Single-mode optical fiber attenuators with SC type connectors (IEC 61751-4) with a rectangular cross-section and an interference system are recommended for new installations (SC stands for Square Connector or Subscriber Connector). The compact SC design allows high packing density and the ability to connect with duplex and multiplex solutions. Although it is one of the oldest fittings, due to its excellent properties, it is still gaining popularity. SC is still the most popular WAN connector all over the world, mainly due to its excellent optical properties. The SC silencers are passive elements of a fiber optic track, and their task is to limit the optical power of the transmission signal and match it to the receiver's operating range.