Direct connect 10GBE with fibre

I haven't worked with 10GbE but AFAIK you only need one fibre connector at each end (unless you're bonding at a guess). Is you vendor confusing the fact you need one at each end ?

You can't mix the interface types because of the cable. At least that's my understanding. We use them for Gig fibre.

You might be surprised that you can pick these little modules up for about £30 off eBay and the likes. Vendors try and force you to buy their massively inflated brand but have a quick look before you buy and you'll probably find they're really cheap elsewhere. I think we got a couple of perfectly good used ones of eBay for £15 each to have some spare in stock.

The "crossover" is already built in to these cables. When working with cables like these you don't have a concept of a DTE side and DCE side as you do with ethernet cables. On a typical ethernet cable the DTE(terminal) side will have transmit on pins 1 and 2, with receive on pins 3 and 6. The DCE(switch) side or the other end of that cable will be flipped with transmit on 3 and 6 and receive on 1 and 2. These direct attach cables are built with the transmit of one side built already connected to the receive of the other.