Low-Power-Consumption and Broadband 16-Channel Variable Optical Attenuator Array Based on Polymer/Silica Hybrid Waveguide

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

This paper demonstrated a 16-channel VOA array based on polymer/silica hybrid waveguide with a low power consumption of 15.53 mW. Overall, the experimental results are reliable but this work seems to be a simple replica of other work about MZI based VOA. Besides of the novelty, there are some other issues that need to be further clarified.

1. It is claimed that the low power consumption makes it possible to hybrid integrated with silica based passive devices. I cannot understand this point and low power consumption may be favorable for integration with CMOS chips. Please explain the reason in detail.

2. For the device itself, the insertion loss is a little high. But for the polymer/silica platform, it can realize a low transmission loss and a low coupling loss with fiber. Please discuss about the reason of such a high loss.

3. As can be seen form Table 1, the extinction ratio and power consumption is also not the optimum for the presented device. Have the authors tried to optimize the mmi? For the power consumption, it may depend on the length of the heater. So the product of power consumption and heater length is usually considered for a given phase shift. Also, the heater length will influence the modulation speed. Please give a detailed discussion about the device performance.

4. Some description may be not so accurate, such as excellent uniformity, significant commercial value, etc.

Comments on the Quality of English Language

It is suggested to have a careful proof-read by a native English speaker.

Author Response

Please see the attachment.

Author Response File: Author Response.docx

Reviewer 2 Report

Comments and Suggestions for Authors

This is an interesting work demonstrating optical signal attenuation and equalization with indegenious polymer/silica waveguide based 16 channel VOA array, in terms of high integration, low power consumption, wide operational wavelength. The authors did an excellent work in describing design/simulation and further fabrication and characterization of the devices with however a concise discussion. While the manuscript is sound in terms of scientific presentation and the results are acceptable with significant scientific and commercial value, this is still a very short report.

Further extensive study on the device with live system results are desirable, however this is sufficient for a short communication. The reviewer, however is hesitant to recommend this work for final publication in a reputed journal, even considering the overall significance of the work and scientific merit of the manuscript is sound.

The reviewer would recommend,

1.    Further study on the device parameters may be interesting.

2. Improving the introduction with recent and significant reports from literatures.

3.    Improving the English language for better comprehension of readers.

 

Comments on the Quality of English Language

Improving the English language for better comprehension of readers desirable. 

 

Author Response

Please see the attachment.

Author Response File: Author Response.docx

Reviewer 3 Report

Comments and Suggestions for Authors

Relevance: This work has a high relevance since VOAs are a critical component in DWDM based systems. New material systems that can advance the performance limits are very relevant and especially if they can lower the power consumption which this paper targets.

Novelty: The work is novel with using polymer based VOAs. Previous works have presented modulators within this material system, but VOAs have not been investigated much. 

Literature Review: The authors have compared this work with other material systems. They have not pointed out any previous work with the same material system. The authors should address this and add any references that specifically talk about VOA designs in SU8/PMMA system. If there is not much work in this area, the authors should identify it as such. 

There is one detail that must be pointed out and I want the authors to address this: The authors have presented a TO based VOA and when drawing a comparison with other SOI based VOAs they refer to plasma-dispersion effect based VOAs. This comparison is unfair and the authors should address this. 

In addition, a drawback of this material system is the footprint compared to SOI and that needs to be pointed out. 

Results: Most results are clearly explained.

The detailed process steps including mentioning the equipment details will benefit the community and is appreciated. Plots showing the change in transmission with applied voltage and calculated (or are they simulated?) results are clear.

As mentioned elsewhere, please specify clearly if the results are calculated or simulated. If they are calculated which equations were used? If they are simulated what was the simulation setup?

In the discussion section, the authors meant to refer to Figure 5(b) and not Figure 4(b) - please correct this. 

Analysis: 

- The analysis largely centers around comparison with other material systems and this is a fair point since using SU8/PMMA for lower power VOA design is the novelty factor in this paper. 

- Referring to a point earlier, please specify what attenuation mechanism is at play in each system. Plasma dispersion/TO/Electro-optic 

Comments on the Quality of English Language

Dear Authors,

Although I congratulate you on the technical soundness and merit of the paper, I must express my disappointment at the language, grammar and phrases used in the paper. To begin with please use a word editor such as MS Word that can spot any errors in sentence construction. I would also recommend getting the paper proof read by someone with adequate knowledge of the language. I do completely understand that English may not be your native language, however, for the benefit of the reader the language needs to be corrected before it can be published

Some examples:

- 'Cooperate' is not the right word in this context 

- Please use 'difference' instead of 'different' in the paper where necessary

- the demand of high capacity should be replaced with the demand for high capacity.

- Is Figure 3 calculated or simulated results? If they are calculated please add the equations used. 

There are other corrections to be made as well.  

Author Response

Please see the attachment.

Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

The authors have responded to all my concerns. I think it can be accepted in the current form.

Author Response

Please see the attachment.

Author Response File: Author Response.docx