Which technology allows communications service providers to enhance fiber-optic network capacity without additional cabling?

The correct answer is based on the concept of wavelength division multiplexing (DWDM), which is a technology specifically designed to increase the capacity of fiber-optic networks. DWDM allows multiple data streams to be sent simultaneously over the same fiber-optic cable by using different wavelengths (or light frequencies) for each stream. This effectively multiplies the amount of data that can be transmitted without the need for additional physical cables, making it a highly efficient solution for maximizing existing fiber infrastructure.

In contrast, technologies like ATM (Asynchronous Transfer Mode) and CDMA (Code Division Multiple Access) relate more to the methods of data transfer and networking rather than enhancing the physical capacity of the fiber medium itself. WAP (Wireless Application Protocol) is focused on enabling internet access on mobile devices, which is unrelated to fiber-optic technology. Thus, DWDM stands out as the most relevant and effective technology for enhancing fiber-optic network capacity.