Capacity of the Weakly Absorbent Turbulent Ocean Channel with the Coaxial Double-Position Power Gaussian Vortex
Round 1
Reviewer 1 Report
The paper addressing the Capacity of the weakly absorbent turbulent ocean channel with the coaxial double-position power Gaussian vortex. Both the novelty and the presentation are well.
Some minor comments are given as below. (1) The evaluation needs to be made over real experiment. (2) BER evaluation is required. (3) Some related works are suggested to discuss in this paper.
- A. H. Qasem, J. Wang, X. Kuai, H. Sun and H. Esmaiel, "Enabling Unique Word OFDM for Underwater Acoustic Communication," in IEEE Wireless Communications Letters, doi: 10.1109/LWC.2021.3085020.
- Qasem, Z. A. H.; Leftah, H. A.; Sun, H.; Qi, J.; Wang, J.; Esmaiel, H., Deep learning-based code indexed modulation for autonomous underwater vehicles systems. Vehicular Communications 2021, 28, 100314.
- A. H. Qasem, H. A. Leftah, H. Sun, J. Qi and H. Esmaiel, "X-Transform Time-Domain Synchronous IM-OFDM-SS for Underwater Acoustic Communication," in IEEE Systems Journal, doi: 10.1109/JSYST.2021.3052470.
Author Response
Thank you very much for the comments of reviewers. The level of writing has been greatly improved through revision
Author Response File: 
Author Response.pdf
Reviewer 2 Report
The manuscript by Yan et al. presents a numerical investigation of the capacity of an underwater optical communication channel when a double-vortex Laguerre-Gauss beam propagates through turbulent seawater. After setting the study in the context of OAM-carrying beam transmission schemes the authors introduce a standard model for a turbulent ocean as well as the double-vortex beam of interest, and derive the detection probabilities and channel capacity. The authors then carry out a numerical study of the influence of the various (ocean and beam) parameters on the channel capacity.
The topic is relevant for underwater optical communications and in principle suitable for a journal such as J. Mar. Sci. Eng. The study investigates a rather specific, but allegedly novel type of beam for improving the performances of such a channel. However, there a number of important issues to be addressed before this manuscript can meet the publication standards of J. Mar. Sci. Eng.
First, the geometry considered, relevant axis, etc. should be introduced in a figure in sec. 2 (there is confusion between z and z', for instance).
Second, the authors should be clearer in explaining "physically" why one can expect better transmission performances with such a double-vortex beam. In this respect, the conclusions drawn from fig. 1 in lines 207-221 are not clear at all. The authors write that "it is not a good choice to use coaxial double-Gaussian vortex laser with inverse spiral as the communication light source"! Fig. 1 shows a maximum for alpha~-1...
The authors should also discuss how a beam as given by eq. 9 could be produced in practice.
Lines 193-196 look like remains of a template.
In figs. 2 and following, the parameters other than those which are varied are not stated. For instance, what are alpha and l0? Figure 3 is completely missing! This nade it impossible to assess the essential discussion in lines 235-246. The authors should better explain how to optimize the beam parameters for each factor influencing the turbulence.
Author Response
Thank you very much for the comments of reviewers. The level of writing has been greatly improved through revision
Author Response File: Author Response.pdf
Reviewer 3 Report
The capacity of the weakly absorbent turbulent ocean channel with the coaxial double-position power Gaussian vortex is studied in the research. Overall the manuscript is well-written, however some necessary corrections are required to improve quality of the publication.
The division of the abstract should include the following four main categories: (i) research problem, (ii) methodology, (iii) results / findings, (iv) conclusion.
The introduction section should explain the article. There is a single too-long paragraph, which should be divided into 5 to 7 sentences. In the second paragraph of the introduction section some words are repeating e.g., “we derive” in line 80 and 82, please change at-least one of the to enhance the beauty of the text.
Under the heading of section 2 please provide few lines to explain the sub-sections 2.1 and 2.2. Same comments are for section 3 to explain the sub-sections 3.1 and 3.2.
The missing section is "discuss" as the proposed work is not compared with the related work to highlight the pros and cons.
Conclusion must be revised thoroughly, grammar and formatting.
In line 290: In this research we focused on ……..
Line 293: after comma “the” should start from small letter.
Line 295: If you are joining two words, there should not be any gap between the hyphen.
Author Response
Thank you very much for the comments of reviewers. The level of writing has been greatly improved through revision
Author Response File: Author Response.pdf
Round 2
Reviewer 2 Report
Unfortunately, the authors have not seriously taken into account my suggestions to improve the presentation of their manuscript, nor have they properly addressed the comments in their (not understandable) response. My evaluation is thus unchanged from the first refereeing round.
Author Response
Please see the attachment
Author Response File: Author Response.pdf
Round 3
Reviewer 2 Report
The authors have satisfactorily addressed my comments.
