Optical output only supports PCM so it won't transmit DTS directly.
- convert DTS to PCM in the software and send it that way to your receiver, or
- use HDMI is it's a possibility; it's by far the best option as it supports everything.

Hope this helps.
M80 v3, 2 x Emotiva UPA-1 Monoblocks, XPA-5, UMC-1 PrePro
Pro-Ject RPM Genie, Carver C2 Phono Preamp