Optical telecommunication: limits to growth?

Fiber-optic telecommunication has seen an unprecedented growth in recent years. Actually, the growth rate of the data rate over fiber has been larger than the growth rate of computer capabilities, as described by Moore's law. One wonders whether such growth can go on forever.
The simple answer is, it can't.

The ultimate data-carrying capacity of an optical fiber is limited, according to Shannon's celebrated theorem, to the available bandwidth times a factor which depends on the coding format. Transmission with binary encoding, which is the standard to date, will soon reach this ultimate limit. Further progress will then be possible only with schemes that allow to transmit more than one bit of information per time slot. However, it has been shown that conventional coding of more than two values in either amplitude or phase is of very limited usefulness due to detrimental nonlinear mixing processes in the fiber.

The only conceivable remedy would be a coding with an 'alphabet' of more than two letters, where the physical representation of each letter has the same self-healing robustness known from solitons. Seems far-fetched?

Here our recent discovery of soliton molecules comes in.
We suggest that the alphabet might consist of the letters 'no pulse', 'standard soliton', 'soliton molecule' as we found, and possibly of more complex soliton molecules whose existence remains to be demonstrated.

Alternatively, our discovery makes it possible to pack signal pulses much more densely (smaller temporal separation), which would also boost the fiber's data carrying capacity.