Pushing data through a wire has always been difficult, especially when there is a continually growing need for pushing the data faster with more information at the same time. Instead of developing more complex wiring technology, tricks and shorter cable lengths were used to make everything quicker. Creating more bandwidth was completed by putting more separate wires into a single strand, but had to be steadily increased while retaining enough robustness in the design to withstand use for many years. Analogue signals used to be sent through these wires, but the biggest breakthrough came from being able to send digital signals over these wires.
In order to have a much stronger core of the Internet and other communications, optical cables were deployed initially to connect data centers. There are an unlimited number of colors available, and the information is transmitted at the speed of light, giving the technology long-standing options. One thing that makes this feasible is the use of Cisco SFP modules. Since optical technology is comparatively expensive to produce now, these modules are the central source of a data center, since they convert optical signals to a format (usually gigabit Ethernet today) that can be used by pieces of equipment that support multiple connection standards. These units are mostly created as hot swaps so they can be easily changed out when new technologies become obtainable that go into the same device.
Long distances are the main need that optical technology fits, but it cannot be implemented within data centers yet given the expensive nature of the technology. Ethernet ports are employed within centers in devices called SFP modules, and are essentially extremely high speed Ethernet. These modules still offer enough bandwidth for the needs of today's engineering, but eventually will be replaced once someone determines how to inexpensively produce optical cables. Luckily, the result nowadays is minimal considering that the main reason optical lines are used over distances is that they transmit quickly, which is not a major issue within a small area. One day, everything will be hooked up through a single optical cable, but until that day comes, there will be many cables.