A cassette for optical fiber includes one or more optical sensors. The cassette has a spool for handling optical fiber. An adjustable shaft is disposed such that the spool is configured to rotate about the adjustable shaft. The adjustable shaft is configured to handle spools having different diameters. A spool controller is coupled to the adjustable shaft and configured to rotate the adjustable shaft to perform one or more of extract and retract the optical fiber. One or more bushings are disposed proximate the spool and are configured to prevent the optical fiber from jumping off the spool.