Fiber Mach-Zehnder interferometer based on microcavities for high-temperature sensing with high sensitivity

Area of Science:

• Optoelectronics
• Fiber optics
• Sensor technology

Background:

• Accurate high-temperature measurement is crucial in various industrial applications.
• Existing fiber optic sensors face limitations in sensitivity and operational range.
• Mach-Zehnder interferometers offer potential for sensitive optical measurements.

Purpose of the Study:

• To propose and fabricate a novel high-temperature sensor.
• To achieve high sensitivity and a wide operational temperature range.
• To ensure the sensor is insensitive to external refractive index variations.

Main Methods:

• Fabrication of a Mach-Zehnder interferometer (MZI) in single-mode optical fiber.
• Creation of two microcavities separated by a middle section using a femtosecond laser.
• Formation of a micro-air-cavity by splicing a microholed fiber end with a normal fiber end.

Main Results:

• The fabricated MZI sensor operates in the high-temperature range of 500-1200 °C.
• A sensitivity of 109 pm/°C was achieved, the highest reported for silica fiber temperature sensors.
• The sensor demonstrated insensitivity to external refractive index changes.

Conclusions:

• The proposed MZI sensor is a highly sensitive and robust solution for high-temperature measurements.
• Its unique design overcomes limitations of existing fiber optic temperature sensors.
• The sensor's refractive index insensitivity makes it ideal for demanding environments.