An optical fiber sensor for the detections of liquid level and strain through cascading Sagnac interference and modal interference

•An optical fiber sensor combining the Sagnac interference and modal interference was fabricated and experimentally investigated for the measurements of liquid level and strain.•A sensitivity of 525 pm/mm for liquid level detection, and 32 pm/με for strain detection were obtained.•This sensor has advantages of simple structure, high sensitivity and good accuracy, which is an ideal candidate of liquid level and strain simultaneous detection.