Novel birefringence interrogation for Sagnac loop interferometer sensor with unlimited linear measurement range

Area of Science:

• Optics and Photonics
• Sensor Technology
• Interferometry

Background:

• Sagnac loop interferometers are widely used in various sensing applications.
• Conventional demodulation methods for these sensors have limitations, including restricted measurable ranges.
• Accurate phase demodulation is crucial for enhancing sensor performance.

Purpose of the Study:

• To propose and demonstrate a novel demodulation method for Sagnac loop interferometer based sensors.
• To verify the feasibility of the proposed method using a temperature sensor.
• To investigate the universality and advantages of the new method over existing techniques.

Main Methods:

• Phase changes were unwrapped using birefringence interrogation.
• A Sagnac loop interferometer based temperature sensor was employed for validation.
• The influence of wavelength sampling interval and span on demodulation error was analyzed.

Main Results:

• The proposed method demonstrated high linearity (0.9996) over a 40 °C temperature range.
• The technique proved to be universal for all Sagnac loop interferometer based sensors.
• An unlimited linear measurable range was achieved, surpassing conventional methods.

Conclusions:

• The novel demodulation method significantly enhances Sagnac loop interferometer sensors.
• The technique offers an unlimited linear range, overcoming limitations of peak/dip tracing.
• This advancement greatly improves the practical applicability of Sagnac loop interferometer sensors.