Phase noise of electro-optic dual frequency combs

Abstract

Dual frequency combs are emerging as new tools for spectroscopy and signal processing. The relative phase noise of the tone pairs determines the performance (e.g. signal to noise ratio) of the detected spectral components. Although previous research has shown that the signal quality generally degrades with the increase of frequency difference between tone pairs, the scaling of the relative phase noise of dual frequency comb systems has not been fully characterized. In this paper, we model and characterize the phase noise of a coherent electro-optic dual frequency comb system. Our results show that at high offset frequencies, the phase noise is an incoherent sum of the timing phase noise of the two combs, multiplied by line number. At low offset frequencies, however, the phase noise scales more slowly due to the coherence of the common frequency reference.

Synchronising Clock and Carrier Frequencies with Low and Coherent Phase Noise for 6G

“…As transmission distance increases, the jitter increases from 83 to 95 fs for 5 GHz, but only increased slightly to 85 fs for the 40 GHz tone. This is because the 5GHz tone results from the beating between more than 10 pairs of 5-GHzspacing optical tones whilst there were only two pairs of 40-GHz-spacing tones in the transmitted comb [12]. The decorrelation due to the different GVD for different optical tones degrades the optical phase coherence between the tone pairs, which increased the jitter.…”

All-fibre heterogeneously-integrated frequency comb generation using silicon core fibre

“…One of the areas in which the all-fibre SCF mixer shows significant promise is in dual-comb applications. It has been previously demonstrated that the phase noise of dual EO frequency combs is highly coherent 49 . However, this phase coherence may degrade when using conventional HNLF for nonlinear broadening due to the relatively long fibre lengths required (typically 100s of metres).…”