In telecommunications and fiber optics, a plastic-clad silica fiber or polymer-clad silica fiber (PCS) is an optical fiber

Optical fiber

An optical fiber is a flexible, transparent fiber made of a pure glass not much wider than a human hair. It functions as a waveguide, or "light pipe", to transmit light between the two ends of the fiber. The field of applied science and engineering concerned with the design and application of...

 that has a silica-based core and a plastic cladding

Cladding (fiber optics)

Cladding is one or more layers of material of lower refractive index, in intimate contact with a core material of higher refractive index. The cladding causes light to be confined to the core of the fiber by total internal reflection at the boundary between the two. Light propagation in the...

. The cladding of a PCS fiber should not be confused with the polymer overcoat of a conventional all-silica fiber

All-silica fiber

All-silica fiber, or silica-silica fiber, is an optical fiber whose core and cladding are made of silica glass. The refractive index of the core glass is higher than that of the cladding. These fibers are typically step-index fibers...

. PCS fibers in general have significantly lower performance characteristics, particularly higher transmission

Transmission (telecommunications)

Transmission, in telecommunications, is the process of sending, propagating and receiving an analogue or digital information signal over a physical point-to-point or point-to-multipoint transmission medium, either wired, optical fiber or wireless...

losses and lower bandwidths, than all-glass fibers.

The main applications of plastic-clad silica fiber are industrial, medical or sensing applications where cores that are larger than those used in standard data communications fibers are advantageous.