High-Visibility Photonic Crystal Fiber Interferometer as Multifunctional Sensor

A photonic crystal fiber (PCF) interferometer that exhibits record fringe contrast (similar to 40 dB) is demonstrated along with its sensing applications. The device operates in reflection mode and consists of a centimeter-long segment of properly selected PCF fusion spliced to single mode optical fibers. Two identical collapsed zones in the PCF combined with its modal properties allow high-visibility interference patterns. The interferometer is suitable for refractometric and liquid level sensing. The measuring refractive index range goes from 1.33 to 1.43 and the maximum resolution is similar to 1.6 x 10(-5).