Devices, systems, and methods for monitoring a powder layer in additive manufacturing are disclosed. A method includes receiving leading and trailing image data from an image signal processor that is optically coupled to a plurality of leading and trailing optical fibers arranged on a moving powder distributor, the leading and trailing image data corresponding to images of the powder layer, selecting at least one point on the powder bed that is located within a leading region of interest, determining first characteristics of the point, when the point is located within a trailing region of interest due to movement of the moving powder distributor, determining second characteristics of the point, and comparing the first characteristics to the second characteristics to monitor the powder layer distributed by the moving powder distributor.