The acronym PCS, in networking terms, refers to standard plastic-clad silica. Silica, also known by the term glass, is the optical core of a fiber-optic cable. The cladding applied to the outside of the fiber is made of plastic, which has a lower angle of refraction and keeps the optical signal inside the glass fiber.

PCS, if it is not damaged, has an excellent range and a wide bandwidth. It is immune to electro-magnetic interference.