An OTDR characterizes the loss of the link for individual splices and connectors by transmitting light pulses into a fiber and measuring the amount of light reflected from each pulse. To be able to judge whether a fiber optic cable plant is good, one does a insertion loss test with a light source and power meter and compares that to an estimate of what is a reasonable loss for that cable plant. The estimate, called a "loss budget" is calculated using typical component losses for. This application note describes fundamental theory and applications behind optical fiber splicing for mechanical and, in particular, fusion spliced joints. Various fiber preparation, alignment, splicing and testing methods are discussed, as well as safety precautions and troubleshooting. Splicing. Recommendation ITU-T G. 3 outlines the tests normally carried out on installed single-mode optical fibre cable links. It includes a collection of references to the main measurement methods and. ity check. As the components like fiber, connectors, splices, LED or laser sources, detectors and receivers are being developed, testing confirms their performance specifications and helps. This application note discusses the splice loss measurement technique and investigates the extrinsic and intrinsic factors a ecting the splice loss measurements when joining two bare fibre strands.