All-POF coupling ratio-imbalanced Sagnac interferometer as a refractive index sensor

Area of Science:

• Photonics
• Optical Sensing
• Fiber Optics

Background:

• Refractive index sensing is crucial for various applications.
• Existing sensors can be complex or costly.
• Polymer optical fibers offer potential for low-cost sensor development.

Purpose of the Study:

• To propose and demonstrate a novel polymer optical Sagnac interferometer.
• To develop a compact and low-cost refractive index sensor.
• To investigate its performance for measuring sugar solution concentrations.

Main Methods:

• Fabrication of a Sagnac interferometer using a single piece of polymer optical fiber.
• Development of a fiber coupler using chemical and twisting techniques.
• Modifying the coupling ratio by varying the surrounding medium's refractive index.
• Measuring transmittance changes in sugar solutions of varying concentrations.
• Calibrating the sensor at 733 nm.
• Estimating refractive index using a linear model based on transmittance data.

Main Results:

• Transmittance decreases with increasing mass concentration of sugar solutions.
• The rate of transmittance decay varies with concentration (faster at low, slower at high).
• The sensor demonstrated larger transmission variations at 733 nm.
• A resolution of 0.057 weight percent of sugar solution was achieved.

Conclusions:

• The polymer optical Sagnac interferometer is a viable compact and low-cost refractive index sensor.
• The sensor shows sensitivity to changes in refractive index, correlated with sugar concentration.
• The proposed method allows for effective refractive index estimation with good resolution.