Geometry is the most fundamental of characteristics of the optical fiber and is indicative of the quality control at the manufacturing stage.
The Geometry of the optical fiber will determine if it is possible to splice two fibers with an acceptably low loss.
The 'Production/Lab/R&D' range is suitable for manufacturers of fiber and cables. It is considered unlikely that this measurement would be required in a field environment. Like most optical characteristics, the geometry of the fiber is frozen at the time of manufacturing and is not known to vary throughout its operating life but does vary along the its length and so it is useful and considered good practice to measure the geometry even within a cable manufacturing environment to ensure the consistency of the product.