Demonstration of a Low-SWaP Terminal for Ground-to-Air Single-Mode Fiber Coupled Laser Links

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

This work presents a demonstration of a low size weight and power terminal for ground-to-air single mode fiber coupled laser link by employing tip/tilt beam-stabilization. This is achieved by autonomously acquiring and tracking the targets using a combination of aircraft transponder and machine vision feedback to a root-mean-square tracking error of 29.4 µrad and at angular rates of up to 0.83 deg/s. Without the constraints of complex adaptive optics systems, this technology offers practical guidance for communication. However, there are certain aspects that require further clarification. Substantial revisions and improvements are needed, and I will make the final decision after reading the revised manuscript.

 1) This technology is recommended for practical quantum communication. Can you further envision the advantages of this technology applied to quantum communication?

 2) How much performance can be improved by using tip/tilt beam-stabilization technology?

 3) How does link budget or geometric loss affect the results? Can the authors give a further explanation about this?

 4) The technology proposed in this paper can be used for quantum communication [Natl. Sci. Rev. 10, nwac228 (2023); Sci. Adv. 10, eadk3258 (2024)]. To increase the generality of this work, the authors can envision related work for quantum communication.

 5) Pay attention to abbreviations. Some abbreviations only appeared once or twice, such as PSD and EM. In the body of the text, it is necessary to repeat the full form of abbreviations that have been mentioned in the abstract. Note that if the abbreviation appears above, you do not need to write the full name in the following text, such as section 2.1.4. tip/tilt.

 6) Some figures lack the necessary statements. Figure should begin with a brief title sentence for the whole figure and continue with a short statement of what is depicted in the figure. Legends should be detailed enough so that each figure and caption can, as far as possible, be understood in isolation from the main text.

Comments on the Quality of English Language

Moderate editing of English language required

Author Response

The authors would like to thank the reviewer for taking the time to review this manuscript and the opportunity to improve it with their suggestions.

 Please find our responses to specific comments attached.

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

This article proposes a new type of free-space optical communication (FSO) system that realizes efficient optical communication links through airborne and ground terminals. The main contents include terminal design, target acquisition and tracking mechanism, and system performance evaluation. The performance and reliability of the system were verified by field tests on aircraft provided by relevant departments. The reviewer thanks the author for his hard work in preparing the manuscript, but I would like to raise some questions as follows:

1. Expand the literature review section to include the latest advances in free-space optical communications and adaptive optics systems. This will better connect your work to the latest research.

2. During the experiment, the impact of environmental factors (such as weather conditions: rain, fog, etc.) on system performance can be analyzed and demonstrated to ensure the validity and authenticity of the experiment.

3. It is recommended to discuss the energy consumption of the system in the paper. Since the focus is on low SWaP (size, weight and power), quantifying the power savings compared to traditional systems will strengthen its efficiency argument.

4. The specific parameter settings of the machine vision-based target recognition and PID controller can be described in detail in the article.

5. On page 10 of the article, the citation format of reference 2 and reference 6 is incorrect. It is recommended to standardize it.

Comments for author File: Comments.pdf

Comments on the Quality of English Language

Needs minor editing for English

Author Response

The authors would like to thank the reviewer for taking the time to review this manuscript and the opportunity to improve it with their suggestions.

 Please find our responses to specific comments attached.

Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

Row 42: Needed to explain why "coherent detection" in sentence "particularly for coherent detection methods that require coupling into an 8-10 micron diameter SMF" It is actually needed 8-10 micron diameter SMF due to coherent detection?

Row 234: explain more precisely "observed coherence time of 7.92 ms" - how it was obtained (estimated)? In general, the numerical values in manuscript should be more precisely explained e.g. by mathematical equations.

Figure 1.: For better understanding it is needed more consistent description of this Figure with text given in manuscript. Some abbreviation are not explained  (EDFA, SBC, DCO, Vis. camera, …) either in list of abbreviation or in text of manuscript.

Author Response

The authors would like to thank the reviewer for taking the time to review this manuscript and the opportunity to improve it with their suggestions.

 Please find our responses to specific comments attached.

Author Response File: Author Response.pdf