Temperature-compensated fiber directional-bend sensor based on a sandwiched MMF-PMPCF structure.

Area of Science:

• Photonics
• Optical Sensing
• Fiber Optics

Background:

• Mach-Zehnder interferometers are sensitive to external perturbations.
• Optical fiber sensors offer advantages in harsh environments.
• Directional bend sensing is crucial for structural health monitoring.

Purpose of the Study:

• To propose and demonstrate an optical fiber directional-bend sensor.
• To investigate the sensor's response to bending curvature and direction.
• To evaluate the sensor's performance regarding sensitivity and temperature cross-talk.

Main Methods:

• Fabrication of an inline Mach-Zehnder interferometer using multimode fiber (MMF) and polarization-maintaining photonic crystal fiber (PMPCF).
• Coupling of high-order modes from MMF to PMPCF for interference.
• Experimental analysis of spectral changes under varying bend curvature and direction.

Main Results:

• A well-defined interference fringe envelope was observed in the transmitted spectrum.
• Bend curvature significantly altered the intensity and fringe visibility.
• Maximum bend sensitivity reached -8.33 dB/m⁻¹ for a specific bending direction.
• The sensor exhibited low cross-talk with environmental temperature variations.

Conclusions:

• The proposed inline Mach-Zehnder interferometer functions as an effective directional-bend sensor.
• The sensor's sensitivity is dependent on bending direction, enabling directional detection.
• The device shows promise for applications requiring precise bend monitoring with temperature stability.