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• The sensor exhibits a sensitivity of 26.3 pm/με in the strain range of 0–300 με. • The CNN-based technique can effectively extract the data information in the spectral. • The strain range that can be measured is greatly enlarged to 0–2000 με. • Temperature crosstalk can be solved by tracking different interference dips. A balloon-type optical fiber sensor (OFS) for strain measurement was proposed, and the measurement range was significantly increased with the assistance of convolutional neural networks (CNN). The presented OFS was prepared by bending a Mach-Zehnder structure based on polarization-maintaining fibers into a balloon-type, which exhibits a sensitivity of 26.3 pm/με under the strain range from 0 to 300 με. The CNN-based signal analysis method can effectively extract the data information in the spectral, and the strain range that can be measured is greatly enlarged to 0–2000 με, while the accuracy of the measurement can be guaranteed. Further, the temperature sensitivity of the OFS is −0.0252 nm/°C; the lower temperature sensitivity can effectively suppress the crosstalk problem caused by temperature changes during strain measurement. The proposed method remarkably increases the strain measurement range of OFS, which is conducive to the application and development of OFSs. [ABSTRACT FROM AUTHOR]

[Display omitted] • The sensor exhibits a sensitivity of − 8.8320 nm/m−1 in the curvature range of 0–3.1171 m−1. • The application of CNNs significantly improves the measurement range to 0–10.4167 m−1. • The sensor can realize curvature measurement and direction recognition over a wide curvature range in four directions. • The OFS can achieve curvature measurements in 12 bending directions with good accuracy. In this work, wide-range curvature sensing in multiple directions was achieved by combining a Mach-Zehnder-based optical fiber sensor (OFS) with convolutional neural networks (CNNs). The experimental results show that the curvature sensitivity of the proposed sensor is − 8.8320 nm/m−1 in the range of 0–3.1171 m−1. The application of CNNs significantly improves the measurement range to 0–10.4167 m−1, and the sensor can realize measurements over a wide curvature range in four directions. The accuracy of the measurements can still be guaranteed despite a sudden decrease in the number of wavelength sampling points, and curvature direction recognition was realized. Further, OFSs can achieve a wide range of curvature sensing in 12 directions by taking full advantage of the information contained in the transmission spectrum. The proposed technique is highly versatile and conducive to the popularization of OFSs in the field of curvature measurement. [ABSTRACT FROM AUTHOR]