Microresonators promise to slash energy consumption of optical communications
The researchers from KIT’s Institute of Photonics and Quantum Electronics (IPQ) and Institute of Microstructure Technology (IMT) together with researchers from EPFL’s Laboratory of Photonics and Quantum Measurements (LPQM) used silicon nitride microresonators that can easily be integrated into compact communication systems and help reduce power consumption.
Within these resonators, solitons circulate continuously, thus generating broadband optical frequency combs that with multiple spectral lines that are aligned on a regular equidistant grid. Traditionally, frequency combs serve as high-precision optical references for measurement of frequencies and use large optical bandwidths along with rather large line spacings, and are particularly well suited for data transmission. Each individual spectral line can be used for transmitting a separate data channel.
In their experiments, the team used two interleaved frequency combs to transmit data on 179 individual optical carriers, which completely cover the optical telecommunication C and L bands, to give the 55Tbit/s data rate.
“This is equivalent to more than five billion phone calls or more than two million HD TV channels. It is the highest data rate ever reached using a frequency comb source in chip format,” said Christian Koos, professor at KIT’s IPQ and IMT.
The low-loss optical silicon nitride microresonators have the potential to drastically reduce the energy consumption of the light source in communication systems say the researchers. The soliton is formed using nonlinear optics and only pumped through a continuous-wave laser from which generates hundreds of new equidistant laser lines. The comb sources are currently being produced by a spin-off of EPFL.
The work is published in Nature and shows that microresonator soliton frequency comb sources can considerably increase the performance of wavelength division multiplexing (WDM) techniques in optical communications.
For coherent communications, the microresonator soliton frequency comb sources can be used not only at the transmitter, but also at the receiver side of WDM systems and produced in large quantities at low costs on compact microchips, say the researchers. This is an important step towards highly efficient chip-scale transceivers for future petabit networks, says Koos.