They're the exact same thing. Lightpeak was the code name for the technology, Thunderbolt is the official name. Sony's implementation (true to their MO) uses a proprietary connector, forcing it to be incompatible with other PCs - not just Macs. This is the same company that pushed ATRAC and Minidisc over MP3 and CD-R, after all.
As far as the optical vs copper argument goes, there's essentially two options for lightpeak: optical without power, and copper with power. Most manufacturers are adopting the copper approach, which is what Apple is using. At the very least, there are upcoming machines from both Lenovo and HP that will use the same design as Apple.
Another point to make on the optical front: because Thunderbolt/Lightpeak externalizes the PCI Express bus, you could theoretically connect any peripheral you want to it. In the case of Sony, the optical cable itself isn't USB 3.0 compatible, but there's chips in their dock that can translate to/from USB 2.0/3.0. Either way, this is a prime example of Sony's ego getting in the way of true interoperability standards.
