We show that filtering of an optical frequency comb with a high quality-factor ring resonator enables the use of amplified low power combs as a multi-wavelength source. This approach improves effective source OSNR by 10 dB.
Optical frequency combs potentially can provide a compact and 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. When applying the proposed distillation to a superchannel system at 18 Gbaud, with 64-QAM sub-channels in a > 10 Tb/s optical superchannel, 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. By filtering with a MRR, we eliminate this degradation in OSNR.
Microring resonators (MRR) can be used as devices for filtering out broadband noise on optical frequency combs, in cases where significant amplification of a generated comb is required. While comb distillation has been demonstrated experimentally for optical communication systems, approaches to optimise device and sub-system parameters have not been explored. Here, we investigate how the performance of comb distillation through micro-ring filtering depends on device parameters. We also explore device parameter dependent performance when the comb and MRR are misaligned in line spacing. For the device platform we investigate, we find that the required optical signal-to-noise ratio (OSNR) of a comb line can be reduced by 16 dB, independent of modulation format, using a MRR with a resonance bandwidth of 100 MHz and coupling loss of 3 dB.
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