ST-3308N handheld return loss tester is used to measure the return loss in the field fiber optic linking, in order to adjust the quality of the optic fiber end-face, and to make sure the fiber optic communication is in good condition. This 3308N handheld return loss tester can realize measurement of Return Loss, Insertion Loss, Output power, and also can be used as the laser source. Moreover, it has the data storage function of 500 measurement items.