The PWR series of plate amps don’t support optical/TOSLINK connections. Easiest is to look for an interface box in that case (Toslink to SPDIF) which are common interfaces. We'd recommend that you look for such an interface on Amazon or eBay. Here are some example of such devices:
http://www.ramelectronics.net/product.aspx?zpid=2749
http://www.amazon.com/Digital-Optical-Toslink-Coaxial-Converter/dp/B000I98ZQY