An article such as a drawn optical fiber (21) or an array of optical fibers is provided with a curable coating material. The array of optical fibers may be held together with a curable matrix material (45). Included in the coating material or the matrix material is a fluorescent constituent the fluorescence emission of which changes as a function of the degree of cure of the coating or matrix material. After the in-line curing of the coating material or of the matrix material, the fluorescence emission of the fluorescent constituent is monitored to determine the degree of cure of the curable material.
