istance needed with xbox 360 + Optical Audio..?

So i bought this cable a href="http://www.amazon.com/gp/product/B0002WPREU/ref=oss_product" rel="nofollow"http://www.amazon.com/gp/product/B0002WP…/a and i plug one end into my 360 and one end into my tv and voilà, no sound. So now im stuck, and do not know what to do. Is it the wrong cable, or is something else at fault? Thanks in advance