Frequency comb distillation for optical superchannel transmission

TL;DR

This paper demonstrates a wideband noise reduction technique for optical frequency combs using a high-Q microring resonator, enabling low-power combs to support high-capacity optical communications with improved OSNR.

Contribution

The authors introduce a novel comb distillation method with a microring resonator to reduce noise in optical comb lines, enhancing their performance in superchannel transmission.

Findings

Reduced OSNR requirement by ~9 dB at transmitter side.

Reduced OSNR requirement by ~12 dB at receiver side.

Enabled high spectral efficiency of 10.6 b/s/Hz with 71 comb lines.

Abstract

Optical frequency combs can potentially provide an efficient light source for multi-terabit-per-second optical superchannels. However, as the bandwidth of these multi-wavelength light sources is increased, it can result in low per-line power. Optical amplifiers can be used to overcome power limitations, but the accompanying spontaneous optical noise can degrade performance in optical systems. To overcome this, we demonstrate wideband noise reduction for comb lines using a high-Q microring resonator whose resonances align with the comb lines, providing tight optical filtering of multiple combs lines at the same time. By distilling an optical frequency comb in this way, we are able to reduce the required comb line OSNR when these lines are used in a coherent optical communications system. Through performance tests on a 19.45-GHz-spaced comb generating 71 lines, using 18 Gbaud, 64-QAM sub-channels at a spectral efficiency of 10.6 b/s/Hz, we find that noise-corrupted comb lines can reduce the optical signal-to-noise ratio required for the comb by ~ 9 dB when used as optical carriers at the transmitter side, and by ~ 12 dB when used as a local oscillator at the receiver side. This demonstration provides a method to enable low power optical frequency combs to be able to support high bandwidth and high-capacity communications.