Yes, can someone tell me the point of this ... we already can get information to travel at bagigahertz down a fibre using light ... I could hide 6 bits in 60 trillion bits over fibre and you'd have a hard time finding them
There are several different aspects to this. First, being able to increase bandwidth over existing infrastructure is worth a good deal. Just because we currently have achieved "lots" does not mean that it is not desirable to achieve "lots more." Quite the contrary, in fact.
Second, you are confounding two different security measures: steganography and encryption. Yes, you can hide a needle in a haystack, but then you have to send the entire haystack along in order to move the needle. While steganography is useful, it generally should be used in conjunction with encryption and not by itself. There are plenty of mass surveillance tools in use these days that are likely to catch all the "needles" no matter how many stacks accompany them.
Finally, the way data is encoded here in part uses the polarization of photons which makes intercept detection a built in feature - desirable for obvious reasons.
There have been a number of articles concerning this here on El Reg. Here too is a primer on the subject: