Intermodal Fiber Interferometer with Spectral Interrogation and Fourier Analysis of Output Signals for Sensor Application

Round 1

Reviewer 1 Report

This article discusses the utilization of intermodal fiber interferometry for measuring external perturbation. Through Fourier analysis and the SMS structure (long grin MMF), the method proposed in this study can acquire a linear response of spectral transfer change to the fiber perturbation. I have a couple of questions that need further clarification from the authors, leading me to recommend a major revision.

1. Given the 40-m MMF length, the 500-MHz laser linewidth seems to be a bit wide for the interferometry. Does the linewidth meet the requirements for coherent detection in your experiments?

2. What is the sweep rate for the 5-THz (40-nm) sweep range in Figure 2 to achieve a small enough scan duration, which is proposed as the first condition? What is the upper limit for the scan duration?

Generally good.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 2 Report

A novel method of Fourier analysis applied to extract information from the output signals of the intermodal fiber interferometer with spectral interrogation is reasearched in this paper. The mathematical model is developed step by step, theoretically correct and fit the experiments results perfectly. This model could be very valuable in fiber sensing field to extract  the information about external perturbation from the spectral transfer function of an intermodal fiber interferometer.  

Author Response

We would like to express our gratitude to the reviewer for their work and for their high appreciation of our manuscript

Reviewer 3 Report

This manuscript can be accepted after major revision.

1. Compared with other papers that discuss the Fourier analysis of IFISI signals, what is the innovation of this study?

2. In section 2.2, did the author consider the situation where the laser output intensity and/or the number of excited mode groups and their amplitudes are related to the optical frequency?

3. Does this method have any drawbacks that were considered by the authors?

4. The author should include additional references, particularly those published after 2023, to improve the study's reliability.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

All the comments and questions have been addressed.

Generally good.

Reviewer 3 Report

This manuscript is now acceptable.