optical digital output would allow the PS2 output to be connected via a fibre optic cable to an external audio processor such as a dolby digital home cinema system. However, this is not yet supported, and you are advised to use the standard audio outputs in the mean time.
This feature may be introduced in a future release of SMS. Anyone who would like to (and has the necessary hardware) is welcome to develop it.