High-order coherent communications using mode-locked dark-pulse Kerr combs from microresonators

Area of Science:

• Integrated photonics
• Nonlinear optics
• Optical communications

Background:

• Microresonator frequency combs utilize the Kerr effect for generating multiple phase-locked frequencies.
• 100 GHz line spacing makes them suitable for fiber-optic communications.
• Dark-pulse combs in normal-dispersion microcavities exhibit high power-conversion efficiency.

Purpose of the Study:

• To demonstrate the first coherent-transmission experiments using dark-pulse frequency combs.
• To evaluate the performance of 64-quadrature amplitude modulation (QAM) encoded onto these combs.
• To assess the feasibility of dark-pulse combs for practical communication systems.

Main Methods:

• Generation of a dark-pulse microresonator frequency comb.
• Encoding of 64-QAM signals onto the comb lines.
• Coherent optical transmission experiments.

Main Results:

• Successful transmission of 64-QAM signals using the dark-pulse comb.
• Achieved optical signal-to-noise ratios exceeding 33 dB.
• Demonstrated compatibility with state-of-the-art hybrid silicon laser pump power levels.

Conclusions:

• Dark-pulse frequency combs are a viable and efficient light source for advanced coherent communications.
• The high power-conversion efficiency is crucial for achieving high signal-to-noise ratios.
• This technology shows promise for next-generation fiber-optic communication systems.