Impact of Chirp in High-Capacity Optical Metro Networks Employing Directly-Modulated VCSELs

Round  1

Reviewer 1 Report

In this paper, the authors introduced new results by utilized a new setup system based on VCSELs. The results confirm the possibility to exploit directly modulated long-wavelength VCSELs for the realization of sliceable bandwidth/bitrate variable transmitters targeting 50-Gb/s capacity per polarization also in presence of 5 crossed WSSs for hundreds of kilometers reaches in multi-span EDFA-amplified metro links, supported by coherent detection. The idea behind this is interesting. However, I still have quite a number of concerns in this manuscript. There are times where there are not enough data to support the conclusions of the author. Please see some of the major concerns below.

1.The information for the optical system is not enough. The authors should give much more information about this, which operated wavelengths can work in this system? so, the readers can get its reproducibility. 

2.  The authors should give much more information about the novelty of this paper, especially the effect of using this setup and compared to other optical networking?

I suggested to add a table which show the benefices of this system.

3. More references need to be included in the introduction part to understand the applications of using WDM devices.

1.       "1 x 4 MMI visible light wavelength demultiplexer based on GaN slot waveguide structures," J. Photonics and Nanostructures – Fundamentals and Applications, (2018).

2.       “An Eight-Channel C-Band Demux Based on Multicore Photonic Crystal Fiber”, Nanomaterials, vol. 8, issue. 845, OCT 2018.

3.       " A visible light RGB wavelength demultiplexer based on silicon-nitride multicore PCF, " Optica&Laser Technology, vol. 11, pp. 411-416, 2019.

4.  Much more discussion about the results should be given in this paper, especially the author needs to provide enough physicals mechanism analysis about the results.

5.  Can this network can support and work in the 0-Band for data-center applications?

Author Response

Please, find in attachment the comments and answers to Reviewer 1.

Author Response File: Author Response.pdf

Reviewer 2 Report

My first recommendation is: please, respect and follow the template of Photonics Journal and the others are below:

·       The authors did not define all acronyms in the abstract. Please, make a decision if you want to define all or not. Definition some of them is not proper.

·       The keywords are better to have in alphabetic order.

·       Line 36: define UHD acronym however it is well known.

·       Line 37: the authors missed OPEX explanation.

·       Some references can support the first paragraph in the Introduction section.

·       Line 66: Please start a new paragraph: In Section 2 ...

·       Line 71: Section 4 concludes the paper.

·       Line 89, 97: You missed the comma after equation.

·       Line 113: the template defines the usage of Figure not Fig.

·       Line 119: Define PIN acronym.

·       May I ask you about more details about PIN photodiode? Is it possible to use APD photodiode, how does it affect your measurement?

·       Line 122, 123: define E/O o/E acronyms.

·       Line 126: Figure 2a) and Figure 2b).

·       Equation 4 missed the comma.

·       Line 159: Do not start a new paragraph when you continue from the equation.

·       Line 209, 2010: Figure 4a)–f)

·       Please, follow the template for the Journal and citation style. For example ref [4]:

o   Svaluto Moreolo, M.; Fabrega, J. M.; Nadal, L.; Vilchez, F. J.; Mayoral, A.; Vilalta, R.; Munoz, R.; Casellas, R.; Martinez, R.; Nishihara, M.; et al. SDN-Enabled Sliceable BVT Based on Multicarrier Technology for Multiflow Rate/Distance and Grid Adaptation. Journal of Lightwave Technology 2016, 34 (6), 1516-1522 DOI: 10.1109/JLT.2015.2510082.

 

In general, coherent detection is well-known from the wireless networks however it is a very important part in optical networks. I am very confused by the article. On one hand, there is not high impact in research field because of the measurement of the chirp in a work for an engineer. The authors will need to more clarify their improvement according to the results in this article. Furthermore, the related works can improve the paper quality. For example:

DOI: 10.1109/JPHOT.2014.2343151

DOI: 10.1109/ICACCI.2016.7732482

DOI: 10.1109/LPT.2006.884239

DOI: https://ieeexplore.ieee.org/document/1361621

 

Some of the articles are quite older but it means that the topic was probably popular before. I suggest re-submission with significant major revisions. You can also provide more details about the simulation tool/s and compare the results. Finally, small suggestions, please, consider the list of the acronyms and use the vector graphic for the graphs (see tikzpicture in LaTeX or other).


In general, the chirp measurement is not nothing "special or scientific", however, the authors provided probably feasible results, the comparison with the current work and results is missing.
Furthermore, the measurement used the very simple scheme but with no satisfied details about photodetector etc. The authors should add a comparison with Fabry-Pérot laser source.

Author Response

Please, find in attachment the comments and answers to Reviewer 2.

Author Response File: Author Response.pdf