High-sensitive Mach-Zehnder interferometers based on no-core optical fiber with large lateral offset

In this work, a fiber Mach-Zehnder interferometer (MZI) based on no-core optical fiber (NCF) with large lateral offset structure was investigated theoretically and experimentally. For this interferometer, the light in the measurement path mainly propagates through the materials to be measured and the light in the reference path is well confined in the fiber. Therefore, the sensitivity for the refractive index measurement can be above 10,000 nm/refractive index unit (RIU), which is much higher than that of previously reported MZIs based on the interference principle of fiber modes. Owing to the high thermo-optical coefficient of polydimethylsiloxane (PDMS), the PDMS packaged sensor can measure temperature with a high sensitivity of 10.45 nm/ºC. Moreover, the PDMS coating layer can also enhance the mechanical strength of the fiber structure for temperature measurement.