A fiber optic attenuator is used to reduce the power of the laser in a fiber link. Sometimes the power of a fiber signal can be too high potentially causing damage to optical receivers in the hardware. In this instance, a fiber attenuator would be used to lower that optical signal.
This particular Optical Attenuator features a fixed reduction of 6 decibels and is applicable to single-mode fiber links requiring SC/APC connectors.
Specification