Strain-insensitive temperature sensing with a dual polarization fiber grating laser

Area of Science:

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

Background:

• Accurate temperature sensing is crucial in various engineering fields.
• Existing sensors can be affected by environmental factors like strain.
• Fiber optic sensors offer potential for robust and precise measurements.

Purpose of the Study:

• To demonstrate a strain-insensitive temperature sensor.
• To investigate the performance of a dual polarization fiber grating laser for temperature sensing.
• To analyze the mechanisms behind strain insensitivity and temperature response.

Main Methods:

• Fabrication of a dual polarization fiber grating laser using two Bragg gratings in an Er-doped fiber.
• Generation of a radio frequency (RF) beat signal from the laser's polarization modes.
• Monitoring the beat frequency shift for temperature measurement.
• Theoretical analysis of thermo-optic and thermal expansion effects.

Main Results:

• The sensor exhibited a temperature sensitivity of -78.46 kHz/°C.
• The sensor demonstrated significant insensitivity to applied axial strain.
• Strain insensitivity was attributed to compensating effects of birefringence change and material properties.
• Temperature response is linked to core-cladding differences in thermo-optic and thermal expansion coefficients.

Conclusions:

• A novel strain-insensitive fiber optic temperature sensor based on a dual polarization fiber grating laser has been successfully demonstrated.
• The sensor provides reliable and precise temperature measurements, independent of strain.
• Potential applications include structural health monitoring, oil-well surveillance, aerospace, and process control.