Performance Analysis of a Single Light Source Bidirectional Visible Light Communication Reverse Reflection Link

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The reviewer found the idea of the submitted manuscript titled ‘Performance analysis of single light source bidirectional visible light communication reverse reflection link’ publishable in Photonics. However, before finalizing this article for publication, please address the following points:

1.      Improve the abstract Part, this is a roughly written abstract part.

2.      I can hardly find the effective recent references in this report.

3.      Figures are not impressive for publication; they must be revised with colourful illustrations. Furthermore, some figures such as s Fig.6 are not numbered.

4.      Conclusion part is not well written, please improve.

 

5.      Improve the Last paragraph in the introductory part. 

Author Response

Dear reviewer,

Thank you very much for your comments and professional advice. These opinions help to improve academic rigor of our article. Based on your suggestion and request, we have made corrected modifications on the revised manuscript. We hope that our work can be improved again. Furthermore, we would like to show the details as follows:

1. Improve the abstract Part, this is a roughly written abstract part.

The author’s answer: We have changed the content of the abstract, Quantitative description of the effects of changing the parameters. When the link distance is 3m, the lens aperture is increased from 100mm to 150mm, and the lens focal length is increased from 100mm to 150mm, the travel distance of the reverse reflector is increased by 60%, and the effective range of the incidence Angle is increased by about twice. In the absence of link loss, each 1m increase in link distance increases the maximum travel distance of the reverse reflector by 0.8m.

2. I can hardly find the effective recent references in this report.

The author’s answer: We have updated the reference, thank you very much for reminding us.

3. Figures are not impressive for publication; they must be revised with colourful illustrations. Furthermore, some figures such as s Fig.6 are not numbered.

The author’s answer: In order to make the data of the data diagram make a profound impact, we have modified the pictures in the paper.

4. Conclusion part is not well written, please improve.

The author’s answer: This is a very good suggestion, and we have modified the conclusion, mainly adding that our research is conducive to a more accurate description of the reflected power, which is conducive to further research on the change characteristics of the receiving power, so as to determine the modulation method that is more in line with the needs of actual channels.

5. Improve the Last paragraph in the introductory part.

The author’s answer: Thank you very much for your suggestion, we have improved the introduction. The main work content description and chapter distribution are added.

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

The manuscript with the title “Performance analysis of single light source bidirectional visible light communication reverse reflection link” presents the theoretical analysis of the factors that affect the optical power of the indoor single-light source visible light communication uplink receiving end.  Prior the final decision is made, the authors should clarify the following:

1.       Equations (4), (5), and (6) contains the variable D that is not described before or after these equations.  Thee authors must give a brief description of this geometrical parameter.

2.       Equations (7) and (8) contains the variables αmin and αmax that are not described before or after these equations.  Thee authors must give a brief description of these geometrical parameters also.

3.       Equations (11), (12), and (13) assume that the value of the left part of the inequality (11) is smaller then the right part of the inequality (12).  The authors must give a brief explanation why is it so.

4.       The complete theoretical analysis is performed by assuming that the lateral movement of the retroreflective end is parallel to the line that connects the receiving lens and LED.  Why is it so?  There must be an analysis that will show the situation when this condition is not fulfilled since it is more general situation.

5.       Also, the authors presented only the situation where the receiving and modulating lenses planes are parallel.  When these lens planes are not parallel we have more general situation and the authors must take into consideration this situation.

Author Response

Dear reviewer,

Thank you very much for your comments and professional advice. These opinions help to improve academic rigor of our article. Based on your suggestion and request, we have made corrected modifications on the revised manuscript. We hope that our work can be improved again. Furthermore, we would like to show the details as follows:

1. Equations (4), (5), and (6) contains the variable D that is not described before or after these equations.  The authors must give a brief description of this geometrical parameter.
2. Equations (7) and (8) contains the variables αmin and αmax that are not described before or after these equations. The authors must give a brief description of these geometrical parameters also.

The author’s answer：Thank you very much for your suggestions, Suggestions 1 and 2 have been explained in the article.

3. Equations (11), (12), and (13) assume that the value of the left part of the inequality (11) is smaller than the right part of the inequality (12). The authors must give a brief explanation why is it so.

The author’s answer：That's a good question, If the left part of formula (11) is equal to the right part of formula (12), because D<=2H, then we get s<=0. 

4. The complete theoretical analysis is performed by assuming that the lateral movement of the retroreflective end is parallel to the line that connects the receiving lens and LED. Why is it so?  There must be an analysis that will show the situation when this condition is not fulfilled since it is more general situation.

The author’s answer：Thank you very much for your suggestion, and I fully agree with your point of view. This paper is mainly from the perspective of geometric optics, and does not have in-depth discussion on the reflected optical power and other variables, so it lacks a deeper consideration of the state of the reverse reflection end. I think you have provided us with a very good suggestion, which is also a guide for our further study.

5. Also, the authors presented only the situation where the receiving and modulating lenses planes are parallel. When these lens planes are not parallel we have more general situation and the authors must take into consideration this situation.

The author’s answer：This is a very good suggestion, in the cat eye reverse modulation system, assuming that the receiving end and the modulation end of the lens are not parallel, will greatly affect the light power reflected to the receiving end, especially the LED light is divergent this case, in order to solve this problem, we believe that further exploration is needed, such as the maximum tilt Angle may be what, Whether the link distance has influence on the size of the inclination Angle and so on.

Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

In the present paper, an indoor visible light communication model is proposed, and the corresponding mathematical calculation formulae are derived. Moreover, the reliability of the formula is confirmed by using Zemax simulation software. Theoretical simulation results show that the movement range of the retroreflective end can be increased by increasing the lens diameter, reducing the focal length, and increasing the link distance. The results shown in the manuscript are interesting and convincing, which can provide some insight in indoor visible light communication. Thus, I recommend it to be accepted by your journal after addressing the following comments.

1、 The experimental results were mentioned in the abstract, but no corresponding experiments were conducted in this article.

2、 This article creates a model well, but how can this model be implemented?

3、 Have the authors considered the impact of H on this model?

Author Response

Dear reviewer,

Thank you very much for your comments and professional advice. These opinions help to improve academic rigor of our article. Based on your suggestion and request, we have made corrected modifications on the revised manuscript. We hope that our work can be improved again. Furthermore, we would like to show the details as follows:

1. The experimental results were mentioned in the abstract, but no corresponding experiments were conducted in this article.

The author’s answer: Thank you very much for your suggestion. As you said, this is an expression error. The simulation analysis we carried out in the article. This error has been corrected in the summary.

2. This article creates a model well, but how can this model be implemented?

The author’s answer: That's a great question. The model is based on the "cat's eye" inverse modulation system, we can achieve signal modulation and transmission by changing the position or Angle of the mirror or the reflectivity, etc. This article does not yet cover signal modulation.

3. Have the authors considered the impact of H on this model?

The author’s answer: That's a great idea. At the beginning of the model, we have considered this problem, if you want to reflect the light power back as large as possible, according to the principle of optics can easily know that you need to put the LED light source as close as possible to the lens. However, for the single light source duplex visible light communication system, such a design is not very reasonable. Because the downlink optical power is often much larger than the uplink optical power, if the downlink is too close, the uplink information transmission will be seriously affected. Of course, H can not be too large, if H takes a large value, it will cause the reflected light power will be smaller, and may even be undetectable. Because, the value of H should be a relatively compromise scheme.

Reviewer 4 Report

Comments and Suggestions for Authors

Authors are thanked for their efforts, however, the manuscript can be improved by considering the following comments:

1- Line 75: the two angle (alpha and beta) are the same according to the reflection law, why choosing two different symbols?

2- Line 199: the sentence is not clear at all ! can you clarify it?

3- when discussing the lens diameter and the link distance on the maximum moving distance of the retroreflection end, authors only describe the dependence without explaining the underlying physics or the responsible behavior beyond this relation. I would strongly suggest that they discuss the results from this aspect.  

  

Author Response

Dear reviewer,

Thank you very much for your comments and professional advice. These opinions help to improve academic rigor of our article. Based on your suggestion and request, we have made corrected modifications on the revised manuscript. We hope that our work can be improved again. Furthermore, we would like to show the details as follows:

1. Line 75: the two angle (alpha and beta) are the same according to the reflection law, why choosing two different symbols?

The author’s answer: Thank you for your suggestion. As you said, we use two different symbols to represent the Angle of incidence and the Angle of reflection, which are two angles of equal magnitude. Due to the different direction and spatial position of the light, we use two different symbols to represent them.

2. Line 199: the sentence is not clear at all ! can you clarify it?

The author’s answer: Thank you very much for your prompt, this is one of our editing errors. It has been corrected in the original.

3. when discussing the lens diameter and the link distance on the maximum moving distance of the retroreflection end, authors only describe the dependence without explaining the underlying physics or the responsible behavior beyond this relation. I would strongly suggest that they discuss the results from this aspect.

The author’s answer: I very much agree with your opinion, which is a very good suggestion. For the reverse modulation end, we mainly considered two issues, one is how to ensure that the reverse end can reflect the optical power back after moving, and the other is how to ensure that the optical power loss reflected back during the moving process is as consistent as possible. Based on this, we discussed in the paper. And then we'll have a deeper discussion by adding experiments.

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

 Authors have improved the manuscript as suggested; this might be ready for publication.

Reviewer 2 Report

Comments and Suggestions for Authors

The revised text of the manuscript is acceptable for publication in the presented form.