An S-Shaped Core M-Z Interferometer Induced by Arc-Discharging for Strain Sensing

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

In this manuscript, a highly sensitive strain sensor based on S-shaped core MZI was designed and fabricated by CO2 laser polishing and ARC-discharging. Simultaneous measurement of temperature and strain was successfully demonstrated with high sensitivity. The results are solid and the idea is novel. It is recommended to be published after minor revision. 

1. In the introduction, the recent progress of the fabrication of in-line fiber MZI should be updated. MZI fiber with cascaded long-period gratings fabricated by CO2 laser writing, which is demonstrated by prof. Chiang Kin Seng in the City University of Hong Kong, should be introduced in the introduction. 

2. The feasibility and repeatability of this technique to fabricate in-line fiber MZI shoulde be discussed in the results. 

Author Response

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Reviewer 2 Report

Comments and Suggestions for Authors

In this work, one novel structure of the fiber sensor was proposed, and experiments on it for measurements of strain and temperature were performed. From the theoretical design to measurements of properties, the work has been fully fulfilled. Due to the novel structure, the work is recommended to be published, provided minor revision is made according to following suggestions.

 

1 There is no comparison between the theoretical model and experiment measurements, especially on fiber sensors with different lengths.

 

2 Simultaneous measurements of temperature and strain, the work has to do some experiment work on this respect, it is not enough to give the matrix theoretically.

 

3 It is not enough to just show the sensitivities of the fiber sensor to give the conclusion of “a highly sensitive sensor”. There is a need of comparison values with that from other fiber sensors opened publically.     

Author Response

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Reviewer 3 Report

Comments and Suggestions for Authors

The paper under review, titled "An S-shaped core M-Z Interferometer Induced by Arc-discharging for Strain Sensing," presents a fiber-optic Mach-Zehnder interferometer (MZI) for strain sensing. The MZI is formed by two S-shaped fiber cores induced by CO2 processing and by arc-discharging on a single-mode fiber (SMF). The sensor was experimentally tested and showed a high strain sensitivity of -66.5 pm/με within the strain range of 0 to 350 με. The sensor also showed temperature sensitivity, which can be used to compensate for temperature effects in strain measurements. The authors claim that the sensor is low-cost and easy to fabricate.

However, the paper suffers from significant shortcomings:

1. Lack of Originality: The concept of an interferometric Mach-Zehnder strain sensor is not novel and has been extensively investigated in previous studies. The S-shaped core MZI structure, CO2 laser microprocessing, and arc-induced processing are all well-known and established fiber technologies. The paper fails to adequately differentiate itself from existing research in this area.
2. Incomplete Literature Review: The references provided in the paper primarily cite detailed or contributory work rather than the original publications that established the fundamental knowledge of fiber optic sensors and Mach-Zehnder interferometers. Additionally, the over-representation of authors from the People's Republic of China (PRC) in the references creates a bias in the scientific contribution to the field of fiber optic sensors.
3. Technical Errors and Inconsistencies: The paper contains technical errors and inconsistencies, such as referring to a single structure in Figure 1 while mentioning two structures in the text. The use of different symbols for the same variable (K and k) and the incorrect use of the term "fringe visibility" instead of "interference contrast" further detract from the paper's clarity and accuracy.
4. Insufficient Analysis and Justification: The paper lacks a thorough analysis and justification of the sensor's performance. For instance, the authors claim a positive correlation between the effective refractive index difference (Δneff) and strain without providing supporting evidence or analysis. Additionally, the experimental setup for temperature measurements is not described, raising concerns about the potential influence of temperature-induced strain on the results.

In conclusion, the paper titled "An S-shaped core M-Z Interferometer Induced by Arc-discharging for Strain Sensing" should be rejected due to its lack of originality, incomplete literature review, technical errors, and insufficient analysis. The paper does not make a significant contribution to the field of fiber optic strain sensing and fails to meet the standards of a high-quality scientific publication.

Comments on the Quality of English Language

Poor English, must be significantly improved.

Author Response

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Author Response File: Author Response.docx

Round 2

Reviewer 3 Report

Comments and Suggestions for Authors

In the revised manuscript, the authors have corrected some previously identified inaccuracies. The corrections in equations and the additional comments on the sensor's temperature response are noted. However, the fundamental concerns regarding the paper's lack of originality and the incomplete literature review remain unaddressed. The core concept of the S-shaped core MZI for strain sensing still lacks novelty, and the references continue to prioritize detailed or contributory work over the foundational publications that established the fundamental knowledge of fiber optic sensors and Mach-Zehnder interferometers. The addition of information about LPFGs (lines 56-58) and the corresponding reference [15] is irrelevant to the focus of the paper, which is strictly on MZI sensors. The authors should consider removing this unnecessary information and reference. The paper's overall contribution to the field remains limited, and major revisions are necessary to enhance its originality and provide a more comprehensive literature review.

Comments on the Quality of English Language

-

Author Response

Dear Reviewer,

Thank you for your valuable comments and constructive suggestions. The revised content has been marked in blue to distinguish it from the content modified in the first revision. Please see the attachment.

Author Response File: Author Response.docx

Round 3

Reviewer 3 Report

Comments and Suggestions for Authors

The revisions made across the three versions have improved the manuscript's clarity and technical soundness. The authors have addressed the initial concerns regarding errors. However, the novelty of the research may still be considered incremental, as the proposed sensor utilizes a combination of existing techniques (CO2 laser polishing and arc-discharging) to create an in-fiber MZI with enhanced strain sensitivity. 

The issue of the first version of the manuscript having a disproportionate number of references to Chinese sources, thereby distorting the representation of the field of interferometric sensors, has been addressed in the third version.

 

Author Response

Dear Reviewer,

Thank you very much for your comments and we express our deep respect for the rigour you have shown in reviewing the manuscript.

Please see the attachment for the detailed responses.

Author Response File: Author Response.docx