Optical Technology for NFV Converged Networks
Round 1
Reviewer 1 Report
This paper reviewed the state of the art and future perspectives regarding optical networking using silicon integrated technology. The review is complete and give an important update in the field. I suggest acceptance after correcting two issues. First, all figures are low quality and letters very small making difficult the reading, and secondly the conclusion looks like abstract. I suggest authors to rewrite conclusion using the main contribution of the paper in this field and also to include future perspectives and their own ideas and proposals.
Author Response
This paper reviewed the state of the art and future perspectives regarding optical networking using silicon integrated technology. The review is complete and give an important update in the field. I suggest acceptance after correcting two issues. First, all figures are low quality and letters very small making difficult the reading, and secondly the conclusion looks like abstract. I suggest authors to rewrite conclusion using the main contribution of the paper in this field and also to include future perspectives and their own ideas and proposals.
Many thanks to the reviewer to provide such comments that allow to improve the quality and the comprehension of the paper.
According the suggestions:
- all the figures have been edited again to improve the quality and facilitate the reading (bigger font-size, modification of colors in some cases)
- the conclusions have been rewritten to better clarify why the integrated silicon photonics is relevant today in the NFV 5G/Beyond network segment. Integrated silicon photonics has been born for data center application and the use on telecom network poses some challenges. For example, the integration of tunable filters in transceiver could have challenges in terms of size and power consumption. Concerning the ROADM, the use of SOA could impact the number of channels that could be supported. The future perspective is to address such open points in telecom scenarios.
Reviewer 2 Report
This paper presents an overview of the potential and challenges that integrated silicon photonics platform currently faces in its integration into today’s 5G/6G network. Several designs and their topologies are presented and analyzed. This paper is well organized and presented very well. I will recommend acceptance to applied science.
- I would suggest the authors also include reference in the caption of all the figures, rather than just in the text. As this is an overview article, it would be much easier for the readers to find the reference if they are interested in the detail of each figure.
Author Response
This paper presents an overview of the potential and challenges that integrated silicon photonics platform currently faces in its integration into today’s 5G/6G network. Several designs and their topologies are presented and analyzed. This paper is well organized and presented very well. I will recommend acceptance to applied science.
I would suggest the authors also include reference in the caption of all the figures, rather than just in the text. As this is an overview article, it would be much easier for the readers to find the reference if they are interested in the detail of each figure.
Many thanks to the reviewer comments that allows to improve the quality of the paper and better define the main messages.
All figures have been replaced to improve the readability. In fig 2,3a and 4 the references have been included in the captions. Fig 1, 3b, and all the others do not report references in the captions because they present innovative results and scenario presented in the paper.
Reviewer 3 Report
Please see attached comments
Comments for author File: 
Comments.pdf
Author Response
The paper throws light on the use of silicon photonics to advance optical communication networks, with the advent of 5G technology. Silicon photonics undoubtedly has advantages, such as enumerated in the paper, that make it highly attractive for optics-based applications. The topic of this paper is thus both relevant and important. However, like everything else, silicon photonics also has its drawbacks, as the authors have noted. All put together paper in its present form that silicon photonics particularly stands out from its competitors, and a more thorough analysis and comparison is needed. For example, is the promise of cost reduction and ease of integration when everything is considered significant enough to make silicon photonics a game changer? Moreover, silicon photonics does not lend itself for use as light sources and hence such sources are currently impractical to be integrated into the rest of the optical circuitry. Thus, how will issues such as coupling external light sources into the photonics chip affect overall efficiency, cost, and size?
The other drawbacks, such as thermal management, polarization control, and optical cross talk, also merits further discussion as solutions need to be found in order to mature silicon technology for optical communications. For example, will these solutions be practical enough as to make this technology still attractive and maintain its competitive edge? These are questions that will linger in the minds of interested readers and stakeholders, and hence need some elucidation.
Many thanks for the valuable comments and the stimulating questions. To clarify better the technology gaps that remain to be filled, and outline possible solutions, we divided Section 3 (Silicon photonics devices in optical transport: challenges and opportunities) in an introductive text followed by 5 subsections, as follows:
- 3.1 “Coupling and polarization control issues in silicon photonics devices”. We added to the existing text, describing grating and edge couplers, a short paragraph mentioning active polarization control based on silicon photonic devices and their issues in guaranteeing endless operation and polarization recovery in WDM systems.
- 3.2 “Integration issues of optical amplifiers and active sources in silicon photonics devices”.
- 3.3 “System applications enabled by SOAs integrated in silicon photonics devices”
- 3.4 “Silicon photonics in optical transceivers and laser integration issues”. In addition to the existing text, we mention the possibility of coupling external light sources and related issues in cost and polarization handling, providing relevant references.
- 3.5 “Thermal management in silicon photonics”. This section has been added. It discusses the main challenges for the thermal management and reports the existing methods to deal with it.
- 3.6 “Is silicon photonics promise of cost reduction and ease of integration, when all issues are considered, significant enough to make silicon photonics a game changer?” This is a completely new paragraph, whose title is borrowed from your comment. Our opinion is that the major obstacles to the success of silicon photonics are not due to technical issues (although they exist and are big) but to the lack of an economically sustainable business model. Considerations are made along this line of opinion (which is, of course, questionable, as any opinion).
Also, it is not so clear to this reviewer the novelty of the results presented. The benefits of silicon photonics, as well as knowledge in integrating optical subcomponents into a chip is already quite well known, so what further new information is being presented in the paper?
The silicon photonic is a mature technology. It was born for data-center, so, up now, there was not a business case to push the use of such technology in telecom network. Hence the paper describes such aspects and report the main issues on the application in telecom context. The innovative part has been reported in chapters 4 and 5, the introduction has been modified to clarify this point. Moreover, the conclusions have been modified to discuss aspects such novelty and the open issues.
Lastly, the English language phraseology could do with some improvement, as some passages in the paper are difficult to comprehend.
English version has been improved, reducing the length of the sentences and, in general, improving the language.
Round 2
Reviewer 3 Report
This reviewer's comments have been satisfactorily addressed and recommends publication of this paper
