Magnetic Field and Temperature Dual-Parameter Optical Fiber Sensor Based on Fe₃O₄ Magnetic Film

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

This paper proposes a dual-parameter fiber optic sensor based on Fe₃O₄ magnetic film and PDMS composite material. ​​However, the paper still needs to be improved in terms of experimental details, data integrity and rigorous expression. The specific modification suggestions are as follows:

 

1. Details of material ratio are missing: Section 2.2 mentions "5% mass fraction of Fe3O4", but it is not clear whether it accounts for the total mass of PDMS or only the mass of the base glue. Additional explanation is needed.
2. The language can be improved with a more careful check.
3. The term "Fabry-Perot interferometer" was abbreviated to "FPI" after its first appearance, but was abbreviated to "FP" many times in the following text. It is recommended to unify it as "FPI" and define it in advance in the abstract.
4. It is necessary to confirm whether Figure 3 (Microscope image of sensor structure) contains the scale and the length of each part.
5. Regarding refractive index sensing, some of the latest work needs to be mentioned, such as, Tunable ultra-sensitive four-band terahertz sensors based on Dirac semimetals; Plasmonic Sensor Based on Multi Fano Resonance in Inverse T Shape Structure for Detection of CO2 Concentration.
6. The immersion process in Section 2.2 mentions "immersion at a speed of 50 μm/s", but does not specify the ambient temperature and humidity control conditions. It is recommended to add this.
7. The introduction does not clearly compare the performance differences between existing magnetostrictive materials (such as Terfenol-D) and Fe₃O₄.

Author Response

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Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

A dual-parameter optical fiber sensor for measuring magnetic field and temperature based on Fabry-Perot interferometer and magnetic polymer film is proposed in this manuscript. The sensor is fabricated by immerging the flat-end of a SMF into a Fe₃O₄-PDMS solution and a PDMS solution successively to create a doubled-layer FP cavity. The Fe₃O₄-PDMS film on the endface of the SMF enables the sensor magnetic field sensitivity. It has a magnetic field sensitivity of 68.66 pm/mT and a temperature sensitivity of 389.51 pm/^oC. I would like to suggest the authors to improve their manuscript by considering the following comments and questions.

1. In terms of theoretical analysis, although section 2 mentioned the effect of magnetic field on refractive index and cavity length of the proposed sensor, there may be a lack of mathematical model derivation, which cannot quantitatively explain the mechanism of the sensor’s magnetic field sensitivity.
2. Is the sensor sensitive to the direction of the magnetic field? It is suggested conducting response experiments on multi-directional magnetic fields (such as both longitudinal and transverse direction) to verify the effects of anisotropy.
3. What is the relationship between sensor sensitivity and its structural parameters? Is a thicker PDMS-Fe₃O₄ layer or the percentage of Fe₃O₄ in the PDMS-Fe₃O₄ solution beneficial for improving magnetic field sensitivity?
4. In the comparative analysis section, although it is mentioned that the sensing range of the proposed sensor is higher than those in references, the magnetic field sensitivity is comparatively low compared to its counterparts. Especially, compared with the SMS-based sensor proposed in reference [24], the sensor in this manuscript has much lower magnetic field sensitivity and much higher temperature sensitivity. The SMS-based sensor is also a simple and cost effective sensor and it has the potential to enlarge its measurement range. What’s the advantage of the proposed sensor compared to its counterparts, especially the SMS-based sensor?
5. What’s the repeatability of the sensor? It is suggested to include repeatability test results in the manuscript.
6. What’s the stability of the sensor? While it is mentioned in the conclusion section that the sensor has excellent stability, the stability data of the sensor are not shown in the manuscript. It is suggested to include stability test results in the manuscript.

Author Response

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Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

Review Photonics -3646363

The article describes the preparation and performance of a dual-parameter optical fiber sensor for measuring magnetic field strength and temperature simultaneously. The obtained sensitivities are compared to values of existing dual-parameter sensors..

The introduction gives an arbitrary overview on existing literature, naming a few challenges encountered so far, i.e. sensitivity, complexity of preparation, repeatability. The paper follows a logical setup.

The following questions should be addressed:

What is the expected temperature sensitivity of the PDMS film?

What is the repeatability of measurements (using the same fiber), what of preparation (doing several fibers)?

Why are the detection ranges chosen (temp: RT to 70 °C)?

The following changes need to be made:

Please check subscripts in the paper, they are missing completely.

State differences in temperature as unit/K instead unit/°C.

Section 1 – Introduction

The reference numbering in the text starts with 8. Please renumber all references acc. Their order of appearance.

Please insert relevant references, i.e.

• DOI 10.1016/j.yofte.2021.102634 (review)
• 1080/09500340.2025.2478643
• 1364/OE.542976
• 1016/j.yofte.2023.103384
• 3390/ma8105361

Furthermore, I suggest summarizing the dual-parameter fiber sensing types along with their achieved sensitivities, detection ranges, and refs. into a table – and include there the data presented in table 1 which is now at the very end of the paper.

Lines 60-64 should be part of experimental section. Here, a general statement on working principle would be sufficient.

Section 2 – Sensor fabrication and principle

Check subscripts – missing in lines 75, 83...

Line 126: From which data did you get the 47+/-2 µm? How did you get this result?

Section 3 – Experimental results and discussion

Lines 173: The number of significant digits should be reasonable, i.e. 390 pm/K instead of 389.51 pm/°C (especially taking into account the cross-sensitivity of 6 mT/K).

Lines 183-191 should be part of introduction section.

Please insert a critical discussion on results.

Why does the line in Fig. 7b) not follow a linear relationship? It is plotted, however there is the appearance of deviation. Why? What is the dependence of viscosity/density as a function of temperature and nanoparticle content?

Section 4 – Conclusions

Check number of significant digits of results. Also, line 199 – the correct the R2 acc. Your results.

Section References

Arrange acc. Order of appearance in text. Delete [J].

Comments on the Quality of English Language

see comments and suggestions

Author Response

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Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

Comments and Suggestions for Authors

The authors have adequately addressed my previous concerns. The revisions demonstrate the authors's commitment to improving the scholarly rigor of this work. I find no remaining technical or presentation issues and therefore recommend accepting the manuscript for publication in Photonics in its current form.