The purpose of this application note is to provide technical and safety details on the choice and use of a visual fault locator (VFL – Visual Fault Locator) commonly called a “red light pen” used to test fiber continuity. monomode optics (also usable for multimode fibers).
Today, mainly class 2 VFL laser pens (a reminder on the classification of lasers is proposed in paragraph 3 and in the appendix) are currently used and widely deployed. They comply with the safety level and do not require any protection device. Other pens of higher power and therefore of higher class appear on the market. It seemed important to us to specify their real performance and their conditions of use.