The fibers used in long distance telecommunications applications are always made of which material?

In long-distance telecommunications applications, fibers are predominantly composed of glass. Glass fibers are utilized for their superior performance characteristics, including low attenuation, high bandwidth, and the ability to transmit signals over much greater distances compared to other materials. This makes them ideal for communications where signal integrity over long routes is critical.

Glass fiber optics work by transmitting light signals through the fiber, allowing for much faster data transmission than what is possible with traditional copper wires. The refractive properties of glass enable the light to be guided through the core of the fiber, which minimizes signal loss and allows for the accommodation of a vast amount of data.

The other materials listed, while they have their own specific applications, do not provide the same level of performance in long-distance telecommunications. Plastic fibers are typically used for shorter distance applications due to higher attenuation and sensitivity to environmental conditions. Copper, though historically used for telecommunication, suffers from significant signal loss over long distances. Silicon is used in semiconductor devices and other electronic components, but not as a fiber material in telecommunications. Thus, glass stands out as the correct choice for fiber optics in long-distance networks.