We have developed three instruments for accurate measurement of optical fiber cladding diameter: a contact micrometer, a scanning confocal micro- scope, and a white-light interference microscope. An optical time domain reflectometer (OTDR) is the portable optical test set used in the field for pre- and post�construction fiber mea-surements. The backscatter concept is illustrated in Figure 1 A lead-in or launch fiber is used to eliminate the effect of dead zone created from the OTDR fiber. Testing fiber cable quality is a mandatory engineering process, not an optional best practice. Check out some of the application examples below. It's possible to stably measure outer diameter in harsh environments using the LS-9000. Each instrument has an es- timated uncertainty (3 standard devia- tions) of 50 nm or less, but the.