A Simple Scheme for Photonic Generation of Microwave Waveforms Using a Dual-drive Mach–Zehnder Modulator

Round 1

Reviewer 1 Report

The paper looks a reasonable contribution to the optical generation of microwave waveforms (rectangular and triangular) through a dual-drive Mach-Zehnder electro-optic modulator (the authors do not use the "dual-drive" keyword but this is what they mean, they say "dual-electrode", maybe the "dual-drive" term could be added). The literature survey could maybe be extended by adding a paper that I do not see cited:

Yuan, J., Ning, T., Li, J. et al. Photonic Generation of Triangular-shaped Waveform Based on External Modulation. Sci Rep 8, 3369 (2018). https://doi.org/10.1038/s41598-018-21613-5.

The description of the experiment is clear enough, only I would immediately state that what is actually generated is a truncated Fourier series of a square o triangular waveform, respectively. I have a problem in Fig. 1 since I do not understand exactly the function of the 90 degree RF hybrid, that should basically generate two phase-shifted versions of the PD output, besides, are the top waveform (square) and the bottom (triangular) associated to the two hybrid outputs, respectively? please explain.

In section A, before (4), the authors say "triangular" but they mean "rectangular".

A general comment on the results: from a system standpoint the generation of triangular or square waveforms through an opto rather than an electronic technique should be justified by some data e.g. on the efficiency of the whole system. Can the authors provide an estimate of the power balance including the laser and the RF input generators and leading to the waveform power? unfortunately in all results the axes are (wisely) labelled with a.u. Also, considering that the total power depends on the laser power but also on the maximum power the PD can handle, in what power range will the source be, nW, microwatt, mW? this is quite relevant to the practical interest of the setup.

Author Response

Manuscript number: Applsci-979573

Title: A Simple Scheme for Photonic Generation of Microwave Waveforms Using a Dual-electrode Mach-Zehnder Modulator

Authors: Jingjing Hu, Jian Li, Jiayi Zhao, Zichen Ren, Mingshan Zhao and Yiying Gu^*

Dear Editor and Reviewers:

We would like to thank the Reviewers for the valuable comments and suggestions. The manuscript has been carefully revised. All changes made in the revised manuscript are underlined.

Author Response File: Author Response.docx

Reviewer 2 Report

The proposed scheme for generating square and triangular waveforms is interesting, and the analysis is complete. The paper is suitable for publication in Applied Sciences. I would suggest a few (very) minor revisions for the authors to make to improve the manuscript:

1) In the abstract, the results at 5GHz are given. A summary of the results at the other tested frequencies would be helpful.

2) In section 2A, line 100 - the text says 'triangular waveform' when it should be square.

3) Lines 108 and 123 give conditions on the harmonic signals to produce square/ triangular waveforms. An explanation should be given of how these conditions are established.

4) Figure 2: it would be useful for the x axis to be given as fractions of pi, as this is how the values are discussed in the text.

5) Line 138: The wavelength of 1949.955nm is very precise. Was there a particular reason for choosing this wavelength?

6) When comparing the measured waveform with the calculated one, it would be better to say 'calculated waveform' or 'theoretical waveform' than ideal waveform. Particularly for the square waveforms, the calculated waveform is clearly not an 'ideal' square wave.

7) A summary of the RMSEs should be given in the conclusion.

Author Response

Manuscript number: Applsci-979573

Title: A Simple Scheme for Photonic Generation of Microwave Waveforms Using a Dual-electrode Mach-Zehnder Modulator

Authors: Jingjing Hu, Jian Li, Jiayi Zhao, Zichen Ren, Mingshan Zhao and Yiying Gu^*

Dear Editor and Reviewers:

We would like to thank the Reviewers for the valuable comments and suggestions. The manuscript has been carefully revised. All changes made in the revised manuscript are underlined.

Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

The authors have clarified a few points and added data as requested, no further objection to acceptance.