Uhh... well I assume you're talking about a fiber optical connection, but I know the ps3 doesnt have any fiber optical internet connection ports (it has one for audio).
You say your modem is slow.... well, it's also dependent on the speed that you get from your ISP, so unless that goes faster your modem won't be any better.
And i don't really know what you mean about using your laptop to connect your ps3 to the internet... because you can't do that, your laptop isn't a router/switch/modem so it can only receive an internet connection not give one.