A sensor assembly (14) for sensing an impact to a vehicle (10) includes a light source (34) for emitting light and a sensing channel (40) for receiving the emitted light. The sensing channel (40) is configured to deform in response to an impact to the vehicle (10) and includes at least one void (70) with dimensions that vary in response to deformation of the sensing channel (40). A detector (36) senses an intensity of the light propagating through the sensing channel (40) and provides a signal indicative of the sensed intensity. The sensed intensity varies as a function of the dimensions of the at least one void (70). The sensor assembly (14) also includes a controller (94) for analyzing the signal from the detector (36) to determine whether the sensing channel (40) has been deformed and thereby, whether an impact to the vehicle (10) has occurred.