Research and Improvement in Magnetic Field Sensors Using Mach–Zehnder Interferometer with Cobalt Ferrite Nanoparticles
, Matheus Rodrigues Araújo 1, Luana Samara Paulino Maia 1, Lidia Quirino Rodrigues 1, Ianna Karollayne Alencar da Silva 2, João Isaac Silva Miranda 2, José Marcos Sasaki 3, Marcus Aurélio Ribeiro Miranda 4, Joacir Soares de Andrade 2, Yosdan Martinez Camejo 2 and Glendo de Freitas Guimarães 2,*
Round 1
Reviewer 1 Report
Comments and Suggestions for AuthorsThis paper presents a magnetic field sensor based on an optical fiber MZI sensor and Cobalt ferrite nanoparticles. The cobalt ferrite nanoparticles treated at different temperatures were coated with one arm of MZI. The sensitivity can reach 1.12 dB/Oe. This research work was well organized. I suggest accepting it with some improvements. There are some questions and suggestions as follows.
1. There is no information about magnetic field sensors in the title, which may mislead the author or decrease the reputation of this research work. Suggest adding “magnetic/current sensors” into the title.
2. Why did the authors choose CoFe2O4 as the magneto-striction material? The magnetostriction coefficient of this material is not very outstanding, compared to TbDyFe and so on.
3. Please add the information and image for the coating process and results of the processed MZI arm. For example, please add the image of the coated arm to make the sensing structure more visual.
4. How does the thermal treatment temperature induce different influences on the nanoparticle, as well as on the sensitivity of the sensors? The temperature can fabricate different nanoparticle sizes and crystal structure? Or the temperature should be below the Curie temperature?
5. Did the process arm with magnetostrictive nanoparticles need to re-magnetize
6. Please give more information about the unit 7, the electronic board. Why did the signal need to be processed by this unit? The design or the Brand and series of the unit?
7. Please compare the sensitivity of the sensor to the existing optical fiber magnetic field sensor. And present the innovation and advancement of this work.
8. There are some errors (words, units, etc). Please check and modify the manuscript carefully.
Comments on the Quality of English LanguageThere are some typos and errors. Please check carefully.
Author Response
Comment # 1: There is no information about magnetic field sensors in the title, which may mislead the author or decrease the reputation of this research work. Suggest adding “magnetic/current sensors” into the title.
Author response: Thank you for this comment.
Author action: The adaptation and the enhancement of the title change were added, including magnetic field sensors.
Comment # 2: Why did the authors choose CoFe2O4 as the magneto-striction material? The magnetostriction coefficient of this material is not very outstanding, compared to TbDyFe and so on.
Author response: Thank you for your question.
Author action: The choice of cobalt ferrite (CoFe2O4) as a magnetostrictive material is due to its specific properties that make it suitable for various applications. Compared to other ferrites, such as nickel, cobalt ferrite has superior magnetic characteristics. Although its magnetostriction coefficient is not as exceptional as that of materials such as TbDyFe, CoFe2O4 is recognized for its good chemical stability, mechanical hardness and moderate magnetostriction properties. These qualities make it a practical choice in sensor applications where stability, durability and moderate sensitivity to magnetic fields are essential. Furthermore, CoFe2O4 may be more economical and easier to manipulate in certain experimental setups compared to rare earth materials such as TbDyFe.
Comment # 3: Please add the information and image for the coating process and results of the processed MZI arm. For example, please add the image of the coated arm to make the sensing structure more visual.
Author response: Thank you for this suggestion.
Author action: The image has been added and modified in Figure 1 to show in more detail how the sensor arm looks when coated with the nanoparticle.
Comment # 4: How does the thermal treatment temperature induce different influences on the nanoparticle, as well as on the sensitivity of the sensors? The temperature can fabricate different nanoparticle sizes and crystal structure? Or the temperature should be below the Curie temperature?
Author response: Thank you for this comment.
Author action: Similar applications suggest that temperature variations often also alter the sensor's sensitivity. As the temperature increases, the size of the crystallites tends to grow due to thermal expansion. This change in crystallite size can affect the electrical and magnetic properties of the material, which in turn alters the sensor's sensitivity. For example, in magnetic sensors, changes in crystallite size can modify the behavior of magnetic domains, impacting the sensor's ability to detect magnetic fields.
Comment # 5: Did the process arm with magnetostrictive nanoparticles need to re-magnetize.
Author response: Thank you for your question.
Author action: No, because nanoparticles magnetize and demagnetize when they are exposed to a magnetic field.
Comment # 6: Please give more information about the unit 7, the electronic board. Why did the signal need to be processed by this unit? The design or the Brand and series of the unit?
Author response: Thank you for your question.
Author action: The electronic circuit shown in item 7 was developed and assembled by the authors themselves and was used exclusively for reading and amplifying the voltage values converted by the photodiode, which were displayed on the oscilloscope. Additionally, the circuit includes a fourth-order active Butterworth band-pass filter, with a passband between 110 and 130 Hz and a gain of 20 for frequencies within this range.
Comment # 7: Please compare the sensitivity of the sensor to the existing optical fiber magnetic field sensor. And present the innovation and advancement of this work.
Author response: Thank you for your question.
Author action: Added suggestions and made comparisons with other articles.
Comment # 8: There are some errors (words, units, etc). Please check and modify the manuscript carefully
Author response: Thank you for your question.
Author action: Made the suggested modification
Author Response File: 
Author Response.pdf
Reviewer 2 Report
Comments and Suggestions for AuthorsDetailed comments are attached.
Comments for author File: Comments.pdf
Author Response
Comment #1 : The first-person "we" is used several times in the abstract, which may be subjective and biased, and is not recommended to be used frequently.
Author response: Thank you for this comment.
Author action: Made the suggested modification.
Comment #2 : The experimental setup is described in detail in the paper, but the principle of the MZI sensor is not clear.
Author response: Thank you for your question.
Author action: Information was added explaining the principle in the methodology.
Comment #3 : The titles of the horizontal and vertical coordinates in Figure 5 are too large and not aesthetically pleasing
Author response: Thank you very much for your observation
Author action: Change made to the figure.
Comment #4: The S of sample if T500 is less than T350 and T800, it should be explain clearly.
Author response: Thank you for this comment.
Author action: The sensor sensitivity at T500 was lower compared to temperatures T350 and T800 due to Mössbauer characterization indicating an ongoing transition from the superparamagnetic to the ferrimagnetic regime in this sample. This suggests that the magnetic moments are disordered, making it difficult to orient them in the presence of an external field. Additionally, VSM measurements showed a disproportionate increase at T500 compared to T350, indicating greater difficulty in orienting these moments. These findings impact the sensor's response, which exhibited reduced sensitivity at T500 compared to temperatures of T350 and T800.
Comment #5: What are the advantages of the sensor compared with other magnetic field sensors? A comparison table should be given.
Author response: Thank you for this comment.
Author action: The advantages of the optical magnetic field sensor are: easy implementation, without electromagnetic interference, application in environments of difficult access and configurations according to the application of interest. These advantages are mentioned in the introduction of the paper.
Author Response File: Author Response.pdf
Reviewer 3 Report
Comments and Suggestions for AuthorsThe paper experimentally demonstrates a current and magnetic field sensor utilizing a fiber Mach-Zehnder interferometer with one of its arms coated with magnetic nanoparticles.
While the paper describes the synthesis and characterization of the nanoparticles in details, it merely describes the utilized interferometer configuration and fails to describe its sensing operation in a suitable level of detail. Some concerns are as follows:
How was the interferometer biased? No phase modulation/demodulation appears to be applied in the used interferometer setup.
What optical phase difference existed initially between the two arms and how it was controlled?
Did the interferometer operate at a zero phase, minimum sensitivity, operating point, or at some arbitrary phase bias which would be sensitive to changes in ambient conditions? How then were the lengths of the two interferometer arms controlled to within a fraction of wavelength?
Was any polarization control applied to mitigate cross polarization deterioration of the interference signal?
These interferometric effects could well cause random run to run variations in the interferometer output as those shown in figures 5 and 6.
What exactly is the output power given in figures 5 and 6? Is it the amplitude of the interferometer output signal captured by the photodiode or variations of the signal at the current frequency after some filtering applied by the processing electronics?
Author Response
Comment #1: How was the interferometer biased? No phase modulation/demodulation appears to be applied in the used interferometer setup.
Author response: Thank you for your question.
Author action: When a magnetic field is applied, the CoFeâ‚‚Oâ‚„ nanoparticles vibrate and transmit this vibration to the optical fiber, causing a variation in the optical path length of the light and resulting in phase modulation. In the interferometer, without the magnetic field, there is no phase difference between the reference arm and the sensing arm. However, when the magnetic field is applied, the vibration of the nanoparticles alters the optical path. At the output of the interferometer, this alteration is recorded as an oscillating sinusoidal signal. We use the Fourier transform directly on the oscilloscope to analyze this signal, identifying a peak at 120 Hz, whose intensity allows us to quantify the phase modulation induced by the magnetic field.
Comment #2: What optical phase difference existed initially between the two arms and how it was controlled?
Author response: Thank you for this comment.
Author action: Theoretically, there should be no initial optical phase difference between the two arms. However, in experimental work, it is very difficult to ensure a zero phase difference between them. There will always be a small difference in the arms due to imperfections in the components. Nevertheless, this phase difference does not interfere with the analysis of the results. High-quality components were used, such as precision couplers and optical fibers with rigorously measured lengths, to ensure that both arms had the same length. Therefore, the small residual phase difference is not relevant to the analysis of the results.
Comment #3: Did the interferometer operate at a zero phase, minimum sensitivity, operating point, or at some arbitrary phase bias which would be sensitive to changes in ambient conditions? How then were the lengths of the two interferometer arms controlled to within a fraction of wavelength?
Author response: Thank you for this suggestion.
Author action: The lengths of the beam splitter arms are equal, thus eliminating concerns about phase differences. The effect resulting from the application of the magnetic field is observed as an angular displacement caused by the Faraday effect. This phase difference occurs when the sensing element interacts with the magnetic field, causing the fiber to vibrate in one of the arms of the IMZ sensor.
Comment #4: Was any polarization control applied to mitigate cross polarization deterioration of the interference signal?
Author response: Thank you for this comment.
Author action: No specific polarization control was applied to mitigate cross-polarization deterioration of the interference signal. During the analysis, we used only references without the insertion of additional polarizers. The lasers used emitted polarized light, and the signals from the reference fiber and sensor fiber were compared taking into account this initial polarization. Additionally, effects from polarization variation and arm length imbalance are not relevant in the experiment due to the short lengths of the interferometer arms. This approach ensured accurate evaluation of interferometric data, minimizing significant variations.
Comment #5: These interferometric effects could well cause random run to run variations in the interferometer output as those shown in figures 5 and 6.
Author response: Thank you for this comment.
Author action: Certainly, interferometric effects can cause random fluctuations, even with rigorous control, repeated testing, and ensuring reproducibility. I appreciate the exploration of this topic, as it will surely enrich future work.
Comment #6: What exactly is the output power given in figures 5 and 6? Is it the amplitude of the interferometer output signal captured by the photodiode or variations of the signal at the current frequency after some filtering applied by the processing electronics?
Author response: Thank you for this comment.
Author action: The variation in output power was measured in samples T350, T500, and T800, with the following values: 23.15 dBm, 21.06 dBm, and 28.47 dBm, respectively. These values were obtained when the sensors were subjected to an applied field of 251 Oe, 282 Oe, and 254 Oe. Under the same conditions, the sensors achieved output power levels of 18.30 dBm, 17.97 dBm, and 17.51 dBm. The signal is detected by the photodiode, which converts the received light into an electrical signal. This electrical signal is then processed by an electronic board with a specific circuit designed to amplify and filter the signal. Finally, the processed signal is analyzed on an oscilloscope.
Author Response File: Author Response.pdf
Round 2
Reviewer 3 Report
Comments and Suggestions for AuthorsSome of the author response points were not included in the revised manuscript:
The interferometer was not intentionally biased.
Theoretically, there should be no initial optical phase difference between the two arms. However, in experimental work, it is very difficult to ensure a zero-phase difference between them. There will always be a small difference in the arms due to imperfections in the components. Nevertheless, this phase difference does not interfere with the analysis of the results.
No specific polarization control was applied to mitigate cross-polarization deterioration of the interference signal. Effects from polarization variation and arm length imbalance are not relevant in the experiment due to the short lengths of the interferometer arms.
Still not mentioned how and at what stage the output power given in figures 5 and 6is calculated from the electrical signal.
These elaborations could improve the benefit of the paper.
Author Response
Comment #1: Some points from the author's response were not included in the revised
manuscript.
Author response: Thank you for this comment
Author action: I am immensely grateful for your observations to improve the article.
Based on your suggestions, the text has been updated with important revisions,
including clarification that the interferometer was not intentionally biased, a
demonstration of the sensor setup along with its explanations, and detailed information
on polarization controls.
Comment #2: Still not mentioned how and at what stage the output power given in
figures 5 and 6 is calculated from the electrical signal.
Author response: Thank you for this comment.
Author action: The power presented in the article does not refer to optical power, but
rather to the electrical signal power corresponding to the oscillation frequency of 120
Hz. The oscilloscope used has the function of performing a Fast Fourier Transform
(FFT), which converts the signal from the time domain to the frequency domain. Thus,
the power value in dBm that we measure indicates the signal intensity in terms of
frequency.
Author Response File: Author Response.pdf
