# A Mini-Two-Path Mach–Zehnder Interferometer Sensor with High Curvature Sensitivity Based on Four-Mode Fiber

## TL;DR

A new fiber sensor design using a mini-two-path Mach–Zehnder interferometer achieves high curvature sensitivity and low temperature sensitivity, making it useful for precise sensing applications.

## Contribution

The paper introduces a novel MTP-MZI sensor with high curvature sensitivity using four-mode fiber and arc discharge technology.

## Key findings

- The sensor achieves a maximum curvature sensitivity of 168.41 dB/m−1, the highest reported for intensity-modulated MZI fiber sensors.
- Temperature sensitivity is only 78 pm/°C, enabling effective cross-sensitivity mitigation between curvature and temperature.
- The mini-two-path structure combined with specialty fibers shows potential for high-sensitivity sensor development.

## Abstract

We have proposed and presented a hybrid mini-two-path Mach–Zehnder interferometer (MTP-MZI) sensor based on four-mode fiber (FMF), where the reference path comprises of a section of a single-mode fiber (SMF), and the sensing path adopts a structure of SMF-FMF-SMF (SFS). Using arc discharge technology, the two paths are effectively fused and coupled, resulting in a robust MTP-MZI structure sensor. In the curvature detection, the maximum intensity sensitivity of curvature reaches 168.41 dB/m−1 when the curvature ranges change from 0 m−1 to 0.091 m−1. To the best of our knowledge, it is the highest curvature sensitivity in the MZI fiber sensor with intensity modulation. Furthermore, we also conducted a temperature-sensing experiment. The experiment results show that the maximum temperature sensitivity is only 78 pm/°C with a temperature range of 30–65 °C. The diverse exhibition of sensing performance for curvature and temperature enables us to effectively mitigate cross-sensitivity challenges. These results provide the experimental basis for developing a high-sensitivity sensor by employing the mini-two-path structure combined with specialty fibers.