# Affordable Highly Sensitive Fiber Optical Sensor Based on Coupled Fibers with Harmonically Varying Refractive Index

## Abstract

**:**

## 1. Introduction

## 2. The Model under Study

**r**) can be written as a superposition of the left (“1”) and the right (“2”) cores, i.e.,

## 3. Exactly Solvable Case (I): Linear Profile

## 4. Generic Formula for Weak Transmission Coefficient

## 5. Analytically Solvable Approximations

#### 5.1. Case II: Parabolic Profile

#### 5.2. Case III: Harmonic Profile

## 6. Summary

## Funding

## Data Availability Statement

## Conflicts of Interest

## References

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**Figure 1.**The optical fiber sensor consists of a couple of fibers with integrated MZ interferometers. (

**a**) A single interferometer, (

**b**) multiple interferometers.

**Figure 2.**Two adjacent fiber cores, where evanescent waves (symbolized by the red arrows) cause crosstalk between them.

**Figure 3.**Transmission coefficient as a function of $\Delta n$. The solid (red) curve represents the exact numerical solution, while the dashed (black) curve represents the analytical approximation. The simulation was taken for the parameters $n=1.5$, $kZ=200$, and $g={10}^{-4}$.

**Figure 4.**Transmission coefficient as a function of $kZ$. The solid (red) curve represents the exact numerical solution, while the dashed (black) curve represents the analytical approximation. The simulation was taken for the parameters $n=1.5$, $\Delta n=0.1$, and $g={10}^{-4}$.

**Figure 6.**The transmission coefficient as a function of the period $\mathsf{\Lambda}/\lambda $ for $N=10$ periods. The solid (red) curve represents the exact numerical solution, while the dashed (black) curve represents the analytical approximation (26). The simulation was taken for the parameters $n=1.5$, $\Delta n=0.1$, and $g={10}^{-6}$.

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**MDPI and ACS Style**

Granot, E.
Affordable Highly Sensitive Fiber Optical Sensor Based on Coupled Fibers with Harmonically Varying Refractive Index. *Photonics* **2024**, *11*, 725.
https://doi.org/10.3390/photonics11080725

**AMA Style**

Granot E.
Affordable Highly Sensitive Fiber Optical Sensor Based on Coupled Fibers with Harmonically Varying Refractive Index. *Photonics*. 2024; 11(8):725.
https://doi.org/10.3390/photonics11080725

**Chicago/Turabian Style**

Granot, Er’el.
2024. "Affordable Highly Sensitive Fiber Optical Sensor Based on Coupled Fibers with Harmonically Varying Refractive Index" *Photonics* 11, no. 8: 725.
https://doi.org/10.3390/photonics11080725