FOPM-201 handheld optical power meter is a fiber optic tester with upgraded appearance and humanized design, which is mainly used in FTTx networks and fiber network testing. It has a wide range of power measurement and high accuracy, and can be used for absolute optical power measurement and relative loss measurement. When combine with a light source, the instrument is called an Optical Loss Test Set, or OLTS, typically used to measure optical power and end-to-end optical loss.