Optoelectronic Oscillators: Progress from Classical Designs to Integrated Systems

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

Dear Editor,

This manuscript is dedicated to a survey of optoelectronic oscillators. Its structure is good in general, but it needs to be revised based on the comments below.

1. Since this article is presented as a review, the latest numerical results are expected to be mentioned in the abstract so that the reader can easily obtain up-to-date information.

2. After reviewing the oscillator structures, it is necessary to explain the oscillator design process. The reader needs to be able to learn the different design steps and just introducing the work of others is not enough.

3. Articles 2023 and 2024 have been reviewed a little. With further searching, other new articles can be added.

4. In the early sections, a subsection should define the important oscillator parameters and examine their mathematical and physical concepts.

5. Also discuss the power and frequency range of oscillators and their applications.

6. Examine the nonlinear properties and phenomena that can be used in oscillators.

Kind regards

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

There are some problems, which must be solved before it is considered for publication. If the following problems are well-addressed, this reviewer believes that the contribution of this paper are important.

1.       The paper outlines the evolution of OEO technology, but when discussing the current research status in this field, it does not clearly highlight the differences and unique contributions of the current review compared to other similar review studies. It is difficult to assess the innovation and value of this paper among numerous related studies. It is recommended to include a comparative analysis with other reviews of the same type, highlighting the unique aspects of this paper in terms of research perspective, coverage, and technical depth, and emphasizing new insights or underappreciated aspects of OEO technology development.

2.       In the transition from frequency-tunable OEO to broadband OEO, there is a lack of an inherent connection between the two in terms of technological development and application needs. It is hoped that when introducing new types or technologies of OEO, the relationship with previous content will first be reviewed, followed by the introduction of the importance and innovative aspects of the new content.

3.       The paper lacks sufficient depth in explaining some key technologies. In the integrated OEO design section, the comparison and analysis of the advantages and disadvantages of different integration platforms is not detailed enough. The rationale for choosing a specific integration platform and the trade-offs involved have not been fully explained. It is hoped that the paper will include a more detailed comparison of the technical specifics, performance characteristics, and other aspects of different integration platforms, highlighting the advantages and limitations of various integration solutions.

4.       In the section on integrated OEO, the prospects of emerging materials in integrated OEO are only briefly mentioned, with no detailed analysis of the challenges and potential solutions these materials face in integration processes and performance improvements. It is recommended that the author incorporate the latest research trends in semiconductor technology, emerging materials science, and photonics, and supplement the discussion on the potential of emerging technologies and materials in addressing existing issues in integrated OEO, making the paper more forward-looking.

5.       The paper does not clearly explain the criteria for selecting each architecture and their advantages in practical application scenarios. It is suggested to include more intuitive methods, such as tables or figures, to compare the differences between different OEO architectures in key performance indicators, complexity, cost, integration difficulty, and so on. Additionally, real-world application cases should be incorporated to analyze the applicable scenarios and limitations of each architecture.

6.       It is hoped that the author can explore in more detail the specific significance behind the data. For key experimental data, the author should combine the working principle and technical characteristics of OEO to analyze in detail the physical processes represented by the trends in the data and the reasons for the performance changes.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

This review article focuses on the development of optoelectronic oscillators (OEOs) within the field of microwave photonics. It explains the different layouts and their basic principles. In particular, the potential of an integrated solution for generating microwave signals is boasted for its attractive features including high stability, low noise, tunability and broadband operation. Though the structure is logic and the English writing is OK, I cannot recommend it in its current form, considering that there exist already abundant reviews regarding OEOs and microwave photonics in general. I suggest the authors dig deeper into the technology, come up with sharp insights and address some key issues before resubmitting.

1) In the introduction, the authors claim that "traditional electronic oscillators struggle to maintain signal quality as frequency increases, but OEOs leverage the advantages of photonics to achieve stable, high-frequency microwave signals, making them superior for these high-performance applications [7]" While Ref. [7] demonstrates that OEO can be used in a radar communication system, it does not justify the "superiority" as the field of high-frequency electronics is also developing very fast. As the very motivation for this work, the authors should make concrete, thorough comparison to top-notch electronic solutions in generating microwave signals and see in which aspect microwave photonics can help improve.

2) In Table 1 and 2, the other key parameters are conveniently left behind. Please add power consumption to the list and please do include the extra electronic power that is absolutely necessary to drive, stabilize the modulators, amplify the optical signals (still fiber-based, I presume?) etc. Please avoid focusing only on the photonic chip and claiming it is small, compact, efficient, while to use such a chip one has to add more electronics, whose power consumption, and other performance issues, should not be neglected.  

3) After over a decade of research, it is high time we see concrete applications of microwave photonics, rather than elaborating on its potential over potentials. As the authors mentioned quite a few applications in the introduction and in the abstract, please draw a picture how many of them are being adopted in a commercial or running systems beyond lab demonstration, e.g., in which "precision instrumentation" it is actually being used.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

Dear Editor,

The manuscript has been well-revised based on the comments. Now, I can recommend the manuscript for publication.

Kind regards

Reviewer 2 Report

Comments and Suggestions for Authors

The author has completed the revisions. Suggested acceptance