I don't have any HDMI wires going to my receiver at all. In this case, Source is the actual TV (SmartTV software) I just need to bring it in 5.1 format to my reviver.
That's what I've been reading too (about 2 channel only), but I did find this (not my model but still a Samsung)
http://support-us.samsung.com/cyber...3328342!1761676444!7501!-1!NONE!1259435613024
I believe this is the TV I have, seems like Samsung states that it does send 5.1
http://www.samsung.com/us/support/SupportOwnersFAQPopup.do?faq_id=FAQ00000636&fm_seq=804
This SOMEWHAT answers the question...perhaps
If the source is a digital component such as a DVD player, and you have connected the source and the TV using HDMI, and then connected the TV to your Home Theater using Digital Optical connections, you will hear only two channel sound from the Home Theater. Your TV can not transmit 5.1 channel audio from an HDMI digital source through the Optical connection.
But the source is SMART TV (TV itself)...so probably doesn't apply (not sure)
Chatting with Samsung rep, and they seem to confirm it
Angelina: Hi, thanks for reaching out to Samsung tech support. How can I help you today?
Visitor: Hi Angelina
Visitor: I have the following TV
Visitor: UN46D6420U
Visitor: and I'm having issues getting 5.1/DTS for SMART TV apps on my reciever after I connected Optical Out on the TV
Visitor: so the question is
Visitor: does my TV send 5.1 thru Optical? Or is it 2 channel only?
Visitor: Note the source is SmartTV apps (not DVD or PC etc)
Angelina: Please allow me to go through the inquiry.
Visitor: In this link
http://www.samsung.com/us/support/SupportOwnersFAQPopup.do?faq_id=FAQ00000636&fm_seq=804
Visitor: I found that if the source is DVD thru HDMI then Optical will not pass 5.1 only 2 channel
Visitor: but my source is SMART TV itself
Visitor: seems like Netflix app etc is not 5.1/DTS

Angelina: I understand that you want to know if you can get 5.1 channel sound using optical cable on the home theater. Is that correct?
Visitor: For SmartTV apps (specifically) yes
Angelina: Thank you for confirming.
Angelina: Yes, you can get 5.1 channel surround sound using optical cable.