Agreed that this needs to be in the Blackmagic forum, but…
Do you have a Decklink Extreme (as stated in your post), Intensity (as stated in your subject line), or Intensity Pro?
Neither of the Intensity cards has SDI out.
Intensity has HDMI I/O only.
Intensity Pro has HDMI, component, and composite I/O.
Decklink HD Extreme has SDI, HDMI, component, and composite I/O.