Sensitivity Enhancement of Fault Detection Utilizing Feedback Compensation for Time-Delay Signature of Chaotic Laser

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The article contains quite a few inaccuracies that should be corrected, so I ask the authors to change the following:

1. Lines 28, 29. An unclear sentence:

“The growing adoption of Fiber to the x (FTTx), primarily using time-division-multiplexing passive optical networks …”

I propose to make the sentence more comprehensible.

2. References to Fig. 1 (Line 85) and other figures are written as follows:

“Fig.Figure 1”  

I propose to write just “Fig. 1.”

3. References to figures are made under the figures (Lines 85, 138, 178 and further). Usually the reference in the text is introduced before the figure.

4. Lines 106, 107. The method of Runge-Kutta is referenced as:

«The equations were solved using the fourth-order Runge-Kutta method.»

It is advisable to indicate the source of information, i.e. the article or book where this method was described.

5. Parameter “tay_n” is used in the equation (Line 110, the third formula). In the text this parameter is given as “tay_N” (Line 114, subscripts are different). I propose to write it in the same way.

The list of remarks could be continued, but that's probably the job of the Text Editor.

The main problem with the article, in my opinion, is this:

The research, the results of which are presented in the article, was carried out with the methods of numerical experiment. Based on the given data, the authors conclude that the sensitivity of the method they proposed can be improved by using a 0.2 lambda long fiber segment L_V (Line 276).

How do the authors suggest obtain a fiber of such length in practice (shorter than the wavelength)? Is it possible to cut a fiber of such length with high precision?

I think that publication of the article is only possible after answering this question.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

Guo et al. proposed a method to enhance the sensitivity of optical fiber fault detection by using feedback compensation based on the time-delay characteristics of optical feedback semiconductor lasers. By adding a feedback compensation branch to the system, the required fault echo intensity for the laser to enter a nonlinear state was significantly reduced, thereby improving the sensitivity of fault detection. This paper could be considered for publication after addressing the observations provided.

Comment 1: The authors employ numerical simulation to evaluate the compensation effect, but it does not include experimental data. What are the obstacles to conducting related experiments? While spontaneous emission noise was disregarded during the simulation process, the compensation effect may be substantially impacted by factors such as fiber loss, device noise, and environmental interference in actual systems. Please comment the potential consequences of these factors.

Comment 2: In the manuscript, the 80:20 coupler is employed to allocate the test branch and the compensation branch; however, the optimality of this ratio has not been demonstrated.

Comment 3: A LD with a fiber-coupled output is employed by the authors. Is it possible to employ a fiber laser directly? What is the impact of utilizing a fiber laser on the results?

Comment 4: The author mentioned using a fiber mirror. Is it similar to the fiber end-facet coated mirror? Or is it a fiber Bragg grating?

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

The aim of the study was to improve the sensitivity of an optical fiber fault detection method based on delay signature of the chaotic laser, previously implemented by the authors. Thus, it is shown through numerical simulation that the detection sensitivity can be significantly increased by applying a newly proposed feedback compensation method, with potential to increase the capacity to identify fiber defects. The study analyzes the impact of the compensation parameters and diode bias current, and clearly presents the advantages of the proposed method.

The conclusions became more consistent with the arguments presented if the paragraph from Lines 281-287 (Conclusions) is included in the Discussion chapter.

Comments:

Line 225: At the sentence “…exceeds 7 dB (indicated by the green area) …”, I suppose that the correct indication is “…red area” because over 7 dB it is a red area;

Lines 231-232: the sentence “No decrease in sensitivity is observed as compensation intensity and bias current vary.“ is not accurate; no decrease in sensitivity is observed in the case of k_c = 0.09%, or at most when k_c varies only between 0.08% and 0.10%, and not on all scale;

Text formatting:

In the case of all references to figures, doubling the term “Figure” (e.g., “Fig./Figure Figure X”) is not a common practice. For this reason, I believe the notation should be simplified to “Fig./Figure X”;

Line 132: Figure 2 must be inserted in the text after it is referred to; the sub-chapter (2.3) cannot begin directly with a figure;

Line 132 / 187: Figures 2 to 4 must be inserted into the text after they are referred to;

Lines 133 – 135: Explains in the Figure 2 Legend the meaning of the gray area from sub-figures a1 and a2; 

Line 171: in Figure 3, for consistency, format the Y scale with the same number of major ticks as in Figure 4;

Line 186: in Figure 4, for clarity, format the X scale, from 0.0 to 1.0, and reduce the major ticks, as it is in Figure 3;

Line 191: indicates the variable "λ" (wavelength) where it is first mentioned in the text;

Line 217: Figure 6 must be inserted in the text after it is referred to; the sub-chapter (3.2) cannot begin directly with a figure;

Line 231: typo error in the case of “kc” parameter;

Line 257: indicates the variable "α" (linewidth enhancement factor) where it is first mentioned in the text;

Lines 281-287: This paragraph is suitable for inclusion in the Discussion chapter.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

Dear Authors!

Corrections have been introduced as required. Now I can recommend the article for publication.

Author Response

Dear Reviewer,

Thank you for reviewing the revised manuscript titled “Sensitivity Enhancement on Fault Detection Utilizing Feedback Compensation to Time-Delay Signature of Chaotic Laser” (Manuscript ID: photonics-3668386).

Noted with thanks for your confirmation that the corrections are satisfactory and for your recommendation for publication.

I appreciate your time and valuable feedback throughout the review process.

Best regards,

Sincerely yours,

Tong Zhao