Enhanced refractive index and temperature sensor based on balloon-shaped Mach-Zehnder interferometer

•The spherical structures were added on the basis of balloon-shaped Mach-Zehnder interferometer (MZI), which can effectively excite higher order cladding mode. Thus, the performance of the sensor is enhanced.•The sensor we proposed has high reliability and sensitivity, which are suitable for most practical sensing applications.•The sensor we proposed has more obvious dips than the traditional balloon-shaped fiber sensors. Moreover, it has a more stable structure compared with the traditional balloon-shaped MZI.