I'd be looking for used titanium or a light steel road bike, in your shoes.

If you're traveling around the world, you'll probably need to box & ship it a few times, and carbon probably needs a little more padding and careful packing than you'll be able to give it.

How much does your current bike weigh, without racks, fenders, and other attachments? THere's a point of diminishing returns with $/gram, and $1500 doesn't buy much weight savings.