The IEC has published a new standard for the testing of fibre optic cabling. IEC 61280-4-5 provides test methods to measure the attenuation of installed multimode and single-mode optical fibre cabling plant as well as the determination of their polarity and length. Fiber optic cabling is the high-performance core of today's datacom networks. What do fiber testers do? Which fiber tester is right for you? In. This Applications Engineering Note (AEN 135) explains and recommends standard measurement methods for characterizing optical fiber system performance. In addition, the fiber does not conduct electricity and is pract lighter and smaller than copper cable.