Flexible Ultra-Wide Electro-Optic Frequency Combs for a High-Capacity Tunable 5G+ Millimeter-Wave Frequency Synthesizer

Round 1

Reviewer 1 Report

The article “Flexible ultra-wide electro-optic frequency combs for high-capacity tunable 5G+ millimeter-wave frequency synthesizer” by Li Liu, Yangguang Liu, Xiao-Zhi Gao and Xiaomin Zhang describes an interesting photonic setup frequency comb generation for application to 5G.

These kind of combs are attracting the scientific and technological community for their potential applications spanning from communication, RF-Photonics, processing and sensing.

The article is well written. The introductory part is complete and didactically presented. References are adequate to the paper. The description of experimental setup is rather concise but clear.

One of the strong point of this paper is the first subsection of section 2. In this part of the manuscript the theoretical modeling of Electro-optic COMB generation is carefully described.

In the section 3, the results are clearly presented. The discussion about COMB stability is complete. In this subsection (3.3), advantages and limitation of such kind of comb are shown.

The application proposed for this setup is an hot topic in this period: 5G transmission.

The RF- comb generated by the photonic setup is useful for K-band and V-band ultra-high capacity communication.

Millimeter wave generated by this kind of photonic frequency synthesizer have a noise level compatible with the application proposed. Maybe not for metrological application.

I have few comment/suggestion in order to improve the quality of the manuscript.

1-In the subsection 3.1 (Flexibility), a comparison with commercial “bulk” Optical Frequency synthesizer performances could be useful for the readers (i.e. Menlo or Toptica lasers)

2-In order to improve the quality of the paper, I suggest to expand the section 3.2 (Flatness).

3-In section 3 or 4, I suggest to add some sentences regarding metrological application for this kind of comb (advantages and limitations).

4-The abstract could be rephrased to be more attractive.

Author Response

Please see the attachment.

Reviewer 2 Report

This paper proposes an innovative compact architecture for ultra-wideband electro-optic frequency combs, which improves efficiency and robustness. Transmissions implementing this millimeter frequency synthesizer have been demonstrated in both the K and the V bands, thus covering the 5G domain.  

The paper clearly introduces the previous approaches, and the benefits of the proposed approach. All the parameters investigated are clearly explained.  Experiments are clearly described, results are convincing.

Comments: authors could add a discussion about the difference of power obtained for the different frequencies. Is it related to the beating frequency generation mechanism?  A physical arguing would be of interest.

Author Response

Please see the attachment.