A novel composite manufacturing process monitoring application using fibre-optic (FO) sensors is reported for vacuum-assisted resin transfer moulding (VaRTM) with a rigid-closed mould. A fully distributed Rayleigh-Backscattering based load-monitoring approach is demonstrated by numerical modelling and experimental application. Lateral fabric compression is reliably tracked throughout the entire VaRTM process, giving live insights on local pressure distribution, fabric stack compaction and fibre-volume fraction. These parameters have a great influence on the quality of fibre-reinforced composites and real-time tracking of them will significantly improve the quality of the manufactured part, while reducing the number of scraps and destructive testing. The final fibre volume fraction of a medium-sized plate manufactured using industrial VaRTM equipment was successfully predicted based on embedded FO sensor readings only. With a low bend-loss single mode optical fibre sensor being designed for process survivability and forming an integral part of the composite component, it enables a true entire life-cycle monitoring.