NK281 series stable light source are mainly used for continuous optical signal power measurement, optical fiber link on-off test, link fault diagnosis and link loss test. It adopts thermal molding process, which is beautiful and durable. The whole machine has the function of adjustable output power, the maximum adjustment is 6dB. NK281 series hand-held stable light source and optical power meter are used together. They are widely used in optical fiber construction and maintenance, optical fiber communication, optical fiber sensing, Optical CATV and other fields. They can also be used to test the insertion loss and splitting ratio of passive devices such as optical splitter, circulator, optical coupler and optical switch.