Ultra-High Voltage NV Center Magnetic Sensing System Based on Power over Fiber

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The authors designed a NV center magnetic sensing system based on power of fiber technology by adopting the high-voltage and low-voltage isolation architecture, and demonstrated good conversion efficiency, output electrical power and sensitivity. The system is promising for high power LPCs, IoTs and other types of power sensing applications. The manuscript is logically organized, methods and experimental results are well presented. 

Minor comment:
(1) The authors should present comparative data on the system's key performance parameters against existing reported ones to strenghen its persuasiveness and highlight its advantages.

Author Response

Comments 1: The authors should present comparative data on the system's key performance parameters against existing reported ones to strenghen its persuasiveness and highlight its advantages.

Response 1: We fully agree that a comparison with existing technologies can better highlight the advantages of our work. Accordingly, we have added a new Section 4.3, "Performance Comparison and Analysis," in the revised manuscript. This section provides a systematic comparison of the key performance metrics (such as sensitivity and power supply method) of our system against recently reported magnetic sensing systems based on NV centers and other technologies.

 

Reviewer 2 Report

Comments and Suggestions for Authors

This manuscript reports a fiber-isolated NV-diamond magnetic sensing system for UHV device powered via power-over-fiber (PoF). The authors developed a high-efficiency, multi-junction GaAs-based laser power converter (LPC) that delivers up to 4.88 W of electrical power with an efficiency of 48.9%. Using this integrated system, the authors demonstrate a magnetic field sensitivity of 6.1~nT/Hz^{1/2} in a simulated UHV environment. In summary, the combination of NV magnetic sensor with PoF technology for UHV measurement is of great significance to Photonics readers interested in optical power transmission and quantum sensing under extreme conditions. 
Here are some of my questions and suggestions:

Table 1 shows that the total power consumption of a single HV module is 3.8 W. When integrating four NV channels, the total power consumption on the high-voltage side is approximately 15.2 W. Does this power consumption take into accountthe conversion efficiency of the LPC? They also shows that the maximum measured power consumption of the LPC is 4.88 W. They should clarify the number of LPCs used and their relationship to the total power consumption.

Can the authors provide a quantitative explanation for the decrease in sensitivity over time in Fig. 6(c),since they did a numerical fit?

The UHV equipment specification is -40°C to 70°C mentioned in introduction，but in the experiment (Fig.7), the temperature range of -30°C to 70°C is tested, these need to be unified.

In the abstract they reports the optimal sensitivity as 6.1~nT/Hz^{1/2}, whereas in Figure 6(c) the test result shows a range of 9.2 - 13.74~nT/Hz^{1/2} under simulated UHV conditions. It would be helpful to briefly clarify the difference,and It  is better to have a comparison table with previous research results.

It would be helpful to add error bars for some important data.

Author Response

Comments 1: Table 1 shows that the total power consumption of a single HV module is 3.8 W. When integrating four NV channels, the total power consumption on the high-voltage side is approximately 15.2 W. Does this power consumption take into accountthe conversion efficiency of the LPC? They also shows that the maximum measured power consumption of the LPC is 4.88 W. They should clarify the number of LPCs used and their relationship to the total power consumption.

Response 1: We thank the reviewer for pointing out this critical aspect. Indeed, the total power consumption of the four-channel system is approximately 15.2 W, which is roughly four times the estimated power consumption of a single channel (3.8 W). To meet this power requirement and ensure system reliability, we adopted a redundant backup design, employing four LPC assemblies connected in parallel for power supply. Each LPC has a maximum output of 4.88 W, providing a theoretical maximum combined output of 19.52 W. This offers sufficient margin for the 15.2 W system power consumption and ensures continued system operation even if a single LPC unit fails. This clarification has been added in a note below Table 1 in the revised manuscript (Page 3, Section 2.1, line 114).

Comments 2: Can the authors provide a quantitative explanation for the decrease in sensitivity over time in Fig. 6(c),since they did a numerical fit?

Response 2: Thank you for this keen observation. We agree with this comment. Therefore, we have provided a more in-depth discussion with quantitative and semi-quantitative physical explanations for the sensitivity degradation over time. The degradation of sensitivity  is directly related to the increase in sensor temperature. As shown in Formula (1),   ASD / k. As the sensor temperature rises due to continuous laser irradiation (we did not implement active temperature control in the experiment), the spin coherence time T₂ of NV centers will shorten. This leads to broadening of the ODMR spectrum and reduced signal-to-noise ratio. According to our data and existing literature [27], T₂ is highly temperature-sensitive, for every 10°C increase above room temperature, T₂ may decrease by approximately 20%. This degradation of coherence is the main reason for the time-dependent decrease in sensitivity. This addition can be found on Page 8, Section 3.3, line 262 of the revised manuscript.

Comments 3: The UHV equipment specification is -40°C to 70°C mentioned in introduction，but in the experiment (Fig.7), the temperature range of -30°C to 70°C is tested, these need to be unified.

Response 3: Thank you for your careful review. We agree with this comment. Therefore, we have revised the description to align with the actual test data. This change can be found on Page 2, Introduction, line 69.

Comments 4: In the abstract they reports the optimal sensitivity as 6.1~nT/Hz^{1/2}, whereas in Figure 6(c) the test result shows a range of 9.2 - 13.74~nT/Hz^{1/2} under simulated UHV conditions. It would be helpful to briefly clarify the difference,and It  is better to have a comparison table with previous research results.

Response 4: Thank you for this valuable comment. We agree that clarification is necessary. Therefore, we have clarified that the sensitivity of 6.1 nT/Hz^{1/2} reported in the abstract represents the optimal value measured under the optimized parameters described in Section 4.2 (modulation frequency of 2.8 kHz and frequency offset of 3 MHz). In contrast, the sensitivity range of 9.2-13.74 nT/Hz^{1/2} reported in Figure 6(c) reflects the system's performance during long-term stability testing under default parameters, without applying the aforementioned optimized modulation settings and while being affected by sensor temperature drift. We have added clarifications in both the Abstract (Page 1, line 27) and the main text (Page 8, Section 3.3, line 271) to prevent potential reader misunderstanding. Furthermore, following the suggestion from you and Reviewer 1, we have added a comparison table with previous research results (Page 11, Section 4.3, line 357).

Comment 5: It would be helpful to add error bars for some important data.

Response 5: 

We thank the reviewer for this suggestion to enhance the rigor of our data presentation. Regarding the suggestion to add error bars, we would like to respectfully clarify the following: The key data used to calculate the magnetic sensitivity (specifically, the Amplitude Spectral Density (ASD) of the system noise and the slope k of the ODMR demodulation curve presented in Figure 6) were already obtained by averaging over 10 consecutive acquisitions. This averaging process effectively suppresses random noise and fluctuations, resulting in a highly stable and representative mean value for each data point. This assures the reader of the statistical reliability of the presented data without relying on error bars for these specific plots. To fully address the reviewer's concern and to demonstrate the reproducibility of our measurements, This clarification can be found on Page 8, Section 3.3, line 260.

Reviewer 3 Report

Comments and Suggestions for Authors

The manuscript presents a timely and relevant study on the design and implementation of a Nitrogen-Vacancy center magnetic sensing system powered by a custom Power-over-Fiber link for ultra-high voltage applications. However, the manuscript requires substantial revision to address several critical points regarding experimental detail, claims of novelty, and the analysis of system performance before it can be considered for publication. Below are my primary concerns and suggestions for improvement:

1.The term "simulated UHV environment" is insufficiently defined; specific experimental conditions, such as electric field strength and insulation arrangement, must be detailed.

2.The authors should more precisely articulate the specific novelty of their system in the introduction, comparing it directly with prior PoF-powered sensing solutions.

3.The manuscript lacks characterization of the LPC's output electrical noise and stability after DC-DC conversion, which is critical for a high-sensitivity quantum sensor.

4.The observed degradation in sensitivity over time requires a more thorough discussion, linking it quantitatively to the thermal characteristics of the sensor and the LPC.

5.The system power budget is unclear; the relationship between the single-channel analysis (Table 1) and the four-channel system's power consumption must be clarified.

6.The phrase "optimal magnetic measurement sensitivity" in the abstract is potentially misleading given the performance degradation shown in Figure 6(c) and should be rephrased.

7.The connection between the LPC's temperature-dependent performance (Section 4.1) and the overall system's stability and noise floor should be explicitly established in the discussion.

8.Figure 5(d) is overly simplistic; a more detailed block diagram showing power distribution and signal flow for the multi-channel system would enhance clarity.

9.Several references are cited with a future publication year of 2025; these must be updated to reflect their current, correct publication status.

Author Response

Comments 1: The term "simulated UHV environment" is insufficiently defined; specific experimental conditions, such as electric field strength and insulation arrangement, must be detailed.

Response 1: Thank you for this comment. We agree that the definition was insufficiently clear. Therefore, we have supplemented the description with the specific conditions of the simulated experiment. This addition can be found on Page 6, Section 3.2, line 205.

Comments 2: The authors should more precisely articulate the specific novelty of their system in the introduction, comparing it directly with prior PoF-powered sensing solutions.

Response 2: Thank you for this suggestion. We agree with this comment. Therefore, we have strengthened the articulation of novelty in the Introduction by comparing it directly with prior PoF-driven sensing solutions. This enhancement can be found on Page 2, Introduction, line 75. Additionally, following the suggestions from both Reviewers 1 and 2, we have included a comprehensive comparison table with previous research results, located on Page 11, Section 4.3, line 357.

Comments 3: The manuscript lacks characterization of the LPC's output electrical noise and stability after DC-DC conversion, which is critical for a high-sensitivity quantum sensor.

Response 3: Thank you for raising this important point. We agree with this comment. We acknowledge the lack of direct measurement on this aspect in the original manuscript. Due to experimental constraints, we were unable to directly characterize the noise spectral density after the DC-DC conversion. However, the achieved magnetic field sensitivity of the system (6.1 nT/Hz^{1/2}) serves as a comprehensive indicator of the robustness against power supply noise. This level of sensitivity indirectly demonstrates that the output noise level of our optimally designed LPC and power management circuit is sufficiently low to support high-sensitivity NV sensing. Future work will include the direct characterization and further suppression of power supply noise.

Comments 4 & Comments 7: The observed degradation in sensitivity over time requires a more thorough discussion, linking it quantitatively to the thermal characteristics of the sensor and the LPC.

Response 4 & Response 7: Thank you for this comment. We agree with this comment. Therefore, we have added quantitative and semi-quantitative physical explanations. While the efficiency of the LPC assembly itself decreases at high temperatures, leading to reduced output power, we have clarified that the temperature-induced performance drop of the LPC was not the primary cause of the system's sensitivity degradation in this experiment. This clarification can be found on Page 8, Section 3.3, line 262.

Comments 5: The system power budget is unclear; the relationship between the single-channel analysis (Table 1) and the four-channel system's power consumption must be clarified.

Response 5: Thank you for pointing this out. We agree with this comment. Therefore, we have clarified that the total power consumption of the four-channel system is 15.2 W, which is approximately four times the power consumption of a single channel (3.8 W). To meet this power requirement and ensure system reliability, we adopted a redundant backup design using four LPC assemblies in parallel. Each LPC has a maximum output of 4.88 W, providing a theoretical maximum combined output of 19.52 W. This offers sufficient margin for the 15.2 W system and ensures continued operation even if a single LPC fails. This clarification has been added in a note below Table 1 in the revised manuscript (Page 3, Section 2.1, line 114).

Comments 6: The phrase "optimal magnetic measurement sensitivity" in the abstract is potentially misleading given the performance degradation shown in Figure 6(c) and should be rephrased.

Response 6: Thank you for this valuable comment. We agree that clarification is necessary. Therefore, we have clarified that the sensitivity of 6.1 nT/Hz^{1/2} reported in the abstract represents the optimal value measured under the optimized parameters described in Section 4.2 (modulation frequency of 2.8 kHz and frequency deviation of 3 MHz). In contrast, the sensitivity range of 9.2-13.74 nT/Hz^{1/2} reported in Figure 6(c) reflects the system's performance during long-term stability testing under default parameters, without applying the aforementioned optimized modulation settings and while being affected by sensor temperature drift. We have added clarifications in both the Abstract (Page 1, line 27) and the main text (Page 8, Section 3.3, line 271) to prevent potential reader misunderstanding. 

Comments 8: Figure 5(d) is overly simplistic; a more detailed block diagram showing power distribution and signal flow for the multi-channel system would enhance clarity.

Response 8: Thank you for this suggestion. We agree with this comment. Therefore, we have redrawn Figure 5(d) to provide a more detailed system block diagram. The revised figure now clearly shows the signal flow directions for the four NV sensor channels. This updated figure can be found on Page 7, Section 3.2, line 229. The description of power distribution has been clarified in our response to Comment 5.

Comments 9: Several references are cited with a future publication year of 2025; these must be updated to reflect their current, correct publication status.

Response 9: We sincerely apologize for this oversight. We agree that this was an error that should not have occurred. Therefore, we have carefully checked and updated all references to their correct published or "Online Published" status (including year, volume, issue, page numbers, or DOI). These corrections can be found in the References section on Page 14, specifically at lines 450, 469, and 483.

Round 2

Reviewer 2 Report

Comments and Suggestions for Authors

I think the revised manuscript meets Phtonics' publication criteria, therefore I recommend its publication in Photonics.

Reviewer 3 Report

Comments and Suggestions for Authors

I have read the all the reviewer's comments and response their response by the authors. I have no further comments.