As rumored nearly a year ago, it appears optical Thunderbolt cables will be making their debut in 2013. The move to fiber-optic will bring a number of changes, but most importantly should allow for greater speeds (possibly up to 100Gbps) and far longer cables (roughly 30 meters in length). Currently, copper-based cables are capped at 10Gbps and a mere three meters. They will also maintain compatibility with existing Thunderbolt devices.
Sumitomo Electric Industries is claiming to be the first company to be certified by Intel for mass-producing optical Thunderbolt cables. Other companies will almost certainly follow, but we can expect to see these cables in 2013.
Pricing is currently unavailable, but optical cables actually tend to be more expensive than their copper-using counterparts. Thus far, Thunderbolt cables haven't exactly been a cheap commodity, so it is reasonable to suspect they'll be even less wallet-friendly as fiber-optic incarnate.
On the other hand, one of the primary reasons Thunderbolt cables continue to be costly is the active silicon-germanium electronics embedded into the cables -- a technology which requires expensive processes to manufacture. However, Intel's second generation cable chipset (due in 2013) promises to greatly reduce those fabrication costs. Intel expects the new design to cut cable costs from today's stiff price of 50-70 bucks to somewhere around $10. However, there's no word on whether Sumitomo's cables will feature these less expensive chips, though.
What their design will feature though is a slightly longer connector (38mm instead of 28mm) and the capacity for far greater lengths (100 feet). Otherwise, Sumitomo's cables should prove physically indistinguishable from traditional metal designs.
In spite of their improved design, the cables will debut with essentially the same specs as their copper cousins, sporting 10Gbps (bi-directional) transmission speeds, the same 4.2mm thickness and the ability to daisy chain up to six devices. Optical cables though should provide room to grow.
One drawback fiber brings with it though is its inability to effectively transmit power: this means powering your devices with pure optical cables is currently not possible. Although Sumitomo admits these cables can't power your Thunderbolt gadgets, perhaps we'll see a hybrid solution in the future though which provides both fiber-optic speeds and appreciable power transmission.