AN-143 Insertion Loss and Return Loss Testing of Short Cables and Assemblies (including TOSA and cassettes)

Overview

As fiber optic infrastructure and components are designed more densely and more compactly, patch cords, cassettes, and optical subassembly cables have followed suit by becoming shorter and shorter. These short cables, which can sometimes be just 20cm in length, present certain problems for testing return loss (RL). Most RL meters, whether pulse-based or Optical Continuous Wave Reflectometer (OCWR) based, have difficulty accurately measuring the return loss of these cables. Often, the return loss from the back connector of the device under test interferes with the measurement of the front connector.