Lightguide Systems Inc.'s OptiTutor training software simulates an optical time-domain reflectometer for characterizing fiber networks. A self-study feature enables students to learn about the principles of characterization at their own pace, and a testing feature allows supervisors to assess the knowledge of their students, candidates or staff. Links up to 100 km in length can be studied, faults can be introduced in single- and multimode fibers under hundreds of scenarios, and different wavelengths can be tested.