Research on Key Technologies of Quantum-Safe Metro-Optimized Optical Transport Networks

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The article Research on Key Technologies of quantum-safe metro-optimized optical transport network is focused on innovative physical layer encryption technique using real-time optical signal time-domain scrambling and decoy-state quantum key distribution. First, the paper introduces the metropolitan optimized optical transport network (M-OTN) using optical service unit (OSU) structure and by using updated and synchronized keys, the encryption is achieved. The experimental setup described in the paper provides the verification of this promising solution.

First, the overall organization of the paper is very good. The length of the paper is, in my opinion, optimal, as it contains almost all the necessary (see below), while the text itself is not overstretched. The language level is also very good, I was not able to notice any major mistake, however, I still recommend performing proofreading prior to the publication. The paper is well balanced in terms of the theoretical problem description and formulation and the experimental results and conclusions.

The experimental results and conclusions are well presented and described. The results indicate that the proposed solution could perhaps provide quite promising results, and the technique proposed and described in this paper is potentially viable.

Generally, I recommend accepting the paper after considering some improvements and including some additional description based on the following comments and questions.

1. I recommend adding some additional information and description of the experimental setup, as I miss some details here.

First, what is the length of the optical scrambler/descrambler? How many temperature control modules (TCM) does it contain and how does their number impact the performance?

Next, I miss the gain of the EDFAs used in the experimental setup. There is some information about the optical loss in the system, but it is not clear whether this loss is covered by EDFAs or not? Additionally, what about the noise that both EDFAs amplifiers superimpose to the optical signal?

What about the temperature stability and impact? Both scramblers/descramblers are based on TCM, however, there is no verification and the experimentation with temperature impact on resulting performance.

There is not much information provided about the quantum channel itself. For example, what is the loss (attenuation) of the channel? Is it possible to use the same optical fiber for both the quantum and transportation channel or not through WDM application?

There is also no information about the FPGA used in the test scenario. What is the minimal computational power the FPGA needs suffice for 10 Gbps transmission? E.g. how computationally extensive is the proposed method?

2. Based upon the description provided in section 2 it can be concluded that mapping/multiplexing OSU services to OPUs presented in the paper to offer guaranteed bandwidth, some kind of transmission jitter is created especially when the scrambling/descrambling combined with DS-QKD technique is used. This jitter could perhaps negatively impact some jitter-delay intolerant network services. I recommend including at least some short elaboration about this in the text.

Author Response

Please see the attached PDF.

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

The manuscript ID applsci-3498155 has been devoted to mainly present a study about particular key technologies related to quantum-safe metro-optimized optical transport networks. Please see below some points to the authors:

1. How was selected the Fabry-Perot cavities instead of other alternatives for this particular research?
2. How is the influence of the incident polarization in the experimental data?
3. Perspectives could be added. The authors are invited to consider for instance the use of multiphotonic effects for processing all-optical functions:  https://doi.org/10.3390/photonics11111029
4. The experimental and numerical results should be better confronted and the discussion about the main findings should be summarized before the conclusions.
5. How is the implementation of the system? A description is missing. You can comparatively see for instance: https://doi.org/10.1364/OFC.2024.Th3B.3
6. The main results should be confronted with updated publications in the topic.
7. The manufacturer and model of the systems employed in the experimental setup should be provided.
8. Some keywords could be added and improved.
9. A photo of the experimental setup would be welcome.
10. Some of the citations presented in collective form should be split in order to better justify the importance of each publication selected for the presentation of the topic.

Comments on the Quality of English Language

A proofreading is suggested

Author Response

Please see the attached PDF.

Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

Comments and Suggestions for Authors

The author have succesfully addressed all the points raised in the initial review stage. The analysis about key technologies of quantum-safe metro-optimized optical transport network is clear and solid. Then, I can recommend this work for publication in present form.

Comments on the Quality of English Language

A proofreading is suggested