Subset-Optimized Eight-Dimensional Trellis-Coded Modulation Scheme in High-Speed Optical Communication

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

In this paper, the author presented the simulation related to the 8-dimensional trellis-coded quadrature amplitude modulation format for higher-order constellations in high-speed optical communications well. The introduction is clear and informative, and the principle, simulation, and results discussion are well organized. The proposed technology is novel and useful for high-speed optical communication applications, especially in long-haul applications.

There are some improvements I spot listing below:

1: In Line 1, adding the abbreviation, 8DTCM-QAM, after 8-dimensional trellis-coded quadrature amplitude modulation would be recommended, otherwise, it will lead to confusion in Line 5, first using the abbreviation, 8DTCM-16QAM.

2: In line 40, this sentence expressed that the gain and interference of high-order modulation format is a key issue, but in previous sentences, the interference was only mentioned, lacking the discussion of gain making this conclusion statement unfaithful.

3: In line 55, remove 'A great deal of research has been done on trellis coding.'.

4: From lines 114 to 139, they are good stuff but must be combined into the introduction section instead of the principle section.

5: In the principle section, it is better to add more mathematical processing to help the reader understand the proposed approach. 

In general, I would recommend this paper to be published after slight revision.

 

 

Comments on the Quality of English Language

Overall, the quality of the English language is good.

The author should carefully check the typing, there are some typos and improvements have been spotted, just listing some of them as examples, not all:

1: In line 43, change 'proven' into 'been proven'

2: In line 57, change 'the 1550nm band' to 'the C band'

3: From lines 58-72, those names should be changed to their family names, instead of full names.

4: In line 148, change 'is' to 'are'.

5: In line 153, replace 'get' with 'obtain' for a more formal tone.

6: In line 163, typo 'whit', change to where.

7: In lines 167 and 168, changing the expression of the probability of misclassification rises in the constellation point judgment to 'thus raise the probability of misclassification in the constellation point judgment', will be more readable and clear.

 

 

 

 

Author Response

Please see the attachment. The revised manuscript is placed after the response.

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

The authors presented an eight-dimensional trellis coded quadrature amplitude modulation scheme with subset optimization and demonstrated improved BER performances with such scheme. The proposed subset-optimized scheme also reduced the decoding computational complexity by 16-fold and 2-fold compared to unoptimized 8-subset and 4-subset schemes, respectively. This work is of interest to the fiber-optic communication community and is suitable for Photonics. I would recommend publishing this work, and I believe it could be strengthened by including the discussion of the following item.

 

The proposed SO-8DTCM-16QAM scheme demonstrates SNR gain at the 7% HD-FEC threshold compared to traditional schemes; however, it shows some limitations in the lower SNR region. Could the authors comment on potential challenges and resolutions for employing such a scheme in real-world ultra-long distance and ultra-high-speed optical communication systems?

Comments on the Quality of English Language

I suggest that the author thoroughly review the manuscript again and correct any typographical and/or grammatical errors. 

Author Response

Please see the attachment. The revised manuscript is placed after the response.

Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

The authors present in this paper an 8-dimensional trellis-coded quadrature amplitude modulation format designed for achieving a higher-order constellations in high-speed optical communications. Then, an optimization of low-dimensional subset segmentation to enhance the system's BER performance and decoding complexity is presented. The proposed method is tested via simulations across various transmission distances and baud rates. The novelty of the paper is good and the complexity was significantly reduced. However, the paper is hard to be followed, many abbreviations are not written with full name, and some additional results are required to make reading the paper clearer. The reviewer has the following comments to be addressed:

1-     The abstract should be rewritten to focus more on the proposed scheme, providing more detailed information about the proposed scheme itself. Furthermore, abbreviations must be clearly written out in full upon their first mention to facilitate comprehension throughout the paper.

2-     I suggest that the literature reviewed in the introduction should also mention the disadvantages of each discussed scheme, rather than solely focusing on their benefits.

3-     The computation of the complexity should be detailed and analyzed more thoroughly in comparison to conventional schemes.

4-     The works from the literature that are compared with the proposed scheme should be cited in the simulation section.

5-     In each figure, the proposed work must be clearly labeled to highlight the advantages of the proposed scheme.

6-     What is the reason of BER outperformance of the conventional scheme over the proposed scheme in lower SNR?

7-     The performance with different (Lower) SNR values should be investigated. 

Comments on the Quality of English Language

NA

Author Response

Please see the attachment. The revised manuscript is placed after the response.

Author Response File: Author Response.pdf

Round 2

Reviewer 3 Report

Comments and Suggestions for Authors

I believe the paper is now ready for publication; however, I have two minor comments:

1. The figures should include the word "Proposed" in front of the proposed scheme to make the results easier to follow.

2. The statement "The proposed scheme outperforms the conventional schemes at high SNR" should be mentioned in the abstract.

Author Response

Please see the attachment. The revised manuscript is placed after the response.

Author Response File: Author Response.pdf