[Refractive Index Insensitive Temperature Sensor Based on Cascading Single Mode Fiber with Few Mode Fiber]

Area of Science:

• Optoelectronics
• Fiber Optics
• Interferometry

Context:

• Developing accurate and selective sensors is crucial for industrial and scientific applications.
• Traditional fiber optic sensors often suffer from cross-sensitivity issues, particularly between temperature and refractive index.
• Few-mode fibers (FMF) offer unique modal properties for advanced sensing applications.

Purpose:

• To propose and demonstrate a refractive index insensitive temperature sensor based on cascading single-mode fiber (SMF) with few-mode fiber (FMF).
• To investigate the sensor's performance in terms of temperature and refractive index sensitivity.
• To highlight the advantages of the FMF-based sensor over traditional fiber optic sensors.

Summary:

• A Mach-Zehnder interferometer is formed by splicing FMF between two SMFs, enabling mode excitation and interference.
• The sensor exhibits a temperature sensitivity of -85.9 pm·℃⁻¹ within a 27.6–93.8 °C range with good linearity.
• The sensor demonstrates refractive index insensitivity, with a sensitivity of 3.69734 nm·RIU⁻¹ in the 1.3471–1.4439 range, and avoids cross-sensitivity.

Impact:

• The proposed FMF sensor offers a simple structure, easy fabrication, and high sensitivity for temperature detection.
• Its ability to avoid cross-sensitivity makes it ideal for applications in power systems, biomedicine, and aerospace.
• This technology advances the development of robust and selective optical fiber sensing systems.