Final answer:
The core network of the Internet, known as the backbone, uses fiber-optic cables because of their low loss, high bandwidth, and reduced crosstalk properties, which support high-speed data transmission over long distances.
Step-by-step explanation:
The Internet backbone is a fundamental network that relies on fiber-optic cables to support very high bandwidth. These extensive optical fiber cables are placed on the ocean floor and underground, enabling the transmission of Internet and telephone communications over long distances. Fiber-optic communication systems provide numerous advantages, such as low loss, which means that light can travel many kilometers without significant dimming and requiring amplification, and high bandwidth, allowing for a high volume of data transfer. Furthermore, they exhibit reduced crosstalk, ensuring that signals in one fiber do not interfere with signals in adjacent fibers. These features make fiber-optic cables suitable for the core infrastructure of the Internet.