Optical fibers are used as medium for telecommunication and computer networking because of their inherent properties such as flexibility. Optical fiber can be grouped together in many forms such as in a loose tube or in a ribbon, before they can be further assembled for cabling. Optical fibers have been developed for long distance telecommunications as they can propagate light for long distances with low levels of attenuation compared to copper cables. Low attenuation allows repeaters to be placed at longer spans contributing to less cost.
From the beginning of optical communications in the early 1970s, we have traveled a long way. Research and developments are progressing all over the world to achieve higher speeds and high bandwidth. For example, the per-channel light signals propagating in the fiber have been modulated at rates as high as 111 gigabits per second (Gbit/s) by NTT. The most commonly speeds are still 10 or 40 Gbit/s in deployed fiber optic systems by different carriers in different parts of the world. Researchers demonstrated transmission of 400 Gbit/s over a single channel using 4-mode orbital angular momentum multiplexing.
In a wavelength division multiplexing system, each optical fiber can carry many independent channels, each using a different wavelength of light. The net data rate, that is the data rate without overhead bytes per fiber is the per-channel data rate reduced by the FEC overhead, multiplied by the number of channels. Usually this is up to eighty in commercial DWDM systems. Bell Labs broke the 100 (petabit per second)×kilometer barrier in 2009. The highest bandwidth on a single core was 101 Tbit/s, which is equivalent to 370 channels at 273 Gbit/s each as of 2011. Multicore fiber can support much more bandwidth. The record for a multicore fiber in 2013 was 1.05 petabits per second.
Optical fibers have clear advantages over copper cables even in short distance applications. For example, in an office building network, fiber optic cables can save space in cable ducts. A single fiber can carry much more data than copper cables, which typically runs at 100 Mbit/s or 1 Gbit/s speeds. An optical fiber is also immune to electrical interference. There is no cross-talk between signals in different cables. Optical fibers do not pickup environmental noise.
In places where there is a fear of electrical surges, dielectric cables can be installed. Unarmored fiber cables are best suitable for communication in areas where there is high chances of lightning strikes. They can also be used in environments where explosive fumes are present, without danger of ignition. As you may know, tapping information out of an optical fiber is very difficult. Concentric dual core optical fibers are used where tap-proof requirements are necessary.
Post a Comment