Design and Analysis of Trench-Assisted Low-Bending-Loss Large-Mode-Field-Area Multi-Core Fiber with an Air Hole

Round 1

Reviewer 1 Report

This paper proposes a trench-assisted multi-core fiber with low-bending-loss and large-mode-field-area. The authors simulate and analyze the influence of structural parameters on fiber performance, including bending loss, effective mode area, and effective mode refractive index. The proposed fiber can realize large effective area of 2003.24 um2 at 1550 nm and bending loss of 2.57×10-3 at 1 cm. I believe these results will be helpful for the design of large-mode-area and bending insensitive fibers. Proposed fiber can be used in optical fiber lasers and FTTH application. The manuscript can be accepted after the issues can be addressed. 1. There are extra spaces in 43 lines and 47 lines. 2. The manuscript should be more objective about the experimental results and discussion. 3. The resolution of Figure 1 is low compared to other figures and should be updated. 4. Conclusion can be better explained.

Author Response

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Reviewer 2 Report

The paper "Design and analysis of trench-assisted low-bending-loss large-mode-field-area multi-core fiber with air hole" proposes a fiber based on the combination of air holes and doped cores. The impact of different parameters like core sizes and pitch is investigated in regards to mode field diameter and bending losses.

The manuscript is well written and easy to follow. It also compares the resulting performance of the fiber to previous publications. Hence, I recommend publishing it. Some comments are as follows:

1. How is the reliability of the proposed fiber?
2. When fiber bends, the distribution of two-dimensional mode field changes compared with straight fiber. Authors can explain more about Fig. 8.

Author Response

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Author Response File: Author Response.doc

Reviewer 3 Report

Title

Design and analysis of trench-assisted low-bending-loss large-mode-field-area multi-core fiber with air hole

 

Brief summary

A large mode area microstructured optical fiber that could be used in high-power high-capacity applications is proposed and analyzed. The 125 um diameter, symmetric fiber design consists of multiple air holes and solid cores modifications in place of a conventional hexagonal lattice 19 core optical fiber. Through numerical simulation using the finite element method (FEM), the calculated effective mode field area of the fundamental mode is approximately 2000 um² at 1550 nm operating wavelength. The fiber structure is also bend insensitive having bending loss ~10^-6  and maintaining 50% of its effective mode field area for single mode operation at 30 mm bending radius. 

 

Broad comments (highlighting areas of strength and weakness. These comments should be specific enough for authors to be able to respond.)

The manuscript is technically sound in describing the fiber structure and its theoretical analysis in terms of mode analysis and bending loss. The section on optimizing the design (heading #5) takes into account useful consideration for potentially fabricating the proposed large mode area microstructured optical fiber.

If there are any overall improvements that could be made the manuscript, the authors are suggested to discuss in the manuscript in areas, but not limited to: 

1. The mechanism to splice, cleave, connect to other fiber or fiber components, which is one common challenge to holely fiber. The air hole(s) collapsing effect incurs optical losses at the fiber-fiber interfaces.
2. Proposing performance improvement possibility such as, but not limited to, further increasing the effective mode field area for dual mode or n-mode transmission, considering larger clad diameter fiber structure design, etc. 

 

Specific comments (referring to line numbers, tables or figures. Reviewers need not comment on formatting issues that do not obscure the meaning of the paper, as these will be addressed by editors.)

1. Figure 1, increasing the image resolution of the fiber structure to improve the image clarity. 
   
   
2. Line 197-205, a comparison table with other recent work and literature will be helpful for reader to view the importance. 
   
   
3. Line 207-208, assume this sentence "This section is not mandatory but can be added to the manuscript if the discussion is unusually long or complex." is for the reviewer to read. Author should remove it. 
   
   
4. Line 209, the starting paragraph in heading #5 can be improved. 
   
   
5. Line 248, the description in the manuscript should be improved by being more  specific. For examples here, air hole are added to the region surrounding the central core; solid cores are added to the silica region in between the 19 core.

Author Response

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Reviewer 4 Report

This work presents a theoretical study on the behavior of a newly created fiber, where the parameters are varied in search for a lossless propagation and better light guiding within it.

In the reviewer opinion, this type of contributions where the objective is to show simulation results are interesting, but must show a useful practical part to verify the veracity of the proposed affirmations. The question is: does it make sense to simulate a fiber with new properties or optimized parameters? Of course. But it does make sense even more whether these simulations are contrasted with experimental results. And what is even more interesting: the results should be realistic, manufacturable and should effectively be applied in actual situations.

There is no doubt about the benefits that the optical structure presented may have. However, it is considered as a very complex structure to handle and even more complex to manufacture. On the other hand, no matter how much it is simulated. Normally the theory suggests an ideal behavior, but then reality may not be so benevolent.

In principle, if a suitable fiber for communications were desired, it should include as many effective cores as possible, through which to guide the light multiplexing information in each of them. This is something that has been claimed in the introduction of the article but that it is not emphasized or addressed later. The contribution focuses only on increasing the effective mode area and how this can be enhanced by playing with the dimensions of all the proposed fiber  parameters and showing the evolution of just a few propagating modes.

To summarize, it is considered that this article should not be published in its current state. In the reviewer opinion, a deeper experimental demonstration showing the true practical potential that can be achieved with this fiber should be carried out, as well as providing evidence about how this fiber can provide an added value over the current state of the art in the field of communications and/or optical fiber sensing.

Author Response

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Author Response File: Author Response.doc

Round 2

Reviewer 4 Report

In this new version, the authors have clarified the pending issues and have provided evidence of the manufacture and subsequent application of the fibers they present. I would like to insist that I am more in favor of supporting publications that experimentally demonstrate what they simulate. But I understand that there are sufficient reasons to think that what has been analyzed is feasible and that the fiber could be manufactured at any time. Therefore, for my part, go ahead with it and congratulations to the authors for the new publication.
Thanks and best regards.