The breathing process monitoring with a biaxially oriented polypropylene (BOPP) film based fiber Fabry–Perot (F–P) sensor is presented. The fiber F–P sensor is fabricated with 3-D printing technology and fixed on a medical respirator for breathing process monitoring. Due to the low Young's modulus of the BOPP film and its thinner thickness, the breathing sensor shows the high pressure sensitivity of -0.581 nm/Pa. By monitoring its intensity response to the pressure induced by breathing, the breathing process can be monitored accurately, including respiratory waveform, respiratory rate, inspiratory duration and amplitude, expiratory duration and amplitude, and inspiratory and expiratory rhythm. Since the sensor is all fiber design with the inherent advantages of small size, anti-electromagnetic interference, green environmental protection, pollution-free and no harm to body, it is expected to be widely used in respiratory disease monitoring. © 2020 Elsevier B.V.