As data transmission gets more and more "heavy," it requires stronger and stronger fibers on which to travel. In the world of technology, there's stronger and then there's denser, and density is what is needed, in most cases. Rather than build more and more fibers, researchers prefer to make it possible to move greater and greater amounts of data on existing fibers. One way to do this is to use DWDM, which stands for Dense Wavelength Division Multiplexing.
Basically, this technology uses less to get more. It can be compared to a band of radio frequencies, where various stations can broadcast their signals without making it impossible for listeners to hear whatever they want to hear. DWDM puts together multiple signals and sends them at the same time along a fiber, with transmissions taking place at different wavelengths. This turns a single fiber into the virtual equivalent of multiple fibers, and not just a few.
Systems with up to 160 wavelengths are not entirely uncommon. Because of this cutting-edge technology, existing fibers have been able to transmit at speeds of up to 400 gigabits a second. The transmission method is extremely adaptable and versatile as well, in that it can vary the kind of data as well as the wavelength at which that data travels.
Telecommunication companies have sought out such technologies to help respond to a growing array of customer demands, including streaming video, which requires large amounts of bandwidth to create transmissions in real time. Some leading service providers have reported the doubling of bandwidths about every six to nine months. DWDM allows such transmissions by virtually splitting the fibers' capabilities into more than two carriers.
In some ways, it can be thought of as a pipeline that allows more and varied substances to go through it at the same time. In the real-world example of a pipeline, however, the all-too-real problem of finite space would have to be overcome. In the world of fiber optics, finite space presents no problem.