Study of the Errors in Interpolated Fast Fourier Transform for Interferometric Applications
Round 1
Reviewer 1 Report
Comments and Suggestions for Authorsline 185: Here the authors introduce for the first time the expression "Two-points IFFT", which should be spelled "Two-point IFFT". It should be clarified that this refers to the interpolation method described by equation (1).
Section 3. Although the message the authors want to convey with the simulations in this section is clear, the parameters of the simulations are not specified completely. There is no description of the original signal simulated signal.
Figure 7. The top panel shows. black curve and a dashed red line. I assume that the red line is there to outline the distortion of the current modulation, but it should be clarified in a legend or in the caption.
Comments on the Quality of English LanguageI detect only a few typos and minor grammar mistakes (see for example line 143 where "trade-off" is spelled without the final f, or line 159, where the sentence "calculates a non-uniform spaced frequency samples" needs some revision). In general, the language is clear and the paper is easy to read. I would recommend a final proofreading before publishing though.
Author Response
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Author Response File: 
Author Response.pdf
Reviewer 2 Report
Comments and Suggestions for AuthorsDear Authors, the manuscript ‘Study of the Errors in Interpolated Fast Fourier Transform for Interferometric Applications’, Manuscript ID: metrology-2814257, has some weaknesses that must be clarified or the paper cannot be accepted.
Please find below some certain comments:
1. The Abstract section is too short and does not emphasise the meaning of the studies proposed. Authors must, i.a., even slightly motivate their proposal and highlight its significance in the measurement area of study.
2. Still, with the previous comment, the Authors must put some words on the experiment proposed in the Abstract, and explain what is the main purpose or the advantage.
3. In the Introduction section, each of the cited items must be presented separately. Each of the references should be introduced with its limitation, e.g. [8-10].
4. About the previous comment, a critical review must be provided. Authors should listed the cited sources while emphasizing their lack in the current state of knowledge. In the presented form, the motivation is hidden from the existing requirements.
5. The motivation is literally hidden in two first sections, 1. Introduction and 2. Single tone frequency measurement techniques. Some clearance is found finally in section 3. Interpolated FFT errors. Cooperation with the information included in those sections must be emphasized that in the current form looks like three separated gaps, each not correlated with others.
6. Some values in the manuscript are not justified, e.g. in the sentence from lines 182-184 or 185-187. Authors must present proposals more comprehensively or reference to the previous studies confirming the values selected.
7. In section 4. Application to absolute distance interferometry, the equation (1) must be references. As far as it is known, the formula is not newly proposed by the Authors. In many cases, it is difficult to restrict what is the novelty. Authors wisely avoid detailed separation of the proposal against previous methods.
8. The 4. Discussion section is weak. In practice, there are no critical assuptions on the study. Further, the advantages and, especially limitations of the proposal are unknown. Authors must propose any advantages with disadvantages of the results indicated.
9. The conclusion section is required. When the discussion is poor or the critical point of view is absent, the Conclusion sentences must be raised. The Authors did not finalize their studies with straight guidance to the readers.
10. In final words, it is difficult to follow what is the main line of study. Authors should add a flow chart of the experiment with many clarifications of what they are trying to convey. Many steps in the experiment did not allow for restriction of what was proposed and what was the main information from the Authors.
Generally, the proposed manuscript cannot be accepted in the current form to the quality journal as the Metrology is.
Author Response
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Author Response File: Author Response.pdf
Reviewer 3 Report
Comments and Suggestions for AuthorsThis manuscript investigates the solutions to the limitations of applying interpolated Fast Fourier Transform (IFFT) in self-mixing interference measurements. It’s a useful topic.
1. Why choose a specific sampling frequency like 8.4 MSPS?
2. The simulation experiment used a 20dB noise level. Is it meant to suggest that there are limitations to increasing the number of points in the IFFT even with a higher signal-to-noise ratio?
3. It should be explained the possible reasons for the distance measurement deviation in Figure 11, and how the measurement accuracy compares to other methods.
4. In the experiment, the main modulation frequency is 9 kHz, and 8 modulation waves are selected between 8.65 kHz and 9 kHz. Is this frequency range and the choice of modulation wave numbers arbitrary?
Author Response
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Author Response File: Author Response.pdf
Round 2
Reviewer 2 Report
Comments and Suggestions for AuthorsThe responses were raised too superficially, not resolving all of the reviewer' doubts and the manuscript was not improved appropiately so the submission cannot be accepted.
Author Response
We do not consider the reviewer's response to be justified and we are unable to identify any changes or additions to be made to the current text.
In the attachment you can find the detailed responce.
Author Response File: Author Response.pdf
Reviewer 3 Report
Comments and Suggestions for AuthorsThe authors have made corresponding revisions to the comments, improving the quality of the paper.
Author Response
Please see the attachment.
Author Response File: 
Author Response.docx
Round 3
Reviewer 2 Report
Comments and Suggestions for AuthorsThe submission can be accepted.
