Scientists set new record for data transmission over 75 km of optical fibre

Telecommunication networks use many different frequencies, or colours, to transfer as much information as possible, the researchers said

Scientists on Monday said they have achieved a world record for high data transmission over 75 kilometres of standard optical fibre, using a powerful class of micro-comb called soliton crystals.

"This is one of the most efficient transmission systems implemented in a standard telecom network, given the record amount of information that can be encoded and propagated in an optical fibre with minimum loss of data," said Professor Roberto Morandotti, of the Institut National de la Recherche Scientifique (INRS) in Canada.

Telecommunication networks use many different frequencies, or colours, to transfer as much information as possible, the researchers said.

Current networks need typically a separate laser for every colour, which is difficult and costly to set up properly, they said.

"Here, we decided to use a micro-comb to replace the multiple lasers. Like a hair comb, we can generate a set of frequencies which are equally distant, and the phase and amplitude of which can be easily and precisely controlled," explained Morandotti, co-author of the research published in the journal Nature Communications.
 

The ability to supply all wavelengths with a single, compact integrated chip, replacing many parallel lasers, offers the greatest benefit, in terms of performance, scalability and power consumption, according to the researchers.

"We took advantage of the fact that a frequency comb could be created with a device known as a micro-ring resonator," Morandotti said.

Previous to this work, a well-behaved comb, resulting in a so-called cavity soliton, required a special and unique balance between colour dispersion and non-linearity, the researchers said.

Such combs are typically difficult to generate and stabilise, and not really power efficient even under ideal conditions, the researchers said.

Therefore, the researchers have developed a new way to achieve them for telecom purposes.

"In particular, if the microresonator is properly designed, it is possible to get a cross point between the optical modes supported by the device," Morandotti said.

"This in turn creates the right condition for realising a different type of micro-comb, leading to so-called crystal solitons, which is both robust and user-friendly," explained Morandotti.

This work demonstrates the capability of optical micro-combs to perform in demanding and practical optical communications networks.

According to Morandotti, the proposed mechanism could be commercially implemented in five years from now since similar micro-ring resonators, intended for less demanding applications such as filtering, are already well known and commercially available.