Broadband Instantaneous Frequency Measurement Using Frequency-to-Time Mapping and Channelization
Round 1
Reviewer 1 Report
Comments and Suggestions for AuthorsThe manuscript presents an instantaneous frequency measurement scheme based on frequency-to-time mapping and channelization, supported by simulation analysis and experimental testing. It aims to push the photonic-assisted instantaneous frequency measurement towards broader frequency ranges, higher precision, and increased resolution for applications in radar, electronic warfare, and related fields. The utilization of channelization significantly extends the frequency measurement capability to 1-39 GHz, achieving a measurement accuracy of <±20 MHz.
1. There is a limited citation of references, particularly in comparing different photonic-assisted frequency measurement schemes with specific references from the paper.
2. It is recommended to annotate the parameters of devices used in simulations and experiments, such as DPMZM, MZM, EDFA, etc.
3. Consider alternative visualization methods for Fig. 5 to improve the clarity of the 3D effect.
4. Further analysis is suggested in Fig. 6 to explore the time-frequency relationship of the linearly chirped signal.
5. Figure 7 lacks the numerical scale of the coordinates, so it is recommended to add text annotation.
6. Additional details on the error calculation method should be provided in Fig. 8.
7. A schematic diagram of the experimental setup would enhance the overall persuasiveness and reproducibility of the presented experiments.
Author Response
Comment 1：There is a limited citation of references, particularly in comparing different photonic-assisted frequency measurement schemes with specific references from the paper.
Response1：Thank your for pointing this out. We agree with this comment. We have added references in page1.
Comment 2：It is recommended to annotate the parameters of devices used in simulations and experiments, such as DPMZM, MZM, EDFA, etc.
Response2：Thank your for pointing this out. We agree with this comment. We have added parameters in Table1.
Comment 3：Consider alternative visualization methods for Fig. 5 to improve the clarity of the 3D effect.
Response3：Thank your for pointing this out. We agree with this comment. However, in the simulation software we do not have a better drawing method, improvement have made to make the picture more clear by adjusting the contrast and sharpness of the picture.
Comment 4：Further analysis is suggested in Fig. 6 to explore the time-frequency relationship of the linearly chirped signal.
Response4：Thank your for pointing this out. We agree with this comment. analsis is added in the last paragraph on page six.
Comment 5：Figure 7 lacks the numerical scale of the coordinates, so it is recommended to add text annotation.
Response5：Thank your for pointing this out. We agree with this comment. analsis is added in the last paragraph on page six.
Comment 6：Additional details on the error calculation method should be provided in Fig. 8.
Response6：Thank your for pointing this out. We agree with this comment. analsis is added on the last paragraph on page seven.
Comment 7：A schematic diagram of the experimental setup would enhance the overall persuasiveness and reproducibility of the presented experiments.
Response7：Thank your for pointing this out. We agree with this comment. While the experimental setup is basically consistent with the schematic diagram in Fig. 1, so it is not listed, and the device description is added in the last paragraph on page six.
Reviewer 2 Report
Comments and Suggestions for AuthorsDear Authors,
Please consider my frank review of your manuscript.
1. An IFM is meant to be a very simple system to estimate the signal frequency quickly. Your proposed concept is in the complex direction, e.g. multiple MZMs, multiple electronic signals including a wideband LFM signal acting as a frequency reference, multiple EDFAs and high-resolution WDM to demultiplex an optical frequency comb with spacing of 10 GHz.
I don't appreciate the advantage of the use of microwave photonics here. I strongly believe that your concept can be implemented in integrated RF electronics. Please clarify this fundamental issue.
2. Figure 1 is extremely difficult to read, and the caption does not define the acronyms.
3. Most of your references are recent. The manuscript fails to reference the pioneering photonic IFM work starting in 2006. In fact, a paper in 2009 first described the "frequency to time" mapping.
4. most of the attention is paid to frequency aspects only in the manuscript. There is little information relating to signal power. In the proposed IFM concept, there is a large self-heterodyned MZM structure, and this will introduce phase-induced intensity noise, significantly affecting the sensitivity of the IFM. Please consider thoroughly improving the manuscript by analysing and assessing system noise affecting the frequency measurement performance.
5. The font size of mathematical symbols varies throughout the manuscript.
6. Both Figs 2 and 3 are also hard to read.
7. It is also worth providing more details of the experimental setup and discussing it further. There are only two small paragraphs on the experimental setup and results.
Comments on the Quality of English LanguagePlease see above.
Author Response
Comment1：An IFM is meant to be a very simple system to estimate the signal frequency quickly. Your proposed concept is in the complex direction, e.g. multiple MZMs, multiple electronic signals including a wideband LFM signal acting as a frequency reference, multiple EDFAs and high-resolution WDM to demultiplex an optical frequency comb with spacing of 10 GHz.I don't appreciate the advantage of the use of microwave photonics here. I strongly believe that your concept can be implemented in integrated RF electronics. Please clarify this fundamental issue.
Response1：Thank you for pointing this out. We agree with this comment. What we currently know about electronic instantaneous frequency measurement receivers, such as the compact IFM receiver produced by TUALCOM, although with a very compact profile (approximately 10 cm × 10 cm × 2.5 cm) , have a limited measurement range of 2-18 ghz.We propose a photonics scheme that can cover the measurement range of 1-39GHz, which is difficult to achieve for electronic systems. On the other hand, with the development of integrated photon technology, optical modulators and filters will be integrated and miniaturized，then the problem you have pointed out can be solved.
Comment2：Figure 1 is extremely difficult to read, and the caption does not define the acronyms.
Response2：Thank your for pointing this out. We agree with this comment. Abbreviations have been defined in Figure 1.
Comment3： Most of your references are recent. The manuscript fails to reference the pioneering photonic IFM work starting in 2006. In fact, a paper in 2009 first described the "frequency to time" mapping.
Response3：Thank your for pointing this out. We agree with this comment. We've added more references, including the groundbreaking one you mentioned.
Comment4： most of the attention is paid to frequency aspects only in the manuscript. There is little information relating to signal power. In the proposed IFM concept, there is a large self-heterodyned MZM structure, and this will introduce phase-induced intensity noise, significantly affecting the sensitivity of the IFM. Please consider thoroughly improving the manuscript by analysing and assessing system noise affecting the frequency measurement performance.
Response4： Thank your for pointing this out. We consider that the frequency measurement range and measurement error are the most important for the proposed system, so the power and dynamic range of the signal are not discussed.
Comment5：The font size of mathematical symbols varies throughout the manuscript.
Response5： Thank your for pointing this out. We agree with this comment. The font size of all mathematics symbols have been unified into size ten .
Comment6：Both Figs 2 and 3 are also hard to read.
Response6：Thank your for pointing this out. We agree with this comment. The font size of all mathematics symbols have been unified into size ten .
Comment7：It is also worth providing more details of the experimental setup and discussing it further. There are only two small paragraphs on the experimental setup and results.
Response7： Thank your for pointing this out. We agree with this comment. We added more descriptions of the experimental setup and results on page 6.
Round 2
Reviewer 1 Report
Comments and Suggestions for AuthorsThis manuscript is well revised and can be published in Photonics.
Author Response
Comment ：This manuscript is well revised and can be published in Photonics.
Response：Thank you！
Reviewer 2 Report
Comments and Suggestions for AuthorsDear Authors,
You chose to overlook my previous comment 4, which I believe is critical to the manuscript's impact. I cannot alter my recommendation until this is fully addressed.
Best regards.
Comments on the Quality of English LanguagePlease see above.
Author Response
Comment1:You chose to overlook my previous comment 4, which I believe is critical to the manuscript's impact. I cannot alter my recommendation until this is fully addressed.
Response1: Thank you. We agree that your previous comment 4 is critical and constructive. We further analyzed the phase-induced intensity noise through simulation and found that when the linewidth parameter of the laser is increased, there will be significant intensity noise in the output of the photodiode. However, in order to achieve frequency to time mapping, we used a bandpass filter after the photodiode. Therefore, most of the noise is eliminated by the filter, the results indicate that the output waveform is almost unaffected by the phase-induced intensity noise. The results and disscusssions have been added to the revised manuscript. We appreciate that you pointing this out, otherwise we won't be able to cognize this.
Round 3
Reviewer 2 Report
Comments and Suggestions for AuthorsThank you for the mods.
Comments on the Quality of English LanguageSee above.
Author Response
Comment1:Thank you for the mods.
Response1:Thank you. We have checked and corrected grammar and spelling.
