Fixed attenuators provide a predetermined, constant level of attenuation, while variable attenuators offer adjustable levels of attenuation. The choice between the two depends on the flexibility and precision required for your specific application. Before diving into the selection process, it's essential to grasp the fundamental principles that govern fiber optic attenuators: Fiber optic attenuators operate on the principle of reducing the intensity of transmitted light signals. for achieving a suitable signal level for a data receiver in a telecom system. Variable attenuators are commonly used for system testing and troubleshooting to assist in diagnosing and correcting optical power issues.