Temperature-insensitive fiber twist sensor based on elliptical-core few-mode fiber

Area of Science:

• Optoelectronics
• Fiber Optics Sensing
• Metrology

Background:

• Fiber optic sensors offer remote and precise measurement capabilities.
• Few-mode fibers enable complex mode manipulation for advanced sensing applications.
• Accurate twist sensing is crucial for structural health monitoring and robotics.

Purpose of the Study:

• To propose and demonstrate a highly sensitive fiber optics twist sensor.
• To utilize elliptical-core few-mode fiber (e-FMF) for twist angle detection.
• To achieve simultaneous twist direction identification and temperature/length insensitivity.

Main Methods:

• Employing an elliptical-core few-mode fiber (e-FMF) as the sensing element.
• Utilizing a fixed-phase plate for mode conversion (LP11 to LP01).
• Monitoring optical power variation at the standard single-mode fiber (SSMF) output to detect twist-induced spatial rotation of the LP11 mode profile.

Main Results:

• A twist sensor with sensitivity exceeding 20 μW/° for angles up to ±39° was demonstrated.
• High sensitivity (>100 μW/°) was achieved for twist angles between -12.5° and 20.1°.
• Simultaneous twist direction identification and temperature-insensitive operation (20°C to 150°C) were verified.

Conclusions:

• The proposed e-FMF based sensor provides a highly sensitive and accurate method for twist measurement.
• The sensor exhibits robust performance, being insensitive to temperature and fiber length variations.
• This technology holds potential for advanced applications requiring precise twist detection.