We have two core switch with 10gig ports , at the edge level i need 40gig speed , how do you plan the network?

Trunk port aggregation is Configuring EtherChannel in Switches will give youGB Data Link.

Is it possible withG ports to attainGbps.I dont think so.for ptp, fiber optics will give Gbps.refer http://searchnetworking.techtarget.com/feature/-Gigabit-Ethernet-The-migration-begins

GB capable ports for your uplinks on these switches. So not every port would need this capacity, just the uplinks. For your single chassis switches this means getting a new box, for ones that have linecards you may just be able to get new blades, but it could be hampered by the chassis' backplane capabilities.

Not really sure what you've got running device-wise though.

It doesn't sound like you have a huge environment though, so those speeds seem a bit overkill (particularly G between cores). What kind of workload is the network actually serving?