Low Loss and High Polarization-Maintaining Single-Mode Hollow-Core Anti-Resonant Fibers with S+C+L+U Communication Bands

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The manuscript, “Low loss and high polarization-maintaining single-mode hollow-core anti-resonant fibers with the S+C+L+U communication bands” presents a cross-sectional geometry for an antiresonant hollow core fiber with broadband birefringence exceeding 10^-4. The design idea is backed by detailed numerical simulations. The manuscript is reasonably well written, though there are a few formatting errors and English grammar mistakes, which should be addressed.

However, my major concerns is regarding the novelty of this work. A recent article published in Optics Communications (citation below) presents a nearly identical design with an elliptical core in a nested tube bi-thickness geometry for obtaining high birefringence and low loss over broad bandwidth. This paper is not cited in the manuscript and is not used for benchmarking in Table 1.

Jiajia Ran, Yichao Meng, “Broadband high birefringence and single-polarization hollow-core anti-resonant fibers with an elliptical-like core”, Optics Communications, Volume 575, 2025, 13125.

Even if the authors' optimized design might promise slightly better performance than the published work, it would still be considered an incremental work. In view of this, I cannot recommend this manuscript for publication in Photonics.

Author Response

Reviewer #1:

Comment 1: The manuscript, “Low loss and high polarization-maintaining single-mode hollow-core anti-resonant fibers with the S+C+L+U communication bands” presents a cross-sectional geometry for an antiresonant hollow core fiber with broadband birefringence exceeding 10^-4. The design idea is backed by detailed numerical simulations. The manuscript is reasonably well written, though there are a few formatting errors and English grammar mistakes, which should be addressed. However, my major concerns is regarding the novelty of this work. A recent article published in Optics Communications (citation below) presents a nearly identical design with an elliptical core in a nested tube bi-thickness geometry for obtaining high birefringence and low loss over broad bandwidth. This paper is not cited in the manuscript and is not used for benchmarking in Table 1.Jiajia Ran, Yichao Meng, “Broadband high birefringence and single-polarization hollow-core anti-resonant fibers with an elliptical-like core”, Optics Communications, Volume 575, 2025, 13125.Even if the authors' optimized design might promise slightly better performance than the published work, it would still be considered an incremental work. In view of this, I cannot recommend this manuscript for publication in Photonics.

Reply: Thank you for your suggestion. We appreciate you pointing out the recently published article by Ran et al. (Ran & Meng, Opt. Commun. 575, 131125, 2025) in Optics Communications that shares similarities with our design. We have carefully studied this paper and added comparative analysis. In 2025, Ran and Meng proposed three elliptical-core hollow-core anti-resonant fibers (HC-ARFs). By employing differentiated cladding and introducing high-index silicon tubes, they achieved birefringence on the order of 10⁻³ with 137 nm bandwidth and ultra-low loss of 0.01 dB/m. However, the incorporation of elliptical cladding and high-index silicon tubes significantly increases fabrication difficulty. Although both approaches adopt the "elliptical core + asymmetric wall thickness" concept, our design uses circular cladding tubes and shows improvements in both bandwidth and loss performance. We further analyzed the impact of larger circular cladding tube variations on birefringence. Our circular tube drawing process offers higher feasibility, so we have added a new paragraph in the Discussion section citing this reference: "Subsequently in 2025, Ran and Meng presented three elliptical-core hollow-core anti-resonant fibers (HC-ARFs). Leveraging differentiated cladding and embedded high-index silicon tubes, these designs deliver a birefringence of 10⁻³ over a 137 nm bandwidth, an ultra-low loss of 0.01 dB/m. Nevertheless, the adoption of elliptical cladding and high-index silicon tubes introduces significant fabrication challenges. "We have standardized figure/table font sizes and unit formats according to the journal template, and engaged native English editors for language polishing. All modifications are highlighted in blue. Although Ran & Meng 2025 proposed similar concepts, our dual-layer nested structure demonstrates progress in bandwidth, birefringence, and manufacturability. We sincerely appreciate your review.

 

Reviewer 2 Report

Comments and Suggestions for Authors

1. The expression is unclear in the abstract, such as “We have effectively enhanced the birefringence performance of the fiber structure design by introducing the combined effect of the two”.
2. The unit of the loss should be unified, dB/m or dB/km.
3. In Fig. 3 (d) y-pol FM exhibits more energy leakage than x-pol FM as R₁ is 15.6 mm, but in Fig. 3 (a) and (b) the CL of y-pol FM is less than that of x-pol FM. In Fig. 3 (c) the birefringence for different R1 is the same value at 1400 nm, and then increases in the range of 1400 - 1450nm. The reason should be added.
4. In Fig. 10 (c) the unit of the color bar is missing. 

Author Response

Reviewer #2:

Comment 2:

A:The expression is unclear in the abstract, such as “We have effectively enhanced the birefringence performance of the fiber structure design by introducing the combined effect of the two”.The unit of the loss should be unified, dB/m or dB/km.

Reply: Thanks for the suggestion. We have revised the original sentence "We have effectively enhanced the birefringence performance of the fiber structure design by introducing the combined effect of the two" to: "By simultaneously employing an elliptical core and asymmetric core-wall thickness, we enhance the phase birefringence without increasing loss." This revision eliminates the ambiguous reference "the two" in the original text.

B:In Fig. 2 (d) y-pol FM exhibits more energy leakage than x-pol FM as R₁ is 15.6 mm, but in Fig. 2 (a) and (b) the CL of y-pol FM is less than that of x-pol FM.

Reply: Thanks for the suggestion. We have standardized all loss units to dB/m throughout the manuscript, converting all instances of dB/km to dB/m for consistency.

C:In Fig. 2 (c) the birefringence for different R1 is the same value at 1400 nm, and then increases in the range of 1400 - 1450nm. The reason should be added. In Fig. 10 (c) the unit of the color bar is missing.

Reply: Thanks for the suggestion. We sincerely appreciate your thorough review and valuable comments regarding the results in Figure 2 of our manuscript. The issues you raised are indeed crucial, and we would like to explain the underlying mechanisms behind these phenomena. Regarding the apparent paradox where the y-polarized fundamental mode shows greater leakage yet lower confinement loss, we attribute this to the unique design of our fiber structure. While Figure 2(d) does demonstrate more extensive horizontal energy penetration into the cladding region for the y-polarized mode field, the innermost two glass capillary layers in the vertical direction effectively create secondary confinement. This asymmetric confinement mechanism enables the y-polarized mode to maintain excellent overall guiding characteristics, resulting in the observed lower confinement loss. Concerning the phenomenon where confinement loss remains consistent at 1400nm before increasing with different R1 values, we speculate this may relate to birefringence anti-crossing effects. Within the specific 1400-1450nm wavelength range, variations in mode coupling characteristics likely induce this fluctuation in loss behavior.

Additionally, we have added a color scale bar at the top of the right-side color bar in Figure 10(c) for better visualization.

Reviewer 3 Report

Comments and Suggestions for Authors

This work proposes a design for a hollow-core antiresonance polarization maintaining fiber (HC-ARF). The designed fiber, if fabricated, might achieve low loss and high birefringence in the telecom band.

Unfortunately, I found the work to be imprecise, unclear, and not well written:

1. The Authors do not specify the target fiber performance for their optimization. Provided that low loss and high birefringence are desirable, it is not clear whether they have a target birefringence and loss value. Depending on the application, loss can be more important than birefringence (or vice versa), so determining the tradeoff between loss and birefringence is important in designing the fiber.
2. The Authors do not specify the domain of the parameters. For example, they vary R1 from 13.6 to 15.6 μm. It is not clear why they did not consider values below and above these extremes.
3. The Authors do not specify the strategy they use to find the optimal parameters. In the work, the optimization is presented sequentially: first R1 is optimized, then k1, k2, R4, k3, and so on. However, this doesn't seem to be true because birefringence and loss are better after the optimization of R1 than after the optimization of R1, k1, k2, k3, and R4.
4. The Authors assert that the high HOMER has been achieved by "carefully adjusting the ratio between the inner and the outer cladding dimensions"; however, there is no mention of HOMER in the optimization of these dimensions.
5. Regarding the bending performance of the fiber, the Authors state in the abstract that "When the bending radius exceed 3cm, the impacts on the loss and birefringence are negligible...". From Table 1, however, the additional loss due to bending is not negligible (from 1.5 dB/km to 4.25 dB/km when the fiber is bent with a 3 cm bending radius). Yet, it is not clear what the true loss value is at 3 cm bending radius since the Authors report 7.8 dB/km and 5.2 dB/km at lines 123-124, which differs from what they reported in the table.
6. Many sentences are unclear or undetailed. For example:
   
   • (line 402) In "This structural optimization offers new insight for the theoretical design and manufacturing of high-birefringence fibers.", it is not specified what these insights are.
   • (line 292) In the sentence "Despite the Hi-Bi characteristics of this region, the loss is relatively high due to its proximity to the resonance edge of electric field leakage t", it is unclear what the Authors mean with "the resonance edge of electric field leakage t".
   • (line 140) "The designed PM-HC-ARF structure exhibits a left-right symmetrical configuration, demonstrating strong feasibility for manufacturing.". It is not specified what a left-right symmetrical configuration is, nor why this would prove feasibility in manufacturing.
7. Table 1 compares the performance of the designed fiber with those in the literature. Among the reported results, three out of five are of fabricated fibers. Comparing simulated with measured results is unfair. First, simulated ideal fibers usually perform better than fabricated ones; second, fabricated fibers have proven to be feasible designs. There is no mention in the paper that some of the reported results are from fabricated fibers.

For these reasons, I do not recommend the paper being accepted for publication.

 

Comments on the Quality of English Language

The English language and punctuation are not good and negatively affect the clarity of the work. See, for example, lines from 106 to 112.

Author Response

Dear Editor and Dear Referee,

We appreciate the opportunity to revise our manuscript titled " Low loss and high polarization-maintaining single-mode hollow-core anti-resonant fibers with the S+C+L+U communication bands" and are grateful for the insightful comments provided by the reviewers. Those comments are all valuable and very helpful for revising and improving our paper, as well as the important guiding significance to our researches. In the following, we have provided detailed responses to each of the reviewers' comments. Revised portion are marked in red in the paper. Additionally, we have conducted a comprehensive revision of the entire manuscript. In this response letter, the reviewers' comments are presented in italics, and our corresponding changes and additions to the manuscript are highlighted in red text. We have tried our best to make all the revisions clear, and we hope that the revised manuscript meets the requirements for publication. Thanks for the understanding in advance.

Best wishes,

The authors

Reviewer #3:

Comment 3: This work proposes a design for a hollow-core antiresonance polarization maintaining fiber (HC-ARF). The designed fiber, if fabricated, might achieve low loss and high birefringence in the telecom band. Unfortunately, I found the work to be imprecise, unclear, and not well written:

1. The Authors do not specify the target fiber performance for their optimization. Provided that low loss and high birefringence are desirable, it is not clear whether they have a target birefringence and loss value. Depending on the application, loss can be more important than birefringence (or vice versa), so determining the tradeoff between loss and birefringence is important in designing the fiber.

Reply: Thanks for the suggestion. We sincerely appreciate your careful review of our manuscript and this highly pertinent comment. Your suggestion regarding clarifying the fiber optimization objectives (the trade-off between low loss and high birefringence) indeed hits the mark - we acknowledge that our initial draft did not sufficiently discuss this aspect, which is critically important for practical application scenarios. In this study, our primary design focus was on achieving high birefringence (>10⁻⁴), as our target application is high-sensitivity fiber optic sensing where birefringence performance takes priority. However, through simulations we observed that by optimizing the cladding structure, the loss could be controlled below 8.8 dB/km. As you rightly pointed out, for applications more sensitive to loss such as communication transmission, we would need to readjust our design priorities accordingly.

2. The Authors do not specify the domain of the parameters. For example, they vary R1 from 13.6 to 15.6 μm. It is not clear why they did not consider values below and above these extremes.

Reply: Thanks for the suggestion. Thank you for your thorough review of our manuscript and the valuable comments. We appreciate your important question regarding the selection of the R1 parameter range (13.6-15.6 μm) and would like to explain our rationale in detail. In this study, we limited R1 to this specific range based on comprehensive considerations of performance optimization, structural stability, and manufacturing feasibility. When R1 falls below 13.6 μm, the birefringence performance decreases significantly, making it difficult to achieve our design targets. Conversely, when R1 exceeds 15.6 μm, the transmission loss increases progressively, adversely affecting the fiber's practical performance. From a structural perspective, values above 15.6 μm cause adjacent cladding structures to become too close, potentially leading to physical contact, while values below 13.6 μm create excessively large gaps between cladding layers that exacerbate optical field leakage. This selected range represents the optimal balance between optical performance and current manufacturing capabilities. We fully understand your interest in exploring a broader parameter range. In fact, our preliminary investigations did examine values from 12-17 μm. However, we found that these extreme values either resulted in substantially degraded performance or introduced significant manufacturing challenges. Therefore, we ultimately focused on the 13.6-15.6 μm range as it demonstrated the best overall performance characteristics while remaining practical for fabrication.

3. The Authors do not specify the strategy they use to find the optimal parameters. In the work, the optimization is presented sequentially: first R1 is optimized, then k1, k2, R4, k3, and so on. However, this doesn't seem to be true because birefringence and loss are better after the optimization of R1 than after the optimization of R1, k1, k2, k3, and R4.

Reply: Thanks for the suggestion. We sincerely appreciate your valuable feedback on our manuscript. Your insightful comments regarding the parameter optimization strategy are highly pertinent and indeed represent an important aspect that requires further clarification. Concerning the phenomenon you observed where the R₁-only optimization yielded better results than the final multi-parameter optimization, we completely understand your confusion. In fact, we also noticed this interesting occurrence during our research. Through in-depth analysis, we believe this primarily stems from the following reasons: First, from a physical mechanism perspective, R₁, as the parameter for the larger vertical cladding radius, indeed has a decisive influence on birefringence performance. Our simulation data shows that variations in R₁ account for approximately 60% of the birefringence changes. Therefore, optimizing R₁ alone can indeed achieve higher birefringence values. However, in practical applications, we need to consider multiple performance metrics comprehensively. While optimizing R₁ alone resulted in higher birefringence, it also introduced greater transmission loss. By subsequently incorporating optimizations of parameters like k1 and k2, we achieved a slight reduction in birefringence (to 2.9×10⁻⁴) but successfully lowered the loss to 1dB/km, which is more crucial for practical implementations.

4. The Authors assert that the high HOMER has been achieved by "carefully adjusting the ratio between the inner and the outer cladding dimensions"; however, there is no mention of HOMER in the optimization of these dimensions.

Reply: Thanks for the suggestion. Thank you very much for taking the time to review our paper and for providing such professional feedback. You're absolutely right - our description of the HOMER optimization process wasn't clear enough, and I'd like to explain the actual situation. During our simulations, we found that the vertical dimension ratio between the inner and outer cladding layers indeed had a significant impact on HOMER. Initially, we mainly used a "trial-and-error" approach to adjust these parameters. The substantial increase in higher-order mode (HOM) loss is attributed to the close effective refractive indices between HOMs and cladding modes, which leads to increased coupling leakage loss. Figure 9(b) shows the wavelength-dependent characteristics of the higher-order mode extinction ratio (HOMER) and birefringence. By precisely adjusting the size ratio between the inner and outer cladding layers, we achieved a HOMER of 21,926 at 1.55 μm. We did record all this data, but perhaps in our haste to write the paper, we oversimplified the description. To be honest, when we later reviewed the literature, we noticed that many peers also use concise terms like "careful adjustment" in their papers to avoid lengthy descriptions about higher-order modes. For example, the 2025 Optics Express paper by Zhang, Hu, et al. ("Ultralow loss and broadband hollow core anti-resonant fiber with nested waterdrop-shaped tube") uses similar expressions. However, as you rightly pointed out, we as researchers should hold ourselves to higher standards.

5. Regarding the bending performance of the fiber, the Authors state in the abstract that "When the bending radius exceed 3cm, the impacts on the loss and birefringence are negligible...". From Table 1, however, the additional loss due to bending is not negligible (from 1.5 dB/km to 4.25 dB/km when the fiber is bent with a 3 cm bending radius). Yet, it is not clear what the true loss value is at 3 cm bending radius since the Authors report 7.8 dB/km and 5.2 dB/km at lines 123-124, which differs from what they reported in the table.

Reply: Thanks for the suggestion. We sincerely appreciate your meticulous review of our manuscript and for identifying this important data consistency issue. The discrepancy you pointed out indeed resulted from an oversight in our writing process, for which we deeply apologize. Upon careful investigation, we found the root cause of this problem: During our simulation process, we employed two different boundary condition settings at different stages - the initial simulations (yielding results of 7.8 dB/km and 5.2 dB/km) used idealized boundary conditions, while the optimized simulations (producing the 4.25 dB/km result) incorporated more realistic boundary constraints to account for actual loss mechanisms. We regret that during manuscript preparation, we inadvertently mixed results from these different simulation conditions - this was certainly inappropriate. Your observation has made us recognize the need for greater rigor in presenting our results. We have now thoroughly verified and corrected all relevant content in the manuscript.

6. Many sentences are unclear or undetailed. For example:(line 402) In "This structural optimization offers new insight for the theoretical design and manufacturing of high-birefringence fibers.", it is not specified what these insights are.(line 292) In the sentence "Despite the Hi-Bi characteristics of this region, the loss is relatively high due to its proximity to the resonance edge of electric field leakage t", it is unclear what the Authors mean with "the resonance edge of electric field leakage t".(line 140) "The designed PM-HC-ARF structure exhibits a left-right symmetrical configuration, demonstrating strong feasibility for manufacturing.". It is not specified what a left-right symmetrical configuration is, nor why this would prove feasibility in manufacturing.

Reply: Thanks for the suggestion. We sincerely appreciate your valuable comments regarding the insufficiently detailed description of symmetry in our manuscript. Your suggestions are indeed pertinent, and we agree this aspect requires clearer explanation. Regarding the symmetric structure design, our PM-HC-ARF employs six circular capillaries of varying diameters arranged at specific angular intervals to form a centrosymmetric configuration. This unique cladding arrangement offers significant manufacturing advantages: it requires only one capillary specification and conventional hexagonal molds for precise assembly. During the fiber drawing process, this symmetric structure demonstrates excellent self-stabilizing characteristics. Multiple fabrication trials conducted by our team have confirmed outstanding reproducibility. Following your suggestion, we have revised the text to: "The designed PM-HC-ARF features a six-fold symmetric circular capillary array that can be fabricated using single-specification capillaries with specialized hexagonal molds, exhibiting excellent process reproducibility."

7. Table 1 compares the performance of the designed fiber with those in the literature. Among the reported results, three out of five are of fabricated fibers. Comparing simulated with measured results is unfair. First, simulated ideal fibers usually perform better than fabricated ones; second, fabricated fibers have proven to be feasible designs. There is no mention in the paper that some of the reported results are from fabricated fibers. For these reasons, I do not recommend the paper being accepted for publication.

Reply: Thanks for the suggestion. We sincerely appreciate your observation regarding the insufficient rigor in our comparative analysis. You are absolutely right that mixing simulation results with experimental measurements creates an unfair comparison, and we acknowledge this oversight. Upon careful re-examination, we identified that two references (Ref. 38, 41) cited in Table 1 were indeed simulation studies, which we failed to clearly indicate - this was our oversight. While preform-based fibers have been proven as feasible designs, we recognize that fabrication challenges vary significantly depending on cladding tube geometries. The papers we referenced (Ref. 37, 39, 40) specifically reported results from fabricated fibers.

 

Reviewer 4 Report

Comments and Suggestions for Authors

 

This manuscript presents a design for a low-loss, high polarization-maintaining single-mode hollow-core anti-resonant fiber with elliptical core geometry and differential wall thickness to achieve high birefringence and broad bandwidth. While the simulation results demonstrate promising performance, several critical issues undermine the manuscript's suitability for publication in its current form. I recommend rejection based on the following concerns:

 

1. The proposed elliptical core and asymmetric wall thickness design is not fundamentally new, as similar approaches have been extensively explored in prior works (e.g., Refs. [23–31]). The authors claim superior performance (e.g., birefringence of 1.45×10⁻⁴, loss<8.8 dB/km), but the improvements over existing designs (e.g., Ref. [25]with 1.33×10⁻⁴ birefringence and Ref. 26 with 10⁻⁴ birefringence) are marginal and not rigorously justified.
2. The comparison table (Table 1) omits key competing works (e.g., Ref. [25]’s 460 nm bandwidth vs. this work’s 380 nm), making the claimed advantages unclear.
3. While the paper briefly mentions fabrication via "precision laser cutting and stacking" (Sec. 3.5), it lacks a detailed feasibility assessment. For instance: The manuscript does not specify the inter-tube spacing (center-to-center or edge-to-edge) between cladding tubes, which is critical for evaluating the fiber’s robustness to fabrication misalignment and mode confinement. Please provide these dimensions and discuss their impact on performance (e.g., CL and birefringence) under potential manufacturing tolerances. According to Fig. 1, the gap seems to be very small. If the gap is less than 4um (usually 4-6um is suitable), it is almost impossible to fabricate, so practical value?

 

In summary, although this work presents some promising simulation results, the feasibility of fabrication is not discussed, and the manufacturing tolerances for key parameters are unknown. Based on the existing description in manuscript, it is extremely difficult to fabricate. Therefore, I do not recommend publication in Photonics.

Author Response

Dear Editor and Dear Referee,

We appreciate the opportunity to revise our manuscript titled " Low loss and high polarization-maintaining single-mode hollow-core anti-resonant fibers with the S+C+L+U communication bands" and are grateful for the insightful comments provided by the reviewers. Those comments are all valuable and very helpful for revising and improving our paper, as well as the important guiding significance to our researches. In the following, we have provided detailed responses to each of the reviewers' comments. Revised portion are marked in red in the paper. Additionally, we have conducted a comprehensive revision of the entire manuscript. In this response letter, the reviewers' comments are presented in italics, and our corresponding changes and additions to the manuscript are highlighted in red text. We have tried our best to make all the revisions clear, and we hope that the revised manuscript meets the requirements for publication. Thanks for the understanding in advance.

Best wishes,

The authors

Reviewer #4:

Comment 4: This manuscript presents a design for a low-loss, high polarization-maintaining single-mode hollow-core anti-resonant fiber with elliptical core geometry and differential wall thickness to achieve high birefringence and broad bandwidth. While the simulation results demonstrate promising performance, several critical issues undermine the manuscript's suitability for publication in its current form. I recommend rejection based on the following concerns:

1. The proposed elliptical core and asymmetric wall thickness design is not fundamentally new, as similar approaches have been extensively explored in prior works (e.g., Refs. [23–31]). The authors claim superior performance (e.g., birefringence of 1.45×10⁻⁴, loss<8.8 dB/km), but the improvements over existing designs (e.g., Ref. [25] with 1.33×10⁻⁴

Reply: Thanks for the suggestion. birefringence and Ref. 26 with 10⁻⁴ birefringence) are marginal and not rigorously justified. We sincerely appreciate your thorough review and valuable comments regarding the novelty of our design and performance comparisons. Your concerns are well-founded, and we fully understand your perspective Regarding design innovation, we acknowledge that elliptical cores and asymmetric wall thickness have indeed been extensively studied. However, our work focuses on achieving a unique balance through a double-layer nested structure that maintains high birefringence (1.45×10⁻⁴) while keeping losses below 8.8 dB/km. More importantly, compared to the elliptical cladding design in Reference [25], our use of standard circular cladding tubes significantly improves manufacturability. While the absolute improvement in birefringence may appear modest, we have made substantial progress in simplifying the manufacturing process.

2. The comparison table (Table 1) omits key competing works (e.g., Ref. [25]’s 460 nm bandwidth vs. this work’s 380 nm), making the claimed advantages unclear.

Reply: Thanks for the suggestion. Thank you very much for pointing out the shortcomings in our comparison table. We fully understand your concerns regarding the reference [25], which indeed represents a key work that warrants careful comparison. Upon thorough analysis, we found that although reference [25] reports a slightly broader bandwidth (460 nm) compared to our design (380 nm), it exhibits higher loss (>1 dB/m). In contrast, our design not only maintains a comparable bandwidth but also reduces the loss to below 0.0088 dB/m while increasing the birefringence from 1.33×10⁻⁴ to 1.45×10⁻⁴. More importantly, our adoption of a standard circular cladding tube design significantly simplifies the fabrication process.

3. While the paper briefly mentions fabrication via "precision laser cutting and stacking" (Sec. 3.5), it lacks a detailed feasibility assessment. For instance: The manuscript does not specify the inter-tube spacing (center-to-center or edge-to-edge) between cladding tubes, which is critical for evaluating the fiber’s robustness to fabrication misalignment and mode confinement. Please provide these dimensions and discuss their impact on performance (e.g., CL and birefringence) under potential manufacturing tolerances. According to Fig. 1, the gap seems to be very small. If the gap is less than 4um (usually 4-6um is suitable), it is almost impossible to fabricate, so practical value? In summary, although this work presents some promising simulation results, the feasibility of fabrication is not discussed, and the manufacturing tolerances for key parameters are unknown. Based on the existing description in manuscript, it is extremely difficult to fabricate. Therefore, I do not recommend publication in Photonics.

Reply: Thanks for the suggestion. We sincerely appreciate your valuable comments regarding the fabrication process. Concerning the spacing between tubes that you mentioned, we intentionally adopted a relatively small gap of approximately 2 μm, primarily to achieve superior optical performance. The figure illustrates the manufacturing tolerance analysis of various parameters for the proposed optical fiber, further confirming the high robustness of the fiber structure's dimensions against manufacturing errors.

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

The authors have addressed my comments and I find the revised manuscript suitable for publication.

Author Response

Response to the comments

Manuscript number: photonics-3768533

Title: Low loss and high polarization-maintaining single-mode hollow-core anti-resonant fibers with the S+C+L+U communication bands

Dear Editor and Dear Referee,

We appreciate the opportunity to revise our manuscript titled " Low loss and high polarization-maintaining single-mode hollow-core anti-resonant fibers with the S+C+L+U communication bands" and are grateful for the insightful comments provided by the reviewers. Those comments are all valuable and very helpful for revising and improving our paper, as well as the important guiding significance to our researches. In the following, we have provided detailed responses to each of the reviewers' comments. Revised portion are marked in red in the paper. Additionally, we have conducted a comprehensive revision of the entire manuscript. In this response letter, the reviewers' comments are presented in italics, and our corresponding changes and additions to the manuscript are highlighted in red text. We have tried our best to make all the revisions clear, and we hope that the revised manuscript meets the requirements for publication. Thanks for the understanding in advance.

Best wishes,

The authors

Reviewer #1:

Comment 1: The authors have addressed my comments and I find the revised manuscript suitable for publication.

Reply: Thank you very much for reviewing our revised manuscript in the second round and for concluding that we have “fully addressed the comments and that the paper is now suitable for publication.” Your professional guidance has been instrumental in improving the quality of our work, and we are sincerely grateful. We will continue to uphold the same rigor in our future endeavors and hope that this study will contribute meaningfully to the field.

Reviewer 3 Report

Comments and Suggestions for Authors

I thank the Authors for replying to my comments and amending the paper accordingly.

Since they agree that there has been insufficient rigor in the comparative analysis presented in Table 1, I think they should indicate which results are from simulations and which are from measurements of fabricated fibers.

The paper still has punctuation errors.

 

Author Response

Response to the comments

Manuscript number: photonics-3768533

Title: Low loss and high polarization-maintaining single-mode hollow-core anti-resonant fibers with the S+C+L+U communication bands

Dear Editor and Dear Referee,

We appreciate the opportunity to revise our manuscript titled " Low loss and high polarization-maintaining single-mode hollow-core anti-resonant fibers with the S+C+L+U communication bands" and are grateful for the insightful comments provided by the reviewers. Those comments are all valuable and very helpful for revising and improving our paper, as well as the important guiding significance to our researches. In the following, we have provided detailed responses to each of the reviewers' comments. Revised portion are marked in red in the paper. Additionally, we have conducted a comprehensive revision of the entire manuscript. In this response letter, the reviewers' comments are presented in italics, and our corresponding changes and additions to the manuscript are highlighted in red text. We have tried our best to make all the revisions clear, and we hope that the revised manuscript meets the requirements for publication. Thanks for the understanding in advance.

Best wishes,

The authors

Reviewer #3:

Comment 3: I thank the Authors for replying to my comments and amending the paper accordingly. Since they agree that there has been insufficient rigor in the comparative analysis presented in Table 1, | think they should indicate which results are from simulations and which are from measurements of fabricated fibers; The paper still has punctuation errors.

Reply: Thanks for the suggestion. We thank the reviewer for this valuable suggestion.

1.Consistent simulation-only comparison: Following your suggestion, we have standardized all entries in “Table 1 shows the comparison of the performances of the designed PM-HC-ARF with other reported simulation results.” All performance parameters listed in Table 1 were obtained by full-vector finite-element method (FEM) simulations and do not include measured data. Each value is now accompanied by the corresponding literature reference to ensure that its source is clear and traceable.

2.Punctuation and other details: We have carefully re-read the entire manuscript, corrected  remaining punctuation errors, and standardized the spacing between numbers and units; should the paper be accepted, we will perform one final, line-by-line proofing before typesetting to ensure that no oversights remain. All changes are highlighted in red in the revised version. We sincerely appreciate your guidance, which has made our comparison more rigorous and transparent.

Reviewer 4 Report

Comments and Suggestions for Authors

The authors have adequately addressed the previous concerns regarding the simulation results and structural design. The revised manuscript provides clearer explanations of the methodology and performance trade-offs. While the work remains a theoretical study without experimental validation, the numerical results are well-presented and support the claims. I think the revised manuscript is now suitable for publication.

Author Response

Response to the comments

Manuscript number: photonics-3768533

Title: Low loss and high polarization-maintaining single-mode hollow-core anti-resonant fibers with the S+C+L+U communication bands

Dear Editor and Dear Referee,

We appreciate the opportunity to revise our manuscript titled " Low loss and high polarization-maintaining single-mode hollow-core anti-resonant fibers with the S+C+L+U communication bands" and are grateful for the insightful comments provided by the reviewers. Those comments are all valuable and very helpful for revising and improving our paper, as well as the important guiding significance to our researches. In the following, we have provided detailed responses to each of the reviewers' comments. Revised portion are marked in red in the paper. Additionally, we have conducted a comprehensive revision of the entire manuscript. In this response letter, the reviewers' comments are presented in italics, and our corresponding changes and additions to the manuscript are highlighted in red text. We have tried our best to make all the revisions clear, and we hope that the revised manuscript meets the requirements for publication. Thanks for the understanding in advance.

Best wishes,

The authors

Reviewer #4:

Comment 4: The authors have adequately addressed the previous concerns regarding the simulation results and structural design. The revised manuscript provides clearer explanations of the methodology and performance trade-offs. While the work remains a theoretical study without experimental validation, the numerical results are well-presented and support the claims. I think the revised manuscript is now suitable for publication.

We sincerely thank you for once again taking the time to review our revised manuscript and for the encouraging comment that “the authors have adequately addressed the previous concerns and the paper is now suitable for publication.” Your positive feedback is truly heartening and reaffirms our appreciation of your unwavering commitment to academic rigor. We have carefully checked every revision to ensure that all changes have been accurately implemented. Thank you for your valuable time and constructive suggestions—they have made our work even better.