Twist sensor based on axial strain insensitive distributed Bragg reflector fiber laser

Area of Science:

• Photonics and Optical Sensing
• Fiber Optic Sensors
• Laser Technology

Background:

• Fiber optic sensors are crucial for measuring physical parameters.
• Distributed Bragg reflector (DBR) fiber grating lasers offer unique properties for sensing applications.
• Polarization-dependent effects in fiber lasers can be exploited for novel sensing mechanisms.

Purpose of the Study:

• To propose and experimentally demonstrate a novel fiber-optic twist sensor.
• To investigate the relationship between twist angle and beat frequency variation.
• To evaluate the sensor's sensitivity and robustness against environmental factors.

Main Methods:

• Utilizing a dual-polarization DBR fiber grating laser operating at 1543.154 nm.
• Analyzing the beat frequency signal generated by the interference of two polarization modes.
• Correlating changes in beat frequency with applied twist angles and lengths.

Main Results:

• Observed a beat frequency signal of 30.78 MHz.
• Demonstrated that twist alters fiber birefringence, causing beat frequency variations.
• Achieved a high twist sensitivity of 6.68 MHz/rad at a twist length of 17.5 cm.
• Showcased insensitivity to temperature and axial strain.

Conclusions:

• The developed fiber-optic twist sensor exhibits high sensitivity and accuracy.
• The sensor's performance is dependent on the twist length of the laser cavity.
• The inherent immunity to temperature and strain simplifies practical implementation, eliminating compensation requirements.