An Optical Micro/Nano Fiber Sensor for Monitoring Respiration

Round 1

Reviewer 1 Report (Previous Reviewer 2)

Comments and Suggestions for Authors

The authors presented an optical micro-nano fiber gas sensor based on the evanescent field absorption principle for monitoring carbon dioxide gas. This innovative sensing approach holds promise for the real-time monitoring of carbon dioxide concentration, offering a novel, straightforward, and cost-effective avenue for real-time sensing. Overall the paper is well written and good organized, but related certain points must be explained in more details. Following modifications are required:

Q. 1. Please carefully check the grammar on line 97 and correct it.

Q. 2. I suggest the author to correct the font format in Figure 3.

Q. 3. I suggest that the author change “The working principle of the micro-nano optical fiber sensor designed in the ex-periment is shown in Figure 7” to “The working principle of the micro-nano optical fiber sensor designed in the experiment is shown in Figure 7.”

Q. 4. Please carefully check the grammar in the entire paper and make corrections.

Comments on the Quality of English Language

The authors presented an optical micro-nano fiber gas sensor based on the evanescent field absorption principle for monitoring carbon dioxide gas. This innovative sensing approach holds promise for the real-time monitoring of carbon dioxide concentration, offering a novel, straightforward, and cost-effective avenue for real-time sensing. Overall the paper is well written and good organized, but related certain points must be explained in more details. Following modifications are required:

Q. 1. Please carefully check the grammar on line 97 and correct it.

Q. 2. I suggest the author to correct the font format in Figure 3.

Q. 3. I suggest that the author change “The working principle of the micro-nano optical fiber sensor designed in the ex-periment is shown in Figure 7” to “The working principle of the micro-nano optical fiber sensor designed in the experiment is shown in Figure 7.”

Q. 4. Please carefully check the grammar in the entire paper and make corrections.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 2 Report (Previous Reviewer 4)

Comments and Suggestions for Authors

Thanks for this resubmission and correction of my suggestions.

Author Response

We are very honored to get your approval of the research content of this manuscript, and thank you for your valuable comments, which are very helpful to the quality improvement and publication of our manuscript.

Reviewer 3 Report (New Reviewer)

Comments and Suggestions for Authors

The topics of the article are interesting and correspond to the theme of the magazine.

In my opinion, the title of the paper should be corrected - the study is about monitoring breathing, not carbon dioxide. Although the operating principle of the sensor presented by the authors indicates that the measurement is about carbon dioxide, but no analysis (e.g., literature) is presented to show that other gases do not impact the measurements for the analyzed wavelength of light.

In the paper, the authors write several times that the "concentration" is measured (e.g., line 165), but no result shows the concentration, but the optical power on the detector. Nor do the authors provide a specific formula for converting these quantities.

In their analysis of the results (lines 208-220), the authors do not take into account at all the fact that the smaller the diameter of the fiber, the longer the reduced diameter section, and therefore the longer the section over which CO2 affects the fiber. There is no proof (literature reports, calculations, or simulations) that this fact can be ignored. There is also no information that the authors have somehow ensured that the length over which CO2 interacts with the sensor is constant, which would allow the results to be accepted without question.

More specific objections and comments, which I suggest taking into account when revising the article:

Line 43: Missing literature reference "Capone5".

Fig. 4a and 4b: The figures are not readable - you can't see much on them.

Lines 166-167: It is written: "and the detection method is more direct and accurate compared with the side-flow method" - no proof of this - for example, a reference to the literature.

Lines 172-173: I have not been able to find the EP2004-0-DMDX1-FM laser - what is the width of the output line? Does its use interact with the CO2 line or also with other gases that may be in the exhaled air?

Fig. 7: I suggest you mark when the measurement begins and when it ends (or when it goes on) - as presented, it looks as if the patient has pauses in breathing.

Fig. 8: Are the results shown in the figure for simultaneous measurements under the same conditions (same patient), or are these measurements obtained separately? It seems to be the second case - so there is no certainty that the amplitudes of change should be the same.

Line 205: I suggest adding literature to confirm the last sentence.

In summary - the work is interesting and worthy of publication, but it needs correction.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Round 2

Reviewer 3 Report (New Reviewer)

Comments and Suggestions for Authors

The vast majority of my comments have been taken into account by the authors - I have no objections to the work.

I recommend its publication.

This manuscript is a resubmission of an earlier submission. The following is a list of the peer review reports and author responses from that submission.

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

This work describes  micro-nano optical fiber as the sensing area, and then detects the presence of carbon dioxide gas exhaled by human body through optical power attenuation. The measurement is achieved by using the principle of high evanescent field absorption, and the operating band is 2.004 μm. Below are some questions and the detail revision points for the authors' consideration.

1. In Abstract, the description of experimental data is incomplete, and data should be used to illustrate the conclusion.

2. In Introduction in line 51-60, the progress of the optical fiber or Micro-nano fiber sensor and gas detection is not introduced. Need to improve.

3. In line 101-123, the letters in the formula need to be represented in italics. Need to improve.

4. In Figure 4, There are problems with schematic diagram of different areas (c-f) of micro-nano fiber. These clearer pictures are needed. Need to improve.

5. In Figure 5, what is the meaning of this graph? What conclusions are to be drawn, please explain clearly.

6. In Figure 7, need to draw a diagram because it's not very clear.

7. In Figure 9, how to eliminate the optical fiber changes caused by breathing pressure or gas flow rate, please explain and give experimental data.

8. The reference literature is not new enough, and the reference literature of the last two years is needed.

Author Response

Thank you very much for taking the time to review this manuscript. Please find the detailed in response letter and the corresponding revisions/corrections highlighted/in track changes in the resubmitted files.

Author Response File: Author Response.docx

Reviewer 2 Report

Comments and Suggestions for Authors

The authors presented an optical micro-nano fiber gas sensor based on the evanescent field absorption principle for monitoring carbon dioxide gas. This innovative sensing approach holds promise for the real-time monitoring of carbon dioxide concentration, offering a novel, straightforward, and cost-effective avenue for real-time sensing. Overall the paper is well written and good organized, but related certain points must be explained in more details. Following modifications are required:

Q. 1. Please carefully check the grammar on line 97 and correct it.

Q. 2. I suggest the author to correct the font format in Figure 3.

Q. 3. I suggest that the author change “The working principle of the micro-nano optical fiber sensor designed in the ex-periment is shown in Figure 7” to “The working principle of the micro-nano optical fiber sensor designed in the experiment is shown in Figure 7.”

Q. 4. Please carefully check the grammar in the entire paper and make corrections.

Comments on the Quality of English Language

Please carefully check the grammar in the entire paper and make corrections.

Author Response

Thank you very much for taking the time to review this manuscript. Please find the detailed in response letter and the corresponding revisions/corrections highlighted/in track changes in the resubmitted files.

Author Response File: Author Response.docx

Reviewer 3 Report

Comments and Suggestions for Authors

Please check the attached file. It contains all my comments to the authors.

Comments for author File: Comments.docx

Comments on the Quality of English Language

Some minor mistakes have been observed. Is not the main issue in the manuscript. Please check the comments to the authors. 

Author Response

Thank you very much for taking the time to review this manuscript. Please find the detailed in response letter and the corresponding revisions/corrections highlighted/in track changes in the resubmitted files.

Author Response File: Author Response.docx

Reviewer 4 Report

Comments and Suggestions for Authors Not all parts of the article are sufficiently understandable. Especially the final discussion is weak and the reader does not have clear consequences of the measured results and conclusions. The article is extremely interesting and I dare to say that even current biomedical applications are not my main domain. Please note that variables are written in italics (ie. line 106).

Author Response

Thank you very much for taking the time to review this manuscript. Please find the detailed in response letter and the corresponding revisions/corrections highlighted/in track changes in the resubmitted files.

Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

The current version is ready for publication.

Reviewer 3 Report

Comments and Suggestions for Authors

After reading the authors' response to my previous comments, I still have the same doubt.

The authors claim to perform a real-time measurement of CO2 concentration, and present the differences between two different wavelengths of attenuation as evidence of such an effect.

However, the same signal pattern is seen, with a change that may be due to the different extent of the evanescent field outside the uniform waist of the tapered fiber. That is, 2 microns of wavelength will produce a larger evanescent field than 1 micron, and therefore any mechanical disturbance will also produce a larger attenuation.

I believe that a real calibration with CO2 concentration should be performed to be able to clearly state that the claimed effect is the one actually observed.

Comments on the Quality of English Language

Only minor typos should be revised

Author Response

please see the attachment

Author Response File: Author Response.pdf